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24Home Power #26 • December 1991 / January 1992Alternative Fuelshy gas? What's so good aboutgas? One could make anargument ad hominem andsimply say, if gas weren't such a goodidea, why is it so abundant in nature. ItWPrologue toMethane GasAl Rutan, the Methane Man©1991 Al RutanGas UseWhat about flammable gas? Why consider it? For thoseof us who spent much of our youth chopping wood to heatand cook at home, the idea of gas is like something fromparadise. The idea and the experience of merely turning avalve to have instant flame without all the "bitching" andcomplaining involved in "go get that wood!" is amazing.Almost everyone likes the ambiance around a campfireon an outing with friends. But for the day to day fuelneeds, we wish to have it as "automatic" as possible, andfor being controlled by a thermostat, gas is unsurpassed.It is clean and uncomplicated. Clean? Yes, clean. Thereis no soot that collects in a chimney from the burning ofmethane gas. Does it need to be vented? It should be, ifat all possible. The fumes from any type of combustionshould be considered suspect.Potential problems from the burning of methane areminimal. If the combustion is complete, what is producedis carbon dioxide and water vapor. Yet we have nopractical assurance that combustion is always as perfectas it could be.An interesting note historically is the fact that the Indiangovernment some 40 years ago pushed the developmentof homestead production of methane because so manypeople were going blind from the effects of burning cowdung for fuel. Our early pioneers had similar experiencesfrom the burning of buffalo chips. Burning raw manureshould always be considered a "no-no."Low-tech methane production information comes fromboth India and China–two countries with vast populations,huge pollution problems from waste, and an immenseneed for fuel, which isn't readily available.At HomeOur interest stems from the fact that homestead methaneproduction is one more way to unplug from a utilitycompany and provide access to energy, whichsubstantially contributes to the quality of life.So, one has to have the heart for it. Unlike electricity, thatis for all practical purposes quite mechanical, gasproduction means tending to living things, like a flock ofchickens, a band of sheep, or milking goats. For abundantgas production, there needs to be a sensitivity to thespecial needs of the microscopic creatures that produceflammable gas as their waste product. This meansproviding for their basic wants and–don't laugh–givingthem a measure of love. All living things–plants, animals,and people–require love in order to flourish. This needextends even to living creatures that can't be seen withthe naked eye.A person we know who had a methane system one daywent up to his tank and gave it a good hefty kick as anexperiment. The gas production stopped immediately,and started slowly again only after some time hadpassed.Because one must assume responsibility for the care of acolony of living entities, producing gas to burn hasanother dimension some may need to consider beforeundertaking such a venture.The advantages of gas are many-fold. It is so easy to use.It is so controllable. It is relatively easy to store. It can beused automatically. It will even run your vacuum cleaner ifyou put the methane gas through a fuel cell which will turnthe gas directly into electricity. Plus, it is so clean–nosoot, no creosote, no ash, and no chopping. What morecould you ask?Making and Using Methane GasMethane is a natural gas. The reason it's called "natural"is because it occurs in nature everywhere. It can be thegas found in a swamp or marsh, the gas found in a coalmine, the smell coming from a septic tank or sewer line,or the gas sold to us by a utility company under the title of"natural gas." The product is substantially the same, CH4.We've heard that methane is odorless, and it is. Sewergas we know is not. So what is the difference? When theprocess that produces gas is underway, there are avariety of gases produced at the same time. All suchgases result from micro-organisms feeding upon organicmatter and producing gas as a waste product. Methane,
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25Home Power #26 • December 1991 / January 1992Alternative Fuelswhich is odorless, is one of them. Hydrogen sulfide, whichis smelly, is another. It is hydrogen sulfide which gives usthe characteristic sewer gas or "fart" smell.When these gases are encapsulated in the ground over along period of time, the smell is purged, leaving anodorless gas. The sewer gas smell can be removed easilyfrom the mixture by simply bubbling all the gas throughcalcium carbonate, which is simple barn lime, and therebyscrubbing it so to speak. The gas becomes odorless. Thegas companies re-introduce an odor to odorless gasbefore selling it as a safety measure so that our nosescan detect "loose gas" that could be potentiallydangerous.All these burnable gases are produced by anaerobicorganisms feeding upon organic matter. To say they areanaerobic means they only live when air is excluded fromthe space in which they are functioning.They are the same organisms that cause us to haveintestinal gas. Each time a warm blooded animaldefecates, some of the gas producing organisms arecontained in the feces. This is why it can be said thatmethane occurs virtually everywhere. Wherever air isexcluded from the decomposition process, the productionof methane and accompanying gases is likely to occur.Stories are legion about a bunch of guys with nothingbetter to do than ignite the intestinal gas of one of theirparticularly "gassy" buddies, and then being amazed athow flammable the experiment was.The micro-organisms that produce flammable gas aretemperature sensitive. They want body temperature inorder to function most effectively. In people that is 98.6°F.In a chicken or a pig the body temperature is 103°F. Soright around 100°F is the optimum temperature for theprocess to work most effectively. The action can occur atlower temperatures. As the temperature drops so doesthe rate at which methane gas is produced.People will sometimes ask, "Why can't I use the gas offmy septic tank to burn in a stove?" The typical septic tankswings through such wide temperature fluctuations, theamount of gas produced is minimal. Each time a toilet isflushed with cold water, the tank goes into "shock." Eachtime some warm wash water from a bath or shower flowsinto the tank, it becomes more active until the next shot ofcold water. Such tanks are ordinarily in the ground, whichstays at a constant 50° to 55°F. The ground is a constantheat sink, draining heat away from the tank. About all onegets from a septic tank, by way of gas, is enough to causean unpleasant odor. Because the temperature cannot bemaintained at the required working level, such tanks haveto be pumped from time to time. The solids cannot beefficiently digested and so keep building up.Key ConsiderationsIt is the concept of a tank which offers us the mostpractical approach to the task of harnessing theproduction of methane. Liquid within a tank gives us twoimmensely important features–transport and the exclusionof air. Both are essential for maximum production.Slurry LevelInputSlurryLevelInputPipeOutputSlurryLevelExitPipeExit BasinGas Line OutMETHANE TANK CONCEPT SKETCH
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26Home Power #26 • December 1991 / January 1992Alternative FuelsSome methane production occurs in such places as anordinary barnyard manure pile. The center of the pile iswithout air and with the heat generated by the pile somemethane gas is bound to be produced. If we want toharness the concept, we will need a great deal of gas. Asolid pile to give us what we would need would have tobe, literally, a small mountain. In a tank, it's an entirelydifferent matter. It is much easier to have the tank "justbubbling away" so that the amount of gas collected in ashort time can be significant.Key QuestionsHow much gas do I need? That will determine how muchgas must be produced. Next is, how much material do Ineed to produce this amount of gas? The third question is,how large must the equipment be to produce and storethis amount of gas?Gas is thought of in terms of cubic feet. We can allvisualize a cubic foot–12 inches square in each direction.The amount of gas within such a space of 12 inchessquare is determined by the compression of the gas.Fortunately, when we are working with methane, we aretalking about only ounces of pressure–just enoughpressure to push the gas to the burner, whether it mightbe a stove, water heater, or refrigerator.For "home-made methane," our pressure regulator is notany more complicated than a heavy rock on an inflatablegas holding bag, or the weight of a solid yet expandablegas holder floating in liquid. It's not very complicated.How Much Gas Does One Need?To estimate the amount of gas needed, the averagefamily of four burns somewhere around 200 cubic feet ofgas a day. This covers the combined tasks of cooking,heating space and heating water. Obviously, individualscan trim this amount considerably by using efficientappliances–such as flow-on-demand water heaters, andhigh-efficiency space heaters.The best way to get a handle on this information is to lookat the amount of consumption listed on the utility bill ofsome family you know and then observe their lifestyle.Processes of GasWe say that the liquid provides transport. That transport istwo-fold. Obviously, we must transport the material to thetank. Equally important, yet not so obvious, is thetransport of the micro organisms to the material orvice-versa, so that the material can be digested by the lifeforms. Within the digestive tract of a warm bloodedanimal, this action takes place by peristalsis. We imitatethis transport by very gently moving the contents withinthe tank from time to time.Concerning The TankA simple paddle mechanism works the best. Somesystems re-circulate some of the gas to providemovement, but this has proven to be less thansatisfactory. Often inorganic material is stirred from thebottom of the tank–material such as sand and small rocksif they are present–and the living organisms are injured inthe process. The best method is a slow mixing action witha paddle of some sort. The paddle may be on a horizontalaxis or a vertical axis. It merely has to move the materialvery gently a few times each day.The exclusion of air is essential to have the process work.While we know that even water contains someair–otherwise how could fish breathe–once the activity ofgas producing bacteria becomes established, even the airis mostly excluded.The tank must be closed so that new air is not able toenter. This is done effectively by having both the fill pipeand the exit pipe extend below the water line. So, airexposure to the tank is limited to the surface of the waterlevel in both the fill and exit pipes.In the past much discussion focused on whether the tankshould be horizontal or vertical. It is the consensus thatwhen the tank is horizontal rather than vertical, it canwork more effectively. (Note the illustration on pg. 25.)The reason is that the fill and exit pipes need to bespaced as far apart as possible. Then the materialentering the tank has greater exposure to the activitywithin the tank before being moved near the exit pipe.The gentle stirring action needed, of course, mixes upeverything. Yet if the new material is forced to "migrate"some distance before reaching the exit pipe, then themicro-organisms will have more time to feed upon itbefore it is replaced by incoming material.How big should the tank be? This is determined by howmuch material is available to the tank on a daily basis,and ultimately how much gas one wants to generate.Production MixtureThe input for the tank needs to be a mixture of manureand carbon material. Carbon material is ordinarilyunderstood as waste vegetation, but it can't be justanything. It needs to be something that when soaked inwater for a few days becomes very soft. The bacteriadon't have any teeth. They have to "gum" it.Hardness can be misleading. A carrot seems hard, but ifsoaked long enough it turns to mush. Grass clippings, onthe other hand, contain a quantity of lignin, that cellulosefiber that makes wood very "woody." Anything with a high
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27Home Power #26 • December 1991 / January 1992GasLineINWaterDrainPipeAlternative Fuelscontent of lignin will not work well in a methane tank.Straw for the most part is acceptable. Hay is not.Even such things as ordinary newspaper work well.Although newspaper at one point was wood, the lignin hasbeen broken down so that when the newspaper is soakedfor a day or so, it turns to mush–good stuff for ourpurposes. The bacteria want a mixture of 30 parts carbonto 1 part nitrogen. Manure is nitrogen rich–about 15 partscarbon to 1 part nitrogen, so manure needs to bebalanced with more straight carbon material. This ratioisn't a critical proportion and the process still functions,but 30 to 1 is the ideal.PotencyThe ability of manure to produce gas varies from animal toanimal. Chicken manure can be especially potent. I haveobserved as high a yield as 10 cubic feet of gas from eachpound of naturally moist chicken manure which wasmixed with some finely ground spilled feed.Hog manure usually yields about 4 cubic feet per wetpound. Cow manure usually yields about 1 cubic foot ofgas for each pound of fresh manure. The reason there issuch a difference is that much of the methane potentialhas already been released when the waste goes throughthe digestive system of a ruminant. There is usually somuch of this kind of manure, using it is still worthwhile.Another good feature of the process is that raw manure ischanged into something which is aged and totallyacceptable to be placed on growing things. With anyquantity of raw, green manure, this is not the case.Sizing the SystemHaving established that we need around 200 cubic feet ofgas a day, we need to set about designing a system thatGas Storage Tank
