80-vx.txt
8ho-x.txt - - - - meth805\txt\pnt see-htm methane digester 8-26-05
Why consider it? For us who spent our youth
chopping wood to heat and cook at home, the idea of gas is paradise. The idea and the joy of turning a valve to have flame is amazing.
It is clean and uncomplicated. Clean? Yes, clean. There is no soot that
collects in a chimney from the burning of methane gas. Does it need to be
vented? if at all possible. The fumes from any type of combustion should be.
If the combustion is complete, what is produced is carbon dioxide and water-vapor. Yet combustion is not always as perfect as it could be.
the Indian government 40 years ago pushed the development of methane for
homes because people were going blind from burning cow dung for fuel. and pioneers also by buffalo chips. Burning raw manure is to be avoided.
methane tests also come from both India and China, big populations, big
pollution problems from waste, and big need for fuel.
At Home: home-made methane is one more way to provide access to energy, which adds quality to living. as electricity?, gas production means tending to living things, like a flock of chickens, a band of sheep, or milking goats. For much gas to grow, there needs to be a sensitivity to the special needs of the micro creatures that produce flammable gas as their waste. This means providing for their wants and ( don't laugh) giving them a measure of love. all living things: plants, animals, and people, require love in order to flourish. even to small creatures that can't be seen with the eye.
A person we know who had a methane system one day gave it a good kick as an experiment. The gas production stopped, and started slowly again only after some time had passed. have responsibility for the care of a colony of living things, so making gas to burn has a side folks may need to think of.
The blessings of gas are many. It is so easy to use. It is controllable.
It is easy to store. It can be used easy. It will even run a vacuum cleaner if you put the methane gas through a fuel-cell which will turn the gas directly into electricity. Plus, it is so clean! no soot, no creosote,
no ash, and no chopping. What more ask?
Making and Using Methane Gas: Methane is a natural gas. The reason it's called"natural" is because it occurs in nature everywhere. It can be the gas found in a swamp or marsh, the gas found in a coal mine, 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 thing is the same, CH-4.
We've heard that methane is odorless, and it is. Sewer gas we know is not.
So what is the difference? When the steps that make gas is working, there are other gases made at the same time. from micro-organisms feeding upon organic matter and producing gas as a waste product. Methane,which is odorless, is one of them. Hydrogen-sulfide, which is smelly, is another. hydrogen-sulfide is what gives us the sewer gas or "fart" smell.
When these gases are trapped in the ground a long time, the smell clears,
leaving an odorless gas. The sewer gas smell can be removed easily from the
mixture by simply bubbling all the gas in calcium-carbonate, which is simple
barn-lime, this is called 'scrubbing' it becomes odorless. gas companies add odor as a safety measure so that our noses can smell"loose gas".
All these burnable gases are produced by anaerobic-organisms feeding upon
organic matter. anaerobic means they only live when no air is in the place
where they are working. They are the same organisms that cause us to have
stomach-intestine gas. Each time a warm-blooded animal shits, some of the gas-producing organisms are contained in the shit. This is why it can be said that methane is everywhere. Wherever air is removed from the decomposing process, the growth of methane and other gases can happen.
The micro-organisms that make gas are sensitive. they want body temperature
to work best. In people, that is 98.6°F. In a chicken or a pig the body
temperature is 103°F. So right around 100°F is the best. it can work at cooler, but as temp drops so the work slows.
People will sometimes ask, "Why can't I use the gas off my septic tank to
burn in a stove?" The septic tank changes temperature to much, the amount of
gas produced is minimal. Each time a toilet is flushed with cold water, the
tank goes into "shock." Each time some warm wash water from a bath or shower
flows into the tank, it works more until the next shot of cold water. those tanks are in the ground, which stays at a constant 50° to 55°F. The ground is a heat-sink, draining heat away from the tank. About all one gets from a septic tank, is enuff gas to make a stink. Because the temperatur cannot be kept at the working level, such tanks have to be pumped. The solids cannot be well digested and so keep building up.
Key Considerations: It is the idea of a tank which offers us the most best way of making methane. Liquid within a tank gives two things, 1.room to move, or transport and 2.no usable air. are needed for the-most growth.
(pic ? ) Slurry Level - Input - Slurry - Level - Input - Pipe - Output
Slurry - Level - Exit - Pipe- Exit Basin - Gas Line Out
METHANE TANK CONCEPT SKETCH
Some methane production occurs in such places as an ordinary barnyard
manure-pile. The center of the pile is without air and with the heat
made by the pile some methane gas grows. but this way is slow, A solid pile we would need would have to be, a small mountain.
In a tank, is much better. It is much easier to have the tank "just bubbling away" so that the gas collected in a short time is very much.How much gas do I need? how much material do I need to produce this amount of gas? how large must the tank be to produce and store this amount of gas? Gas is thought of in terms of cubic feet. a cubic-foot is a box 12x12x12 inches. How much gas is in the box may change if the pressure is hi or lo. when we are working with methane, we are talking about only ounces of pressure, just enough pressure to push the gas to the burner, = a stove, water heater, or refrigerator. For "home-made methane," our pressure regulator is not any more than a heavy rock on a gas-holding bag, or the weight of a solid yet expandable gas-holder floating in liquid. nothing difficult.
How Much Gas Does One Need? : To find the amount of gas needed, the average family of four burns around 200 cubic feet of gas a day. if adding chores of cooking, heating space and heating water. you can trim this by using ones that dont use much gas, such as flow-on-demand water heaters, and high-efficiency space heaters. or get a list from some family that uses gas, and see how much it is. then find how they could use gas better.
Processes of Gas: We say liquid provides transport. transport is two-.
1.we must transport the material to the tank. 2. is the transport of the micro-organisms to the material, or it to them, so that it can be digested by them. inside an animal it is called peristalsis. We copy this transport by very gently moving the contents within the tank from time to time.
The Tank: A simple paddle tool works best. Some sytems re-circulate some of
the gas to make movement, but not always well. Often inorganic-material is stirred from the bottom of the tank, such as sand and small rocks that hurt the living organisms. The best way is a slow-mixing action with a paddle of some sort. just to move the material very gently a few times each day.
The exclusion of air is important to make it work. even if we know
that water contains some air ( otherwise how could fish breathe? ) once the activity of gas-producing bacteria starts, even the air is mostly removed.
The tank must be closed so that new air is not able to enter. This is done
good-enuff by having both the fill-pipe and the exit-pipe reach below the
water line. So, air exposure to the tank is limited to the surface of the
water level in both the fill and exit pipes.
In the past much talk was on whether the tank should be vertical(up-down)or horozontal. It is agreed that when the tank is horizontal it works best. (Note the pic on pg. 25.)The reason is that the fill and exit pipes need to be spaced as far apart as possible. Then the material entering the tank has greater exposure to the activity within the tank before being moved near the exit pipe. The gentle stirring action needed, mixes up everything. Yet if
the new material is forced to "travel" some distance before reaching the
exit pipe, then the micro-organisms will have more time to feed upon it
before it is replaced by incoming material.
How big should the tank be? This is figrd by how much material you give to the tank on a daily basis, and also how much gas one wants.
Production Mixture:
The input for the tank needs to be a mixture of manure and carbon material.
Carbon material is mostly waste-vegetation, but it can't be just anything. It needs to be something that when soaked in water for a few days becomes very soft. The bacteria don't have any teeth. They have to "gum" it.
Hardness can be misleading. A carrot seems hard, but if soaked long enough
it turns to mush. Grass clippings, on the other hand, contain a quantity of
'lignin', that cellulose-fiber that makes wood very "woody." Anything with
a high content of lignin will not work well in a methane tank. Straw for the
most part is acceptable. Hay is not. Even newspaper works well.
Although newspaper at one point was wood, the lignin has been broken down
so that when the newspaper is soaked for a day or so, it turns to mush,
good stuff for our purposes. The bacteria want a mixture of 30 parts carbon
to 1 part nitrogen. Manure is nitrogen rich, about 15 parts carbon to 1
part nitrogen, to much, so manure needs more straight carbon material, such
as straw, paper, sawdust,(wood is high in carbon) The ratio 30-1 isn't to
important, but the 30-1 is the ideal. Potency:different animal manures make
different amounts of methane. Chicken-manure can be really hi. I seen as high a yield as 10 cubic feet of gas from each pound of naturally moist chicken manure when mixed with some finely ground spilled feed.
Hog manure usually yields about 4 cubic feet per wet pound. Cow manure
usually yields about 1 cubic foot of gas for each pound of fresh manure.
The reason there is such a difference is that much of the methane has already been released when the waste goes through the digestive system
of a ruminant. but There is usually so much cow manure, its still worth it.
Another thing happens also, the raw manure becomes aged and totally acceptable to be placed on growing things. green fresh manure is not.
Sizing the System:Having said that we need around 200 cubic feet of gas a day, we need to set about designing a system that...(jump to 112)
Gas Storage Tank: ...considerably over ordinary sheet metal. The acids within the mixture do not work rapidly on the tank, but they will eat it over an extended period of time. at first, I had an 250 gallon fuel-oil tank that I used for show-tell purposes. It lasted years. It finally rusted, but the metal was light-gauge to begin with, but the tank served well. Because oxygen is excluded in the process and the pH must be kept at neutral (7,0-15), the deterioration of the tank was not rapid.
And a milk bulk tank already has a mixing paddle. All access ports above the
water-line are to be sealed air tight for gas production and safety. The Gas Holder: Regarding a gas holder, one may use a solid vessel open at the top filled with liquid with another vessel open at the bottom placed in it.