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28Home Power #26 • December 1991 / January 1992considerably over ordinary sheet metal. The acids withinthe mixture do not work rapidly on the tank, but they willdeteriorate it over an extended period of time.Originally, I had an ordinary 250 gallon fuel-oil tank that Iused for demonstration purposes. It lasted for severalyears. It finally rusted through, but considering the fact themetal was relatively light gauge to begin with, the tankserved well. Because oxygen is excluded in the processand the pH must be kept at neutral, the deterioration ofthe tank was not rapid.Another great feature of a milk bulk tank is the fact italready has a mixing paddle as part of the tank's design.All access ports above the water line would have to besealed air tight for effective gas production and, moreimportantly, just common sense safety.The Gas HolderRegarding a gas holder, one may use a solid vessel openat the top filled with liquid into which another solid vesselopen at the bottom is placed. The gas pushes the top unitup out of the liquid as the gas is produced (see illustrationon pg. 27).The simplest type of gas holder is an expandable bag. Itcan be something like a waterbed mattress upon which aweight is placed to produce enough pressure to send thegas to the point where it is used–a burner of some type.One may use simply a vinyl of some type, but the besttype of material is a nylon fabric that is impregnated withvinyl–not laminated, but impregnated–which becomesexceedingly durable. If this inflatable bag is placed insidea "silo" of some type, then there is a measure ofassurance that the bag is not going to be punctured. Thepeople who work with the nylon impregnated vinyl–one ofthe trade names is Herculite–seal it by a process ofelectro-statically welding it. Using an ordinary adhesivemay not work because methane has a tendency todissolve a number of adhesivesFor NowThe process of making methane gas is relatively simple ifone is attuned to the basic needs of the process. Theyare: the right balance of material, the right temperature,and the exclusion of air. Given these three conditions, themethane process is virtually unavoidable. The trick is tobe sensitive to the fine-tuning of each of theserequirements. As we continue with more methane articlesin Home Power, we will do just that.AccessAuthor: Al Rutan, POB 289, Delano, MN 55328Alternative Fuelswill provide this. How much is 200 cubic feet? Visualize aninflatable bag that is six feet wide, six feet long and sixfeet high, and you're seeing a space of 200 cubic feet.If we say that a mixture of manures will give us 4 to 5cubic feet of gas per pound of naturally wet manure weare going to need about 40 to 50 pounds of manure a day.We would need even less manure if we use chickenwaste. These forty pounds are going to be mixed withsome type of additional carbon material, to which water,preferably warm water, will be added to give us a "slurry."This will most likely be about 15 gallons of bulk. Visualizethe content in three five gallon buckets.Size of the TankIt is generally a rule of thumb that the size of the tankneeds to be 40 times the size of daily input. This meansthat when 1/40th of the volume of the tank is introduced atthe input end then 1/40th of the volume will exit theoverflow end simply by being displaced. Allowing somespace at the top of the liquid for the gas to collect, thetank should be about 50 times the size of daily input.Sewage plants that employ the methane process–andmany do–like to have a holding time of 90 days. In otherwords the preference is to have the tank 90 times the sizeof the daily input. The purpose of this is to totally destroyany potential pathogens. That length of time within thetank does exactly that. Periodic inspections by the varioushealth departments around the country keep a check onsuch activity and find consistently that the 90 day holdingtime accomplishes this goal.Within a 40 day holding period most of the pathogens areeliminated. Because we are not dealing primarily withhuman feces (although this material may be used withanimal waste) the longer holding time is not as imperative.Within a 40 day time span the greatest amount of gas isproduced. In a period longer than 40 days, the gasproduction begins to slow down considerably.We need a tank that is 50 times the volume of the dailyinput of 15 gallons, or a 750 gallon tank. Obviously, a1,000 gallon tank would be ideal to take care of extrademand for production or additional material input.Tank ChoiceA 1,000 gallon discarded milk bulk tank would be ideal.Because bulk tanks already have a system for cooling thetank, this system could be easily adapted for holding thetemperature of the tank at 100°F. rather than cooling it.One type has the "radiator" already built-in.The fact that the tank is stainless steel is also anadvantage because it would extend the life of the tank
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44Home Power #27 • February / March 1992Alternative FuelsThe article in HP26 says that we need about 50 pounds ofwaste daily, a mixture of manure and carbon material tofeed the digester that will turn this material into about 200cubic feet of gas.The focus of this article is just this problem. As anyonewho has done any kind of homesteading knows, there is aMore OnMethaneAl Rutan, the Methane Man©1992 Al Rutann the last issue of HP, the methanearticle praised the ease with which gasis used – merely turning a valve tohave instant vapor fuel. It takes so littleeffort. If gas is so easy, how does fiftypounds of stuff get pushed aroundwithout any effort? Aw...you caught theinconsistency!Ihard way and an easy way to doevery job. Part of the endearingquality of American ingenuity is tosee how people can approach atask that is downright tedious, andby some clever manipulation, makeit easier.Easy is BetterThis really became a lesson takento heart while living at Red Lodge,Montana. I was in the middle of aproject raising rabbits for market –lots of them, about 200 breedingdoes producing litters.Feeding and watering this numberwas a time-consuming chore. I madehoppers for the hay and feed pellets early on, butproviding abundant water was a drag. I upgraded fromwater dishes to water bottles with a valve. This was animprovement in cutting down the labor. The big jump wasto a system of watering valves fed by little plastic linesfrom a central tank with a float valve to control both thewater level and pressure on the water lines.In one situation, the water was put into 200 little waterbowls which were constantly being spilled or fouled withwaste. In the other, water was supplied by a smallpipeline with drinking valves in each cage. The result wasthe same – water to drink, but the effort needed wastotally different. The two situations accomplished thesame effect – abundant fresh water.Consider the CrittersThere is another consideration that must be brought tomind at this point. In the methane process, we areworking with living creatures. Therefore a moraldimension must be considered if we are going to achievea measure of serenity for ourselves in this whole process.To have a genuine sense of well-being about the entireoperation, the animals and the space for which the personis responsible must have an ongoing atmosphere ofserenity. If this sounds a little bit like St. Francis of Assisi,well, so be it and no apologies. The purpose of life is notmerely accomplishment, but accomplishment in a caringand respectful way.As people, we harness the work of creatures. Some maymaintain this is not right. I don't agree. I do feel stronglythat the animals with which we work and upon which wedepend do have the right to a reasonable quality of life.So at this point we are talking about animal rights. Theconcept of animal rights means different things to different
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45Home Power #27 • February / March 1992Alternative FuelsMoving the Material While It's WarmIt is the matter of manure itself. How can a person move itwith the least effort possible? Manure delivery systemshave been devised for various types of critters, except thehorse. To my knowledge, there is no device moreautomatic than a scoop shovel for cleaning out a horsestall.If one DOES have animals, the feces HAVE to gosomewhere. So at that point it makes a great deal ofsense to turn the waste into vapor fuel (methane) andcompost.When the waste comes out of an animal, it is at exactlythe right temperature – body temperature. As it lies on theground, it cools off. This cooling during the cold time ofthe year is severe. The sooner the waste is transportedfrom the animal to the tank the better. If the waste losesheat, then the heat must be restored to have the methanedigestive process occur in the best manner possible.This brings us to the biggest challenges in the entiremethane procedure. How do we gather the manure tobegin with? How do we gather it as soon as possible afterit leaves the animal and before it cools down?There are two natural forces that work well for us. One isgravity and the other is water. In rolling countrysides,barns are commonly built on hillsides. The hayloft iseasily accessible by simply driving in rather than having togo through the labor of hoisting every bit of hay with somekind of sling mechanism. The hay is forked down to theanimals below, using gravity.people. To me, it means that an animal has a right to areasonable quality of life. An animal has a quality lifewhen it feels good about itself. This is most clearlyevidenced by grooming. Animals, if they feel good aboutthemselves, groom themselves and their friends.Quality of LifeDeath for an animal, or a person for that matter, is not theworst thing that can happen. Quality of life whilesomething is alive, be it plant, animal or person, is ofmajor importance in the scheme of things. One whohomesteads can not be mentally well off if such a personis not sensitive to the quality of life of the living thingsaround the homestead. Are the animals feeling good, asevidenced by their grooming?A DilemmaNow, why make a point of this if we are talking aboutmethane and manure? We are faced with a dilemma. Onthe one hand we want to collect waste with the least effortpossible and do it as automatically as possible. On theother hand, we need to have a measure of sensitivity tothe needs and quality of life for the animals on which wedepend.If the animal wanders about freely, it will be very difficult tocollect its waste. On the other hand, if the animal is tightlycaged or tied, its quality of life is virtually nil. So what's theanswer?Somewhere there is a middle ground. Chickens, forinstance, do most of their pooping while they are perchedat night. Milk cows leave a quantity of used grass in thegutter while being milked or held in the barn during thenight.Hogs that are totally confined don't have much of a life.Hogs that are confined only through the night will leave agood share of their waste behind when penned only partof the time.Chickens do not do well housed on hardware clothbecause their natural inclination is to peck and scratch.I've seen a roost system where the area under the roostwas wired with large chicken wire mesh. The chickenscould not get to the manure to disturb it after a night ofroosting. They were free to roam at will during thedaytime.Slatted floors are useful for both hogs and cattle from thestandpoint of cleanliness if the animals are not required tostand on them at all times. In all these designconsiderations for an enclosed area, the needs of theanimal must be considered if we are to have happyanimals.
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46Home Power #27 • February / March 1992Do We Really Need Animals?So just how practical is the thought of having animalsaround a homestead? The trend is increasing for relyingless and less on animal parts for human food. Folks tendto become more and more vegetarian. We still need thefamily mule to plow the garden, a few milk goats for thedelicious and healthful treat of fresh goat's milk, or a fewsheep to produce wool for hand spinning and the cottageloom. There is wisdom in involving some kind of animalsupport in our homesteading.Farmers who raise nothing but corn are still hooked intothe food "grid" when they drive to the store for their butter,milk, and eggs. Our great grandparents would shake theirheads!AccessAuthor: Al Rutan, the Methane Man, P O Box 289,Delano, MN 55328Alternative FuelsGravity Works for FreeThe more that gravity can be utilized for tasks the better.The animal walks around. It can walk up as well as down.If the housing for the animals can be above the digester,then this saves work.Water has long been used for transport. Since thedevelopment of the flush toilet, in the 1850's in Englandby Mr. Crapper (no kidding...that really was his name!),we have been using water to move feces.Using water has a problem. What I am going to say now isexceedingly important. Many an engineer and universityprofessor working with the methane concept cannot seemto grasp a simple fact. It is the nature of liquid – especiallywater – to release heat. When water is heated, it will notretain its heat. We say, "It cools down."Water Must Be WarmIf we are going to use water in the process of transportingmanure, and have it work well, we must understand thatwater cannot be allowed to stand around waiting for thewaste. Warm water can and certainly should be used towash down a gathering point below a slatted floor. Thegathering point had better not be a holding pit in theground because the whole thing will cool off to groundtemperature. Another consideration is that in a pit themethane activity begins right away, so animals above a pitare breathing contaminated air. This is why holding pitsMUST have ventilation fans if they are under confinementareas.Think in Terms of Free EnergyHow does one have warm water with which to transport?Each location will have its own plusses and minuses inworking out this design problem. A person has to considerall the ways of capturing "free" thermal energy – solar,wind, whatever, and applying it to the situation at hand.We're most likely looking at periodic washing down of agathering area with warm pressurized water. This will bothincrease the force of the wash and cut down on theamount of warm water needed. The more automatic theconcept can be and the less labor intensive, the more of aideal situation a person can enjoy.
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39Home Power #28 • April / May 1992old and mildew have been seenby everyone. Most people haveobserved the process of rotting.We know it is common in nature.Methane gas is just as common, but notas observable. Anyone near a sewermanhole or a plumbing vent pipe can geta whiff of the methane process in action.The reason for saying this is to alleviatethe apprehension that the methaneprocess is going to be difficult to harness.It's no more difficult than making a loaf ofbread. If the conditions needed arepresent, the desired result will invariablyoccur.MThe MethaneProcessThird in a series by Al Rutan,the Methane ManAl Rutan© Al Rutan 1992What we are considering is a biological process in whichwe use the waste product of bacteria. We shouldn't evencall the little creatures bacteria but more accurately"methogenic micro-organisms."Primeval LifeIn the process of evolution, they antedate the formation ofbacteria. They are one of the very earliest forms of life.When scientists explore outer space with telescopes thatAlternative Fuelscan separate light spectrums, they look for the presenceof methane gas. If the gas is present, there is evidencefor the beginning of life.For our purpose, we are going to refer to thesemethogenic micro-organisms simply as "bacteria." Theyare curious little critters. Their waste product burns. Notonly does it burn, it burns very well. Combustionproduces only carbon dioxide and water vapor. There isno ash, no soot, no tar, no dirt of any kind. It's a veryefficient fuel.CharacteristicsThis fuel is composed of carbon and hydrogen. Itschemical formula is CH4. It has an octane rating of 110and produces around 1,000 BTUs (British Thermal Units)of heat per cubic foot of gas. Because most gas isinvisible, it seems mysterious. If we think about our ownchemistry for a minute, it won't seem so strange. Weknow that we breathe in oxygen and exhale carbondioxide. So we, ourselves, are gas producing organisms.Gas MakersIf we think about this, then the process of the methanebacteria doesn't seem so strange. The part that is"strange" is that it burns. If mixed with sufficient amountsof air, it burns very rapidly... explosion!In nature, some bacteria operate best in the presence ofair because they require oxygen, and some function onlywhen air is excluded. The methane bacteria are of thislatter type. When exposed to air, they die. Because theylive and function only when air is not present, they arecalled anaerobic or "without air" bacteria.Natural Gas and Sewage GasWhat is the difference between natural gas and sewagegas? Virtually none. For all practical purposes thebacteria which make the gas are the same. Natural gassold by the utilities is 90%, or better, methane. It hasbeen made in the ground over eons of time and in mostinstances is almost pure methane because the groundhas purified or "scrubbed" the gas. The only differencebetween gas produced in the earth and gas made in
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40Home Power #28 • April / May 199212345678910 11 12 13 140AcidicAlkalineThe pH Scalea healthydigesterNeutralAlternative Fuelssewage plants is that in the sewage plants the process isspeeded up. In speeding up the action there are severalgases produced, notably, carbon dioxide. In a sewageplant the mixture is about 70% methane and 30% carbondioxide, with trace amounts of hydrogen sulfide. Thecarbon dioxide largely dissipates from "natural gas" overtime. The speeded-up process product, including thecarbon dioxide, is referred to as "biogas."Actually all natural gas is "biogas" because all of it wasproduced from something that was at one time living. Theonly distinction is that so-called "biogas" is produced in ashorter time from things that have been living recently.Making methane for ourselves, we hasten the process.How Does it All Happen?There are two types of "without air" or anaerobic bacteriathat work together to make methane. The first type we'llcall "acid forming." Their function is to feed upon raworganic material. They produce no methane, only carbondioxide and some acids and "food" for the second bacteriatype, the methogenic micro-organisms. The "food"consists of simple sugars, simple alcohols and peptides.When the methogenic micro-organisms in turn feed uponthis simpler fare they produce methane. Thus whenorganic material is placed in a container where air isexcluded, both carbon dioxide and methane areproduced.Need for BalanceThe methanogenic micro-organisms need the foodprovided by the acid-forming bacteria, but they also needa neutral environment. If the right balance between acidand base (alkaline) is not present, the methanemicro-organisms are in trouble and no methane isproduced. They have to have a pH of 7 to 8.5 in order tobe normally active.What Does pH Mean?I think it's important not to assume that everyone isfamiliar with pH. Websters defines pH as "the negativelogarithm of the effective hydrogen ion concentration...used in expressing both acidity and alkalinity on a scale of0 to 14 with 7 representing neutrality. Numbers less than7 represent increasing acidity and numbers greater than 7represent increasing alkalinity." So the term pH means percentage of hydrogen, or moreprecisely, proportion of hydrogen in relation to thehydroxide ion in a given material. It's the negativelogarithm of the hydrogen ion concentration, so a pH of 7means that the concentration of hydrogen ions is 10- 7.Aren't you glad you asked?Anyway, it's important information for keeping the digesterhealthy and happy. The ideal pH for digestion is from 7.5to 8.5.How to Get a ReadingHow does one measure pH? This is the easy part.Chemical supply houses and even most drug stores sellrolls of paper (called litmus paper) and/or little plasticstrips that turn color when dipped in solution to tell youwhat the pH is. There is a slightly different color for eachof the different pH numbers. You tear off a piece of thelitmus paper about 1 1/2 inches long and dip it into a littleof the slurry. The paper will start to change color withinseconds. When compared to the color scale on thecontainer, you can tell right away what the pH of the slurryis.Why the Process May DragGenerally if there's a problem, it's that the slurry is tooacidic (pH below 7).If there is a lot of new, raw, green material placed in thedigester, the acid forming bacteria have a field day. Themethane bacteria are so annoyed by the high acidconcentration, they simply can't function. When thisoccurs, it can take a long, long time for the methaneprocess to get under way naturally.This generally occurs only in the beginning with start upor if too much new material is added at any one time. If ameasured amount of new material – no more than 1/40thof the total liquid volume of the tank – is added, then thenew material is dilute enough not to upset the balance. Atstart up, though, there's a lack of micro-organisms, andan inclination towards excessive acidity. Understandingthis, we can see why some of the early literature onmaking methane states that the start-up time can beanywhere from three weeks to three months. This isassuming that one is beginning with totally "new" materialwithout the assist of some already partially digestedslurry. A three month start-up would discourage almostanyone from attempting to harness the process.
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41Home Power #28 • April / May 1992Alternative FuelsStarting UpPartially digested slurry is kind of like sourdough starter. Ithas large populations of the right kind of micro-organismsto digest raw material and make methane. You can startfrom scratch, but it's faster if you can get some activitythat's already established. When I started a small digester in 1976, I seeded it withsome slurry from the St. Cloud, Minnesota, sewage plant.The plant engineer told me at the time that the plant wasso overloaded with wastes from a local meat packinghouse that the digester was just "going through themotions" and really not working properly. I took some ofthe slurry anyway. What the heck. It was free and Ineeded something to get the tank producing.After a few days I started to get methane and then I lost it.The tank was still producing a lot of gas, but it was carbondioxide – it didn't burn. The pig manure I had begun tofeed the digester along with the slurry from the St. Cloudplant was just too much raw material for the process. Sothere was a lot of carbon dioxide and acid. The acidforming bacteria were having a feast.I mentioned the problem to friend with whom I wasworking at the time. He said, "I make a lot of wine athome. Every once in a while I have the same problem.When I do I add a little baking soda. It straightens out thecondition right away. The nice thing is it doesn't leave anafter taste. In your case that isn't a problem!"The Benefits of Baking SodaSo I tried the baking soda. It worked like a charm. Withinthree days I had methane on the way. At a seminar I waspresenting a few weeks later, I mentioned this to thegroup. Baking soda was my "discovery" for straighteningout the pH in the digester.One of the people at the seminar sent me a clipping fromBusiness Week magazine a couple weeks later. It wasdated June 14, 1976. The headline for the article read"Dosing Sewage With Baking Soda." It went on to say thiswas a whole new idea for treating sewage plants; theyused to use large amounts of ammonia.The article further proclaimed that soda not only assistedin the more efficient digestion of sludge but increased thevolume of burnable methane gas. The most surprisingstatement of all: bicarbonate of soda "acts as a sort ofvitamin for bacteria."This is the secret for keeping your digester sweet andhappy. Just add a little at a time until the pH is just right.Keep adding it periodically if the pH keeps dropping untilthe acid forming bacteria are no longer producing anoverride of acid. Don't be fooled if a lot of gas startscoming. The baking soda itself will produce some carbondioxide.The Nature Of HeatHeat is essential for abundant methane production. Inwarm climates the process works with little help when theother conditions needed occur. For many of us who live ina cold climate, making methane work is a challenge. One needs to keep in mind that heat stratifies, whether inair or water. Heated fluids are less dense and tend to rise.This natural thermal stratification in liquid is, of course,the very reason why the thermal syphon principle in waterheaters works so well.It was this very fact which suggested a digester designwith a false floor containing only water. The bottom, thelowest point of the "working" tank, could be heated by athermosyphon action from some heat source such assolar, or even a little of the gas itself.CUTAWAY SIDE VIEW30 INCH SERVICE DOME8 INCH FILL PIPEGATEVALVESOLARHEATER INPUTVIEW WINDOW 12 BY 18 INCHESFLOOR BETWEEN SLURRYAND SOLAR HEATED WATER41.5 FEET LONGSUPPORT PIERSSOLAR HEATER OUTLETTANK DRAIN4 INCH DRAINWITH 12 INCH DIPGATEVALVEBAFFLE PLATESPILL-OVERDAM WALLGAS LINEAl Rutan's Methane Digester Design
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42Home Power #28 • April / May 1992The heat from the lowest part of this "double boiler" typedesign would rise through the slurry so that the verybottom of the "working" tank could more easily be kept atthe desired temperature in the entire digesting area. Sucha tank would most easily be constructed of fiberglass. Itcould be virtually any size.Next time we'll think about the barriers to the transfer ofheat – insulation – a critical key to any successfuloperation. This brings us to the question of whether theoperation is a net energy producer or an energyconsumer.AccessAuthor: Al Rutan, POB 289, Delano, MN 55328Alternative Fuels