The gas pushes the top up out of the liquid as the gas is produced (see illustration on pg. 27). The simplest type of gas-holder is an expandable bag. It can be something like a waterbed-mattress upon which a weight is placed to produce enough pressure to send the gas to the place for use, a burner or somethn. One may use simply a vinyl of some type, but the best type of material is a nylon fabric that is impregnated with vinyl, not laminated, which becomes durable. If this inflatable bag is placed inside
a "silo" or? , then its sure that the bag is not going to be punctured. The people who work with the nylon impregnated-vinyl ( one names is Herculite) seal it by a process of electro-statically welding it. Using an ordinary adhesive may not work because methane tends to dissolve a number of adhesives..end?
For Now: The process of making methane gas is simple, watch the basic needs of the process. They are: 1the right balance of material,
2the right temperature, and 3the exclusion of air. Give these three and the methane process is unavoidable. The trick is to be sensitive to the fine-tuning of each of these three. As we
continue with more methane articles in Home Power...?, we will do just that.
Access Author: Al Rutan, POB 289, Delano, MN 55328
112...will provide this. How much is 200 cubic feet? a bag that is six feet wide, six feet long and six feet high, and you're seeing a space of 200 cubic feet. If we say that a mix of manures will give 4 to 5 cubic feet of gas per pound of naturally wet manure we need about 40 pounds of manure a day.
We need even less manure if we use chicken waste. These 40 pounds are going to be mixed with some type of additional carbon material, to which water ( warm water if can) will be added to give us a "slurry." This will most likely be about 15 gallons of bulk. think of it as in three 5-gal. buckets. Size of the Tank: It is generally a rule of thumb that the size of the tank needs to be 40-times the size of daily input. This means that when 1/40th of the volume of the tank is entered at the input-end then 1.40th of the volume will exit the overflow-end simply by being displaced. Add some space at the top of the liquid for the gas to collect, so the tank should be about 50 times the size of daily input. (eating habit?)
Sewage plants that employ the methane process ( and many do ) like to have
a holding time of 90 days. In other words, to have the tank 90 times the size of the daily input. The purpose of this is to totally destroy any possible pathogens. That length of time within the tank does it. inspections by health departments around the country keep a check on such activity and find that the 90-day holding time accomplishes this goal. Within a 40-day holding period most of the pathogens are destroyed. Because we are not dealing mostly with human feces (although this material may be
used with animal waste) the longer holding time is not as needful.
Within a 40-day time span the greatest amount of gas is produced. In a
period longer than 40 days, the gas production begins to slow down very.
We need a tank that is 50-times the amount of the daily input of 15 gallons,
or a 750 gallon tank. so, a 1,000 gallon tank would be ideal to take
care of extra demand or additional material.
Tank Choice: A 1,000 gallon discarded milk bulk tank would be ideal. Because bulk tanks already have a system for cooling the tank, this system could be easily adapted for holding the temperature 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 an advantage because it would extend the life of the tank...end?
Home Power #27 • February / March 1992
The article in HP26? says that we need about 50 pounds of waste daily,
a mixture of manure and carbon material to feed the digester that will turn
this material into about 200 cubic feet of gas.
The focus of'this'article is just this problem. As anyone who has done any
kind of homesteading knows, there is a ... ( jump to ? )
More On Methane:...in the last issue of HP, the methane article praised the ease with which gas is used, merely turning a valve to have instant vapor fuel. It takes so little effort. If gas is so easy, how does fifty pounds of manure get pushed around without any effort? Aw...you caught me! I...
hard way and an easy way to do every job. Part of skill is to see how people can approach a task that is downright tedious, and by some clever spin, make it easier.
Easy is Better:This became a lesson of heart while living at Red Lodge, MT.
I was raising rabbits for market, lots of them, about 200 breeding does.
Feeding and watering this number was a time-consuming chore. I made hoppers
for the hay and feed-pellets early on, but providing abundant water was a
drag. I upgraded from water dishes to water bottles with a valve. This was
an improvement in cutting down the labor. The big jump was to a system of
watering-valves fed by little plastic lines from a central tank with a float
valve to control both the water level and pressure on the water lines.
the water put into 200 little water bowls which were constantly being spilled or fouled with waste. In the other, water was supplied by a small pipeline with drinking valves in each cage. The result was the same, water to drink, but the effort needed was totally different.
The two situations accomplished the same effect, abundant fresh water.
Consider the Critters: To have a genuine sense of well-being in the work, the animals and the space must be happy. St. Francis of Assisi- the purpose of life is not income only, but income in a caring and respectful way.
animals with which we work and depend do have right to quality of life.
Page 7 , 45 Home Power #27 • February / March 1992
Alternative Fuels, Moving the Material While It's Warm:
It is manure itself. How can a person move it with the least effort? Manure-delivery-systems have been made for many critters, except the horse. there is no device more automatic than a scoop shovel for cleaning out a horse-stall.
If one DOES have animals, the shit has to go somewhere. So why not turn the waste into vapor fuel (methane) and compost.
When the waste comes out of an animal, its the right temp, body temperature. The sooner the waste is moved from the animal to the tank the better. If the waste loses heat, then the heat must be restored to have the methane digestive process work best.
How do we gather the manure to begin with? How do we gather it as soon as
possible after it leaves the animal and before it cools down?
There are two, One is gravity and the other is water. The hay is forked down to the animals below, using gravity. Animals, if they feel good about
themselves, they groom themselves and their friends.
Quality of Life: Death for an animal, or a person , is not the worst thing
that can happen. Quality of life while something is alive, be it plant,
animal or person, is of big importance. is a person is sensitive to
the quality of life of the living things around the homestead. Are the
animals feeling good, are they grooming?
Now, why make a point of this if we are talking about methane and manure?
On the one hand we want to collect waste with the least effort possible and do it as easy as possible. On the other hand, we need to have sense for the animals on which we depend. If the animal wanders about freely, it will be very difficult to collect its waste. On the other hand, if the animal is tightly caged or tied, its quality of life bad. So what's the answer?
Somewhere there is room. Chickens, for instance, do most of their shit while perched at night. Milk cows leave much in the gutter while being milked or held in the barn during the night. Hogs that are always caged don't have much of a life, if caged only for the night they will leave much waste.
Chickens need to peck and scratch. the area under the roost was wired so The chickens could not get to the manure to disturb it. Slatted floors are useful for both hogs and cattle if not asked to stand on them all day. In all these plans, animal must be happy with it.
Page 8 , Home Power #27 • February / March 1992 Do We Really Need Animals? We still need the family-mule to plow the garden, a few milk goats or sheep wisdom is in some kind of animal-support in our homesteading.
Farmers who drive to the store for their butter, milk, and eggs? Our great
grandparents would shake their heads!
Author: Al Rutan, the Methane Man, P O Box 289, Delano, MN 55328
Gravity Works for Free:gravity can be used for more tasks the better. The animals can walk up as well as down. If housing for animals can be above the digester, then this saves work. Water has long been used for
transport. Since the development of the flush-toilet, in the 1850's in
England by Mr. Crapper (no kidding...that really was his name!), we have been using water to move shit. but Using water has a problem. important: liquid or water, wants to release heat. When water is heated, it will not retain its heat. We say, "It cools down."
Water Must Be Warm:If we are going to use water for moving manure, and have it work well, we must learn that water cannot be allowed to stand around waiting for the waste. Warm water can and should be used to wash down a gathering-point below a slatted floor. The gathering point had better not be a holding pit in the ground because the whole thing will cool off to ground temperature. In a pit, the methane activity begins right away, so animals above a pit are breathing its unclean air. This is why holding-pits MUST have vents fans if they are under cage areas.
Think in Terms of Free Energy:How can warm-water work for us? every place is different, but think of all the ways of getting "free" heat-energy, solar, wind, whatever, and use it.
Daily washing down of a gathering area with warm pressurized water. will increase the force of the wash and use less water.
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Page 9 Home Power #28 • April / May 1992
M ?...old and mildew have been seen by everyone. Most people have seen the process of rotting. We know it is common in nature. Methane gas is just
as common, but not as seen. Anyone near a sewer-manhole or a plumbing-vent pipe can smell of the methane process in action.
im saying this to show the methane-process is not difficult to harness. as making a loaf of bread. If condition is there, results happen.
Third in a series by Al Rutan,the Methane Man, Al Rutan © Al Rutan 1992
The Methane:it is a biological-process that uses the waste of bacteria. we call the little critters bacteria, or "methogenic micro-organisms."
creatures :In the plans of the creator, they are bacteria, one of the very smallest forms of life. When men explore stars with telescopes that can separate colors, they look for the presence of methane gas.
If the gas is present, life is possible. For our purpose, we are going to
call them "bacteria." They are curious little critters. Their waste product burns. Not only does it burn, it burns very well. Combustion(heating them) produces only carbon-dioxide and water vapor. There is no ash, no soot, no tar, no dirt of any kind. It's a very true fuel.
Characteristics: it is made of carbon and hydrogen. Its chemical formula is CH-4. It has an octane rating of 110 and produces around 1,000 BTUs (British- Thermal- Units) of heat per cubic-foot of gas. Because most gas is invisible, it seems mysterious. If we think about our own chemistry for a minute, it won't seem so strange. We know that we breathe in oxygen and exhale carbon-dioxide. So we, ourselves, have gas-producing organisms.
Gas Makers:The part that is "strange" is that it burns. If mixed with enuff air, it burns very rapidly... explosion! In nature, some bacteria work with air because they need oxygen, and some work only with no air. The methane
bacteria are anaerobic ( no-air ). When exposed to air, they die.