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42Home Power #30 • August / September 1992Alternative Fuelsemperature is critical to thesuccess of any methane operationif it is to be considered an energysystem. If the primary concern is wastemanagement and not energy production,then a net energy loss is not a majorconsideration. If the intent is to produceenergy, a net energy gain from theprocess is everything.TEven More OnMethaneAl Rutan, the Methane Man©1992 Al RutanBody HeatMethane activity, in one of its natural situations, is foundin the digestive tract of warm blooded animals, peopleincluded. For people, the normal body temperature is98.6° F. In a chicken or pig it is 103° F. So right at 100° Fis the ideal working temperature for the methane process.To maintain this temperature outside an animal is aproblem if the ambient temperature is cool or cold.Sewage Plants ? Energy ProducersThere were several methane farm operations launched inthe upper midwest with much bravado and publicity. All ofthem are now out of business. On the other hand, sewageplants of medium size still commonly use the process totreat toilet waste and destroy pathogens, but in eachinstance they consume much more energy during the coldpart of the year than they produce. The toilet water flowinginto each sewage plant is ordinarily cold. It would beexceedingly difficult for sewage plants to be anything butenergy users rather than producers at any time except inthe hottest part of the summer.Universities’ verdicts at the end of the methane studieswere always the same: “It's possible, but it isn't practical.It takes more energy to run the system than the systemcan provide.” In harnessing methane as an energysystem, it is important to conserve heat in the process ofproducing gas. A few years ago a new sewage plant wasbuilt at St. Cloud, Minnesota to the tune of 17 milliondollars. I asked the engineer, “Did you insulate the tank?”He said, “Oh yes. The old one used to actually freeze onthe north side during the winter.” My next question was,“Did you run the insulation into the ground?” His reply,“No. The ground never gets cold.” My reply was, “That’sright, but it never gets warm either.” This sewage plantburned $750,000 a year in fuel oil to keep the digester at100° F. It costs big bucks to flush the toilet in St. Cloud.Capturing WarmthHeat has to be considered as something that is veryslippery. Conserving heat requires understandinginsulation. We are fortunate that there are many types ofinsulation available now that simply did not exist a fewdecades back. On the other hand, there’s a general lackof understanding of insulating properties of commonbuilding materials such as wood, metal, and concrete. Irecommend Movable Insulation, published by the RodalePress in 1980.Anyone familiar with insulation knows that if it gets wet, itis no longer insulation. Some "closed cell" insulatingmaterials such as urethane, styrofoam, and polyethylenefoam are more impervious to moisture than cellulose orfiberglass insulation. Even closed cell materials can breakdown if moisture under pressure is present.Styrofoam is used on the outside of the foundations toprovide a frost barrier for basements. Soil pressure andmoisture can cause the styrofoam to be less than "bonedry" and thereby lose much of its insulating ability.Situating the TankMy personal preference is that the methane tank be aseffectively insulated as possible. Insulation should bebelow the flow line of the material entering the tank, butshould not be buried in the dirt, regardless of theinsulation. The temperature of the ground several feetbelow the surface stays quite constant at 50° F – 55° F.To the methane tank, the earth is a “heat sink”, a coolmass always ready to absorb its heat. The best way tofight this heat sink is to insulate the tank and build itabove the ground. Another good reason for a free-standing tank is access to the grit trap at the bottom. Afree-standing tank should be covered with six to eightinches of high quality insulation.Various people have asked if a buried tank would work. Ican't say that it won't, but I've never seen any that work ina cold climate, and I have seen several that don't.Restoring WarmthWhen feces leaves the body, the waste is at exactly theright temperature for working within the methane digester.Whatever heat is lost in the interval between leaving the
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43Home Power #30 • August / September 1992Alternative Fuelsanimal and entering the digester has to be restored. If theheat needed is significant, there needs to be a heatsource available with an abundance of "free" energy, suchas solar or wind.Relation to FermentationThe methane process is a type of fermentation. Most folkshave baked bread or made homebrew beer or wine at onetime or another. For instance, after a yeast dough iskneaded, it is put in a warm place free of draft andallowed to rise. A draft could produce cooling. The yeastorganisms feed upon the mixture’s sugar. This producescarbon dioxide bubbles, which cause the dough to rise.There is a similar activity within the methane tank. Themethane organisms feed upon simple sugars, alcohols,and peptides produced by acid forming bacteria. Methanegas, CH4, is the result.I've been asked if the digestion process within the tankdoesn't produce some heat, such as the heat produced ina compost pile. It probably does. Because the metabolicactivity is so diluted and spread out within the tank, theheat available is minimal in comparison to the targettemperature.Awareness is EssentialYou’ll need to know how hot the tank is, day to day,season to season. To eliminate the guesswork, installsensors both inside the tank and outside the tank. Recordtemperature both inside and outside the tank over aperiod of time. Then you will know how efficiently the tankis retaining heat, at what rate the temperature drops whenno heat is added, and how much energy is needed toraise the temperature. If this is done, then a reliablecalculation can be made of how much gas is needed tomaintain working temperature if "free" heat is notavailable.Producing methane gas is relatively easy. Theconservation of heat more than any other factordetermines whether a methane system will "fly" or not. Ofall the systems I've seen that failed, the principal reason isimproper handling of heat.Care and Feeding of your Methane DigesterHaving thought about temperature, we can turn ourattention to feedstock. I work with a mixture of manureand vegetation. Sometimes the question is asked: can'tone use just vegetation to produce methane? It can bedone because Mother Nature does. Swamp gas burningover a marsh is just that. Because the methane bacteriaare part of the "flora and fauna" of the digestive tract,every time there is a fresh deposit, there is fresh input ofthe microbiological organisms needed.How Much Gas Can I Get?There’s a wide range of mixes of material you feed amethane digester. It's similar to what happens when weeat. Some of the material enters our system to maintain itand some of it passes on as waste. When manure isconsidered, all of it, minus the water, is designated as"total solids", and the part that is digestible to the bacteriais labeled "volatile solids". The numbers of what is andwhat isn't available for gas production have beengathered repeatedly over the years. Each account isquick to qualify any statement by saying that there is anynumber of variables when dealing with animals regardingwhat they are eating and how they are housed. One ofthe clearest reference sources is a newsletter printed in1973 by the New Alchemy Institute in California. Theirfigures correspond to what I've experienced.The numbers run like this: a cow drops an average of 52lbs. of feces a day, of which about 10 pounds are solids,the rest being water. Of the 10 pounds of solids, 80% or 8lbs. are volatile—can be turned into gas. A horseproduces an average of 36 pounds of feces a day, ofwhich 5.5 lbs. are volatile solids. A pig produces 7.5 lbs.per day of which 0.4 pounds are volatile solids. A humanproduces 0.5 pounds of feces a day of which 0.13 poundsis volatile solid. Chickens produce 0.3 pounds a daywhich 0.06 pounds is a volatile solid.All of this is good information, but it still doesn't tell us howmuch gas we can reasonably expect. If you ask an"expert" in the field, you'll get an answer something like,"It all depends..." All manure contains a degree ofnitrogen, but because nitrogen exists in so many chemicalforms in nature—ammonia (NH3), nitrates (NO3),proteins, etc.—it's difficult to test the total amount ofnitrogen in a given material.Why Consider Nitrogen?The process wants one part nitrogen to every 30 parts ofcarbon. Manure is nitrogen rich, averaging about 15 partscarbon for each part nitrogen, so all the studies show thatgas production is substantially increased by includingsome carbon material along with the manure. The
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44Home Power #30 • August / September 1992Alternative Fuelsnitrogen proportion may be even higher in animal waste ifurine is included with the feces because urination is theprinciple way an animal rids itself of excess nitrogen.To illustrate, straight chicken manure will produce onlyfive cubic feet of gas for each pound of manure, butchicken manure mixed with paper pulp will produce eightcubic feet of gas for each pound of manure used. Myexperience was an outstanding ten cubic feet of gas foreach pound of chicken manure when the manurecontained some ground feed that had been spilled. Cowmanure will produce only 1.5 cubic feet of gas per pound,but cow manure mixed with grass clippings will produce4.5 cubic feet of gas per pound of manure.The Nature of BiogasAssume that we have a gas producing system and it'smaking gas nicely and filling the gas holder. What do weactually have? It's important to understand that it isn't allmethane. A proportion of it is carbon dioxide, produced bythe acid forming bacteria, which doesn't burn. This factisn't immediately evident because if one ignites the end ofa hose coming from the gas holder, there is a blue flame.The fact that is important to know is: if we had puremethane we would have a hotter flame—about 1000 BTU(British Thermal Unit) for each cubic foot of gas. With thedilution of carbon dioxide, we have roughly 600 BTU foreach cubic foot of gas.The composition of the gas in our gas holder will be:CH4methane: 54 – 70%CO2carbon dioxide: 27 – 45%N2nitrogen: 0.5 – 3%H2hydrogen: 1 – 10%CO carbon monoxide: 0.1%O2oxygen: 0.1%H2S hydrogen sulfide: traceWouldn't it be nice if we could separate out the methaneand dump the carbon dioxide. Interestingly enough,Mother Nature has made it very easy to do just thatbecause these gases all have different specific gravityweights.How to Get Pure MethaneThe specific gravity of methane is about 0.55 inrelation to the weight of air, so it rises, as doeshydrogen. Carbon dioxide on the other hand is twicethe weight of air. Within a vertical gas container, if thegases are allowed to settle, they will naturally separatethemselves, the flammable gases rise to the top. Thisfact suggests that a good design should have apetcock at the bottom of a vertical gas holder. Use it tobleed off the accumulated carbon dioxide. In the rightsetting, this isn't environmentally harmful, because thetrees and growing things around the yard will welcome afresh sniff of carbon dioxide.Next time we'll consider some of the safety aspectsneeded in working with homemade gas.AccessAuthor: Al Rutan, the Methane Man, POB 289, Delano,MN 55328 • 612-860-3998
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82Home Power #40 • April / May 1994MethaneMore onMethaneAl Rutan the Methane Man©1994 Al RutanAlmost two years have passedsince the last mention ofmethane in these pages. HomePower issues 26, 27, 28, and 30described the basics of methaneproduction from animal feces. Idiscussed a low pressure storage tank,tank insulation, pH balance, animaltreatment, and heat retention. I’d like toshare some new information I havelearned since then. Some thingsworked and other things didn’t, but allfacts whether positive or negative arepart of the mastering process.Currently, my methane demonstration is beingupgraded. I am discarding the plastic tank that servedas a digestion vessel for the last year in favor of ametal tank. Why the change? For several reasons.First, the problems.Bonding DifficultiesThe primary difficulty is maintaining a vapor tight sealbetween the fill and overflow pipes and the tank. Theplastic tank didn’t cost much when new, so it was tootempting to pass up. But experience has shown that itwas not a good choice. The tank material ispolyethylene and the pipes are PVC plastic. While it’spossible to weld polyethylene with heat and produce abond, it isn’t something that an amateur can do easily. Iattempted to produce a vapor tight seal with varioustypes of glues and epoxies, which was achieved withsome success.But the tank was often moved from one location toanother by the trailer on which it is mounted. Thesloshing within the tank caused the pipes to break thebond with the tank.A second reason for replacing the plastic tank is that itis too short; the tank is three feet in diameter and onlyfive feet long. The best proportion for a tank is three tofive times as long as the diameter. This rule of thumbbecame obvious when new material was introducedinto the tank at the fill pipe. What exited through theoverflow was working nicely, still bubbling like crazy.Slurry Still WorkingThe supposed “waste” or “spent” bucket wasn’t spentat all, but continued to be active after it had beenforced out of the tank. A short tank is truly an inefficientdesign. The fill and overflow pipes are just too closetogether. Also, the fill and overflow pipes should not bein line with each other. One should be at either the rightor left side of center and the pipe at the opposite end ofthe tank should be on the other side of center. Itdoesn’t make any difference to which side of center thepipes are placed. But it’s important that the pipes at theends of the tank not be in line with each other.Such a placement of the pipes provides anotherimportant advantage — the best position for the stirringmechanism. On the plastic tank, the stirringmechanism was vertical with a crank at the top. After ashort time, I learned that this was a poor design for astirring device. The seal at the top is difficult to keepvapor tight. If the bearings for the stirring mechanismare below the water line, then any leakage is no morethan a little moisture, but not vapor.When the Tank Gets “Cranky”Also an oversight in the vertical stirring device designwas the omission of a bearing point at the bottom endof the shaft. It was left to “float”. With the resistance ofthe material within the tank, the pressure on the onebearing at the crank end of the shaft tended to distortthe cover of the tank as the crank was turned.Ideas that Worked — the Heat BathThat’s the bad news. So what’s the good news? Thewater bath for providing heat to the tank. I originallythought that this would be an effective way to transferheat from whatever source to the tank. In actualoperation, the concept worked even better thananticipated.Heat is supplied from a two foot square hot water boxplaced below the level of the water bath. Theplacement of the source of hot water under the waterbath allows the water to circulate via a thermosiphon:hot water rises in a closed circuit of water. Theconnecting pipes are two inches in diameter — one forsupplying warm water and another for the return of thecooler water. The pipes from the hot water box connectto an 18 inch deep metal water bath underneath thetank. The tank is placed on supports six inches abovethe floor of this water bath.