Natural Gas and Sewage Gas:
What is the difference between natural gas and sewage gas? none.
Natural gas sold by the utilities is 90%, or better, methane. It has been
made in the ground over years of time and in most is almost pure methane because the ground has purified or "scrubbed" the gas. The only difference of gas made in the earth and gas made in sewage-plants is less time.
Home Power #28 • April / May 1992
( pic )1 ? 2 345 6 7 8 9 10 11 12 13 14 0 Acidic, Alkaline , The pH Scale
( pic ) a healthy digester, Neutral Alternative Fuels
Speeding up the action makes several gases, lots of carbon-dioxide. In a sewage-plant the mixture is about 70% methane and 30% carbon-dioxide, with trace amounts of hydrogen-sulfide. The carbon-dioxide departs from "natural gas" over time. The product,with the carbon dioxide, is called "biogas."
really, all natural gas is "biogas",all of it was from something that was,at one time, living. but "biogas" is produced in shorter time, and from things that were living recently. and made to process faster.
How Does it All Happen?:There are two breeds of anaerobic(no-air)bacteria that work together in two steps to make methane. The first is "acid-forming." they feed upon raw organic material. They produce no methane, only carbon-dioxide and some acids and "food" for the second bacteria.
The "food" consists of simple sugars, simple alcohols and peptides.
( see info on 'turning cellulose-material, plants, into sugar + alcohol )
The next, bacteria#2, feed upon this simpler food and produce methane. so now you see, when organic-material is placed in a container where no air is, both carbon-dioxide and methane are produced.
Need for Balance: bacteria#2 (methanogenic micro-organisms) need the food provided by the acid-forming bacteria#1, but they also need a balanced place to work. If the right balance between acid and base (alkaline) is not, the methane micro-organisms are in trouble and no methane is produced. they must have a pH of 7 to 8.5 in order to be normally active. What Does pH Mean?
bla bla bla, pH is "the negative logarithm of the effective hydrogen-ion concentration... used in expressing both acidity and alkalinity on a scale of 0 to 14 with 7 as neutral. Numbers less than 7 represent increasing acidity, numbers greater than 7 represent increasing alkalinity."
So pH means % of hydrogen, or proportion of hydrogen to the hydroxide-ion in a given material. It's a negative-log of hydrogen-ion concentration, so a pH of 7 means concentration is 10 - 7. bla bla bla Aren't you glad you asked?
Anyway, it's important info for keeping the digester healthy and happy.
The best pH for digestion is from 7.5 to 8.5.
How to Get a Reading:How does one measure pH? This is the easy part. Chemical supply houses and even most drug stores sell rolls of paper (called litmus paper) and/or little plastic strips that turn color when dipped in solution to tell you what the pH is. There is a slightly different color for each of the different pH numbers. You tear off a piece of the litmus paper about 1 1/2 inches long and dip it into a little of the slurry. The paper will start to change color within seconds. When compared to the color scale on the container, you can tell right away what the pH of the slurry is.
Why the Process May slow:
Generally if there's a problem, it's that the slurry is too acidic
(pH below 7). If there is a lot of new, raw, green material placed in the
digester, the acid forming bacteria have a party. The methane bacteria
are so disturbed by the high-acid concentration, they simply can't work.
Then it can take a long time for the methane-process to get to normal.
This generally occurs only in the beginning with start up or if too-much new
material is added at one time. ( like eating to much, acid-stomach )
If a measured amount of new material ( no more than 1/40th of the total liquid volume of the tank ) is added, then the new material is dilute enough not to upset the balance. But at first start-up, there is a lack of micro-organisms, and a moving to more acidity.
now you see why some early books on making-methane say start-up time can be from three weeks to three months. This is if you are beginning with all "new" material without the help of some already partially digested slurry.
A three-month start would stop almost anyone from trying to do it.
Home Power #28 • April / May 1992Alternative Fuels
Starting Up: Partly-digested slurry is kind of like sourdough starter. It has large populations of the right kind of micro-organisms to digest raw material and make methane. You can start from scratch, but it's faster if you can get some activity that's already established.
When I started a small digester in 1976, I seeded it with some slurry from
the St. Cloud, Minnesota, sewage-plant. The plant engineer told me at the
time that the plant was so overloaded with wastes from a local meat packing
house that the digester was just "going through the motions" and really not
working properly. I took some of the slurry anyway. Why not ? It was free
and I needed 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 carbon-dioxide, it didn't burn.
The pig manure , with the slurry from the St. Cloud plant was just too much raw material to feed to the digester. So there was a lot of carbon-dioxide and acid. The acid-forming bacteria were having a feast.