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83Home Power #40 • April / May 1994MethaneMore Art Than ScienceLet’s back up for a bit.People will sometimes ask,“Does it take a degree inengineering to understandthe methane process?” Myanswer is, “Not at all. Whatis most helpful is theexperience of baking bread,or making wine or beer.Each of these skills is bothan art and a science. Thereare some things that mustbe known. But basically, it’sexperience with the processof fermentation. And in thefinal analysis, the skill ismore an art than a science.”For bread to rise — which isthe critical test of whetheror not it will be a handsomeloaf — and for wine toferment, the temperatureconditions have to be, aswe say, just right. The same is true of the methaneprocess, which is another example of fermentation.Methane production occurs virtually automatically in oldlandfills, but we’re talking about maximum productionfrom a minimum amount of input. As for good bread,heat supplied during the rising process needs to be justwhat bread wants and free of drafts. For maximummethane production, the optimum temperature needsto be supplied evenly.Written in South Africa some years ago, L. John Fry’sbook Practical Building of Methane Power Plantsobserved that pipes supplying heat to the slurry had tobe hotter than the optimum temperature in order to getenough heat to the mass. This caused two unfavorableeffects. The methane organisms in the proximity of thepipe were cooked to the kill point. Such heating causeda crust to form on the heating pipe that eventuallycaused the heat within the pipe to be insulated from theslurry.Using pipes for the heat transfer is not the way to go.But body warmth for the process is essential, as is theright temperature for causing bread to rise or beer toferment. So the next question is, “How best to heat thetank?”The Key to Even HeatingIn my book, The Do’s & Don’t’s of Methane, theproposal to solve the problem was a false floor withinthe methane tank. This would separate the active slurryfrom the water beneath; the warm water provides heattransfer to the slurry above. The false floor thus acts asa double-boiler.The source of heat is below the slurry, providing heat atthe very lowest point. Because the heat transfer isspread over the entire lower surface, there are no hotspots that produce a kill temperature or crustingproblem.Thermosiphon Provides Effective CirculationSetting the tank in some sort of a water bath was agiven. But the surprise benefit in this design is howeasily and how well the principal of thermosiphonworked for the heat transfer. The water heater providesheat from either a small gas burner or solar panel. Thiswarm water moves up into the water bath, circulatingso effectively that one would assume there is acirculating pump somewhere in the system.But there is no pump, just a closed circuit of watermoving by a heat differential. In the 18 inch deep waterbath, the hot pipe enters the bath at the mid point — ornine inches above the floor. The return pipe at theopposite end of the bath is as low as possible. Withonly a nine inch difference between the input and thereturn pipes, the circulation is wonderful.The reason for the input entering the bath at themidpoint is to provide as much of a strata of warmwater above the input as possible. And it worksamazingly well. The water bath heats the tank evenlyAbove: The new metal tank methane digester on its trailer.Photo by Al Rutan
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84Home Power #40 • April / May 1994Methaneand effectively from the bottom up so that the workingtemperature within the slurry is even and constant. Thisapproach to handling the heating problem has beendesignated the Rutan Design.What’s in the WordsAs I write this, a new methane display is beingconstructed. It consists of a new trailer — a 16 foot carhauler — fitted with metal tank three feet in diameterand ten feet long. The tank has three windows so thatone can watch the methane activity within the tank. Itwill be heated with a solar collector, using some storedgas for backup. With the right kind of feeding andmanagement, this size is large enough to provide thecooking and heating needs for an energy efficienthomestead.AccessAl Rutan, POB 50, Liberty Center, IA 50145
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24Home Power #26 • December 1991 / January 1992Alternative Fuelshy gas? What's so good aboutgas? One could make anargument ad hominem andsimply say, if gas weren't such a goodidea, why is it so abundant in nature. ItWPrologue toMethane GasAl Rutan, the Methane Man©1991 Al RutanGas UseWhat about flammable gas? Why consider it? For thoseof us who spent much of our youth chopping wood to heatand cook at home, the idea of gas is like something fromparadise. The idea and the experience of merely turning avalve to have instant flame without all the "bitching" andcomplaining involved in "go get that wood!" is amazing.Almost everyone likes the ambiance around a campfireon an outing with friends. But for the day to day fuelneeds, we wish to have it as "automatic" as possible, andfor being controlled by a thermostat, gas is unsurpassed.It is clean and uncomplicated. Clean? Yes, clean. Thereis no soot that collects in a chimney from the burning ofmethane gas. Does it need to be vented? It should be, ifat all possible. The fumes from any type of combustionshould be considered suspect.Potential problems from the burning of methane areminimal. If the combustion is complete, what is producedis carbon dioxide and water vapor. Yet we have nopractical assurance that combustion is always as perfectas it could be.An interesting note historically is the fact that the Indiangovernment some 40 years ago pushed the developmentof homestead production of methane because so manypeople were going blind from the effects of burning cowdung for fuel. Our early pioneers had similar experiencesfrom the burning of buffalo chips. Burning raw manureshould always be considered a "no-no."Low-tech methane production information comes fromboth India and China–two countries with vast populations,huge pollution problems from waste, and an immenseneed for fuel, which isn't readily available.At HomeOur interest stems from the fact that homestead methaneproduction is one more way to unplug from a utilitycompany and provide access to energy, whichsubstantially contributes to the quality of life.So, one has to have the heart for it. Unlike electricity, thatis for all practical purposes quite mechanical, gasproduction means tending to living things, like a flock ofchickens, a band of sheep, or milking goats. For abundantgas production, there needs to be a sensitivity to thespecial needs of the microscopic creatures that produceflammable gas as their waste product. This meansproviding for their basic wants and–don't laugh–givingthem a measure of love. All living things–plants, animals,and people–require love in order to flourish. This needextends even to living creatures that can't be seen withthe naked eye.A person we know who had a methane system one daywent up to his tank and gave it a good hefty kick as anexperiment. The gas production stopped immediately,and started slowly again only after some time hadpassed.Because one must assume responsibility for the care of acolony of living entities, producing gas to burn hasanother dimension some may need to consider beforeundertaking such a venture.The advantages of gas are many-fold. It is so easy to use.It is so controllable. It is relatively easy to store. It can beused automatically. It will even run your vacuum cleaner ifyou put the methane gas through a fuel cell which will turnthe gas directly into electricity. Plus, it is so clean–nosoot, no creosote, no ash, and no chopping. What morecould you ask?Making and Using Methane GasMethane is a natural gas. The reason it's called "natural"is because it occurs in nature everywhere. It can be thegas found in a swamp or marsh, the gas found in a coalmine, the smell coming from a septic tank or sewer line,or the gas sold to us by a utility company under the title of"natural gas." The product is substantially the same, CH4.We've heard that methane is odorless, and it is. Sewergas we know is not. So what is the difference? When theprocess that produces gas is underway, there are avariety of gases produced at the same time. All suchgases result from micro-organisms feeding upon organicmatter and producing gas as a waste product. Methane,
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25Home Power #26 • December 1991 / January 1992Alternative Fuelswhich is odorless, is one of them. Hydrogen sulfide, whichis smelly, is another. It is hydrogen sulfide which gives usthe characteristic sewer gas or "fart" smell.When these gases are encapsulated in the ground over along period of time, the smell is purged, leaving anodorless gas. The sewer gas smell can be removed easilyfrom the mixture by simply bubbling all the gas throughcalcium carbonate, which is simple barn lime, and therebyscrubbing it so to speak. The gas becomes odorless. Thegas companies re-introduce an odor to odorless gasbefore selling it as a safety measure so that our nosescan detect "loose gas" that could be potentiallydangerous.All these burnable gases are produced by anaerobicorganisms feeding upon organic matter. To say they areanaerobic means they only live when air is excluded fromthe space in which they are functioning.They are the same organisms that cause us to haveintestinal gas. Each time a warm blooded animaldefecates, some of the gas producing organisms arecontained in the feces. This is why it can be said thatmethane occurs virtually everywhere. Wherever air isexcluded from the decomposition process, the productionof methane and accompanying gases is likely to occur.Stories are legion about a bunch of guys with nothingbetter to do than ignite the intestinal gas of one of theirparticularly "gassy" buddies, and then being amazed athow flammable the experiment was.The micro-organisms that produce flammable gas aretemperature sensitive. They want body temperature inorder to function most effectively. In people that is 98.6°F.In a chicken or a pig the body temperature is 103°F. Soright around 100°F is the optimum temperature for theprocess to work most effectively. The action can occur atlower temperatures. As the temperature drops so doesthe rate at which methane gas is produced.People will sometimes ask, "Why can't I use the gas offmy septic tank to burn in a stove?" The typical septic tankswings through such wide temperature fluctuations, theamount of gas produced is minimal. Each time a toilet isflushed with cold water, the tank goes into "shock." Eachtime some warm wash water from a bath or shower flowsinto the tank, it becomes more active until the next shot ofcold water. Such tanks are ordinarily in the ground, whichstays at a constant 50° to 55°F. The ground is a constantheat sink, draining heat away from the tank. About all onegets from a septic tank, by way of gas, is enough to causean unpleasant odor. Because the temperature cannot bemaintained at the required working level, such tanks haveto be pumped from time to time. The solids cannot beefficiently digested and so keep building up.Key ConsiderationsIt is the concept of a tank which offers us the mostpractical approach to the task of harnessing theproduction of methane. Liquid within a tank gives us twoimmensely important features–transport and the exclusionof air. Both are essential for maximum production.Slurry LevelInputSlurryLevelInputPipeOutputSlurryLevelExitPipeExit BasinGas Line OutMETHANE TANK CONCEPT SKETCH
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26Home Power #26 • December 1991 / January 1992Alternative FuelsSome methane production occurs in such places as anordinary barnyard manure pile. The center of the pile iswithout air and with the heat generated by the pile somemethane gas is bound to be produced. If we want toharness the concept, we will need a great deal of gas. Asolid pile to give us what we would need would have tobe, literally, a small mountain. In a tank, it's an entirelydifferent matter. It is much easier to have the tank "justbubbling away" so that the amount of gas collected in ashort time can be significant.Key QuestionsHow much gas do I need? That will determine how muchgas must be produced. Next is, how much material do Ineed to produce this amount of gas? The third question is,how large must the equipment be to produce and storethis amount of gas?Gas is thought of in terms of cubic feet. We can allvisualize a cubic foot–12 inches square in each direction.The amount of gas within such a space of 12 inchessquare is determined by the compression of the gas.Fortunately, when we are working with methane, we aretalking about only ounces of pressure–just enoughpressure to push the gas to the burner, whether it mightbe a stove, water heater, or refrigerator.For "home-made methane," our pressure regulator is notany more complicated than a heavy rock on an inflatablegas holding bag, or the weight of a solid yet expandablegas holder floating in liquid. It's not very complicated.How Much Gas Does One Need?To estimate the amount of gas needed, the averagefamily of four burns somewhere around 200 cubic feet ofgas a day. This covers the combined tasks of cooking,heating space and heating water. Obviously, individualscan trim this amount considerably by using efficientappliances–such as flow-on-demand water heaters, andhigh-efficiency space heaters.The best way to get a handle on this information is to lookat the amount of consumption listed on the utility bill ofsome family you know and then observe their lifestyle.Processes of GasWe say that the liquid provides transport. That transport istwo-fold. Obviously, we must transport the material to thetank. Equally important, yet not so obvious, is thetransport of the micro organisms to the material orvice-versa, so that the material can be digested by the lifeforms. Within the digestive tract of a warm bloodedanimal, this action takes place by peristalsis. We imitatethis transport by very gently moving the contents withinthe tank from time to time.Concerning The TankA simple paddle mechanism works the best. Somesystems re-circulate some of the gas to providemovement, but this has proven to be less thansatisfactory. Often inorganic material is stirred from thebottom of the tank–material such as sand and small rocksif they are present–and the living organisms are injured inthe process. The best method is a slow mixing action witha paddle of some sort. The paddle may be on a horizontalaxis or a vertical axis. It merely has to move the materialvery gently a few times each day.The exclusion of air is essential to have the process work.While we know that even water contains someair–otherwise how could fish breathe–once the activity ofgas producing bacteria becomes established, even the airis mostly excluded.The tank must be closed so that new air is not able toenter. This is done effectively by having both the fill pipeand the exit pipe extend below the water line. So, airexposure to the tank is limited to the surface of the waterlevel in both the fill and exit pipes.In the past much discussion focused on whether the tankshould be horizontal or vertical. It is the consensus thatwhen the tank is horizontal rather than vertical, it canwork more effectively. (Note the illustration on pg. 25.)The reason is that the fill and exit pipes need to bespaced as far apart as possible. Then the materialentering the tank has greater exposure to the activitywithin the tank before being moved near the exit pipe.The gentle stirring action needed, of course, mixes upeverything. Yet if the new material is forced to "migrate"some distance before reaching the exit pipe, then themicro-organisms will have more time to feed upon itbefore it is replaced by incoming material.How big should the tank be? This is determined by howmuch material is available to the tank on a daily basis,and ultimately how much gas one wants to generate.Production MixtureThe input for the tank needs to be a mixture of manureand carbon material. Carbon material is ordinarilyunderstood as waste vegetation, but it can't be justanything. It needs to be something that when soaked inwater for a few days becomes very soft. The bacteriadon't have any teeth. They have to "gum" it.Hardness can be misleading. A carrot seems hard, but ifsoaked long enough it turns to mush. Grass clippings, onthe other hand, contain a quantity of lignin, that cellulosefiber that makes wood very "woody." Anything with a high