I mentioned the problem to friend with whom I was working at the time. He
said, "I make a lot of wine at home. Every once in a while I have the same
problem. When I do I add a little baking soda. ( cure for acid-stomach )
It straightens out the condition right away. The nice thing is it doesn't
leave an after taste. In your case that isn't a problem!"
I tried the baking soda: Within three days I had methane on the way. a few weeks later, I told this to the group. Baking soda was'my'discovery for correcting the pH in digesters, sewage-plants used large amounts of ammonia.
soda helps digestion of sludge and makes more burnable methane gas. and may act as a vitamin for bacteria. keeps your digester sweet and happy. Just add a little at a time until the pH is just right. Keep adding it periodically if the pH keeps dropping until the acid-forming bacteria do not over-acid. Don't be fooled if a lot of gas starts coming. The baking soda itself will produce some carbon-dioxide gas.
The Nature Of Heat:Heat is a need for methane-production. In warm countys the process works with little help. In cold climate, making methane work is a challenge. like dirt,heat stratifies into layers, in air or water.
Heated fluids are less dense and tend to rise. This natural thermal
stratification in liquid is the very reason why the thermal-syphon principle in water-heaters works so well. It was this very fact which suggested a digester design with a false-floor containing only water. The bottom, the lowest point of the "working" tank, could be heated by a thermosyphon action from some heat source such as solar, or even a little of the gas itself.
( pic ) CUTAWAY SIDE VIEW , 30 INCH SERVICE DOME, 8 INCH FILL PIPE
GATE, VALVE , SOLAR ,HEATER INPUT, VIEW WINDOW 12 BY 18 INCHES
FLOOR BETWEEN SLURRY AND SOLAR HEATED WATER , 41.5 FEET LONG
SUPPORT PIERS, SOLAR HEATER OUTLET, TANK DRAIN, 4 INCH DRAIN WITH 12 INCH DIP GATE, VALVE, BAFFLE PLATE , SPILL-OVER , DAM WALL , GAS LINE
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The heat from the lowest part of this "double boiler" design would rise
through the slurry so that the very bottom of the "working" tank could more
easily be kept at the desired temperature in the entire digesting area. Such
a tank would most easily be constructed of fiberglass. It could be virtually
any size. Next time we'll think about the barriers to the transfer of heat,
( insulation ) a critical key to any successful operation. This brings us to the question of whether the operation is a net energy producer or an energy consumer. Author: Al Rutan, POB 289, Delano, MN 55328
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HITNEY SOLAR PRODUCTS Harmony with Nature Page 13Home Power#30Aug/Sept 1992
Temperature is critical to the success of any methane operation if it is to
be considered an energy system. If the main concern is waste-management
and not energy-production, then a net energy loss is not a major goal. If the intent is to produce energy, a net energy gain from the process is everything. Even More On Methane, Al Rutan, the Methane Man, ©1992 Al Rutan
Body Heat:Methane activity, in one of its natural situations, is found in the digestive tract of warm blooded animals, people included. For people, the normal body temperature is 98.6° F. In a chicken or pig it is 103° F. So right at 100° F is the ideal working temperature for the methane process.
To maintain this temperature outside an animal is a problem if the ambient
temperature is cool or cold. ( so make your methane right on/in the cow ? )
Sewage Plants ? Energy Producers
There were several methane farm operations launched in the upper midwest. All of them are now out of business. On the other hand, sewage plants of medium size still commonly use the process to treat toilet waste and destroy pathogens, but in each instance they consume much more energy during the cold part of the year than they produce. The toilet water flowing into each sewage plant is cold. It would be exceedingly difficult for sewage plants to be anything but energy-users rather than producers at any time except in the hottest part of the summer.
a persons verdict at the end of the methane studies were always the same:
"It's possible, but it isn't practical. It takes more energy to run the
system than the system can provide." In harnessing methane as an energy
system, it is important to conserve heat in the process of producing gas.
A few years ago a new sewage plant was built in Minnesota to at 17 million dollars. I asked the engineer, "Did you insulate the tank?" He said, "Oh yes. The old one used to actually freeze on the 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's right, but it never gets warm either." This sewage plant burned $750
thousand a year in fuel oil to keep the digester at 100° F. It costs big
bucks to flush the toilet in St. Cloud.MN
Capturing Warmth: Heat has to be considered as something that is very slippery. Conserving heat requires understanding insulation. there are many types of insulation available now that did not exist a few decades back.
But there's a general lack of understanding of insulating properties of common building materials such as wood, metal, and concrete. I recommend Movable Insulation, published by the Rodale Press in 1980.Anyone familiar with insulation knows that if it gets wet, it is no longer insulation. Some "closed cell" insulating such as urethane, styrofoam, and polyethylene-foam are more impervious to moisture than cellulose or fiberglass insulation. Closed cell materials can break-down if moisture-under-pressure is present.
Styrofoam on the outside of foundations is a frost-barrier for basements. Soil-pressure and moisture can cause styrofoam to be less than "bone dry" and so loose much of its insulating ability.