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27Home Power #26 • December 1991 / January 1992GasLineINWaterDrainPipeAlternative Fuelscontent of lignin will not work well in a methane tank.Straw for the most part is acceptable. Hay is not.Even such things as ordinary newspaper work well.Although newspaper at one point was wood, the lignin hasbeen broken down so that when the newspaper is soakedfor a day or so, it turns to mush–good stuff for ourpurposes. The bacteria want a mixture of 30 parts carbonto 1 part nitrogen. Manure is nitrogen rich–about 15 partscarbon to 1 part nitrogen, so manure needs to bebalanced with more straight carbon material. This ratioisn't a critical proportion and the process still functions,but 30 to 1 is the ideal.PotencyThe ability of manure to produce gas varies from animal toanimal. Chicken manure can be especially potent. I haveobserved as high a yield as 10 cubic feet of gas from eachpound of naturally moist chicken manure which wasmixed with some finely ground spilled feed.Hog manure usually yields about 4 cubic feet per wetpound. Cow manure usually yields about 1 cubic foot ofgas for each pound of fresh manure. The reason there issuch a difference is that much of the methane potentialhas already been released when the waste goes throughthe digestive system of a ruminant. There is usually somuch of this kind of manure, using it is still worthwhile.Another good feature of the process is that raw manure ischanged into something which is aged and totallyacceptable to be placed on growing things. With anyquantity of raw, green manure, this is not the case.Sizing the SystemHaving established that we need around 200 cubic feet ofgas a day, we need to set about designing a system thatGas Storage Tank
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28Home Power #26 • December 1991 / January 1992considerably over ordinary sheet metal. The acids withinthe mixture do not work rapidly on the tank, but they willdeteriorate it over an extended period of time.Originally, I had an ordinary 250 gallon fuel-oil tank that Iused for demonstration purposes. It lasted for severalyears. It finally rusted through, but considering the fact themetal was relatively light gauge to begin with, the tankserved well. Because oxygen is excluded in the processand the pH must be kept at neutral, the deterioration ofthe tank was not rapid.Another great feature of a milk bulk tank is the fact italready has a mixing paddle as part of the tank's design.All access ports above the water line would have to besealed air tight for effective gas production and, moreimportantly, just common sense safety.The Gas HolderRegarding a gas holder, one may use a solid vessel openat the top filled with liquid into which another solid vesselopen at the bottom is placed. The gas pushes the top unitup out of the liquid as the gas is produced (see illustrationon pg. 27).The simplest type of gas holder is an expandable bag. Itcan be something like a waterbed mattress upon which aweight is placed to produce enough pressure to send thegas to the point where it is used–a burner of some type.One may use simply a vinyl of some type, but the besttype of material is a nylon fabric that is impregnated withvinyl–not laminated, but impregnated–which becomesexceedingly durable. If this inflatable bag is placed insidea "silo" of some type, then there is a measure ofassurance that the bag is not going to be punctured. Thepeople who work with the nylon impregnated vinyl–one ofthe trade names is Herculite–seal it by a process ofelectro-statically welding it. Using an ordinary adhesivemay not work because methane has a tendency todissolve a number of adhesivesFor NowThe process of making methane gas is relatively simple ifone is attuned to the basic needs of the process. Theyare: the right balance of material, the right temperature,and the exclusion of air. Given these three conditions, themethane process is virtually unavoidable. The trick is tobe sensitive to the fine-tuning of each of theserequirements. As we continue with more methane articlesin Home Power, we will do just that.AccessAuthor: Al Rutan, POB 289, Delano, MN 55328Alternative Fuelswill provide this. How much is 200 cubic feet? Visualize aninflatable bag that is six feet wide, six feet long and sixfeet high, and you're seeing a space of 200 cubic feet.If we say that a mixture of manures will give us 4 to 5cubic feet of gas per pound of naturally wet manure weare going to need about 40 to 50 pounds of manure a day.We would need even less manure if we use chickenwaste. These forty pounds are going to be mixed withsome type of additional carbon material, to which water,preferably warm water, will be added to give us a "slurry."This will most likely be about 15 gallons of bulk. Visualizethe content in three five gallon buckets.Size of the TankIt is generally a rule of thumb that the size of the tankneeds to be 40 times the size of daily input. This meansthat when 1/40th of the volume of the tank is introduced atthe input end then 1/40th of the volume will exit theoverflow end simply by being displaced. Allowing somespace at the top of the liquid for the gas to collect, thetank should be about 50 times the size of daily input.Sewage plants that employ the methane process–andmany do–like to have a holding time of 90 days. In otherwords the preference is to have the tank 90 times the sizeof the daily input. The purpose of this is to totally destroyany potential pathogens. That length of time within thetank does exactly that. Periodic inspections by the varioushealth departments around the country keep a check onsuch activity and find consistently that the 90 day holdingtime accomplishes this goal.Within a 40 day holding period most of the pathogens areeliminated. Because we are not dealing primarily withhuman feces (although this material may be used withanimal waste) the longer holding time is not as imperative.Within a 40 day time span the greatest amount of gas isproduced. In a period longer than 40 days, the gasproduction begins to slow down considerably.We need a tank that is 50 times the volume of the dailyinput of 15 gallons, or a 750 gallon tank. Obviously, a1,000 gallon tank would be ideal to take care of extrademand for production or additional material input.Tank ChoiceA 1,000 gallon discarded milk bulk tank would be ideal.Because bulk tanks already have a system for cooling thetank, this system could be easily adapted for holding thetemperature of the tank at 100°F. rather than cooling it.One type has the "radiator" already built-in.The fact that the tank is stainless steel is also anadvantage because it would extend the life of the tank
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44Home Power #27 • February / March 1992Alternative FuelsThe article in HP26 says that we need about 50 pounds ofwaste daily, a mixture of manure and carbon material tofeed the digester that will turn this material into about 200cubic feet of gas.The focus of this article is just this problem. As anyonewho has done any kind of homesteading knows, there is aMore OnMethaneAl Rutan, the Methane Man©1992 Al Rutann the last issue of HP, the methanearticle praised the ease with which gasis used – merely turning a valve tohave instant vapor fuel. It takes so littleeffort. If gas is so easy, how does fiftypounds of stuff get pushed aroundwithout any effort? Aw...you caught theinconsistency!Ihard way and an easy way to doevery job. Part of the endearingquality of American ingenuity is tosee how people can approach atask that is downright tedious, andby some clever manipulation, makeit easier.Easy is BetterThis really became a lesson takento heart while living at Red Lodge,Montana. I was in the middle of aproject raising rabbits for market –lots of them, about 200 breedingdoes producing litters.Feeding and watering this numberwas a time-consuming chore. I madehoppers for the hay and feed pellets early on, butproviding abundant water was a drag. I upgraded fromwater dishes to water bottles with a valve. This was animprovement in cutting down the labor. The big jump wasto a system of watering valves fed by little plastic linesfrom a central tank with a float valve to control both thewater level and pressure on the water lines.In one situation, the water was put into 200 little waterbowls which were constantly being spilled or fouled withwaste. In the other, water was supplied by a smallpipeline with drinking valves in each cage. The result wasthe same – water to drink, but the effort needed wastotally different. The two situations accomplished thesame effect – abundant fresh water.Consider the CrittersThere is another consideration that must be brought tomind at this point. In the methane process, we areworking with living creatures. Therefore a moraldimension must be considered if we are going to achievea measure of serenity for ourselves in this whole process.To have a genuine sense of well-being about the entireoperation, the animals and the space for which the personis responsible must have an ongoing atmosphere ofserenity. If this sounds a little bit like St. Francis of Assisi,well, so be it and no apologies. The purpose of life is notmerely accomplishment, but accomplishment in a caringand respectful way.As people, we harness the work of creatures. Some maymaintain this is not right. I don't agree. I do feel stronglythat the animals with which we work and upon which wedepend do have the right to a reasonable quality of life.So at this point we are talking about animal rights. Theconcept of animal rights means different things to different
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45Home Power #27 • February / March 1992Alternative FuelsMoving the Material While It's WarmIt is the matter of manure itself. How can a person move itwith the least effort possible? Manure delivery systemshave been devised for various types of critters, except thehorse. To my knowledge, there is no device moreautomatic than a scoop shovel for cleaning out a horsestall.If one DOES have animals, the feces HAVE to gosomewhere. So at that point it makes a great deal ofsense to turn the waste into vapor fuel (methane) andcompost.When the waste comes out of an animal, it is at exactlythe right temperature – body temperature. As it lies on theground, it cools off. This cooling during the cold time ofthe year is severe. The sooner the waste is transportedfrom the animal to the tank the better. If the waste losesheat, then the heat must be restored to have the methanedigestive process occur in the best manner possible.This brings us to the biggest challenges in the entiremethane procedure. How do we gather the manure tobegin with? How do we gather it as soon as possible afterit leaves the animal and before it cools down?There are two natural forces that work well for us. One isgravity and the other is water. In rolling countrysides,barns are commonly built on hillsides. The hayloft iseasily accessible by simply driving in rather than having togo through the labor of hoisting every bit of hay with somekind of sling mechanism. The hay is forked down to theanimals below, using gravity.people. To me, it means that an animal has a right to areasonable quality of life. An animal has a quality lifewhen it feels good about itself. This is most clearlyevidenced by grooming. Animals, if they feel good aboutthemselves, groom themselves and their friends.Quality of LifeDeath for an animal, or a person for that matter, is not theworst thing that can happen. Quality of life whilesomething is alive, be it plant, animal or person, is ofmajor importance in the scheme of things. One whohomesteads can not be mentally well off if such a personis not sensitive to the quality of life of the living thingsaround the homestead. Are the animals feeling good, asevidenced by their grooming?A DilemmaNow, why make a point of this if we are talking aboutmethane and manure? We are faced with a dilemma. Onthe one hand we want to collect waste with the least effortpossible and do it as automatically as possible. On theother hand, we need to have a measure of sensitivity tothe needs and quality of life for the animals on which wedepend.If the animal wanders about freely, it will be very difficult tocollect its waste. On the other hand, if the animal is tightlycaged or tied, its quality of life is virtually nil. So what's theanswer?Somewhere there is a middle ground. Chickens, forinstance, do most of their pooping while they are perchedat night. Milk cows leave a quantity of used grass in thegutter while being milked or held in the barn during thenight.Hogs that are totally confined don't have much of a life.Hogs that are confined only through the night will leave agood share of their waste behind when penned only partof the time.Chickens do not do well housed on hardware clothbecause their natural inclination is to peck and scratch.I've seen a roost system where the area under the roostwas wired with large chicken wire mesh. The chickenscould not get to the manure to disturb it after a night ofroosting. They were free to roam at will during thedaytime.Slatted floors are useful for both hogs and cattle from thestandpoint of cleanliness if the animals are not required tostand on them at all times. In all these designconsiderations for an enclosed area, the needs of theanimal must be considered if we are to have happyanimals.
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46Home Power #27 • February / March 1992Do We Really Need Animals?So just how practical is the thought of having animalsaround a homestead? The trend is increasing for relyingless and less on animal parts for human food. Folks tendto become more and more vegetarian. We still need thefamily mule to plow the garden, a few milk goats for thedelicious and healthful treat of fresh goat's milk, or a fewsheep to produce wool for hand spinning and the cottageloom. There is wisdom in involving some kind of animalsupport in our homesteading.Farmers who raise nothing but corn are still hooked intothe food "grid" when they drive to the store for their butter,milk, and eggs. Our great grandparents would shake theirheads!AccessAuthor: Al Rutan, the Methane Man, P O Box 289,Delano, MN 55328Alternative FuelsGravity Works for FreeThe more that gravity can be utilized for tasks the better.The animal walks around. It can walk up as well as down.If the housing for the animals can be above the digester,then this saves work.Water has long been used for transport. Since thedevelopment of the flush toilet, in the 1850's in Englandby Mr. Crapper (no kidding...that really was his name!),we have been using water to move feces.Using water has a problem. What I am going to say now isexceedingly important. Many an engineer and universityprofessor working with the methane concept cannot seemto grasp a simple fact. It is the nature of liquid – especiallywater – to release heat. When water is heated, it will notretain its heat. We say, "It cools down."Water Must Be WarmIf we are going to use water in the process of transportingmanure, and have it work well, we must understand thatwater cannot be allowed to stand around waiting for thewaste. Warm water can and certainly should be used towash down a gathering point below a slatted floor. Thegathering point had better not be a holding pit in theground because the whole thing will cool off to groundtemperature. Another consideration is that in a pit themethane activity begins right away, so animals above a pitare breathing contaminated air. This is why holding pitsMUST have ventilation fans if they are under confinementareas.Think in Terms of Free EnergyHow does one have warm water with which to transport?Each location will have its own plusses and minuses inworking out this design problem. A person has to considerall the ways of capturing "free" thermal energy – solar,wind, whatever, and applying it to the situation at hand.We're most likely looking at periodic washing down of agathering area with warm pressurized water. This will bothincrease the force of the wash and cut down on theamount of warm water needed. The more automatic theconcept can be and the less labor intensive, the more of aideal situation a person can enjoy.
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39Home Power #28 • April / May 1992old and mildew have been seenby everyone. Most people haveobserved the process of rotting.We know it is common in nature.Methane gas is just as common, but notas observable. Anyone near a sewermanhole or a plumbing vent pipe can geta whiff of the methane process in action.The reason for saying this is to alleviatethe apprehension that the methaneprocess is going to be difficult to harness.It's no more difficult than making a loaf ofbread. If the conditions needed arepresent, the desired result will invariablyoccur.MThe MethaneProcessThird in a series by Al Rutan,the Methane ManAl Rutan© Al Rutan 1992What we are considering is a biological process in whichwe use the waste product of bacteria. We shouldn't evencall the little creatures bacteria but more accurately"methogenic micro-organisms."Primeval LifeIn the process of evolution, they antedate the formation ofbacteria. They are one of the very earliest forms of life.When scientists explore outer space with telescopes thatAlternative Fuelscan separate light spectrums, they look for the presenceof methane gas. If the gas is present, there is evidencefor the beginning of life.For our purpose, we are going to refer to thesemethogenic micro-organisms simply as "bacteria." Theyare curious little critters. Their waste product burns. Notonly does it burn, it burns very well. Combustionproduces only carbon dioxide and water vapor. There isno ash, no soot, no tar, no dirt of any kind. It's a veryefficient fuel.CharacteristicsThis fuel is composed of carbon and hydrogen. Itschemical formula is CH4. It has an octane rating of 110and produces around 1,000 BTUs (British Thermal Units)of heat per cubic foot of gas. Because most gas isinvisible, it seems mysterious. If we think about our ownchemistry for a minute, it won't seem so strange. Weknow that we breathe in oxygen and exhale carbondioxide. So we, ourselves, are gas producing organisms.Gas MakersIf we think about this, then the process of the methanebacteria doesn't seem so strange. The part that is"strange" is that it burns. If mixed with sufficient amountsof air, it burns very rapidly... explosion!In nature, some bacteria operate best in the presence ofair because they require oxygen, and some function onlywhen air is excluded. The methane bacteria are of thislatter type. When exposed to air, they die. Because theylive and function only when air is not present, they arecalled anaerobic or "without air" bacteria.Natural Gas and Sewage GasWhat is the difference between natural gas and sewagegas? Virtually none. For all practical purposes thebacteria which make the gas are the same. Natural gassold by the utilities is 90%, or better, methane. It hasbeen made in the ground over eons of time and in mostinstances is almost pure methane because the groundhas purified or "scrubbed" the gas. The only differencebetween gas produced in the earth and gas made in
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40Home Power #28 • April / May 199212345678910 11 12 13 140AcidicAlkalineThe pH Scalea healthydigesterNeutralAlternative Fuelssewage plants is that in the sewage plants the process isspeeded up. In speeding up the action there are severalgases produced, notably, carbon dioxide. In a sewageplant the mixture is about 70% methane and 30% carbondioxide, with trace amounts of hydrogen sulfide. Thecarbon dioxide largely dissipates from "natural gas" overtime. The speeded-up process product, including thecarbon dioxide, is referred to as "biogas."Actually all natural gas is "biogas" because all of it wasproduced from something that was at one time living. Theonly distinction is that so-called "biogas" is produced in ashorter time from things that have been living recently.Making methane for ourselves, we hasten the process.How Does it All Happen?There are two types of "without air" or anaerobic bacteriathat work together to make methane. The first type we'llcall "acid forming." Their function is to feed upon raworganic material. They produce no methane, only carbondioxide and some acids and "food" for the second bacteriatype, the methogenic micro-organisms. The "food"consists of simple sugars, simple alcohols and peptides.When the methogenic micro-organisms in turn feed uponthis simpler fare they produce methane. Thus whenorganic material is placed in a container where air isexcluded, both carbon dioxide and methane areproduced.Need for BalanceThe methanogenic micro-organisms need the foodprovided by the acid-forming bacteria, but they also needa neutral environment. If the right balance between acidand base (alkaline) is not present, the methanemicro-organisms are in trouble and no methane isproduced. They have to have a pH of 7 to 8.5 in order tobe normally active.What Does pH Mean?I think it's important not to assume that everyone isfamiliar with pH. Websters defines pH as "the negativelogarithm of the effective hydrogen ion concentration...used in expressing both acidity and alkalinity on a scale of0 to 14 with 7 representing neutrality. Numbers less than7 represent increasing acidity and numbers greater than 7represent increasing alkalinity." So the term pH means percentage of hydrogen, or moreprecisely, proportion of hydrogen in relation to thehydroxide ion in a given material. It's the negativelogarithm of the hydrogen ion concentration, so a pH of 7means that the concentration of hydrogen ions is 10- 7.Aren't you glad you asked?Anyway, it's important information for keeping the digesterhealthy and happy. The ideal pH for digestion is from 7.5to 8.5.How to Get a ReadingHow does one measure pH? This is the easy part.Chemical supply houses and even most drug stores sellrolls of paper (called litmus paper) and/or little plasticstrips that turn color when dipped in solution to tell youwhat the pH is. There is a slightly different color for eachof the different pH numbers. You tear off a piece of thelitmus paper about 1 1/2 inches long and dip it into a littleof the slurry. The paper will start to change color withinseconds. When compared to the color scale on thecontainer, you can tell right away what the pH of the slurryis.Why the Process May DragGenerally if there's a problem, it's that the slurry is tooacidic (pH below 7).If there is a lot of new, raw, green material placed in thedigester, the acid forming bacteria have a field day. Themethane bacteria are so annoyed by the high acidconcentration, they simply can't function. When thisoccurs, it can take a long, long time for the methaneprocess to get under way naturally.This generally occurs only in the beginning with start upor if too much new material is added at any one time. If ameasured amount of new material – no more than 1/40thof the total liquid volume of the tank – is added, then thenew material is dilute enough not to upset the balance. Atstart up, though, there's a lack of micro-organisms, andan inclination towards excessive acidity. Understandingthis, we can see why some of the early literature onmaking methane states that the start-up time can beanywhere from three weeks to three months. This isassuming that one is beginning with totally "new" materialwithout the assist of some already partially digestedslurry. A three month start-up would discourage almostanyone from attempting to harness the process.
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41Home Power #28 • April / May 1992Alternative FuelsStarting UpPartially digested slurry is kind of like sourdough starter. Ithas large populations of the right kind of micro-organismsto digest raw material and make methane. You can startfrom scratch, but it's faster if you can get some activitythat's already established. When I started a small digester in 1976, I seeded it withsome slurry from the St. Cloud, Minnesota, sewage plant.The plant engineer told me at the time that the plant wasso overloaded with wastes from a local meat packinghouse that the digester was just "going through themotions" and really not working properly. I took some ofthe slurry anyway. What the heck. It was free and Ineeded something to get the tank producing.After a few days I started to get methane and then I lost it.The tank was still producing a lot of gas, but it was carbondioxide – it didn't burn. The pig manure I had begun tofeed the digester along with the slurry from the St. Cloudplant was just too much raw material for the process. Sothere was a lot of carbon dioxide and acid. The acidforming bacteria were having a feast.I mentioned the problem to friend with whom I wasworking at the time. He said, "I make a lot of wine athome. Every once in a while I have the same problem.When I do I add a little baking soda. It straightens out thecondition right away. The nice thing is it doesn't leave anafter taste. In your case that isn't a problem!"The Benefits of Baking SodaSo I tried the baking soda. It worked like a charm. Withinthree days I had methane on the way. At a seminar I waspresenting a few weeks later, I mentioned this to thegroup. Baking soda was my "discovery" for straighteningout the pH in the digester.One of the people at the seminar sent me a clipping fromBusiness Week magazine a couple weeks later. It wasdated June 14, 1976. The headline for the article read"Dosing Sewage With Baking Soda." It went on to say thiswas a whole new idea for treating sewage plants; theyused to use large amounts of ammonia.The article further proclaimed that soda not only assistedin the more efficient digestion of sludge but increased thevolume of burnable methane gas. The most surprisingstatement of all: bicarbonate of soda "acts as a sort ofvitamin for bacteria."This is the secret for keeping your digester sweet andhappy. Just add a little at a time until the pH is just right.Keep adding it periodically if the pH keeps dropping untilthe acid forming bacteria are no longer producing anoverride of acid. Don't be fooled if a lot of gas startscoming. The baking soda itself will produce some carbondioxide.The Nature Of HeatHeat is essential for abundant methane production. Inwarm climates the process works with little help when theother conditions needed occur. For many of us who live ina cold climate, making methane work is a challenge. One needs to keep in mind that heat stratifies, whether inair or water. Heated fluids are less dense and tend to rise.This natural thermal stratification in liquid is, of course,the very reason why the thermal syphon principle in waterheaters works so well.It was this very fact which suggested a digester designwith a false floor containing only water. The bottom, thelowest point of the "working" tank, could be heated by athermosyphon action from some heat source such assolar, or even a little of the gas itself.CUTAWAY SIDE VIEW30 INCH SERVICE DOME8 INCH FILL PIPEGATEVALVESOLARHEATER INPUTVIEW WINDOW 12 BY 18 INCHESFLOOR BETWEEN SLURRYAND SOLAR HEATED WATER41.5 FEET LONGSUPPORT PIERSSOLAR HEATER OUTLETTANK DRAIN4 INCH DRAINWITH 12 INCH DIPGATEVALVEBAFFLE PLATESPILL-OVERDAM WALLGAS LINEAl Rutan's Methane Digester Design
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42Home Power #28 • April / May 1992The heat from the lowest part of this "double boiler" typedesign would rise through the slurry so that the verybottom of the "working" tank could more easily be kept atthe desired temperature in the entire digesting area. Sucha tank would most easily be constructed of fiberglass. Itcould be virtually any size.Next time we'll think about the barriers to the transfer ofheat – insulation – a critical key to any successfuloperation. This brings us to the question of whether theoperation is a net energy producer or an energyconsumer.AccessAuthor: Al Rutan, POB 289, Delano, MN 55328Alternative Fuels
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42Home Power #30 • August / September 1992Alternative Fuelsemperature is critical to thesuccess of any methane operationif it is to be considered an energysystem. If the primary concern is wastemanagement and not energy production,then a net energy loss is not a majorconsideration. If the intent is to produceenergy, a net energy gain from theprocess is everything.TEven More OnMethaneAl Rutan, the Methane Man©1992 Al RutanBody HeatMethane activity, in one of its natural situations, is foundin the digestive tract of warm blooded animals, peopleincluded. For people, the normal body temperature is98.6° F. In a chicken or pig it is 103° F. So right at 100° Fis the ideal working temperature for the methane process.To maintain this temperature outside an animal is aproblem if the ambient temperature is cool or cold.Sewage Plants ? Energy ProducersThere were several methane farm operations launched inthe upper midwest with much bravado and publicity. All ofthem are now out of business. On the other hand, sewageplants of medium size still commonly use the process totreat toilet waste and destroy pathogens, but in eachinstance they consume much more energy during the coldpart of the year than they produce. The toilet water flowinginto each sewage plant is ordinarily cold. It would beexceedingly difficult for sewage plants to be anything butenergy users rather than producers at any time except inthe hottest part of the summer.Universities’ verdicts at the end of the methane studieswere always the same: “It's possible, but it isn't practical.It takes more energy to run the system than the systemcan provide.” In harnessing methane as an energysystem, it is important to conserve heat in the process ofproducing gas. A few years ago a new sewage plant wasbuilt at St. Cloud, Minnesota to the tune of 17 milliondollars. I asked the engineer, “Did you insulate the tank?”He said, “Oh yes. The old one used to actually freeze onthe north side during the winter.” My next question was,“Did you run the insulation into the ground?” His reply,“No. The ground never gets cold.” My reply was, “That’sright, but it never gets warm either.” This sewage plantburned $750,000 a year in fuel oil to keep the digester at100° F. It costs big bucks to flush the toilet in St. Cloud.Capturing WarmthHeat has to be considered as something that is veryslippery. Conserving heat requires understandinginsulation. We are fortunate that there are many types ofinsulation available now that simply did not exist a fewdecades back. On the other hand, there’s a general lackof understanding of insulating properties of commonbuilding materials such as wood, metal, and concrete. Irecommend Movable Insulation, published by the RodalePress in 1980.Anyone familiar with insulation knows that if it gets wet, itis no longer insulation. Some "closed cell" insulatingmaterials such as urethane, styrofoam, and polyethylenefoam are more impervious to moisture than cellulose orfiberglass insulation. Even closed cell materials can breakdown if moisture under pressure is present.Styrofoam is used on the outside of the foundations toprovide a frost barrier for basements. Soil pressure andmoisture can cause the styrofoam to be less than "bonedry" and thereby lose much of its insulating ability.Situating the TankMy personal preference is that the methane tank be aseffectively insulated as possible. Insulation should bebelow the flow line of the material entering the tank, butshould not be buried in the dirt, regardless of theinsulation. The temperature of the ground several feetbelow the surface stays quite constant at 50° F – 55° F.To the methane tank, the earth is a “heat sink”, a coolmass always ready to absorb its heat. The best way tofight this heat sink is to insulate the tank and build itabove the ground. Another good reason for a free-standing tank is access to the grit trap at the bottom. Afree-standing tank should be covered with six to eightinches of high quality insulation.Various people have asked if a buried tank would work. Ican't say that it won't, but I've never seen any that work ina cold climate, and I have seen several that don't.Restoring WarmthWhen feces leaves the body, the waste is at exactly theright temperature for working within the methane digester.Whatever heat is lost in the interval between leaving the