Situating the Tank: i say that the tank be insulated as possible. Insulation should be below the flow-line of material entering the tank, but should not be buried in the dirt, regardless of the insulation. The temperature of the ground several feet below the surface stays quite constant at 50° F – 55° F.
To the methane tank, the earth is a "heat sink", a cool mass always ready to
absorb its heat. The best way to fight this heat sink is to insulate the tank and build it above the ground. (like god did a cow ) Another good reason for a free-standing tank is access to the grit trap at the bottom.
A free-standing tank should be covered with six to eight inches of high
quality insulation. Various people have asked if a buried tank would work.
I can't say that it won't, but I've never seen any that work in a cold
climate, and I have seen several that don't.
Restoring Warmth:When feces leaves the body, the waste is at exactly the right temperature for working within the methane digester. Whatever heat is lost in the interval between leaving the animal and entering the digester has to be restored. If the heat needed is lots, there needs to be a heat source available with an abundance of "free" energy, such as solar or wind.
Relation to Fermentation: The methane-process is a type of fermentation. Most folks have baked bread or made homebrew beer or wine at one time. after yeast dough is kneaded, it is put in a warm place free of draft and allowed
to rise. A draft could produce cooling. The yeast organisms feed upon the
mixture's sugar. This produces carbon dioxide bubbles, which cause the dough
to rise. similar activity is within the methane tank. The methane organisms
feed upon simple sugars, alcohols, and peptides produced by acid forming
bacteria. Methane gas, CH-4 , is the result.
I've was asked if the digestion process within the tank doesn't produce some
heat, such as the heat produced in a compost pile. It probably does. Because
the metabolic-activity is so diluted and spread out within the tank, the heat available is less than the desired temperature.
Awareness is Essential:You'll need to know how hot the tank is, day to day, season to season. install sensors both inside the tank and outside the
tank. Record temperature both inside and outside the tank over a period of
time. Then you will know how well the tank is retaining heat, at what
rate the temperature drops when no heat is added, and how much energy is
needed to raise the temperature. If this is done, then a reliable figur can be made of how much gas is needed to maintain working temperature if "free" heat is not available.
Producing methane gas is easy. The keeping of heatdetermines whether a methane system will "work" or not. Of all the systems I've seen that failed, the reason was improper handling of heat.
Birdy, birdy, in the sky. why did you do that in my eye ? I'm a big boy now
so I wont cry, but im sure glad 'cows' cant fly.
Care and Feeding of your Methane Digester:
I work with a mixture of manure and vegetation. Sometimes the question is
asked: can't one use just vegetation to produce methane? It can be done
because motherly Nature does. as Swamp-gas burning over a marsh.
Because the methane-bacteria is one of many things of the digestive tract, every time there is a fresh deposit, there is fresh input of the micro-biological organisms needed.How Much Gas Can I Get?:
There is many mixes of mater you can feed a methane digester. What happens when we eat? Some of it stirs us and some of it passes on as waste. manure, all of it, but the water, are the "total solids", and the part digestible to bacteria is "volatile solids". what is and what isn't for gas production have been gathered over years. Each say that there is other changes when dealing with animals, what they are eating, how they are housed.
the clearest is by New Alchemy Institute in California. in 1973 Their figures are as to what I've experienced.
The numbers run like this: a cow drops 52 lbs. of shit a day, 10 pounds are solids, the rest being water. Of the 10 pounds of solids, 80% or 8 lbs. are volatile, can be turned into gas. A horse produces 36 pounds of a day, of which 5.5 lbs. are volatile solids. A pig produces 7.5 lbs., of which 0.4 pounds are volatile solids. A person produces 0.5 pounds of shit a day, of which 0.13 pounds is volatile solid. Chickens produce 0.3 pounds a day which 0.06 pounds is a volatile solid. good information, but still doesn't tell us how much gas to expect. an "expert" would say"It all depends..." All manure contains a degree of nitrogen, but because nitrogen exists in so many chemical forms in nature ( ammonia (NH3), nitrates (NO3),proteins, etc. ) it's difficult to test the total amount of nitrogen in a given material. ( dont eat alot of beans )Why Nitrogen?:
The process wants one-part nitrogen to every 30-parts of carbon. Manure is
nitrogen-rich, 15 parts carbon for each one-part nitrogen, so all the studies show that gas production is increased by adding carbon-material ( plants, wood ) along with the manure. The nitrogen proportion may be even higher in animal waste if urine is included with the feces because urination is the principle way an animal rids itself of excess nitrogen.
example: straight chicken manure will produce only five cubic feet of gas for each pound of manure, but chicken manure mixed with paper pulp will
produce eight cubic feet of gas for each pound of manure used. My experience
was an amazing ten-cubic-feet of gas for each pound of chicken manure
when the manure contained some ground-feed that had been spilled.