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43Home Power #30 • August / September 1992Alternative Fuelsanimal and entering the digester has to be restored. If theheat needed is significant, there needs to be a heatsource available with an abundance of "free" energy, suchas solar or wind.Relation to FermentationThe methane process is a type of fermentation. Most folkshave baked bread or made homebrew beer or wine at onetime or another. For instance, after a yeast dough iskneaded, it is put in a warm place free of draft andallowed to rise. A draft could produce cooling. The yeastorganisms feed upon the mixture’s sugar. This producescarbon dioxide bubbles, which cause the dough to rise.There is a similar activity within the methane tank. Themethane organisms feed upon simple sugars, alcohols,and peptides produced by acid forming bacteria. Methanegas, CH4, is the result.I've been asked if the digestion process within the tankdoesn't produce some heat, such as the heat produced ina compost pile. It probably does. Because the metabolicactivity is so diluted and spread out within the tank, theheat available is minimal in comparison to the targettemperature.Awareness is EssentialYou’ll need to know how hot the tank is, day to day,season to season. To eliminate the guesswork, installsensors both inside the tank and outside the tank. Recordtemperature both inside and outside the tank over aperiod of time. Then you will know how efficiently the tankis retaining heat, at what rate the temperature drops whenno heat is added, and how much energy is needed toraise the temperature. If this is done, then a reliablecalculation can be made of how much gas is needed tomaintain working temperature if "free" heat is notavailable.Producing methane gas is relatively easy. Theconservation of heat more than any other factordetermines whether a methane system will "fly" or not. Ofall the systems I've seen that failed, the principal reason isimproper handling of heat.Care and Feeding of your Methane DigesterHaving thought about temperature, we can turn ourattention to feedstock. I work with a mixture of manureand vegetation. Sometimes the question is asked: can'tone use just vegetation to produce methane? It can bedone because Mother Nature does. Swamp gas burningover a marsh is just that. Because the methane bacteriaare part of the "flora and fauna" of the digestive tract,every time there is a fresh deposit, there is fresh input ofthe microbiological organisms needed.How Much Gas Can I Get?There’s a wide range of mixes of material you feed amethane digester. It's similar to what happens when weeat. Some of the material enters our system to maintain itand some of it passes on as waste. When manure isconsidered, all of it, minus the water, is designated as"total solids", and the part that is digestible to the bacteriais labeled "volatile solids". The numbers of what is andwhat isn't available for gas production have beengathered repeatedly over the years. Each account isquick to qualify any statement by saying that there is anynumber of variables when dealing with animals regardingwhat they are eating and how they are housed. One ofthe clearest reference sources is a newsletter printed in1973 by the New Alchemy Institute in California. Theirfigures correspond to what I've experienced.The numbers run like this: a cow drops an average of 52lbs. of feces a day, of which about 10 pounds are solids,the rest being water. Of the 10 pounds of solids, 80% or 8lbs. are volatile—can be turned into gas. A horseproduces an average of 36 pounds of feces a day, ofwhich 5.5 lbs. are volatile solids. A pig produces 7.5 lbs.per day of which 0.4 pounds are volatile solids. A humanproduces 0.5 pounds of feces a day of which 0.13 poundsis volatile solid. Chickens produce 0.3 pounds a daywhich 0.06 pounds is a volatile solid.All of this is good information, but it still doesn't tell us howmuch gas we can reasonably expect. If you ask an"expert" in the field, you'll get an answer something like,"It all depends..." All manure contains a degree ofnitrogen, but because nitrogen exists in so many chemicalforms in nature—ammonia (NH3), nitrates (NO3),proteins, etc.—it's difficult to test the total amount ofnitrogen in a given material.Why Consider Nitrogen?The process wants one part nitrogen to every 30 parts ofcarbon. Manure is nitrogen rich, averaging about 15 partscarbon for each part nitrogen, so all the studies show thatgas production is substantially increased by includingsome carbon material along with the manure. The
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44Home Power #30 • August / September 1992Alternative Fuelsnitrogen proportion may be even higher in animal waste ifurine is included with the feces because urination is theprinciple way an animal rids itself of excess nitrogen.To illustrate, straight chicken manure will produce onlyfive cubic feet of gas for each pound of manure, butchicken manure mixed with paper pulp will produce eightcubic feet of gas for each pound of manure used. Myexperience was an outstanding ten cubic feet of gas foreach pound of chicken manure when the manurecontained some ground feed that had been spilled. Cowmanure will produce only 1.5 cubic feet of gas per pound,but cow manure mixed with grass clippings will produce4.5 cubic feet of gas per pound of manure.The Nature of BiogasAssume that we have a gas producing system and it'smaking gas nicely and filling the gas holder. What do weactually have? It's important to understand that it isn't allmethane. A proportion of it is carbon dioxide, produced bythe acid forming bacteria, which doesn't burn. This factisn't immediately evident because if one ignites the end ofa hose coming from the gas holder, there is a blue flame.The fact that is important to know is: if we had puremethane we would have a hotter flame—about 1000 BTU(British Thermal Unit) for each cubic foot of gas. With thedilution of carbon dioxide, we have roughly 600 BTU foreach cubic foot of gas.The composition of the gas in our gas holder will be:CH4methane: 54 – 70%CO2carbon dioxide: 27 – 45%N2nitrogen: 0.5 – 3%H2hydrogen: 1 – 10%CO carbon monoxide: 0.1%O2oxygen: 0.1%H2S hydrogen sulfide: traceWouldn't it be nice if we could separate out the methaneand dump the carbon dioxide. Interestingly enough,Mother Nature has made it very easy to do just thatbecause these gases all have different specific gravityweights.How to Get Pure MethaneThe specific gravity of methane is about 0.55 inrelation to the weight of air, so it rises, as doeshydrogen. Carbon dioxide on the other hand is twicethe weight of air. Within a vertical gas container, if thegases are allowed to settle, they will naturally separatethemselves, the flammable gases rise to the top. Thisfact suggests that a good design should have apetcock at the bottom of a vertical gas holder. Use it tobleed off the accumulated carbon dioxide. In the rightsetting, this isn't environmentally harmful, because thetrees and growing things around the yard will welcome afresh sniff of carbon dioxide.Next time we'll consider some of the safety aspectsneeded in working with homemade gas.AccessAuthor: Al Rutan, the Methane Man, POB 289, Delano,MN 55328 • 612-860-3998
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82Home Power #40 • April / May 1994MethaneMore onMethaneAl Rutan the Methane Man©1994 Al RutanAlmost two years have passedsince the last mention ofmethane in these pages. HomePower issues 26, 27, 28, and 30described the basics of methaneproduction from animal feces. Idiscussed a low pressure storage tank,tank insulation, pH balance, animaltreatment, and heat retention. I’d like toshare some new information I havelearned since then. Some thingsworked and other things didn’t, but allfacts whether positive or negative arepart of the mastering process.Currently, my methane demonstration is beingupgraded. I am discarding the plastic tank that servedas a digestion vessel for the last year in favor of ametal tank. Why the change? For several reasons.First, the problems.Bonding DifficultiesThe primary difficulty is maintaining a vapor tight sealbetween the fill and overflow pipes and the tank. Theplastic tank didn’t cost much when new, so it was tootempting to pass up. But experience has shown that itwas not a good choice. The tank material ispolyethylene and the pipes are PVC plastic. While it’spossible to weld polyethylene with heat and produce abond, it isn’t something that an amateur can do easily. Iattempted to produce a vapor tight seal with varioustypes of glues and epoxies, which was achieved withsome success.But the tank was often moved from one location toanother by the trailer on which it is mounted. Thesloshing within the tank caused the pipes to break thebond with the tank.A second reason for replacing the plastic tank is that itis too short; the tank is three feet in diameter and onlyfive feet long. The best proportion for a tank is three tofive times as long as the diameter. This rule of thumbbecame obvious when new material was introducedinto the tank at the fill pipe. What exited through theoverflow was working nicely, still bubbling like crazy.Slurry Still WorkingThe supposed “waste” or “spent” bucket wasn’t spentat all, but continued to be active after it had beenforced out of the tank. A short tank is truly an inefficientdesign. The fill and overflow pipes are just too closetogether. Also, the fill and overflow pipes should not bein line with each other. One should be at either the rightor left side of center and the pipe at the opposite end ofthe tank should be on the other side of center. Itdoesn’t make any difference to which side of center thepipes are placed. But it’s important that the pipes at theends of the tank not be in line with each other.Such a placement of the pipes provides anotherimportant advantage — the best position for the stirringmechanism. On the plastic tank, the stirringmechanism was vertical with a crank at the top. After ashort time, I learned that this was a poor design for astirring device. The seal at the top is difficult to keepvapor tight. If the bearings for the stirring mechanismare below the water line, then any leakage is no morethan a little moisture, but not vapor.When the Tank Gets “Cranky”Also an oversight in the vertical stirring device designwas the omission of a bearing point at the bottom endof the shaft. It was left to “float”. With the resistance ofthe material within the tank, the pressure on the onebearing at the crank end of the shaft tended to distortthe cover of the tank as the crank was turned.Ideas that Worked — the Heat BathThat’s the bad news. So what’s the good news? Thewater bath for providing heat to the tank. I originallythought that this would be an effective way to transferheat from whatever source to the tank. In actualoperation, the concept worked even better thananticipated.Heat is supplied from a two foot square hot water boxplaced below the level of the water bath. Theplacement of the source of hot water under the waterbath allows the water to circulate via a thermosiphon:hot water rises in a closed circuit of water. Theconnecting pipes are two inches in diameter — one forsupplying warm water and another for the return of thecooler water. The pipes from the hot water box connectto an 18 inch deep metal water bath underneath thetank. The tank is placed on supports six inches abovethe floor of this water bath.
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83Home Power #40 • April / May 1994MethaneMore Art Than ScienceLet’s back up for a bit.People will sometimes ask,“Does it take a degree inengineering to understandthe methane process?” Myanswer is, “Not at all. Whatis most helpful is theexperience of baking bread,or making wine or beer.Each of these skills is bothan art and a science. Thereare some things that mustbe known. But basically, it’sexperience with the processof fermentation. And in thefinal analysis, the skill ismore an art than a science.”For bread to rise — which isthe critical test of whetheror not it will be a handsomeloaf — and for wine toferment, the temperatureconditions have to be, aswe say, just right. The same is true of the methaneprocess, which is another example of fermentation.Methane production occurs virtually automatically in oldlandfills, but we’re talking about maximum productionfrom a minimum amount of input. As for good bread,heat supplied during the rising process needs to be justwhat bread wants and free of drafts. For maximummethane production, the optimum temperature needsto be supplied evenly.Written in South Africa some years ago, L. John Fry’sbook Practical Building of Methane Power Plantsobserved that pipes supplying heat to the slurry had tobe hotter than the optimum temperature in order to getenough heat to the mass. This caused two unfavorableeffects. The methane organisms in the proximity of thepipe were cooked to the kill point. Such heating causeda crust to form on the heating pipe that eventuallycaused the heat within the pipe to be insulated from theslurry.Using pipes for the heat transfer is not the way to go.But body warmth for the process is essential, as is theright temperature for causing bread to rise or beer toferment. So the next question is, “How best to heat thetank?”The Key to Even HeatingIn my book, The Do’s & Don’t’s of Methane, theproposal to solve the problem was a false floor withinthe methane tank. This would separate the active slurryfrom the water beneath; the warm water provides heattransfer to the slurry above. The false floor thus acts asa double-boiler.The source of heat is below the slurry, providing heat atthe very lowest point. Because the heat transfer isspread over the entire lower surface, there are no hotspots that produce a kill temperature or crustingproblem.Thermosiphon Provides Effective CirculationSetting the tank in some sort of a water bath was agiven. But the surprise benefit in this design is howeasily and how well the principal of thermosiphonworked for the heat transfer. The water heater providesheat from either a small gas burner or solar panel. Thiswarm water moves up into the water bath, circulatingso effectively that one would assume there is acirculating pump somewhere in the system.But there is no pump, just a closed circuit of watermoving by a heat differential. In the 18 inch deep waterbath, the hot pipe enters the bath at the mid point — ornine inches above the floor. The return pipe at theopposite end of the bath is as low as possible. Withonly a nine inch difference between the input and thereturn pipes, the circulation is wonderful.The reason for the input entering the bath at themidpoint is to provide as much of a strata of warmwater above the input as possible. And it worksamazingly well. The water bath heats the tank evenlyAbove: The new metal tank methane digester on its trailer.Photo by Al Rutan
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84Home Power #40 • April / May 1994Methaneand effectively from the bottom up so that the workingtemperature within the slurry is even and constant. Thisapproach to handling the heating problem has beendesignated the Rutan Design.What’s in the WordsAs I write this, a new methane display is beingconstructed. It consists of a new trailer — a 16 foot carhauler — fitted with metal tank three feet in diameterand ten feet long. The tank has three windows so thatone can watch the methane activity within the tank. Itwill be heated with a solar collector, using some storedgas for backup. With the right kind of feeding andmanagement, this size is large enough to provide thecooking and heating needs for an energy efficienthomestead.AccessAl Rutan, POB 50, Liberty Center, IA 50145
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