Cow manure will produce only 1.5 cubic feet of gas per pound, but cow manure
mixed with grass clippings will produce 4.5 cubic feet of gas per pound of
manure. The Nature of Biogas:
Assume that we have a gas-producing system and it's making gas nicely and
filling the gas holder. What do we actually have? It's important to under-
stand that it isn't all methane. A proportion of it is carbon dioxide,
produced by the acid forming bacteria, which doesn't burn. This fact isn't
seen because if one ignites the end of a hose coming from the gas holder, there is a blue flame.
The fact that is important to know is: if we had pure methane we would have
a hotter flame, about 1000 BTU (British Thermal Unit) for each cubic foot of
gas. With carbon dioxide in it, we have 600 BTU for each cubic foot of gas.
The ingredients of the gas in our gas-holder will be: CH-4 methane: 54 , 70%
CO-2 carbon dioxide: 27 , 45% N2 nitrogen: 0.5 , 3%
H2 hydrogen: 1 , 10% CO carbon monoxide: 0.1%
O2 oxygen: 0.1% H2S hydrogen sulfide: traces
What if we could separate out the methane and dump the carbon-dioxide?. but look, Motherly Nature has made it very easy to do that, because these gases all have different specific-gravity weights.
How to Get Pure Methane:
The specific-gravity of methane is about half 0.55 as to air, so it rises, so does hydrogen. Carbon-dioxide is twice 2.00 the weight of air. Within a tall gas container, if the gases are allowed to settle, they will naturally separate themselves, the flammable gases rise to the top.
This fact says that a good design should have a petcock at the bottom of
a vertical gas holder. Use it to remove the carbon dioxide below. plants or trees growing around it will welcome a fresh sniff of carbon-dioxide.
Next time: safety aspects needed in working with homemade-gas.
Author: Al Rutan, the Methane Man, POB 289, Delano, MN 55328 ph.612-860-3998
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Home Power #40 • April / May 1994 <--- !
Methane More on Methane , Al Rutan the Methane Man ©1994 Al Rutan
Two years have passed since i wrote of methane in these pages.
HomePower.com issues 26, 27, 28, and 30 described the basics of methane
production from animal shit. I told of a low-pressure storage tank, tank
insulation, pH balance, animal treatment, and heat retention. I'd like to
share some new information I have learned since then. Some things worked and
other things didn't, but all facts whether positive or negative are part of
the mastering process. Today, my methane show-tell is better. I am removing the plastic tank used as a digestion-vessel last year, to use a metal tank. Why the change? reasons:First, the problems:Bonding Difficulties, a vapor-tight seal between the fill and overflow-pipes and the tank. The plastic tank didn't cost much to get. But experience has shown that it was not a
good choice. The tank material is polyethylene and the pipes are PVC plastic. you can weld polyethylene with heat and produce a bond easy. and I tried to make a vapor -tight seal with various types of glues and epoxies, which worked with some success.
But the tank was often moved from one place to annother. The sloshing in the tank caused pipes to break the bond with the tank. next reason:the plastic tank is too short; the tank is three feet in diameter and only five feet long. The best for a tank is three to five times as long as the diameter. This rule-of-thumb became useful when new material was moved into the tank
at the fill pipe. What came out the overflow was still bubbling, working.
Slurry Still Working:The supposed "waste" or "spent" bucket wasn't spent at all, but continued to be active after it had been forced out of the tank. A short tank is truly an better design. The fill-pipes and overflow-pipes were too close together. Also, the fill and overflow pipes should not be in line with each other. One should be at either the right or left side of center and the pipe at the opposite end of the tank should be on the other side of center. It doesn't make any difference to which side of center the pipes are placed. But it's important that the pipes at the ends of the tank not be in line with each other.
placement of pipes also provides the best position for the stirring-tool. On the plastic tank, the stirring-tool was tall with a crank at the top. After a short time, this was a poor design for a stirring device. The seal at the top is difficult to keep vapor-tight. If the bearings for the stirring-tool are below the water-line, then leakage is only moisture, but not vapor.
When the Tank Gets "Cranky":
Also a bearing-point at the bottom end of the shaft was missing. so it had to "float". With the resistance of the material within the tank, the pressure on one-bearing at the crank end of the shaft bent the tanks cover
as the crank was turned.
Ideas that Worked - the Heat Bath:
That's the bad news. So what's the good news? The water-bath for providing
heat to the tank. this would be an effective way to move heat from x? to the tank. and it worked even better than planned. Heat is supplied from a two foot square hot-water box placed below the level of the water bath. Placing the source of hot water under the water-bath allows the water to circulate itself, thermosiphon: hot water rises in a closed-circle of water. The connecting-pipes are two inches in diameter, one for supplying warm water and another for the return of the cooler water. The pipes from the hot water box connect to an 18 inch deep metal water bath underneath the tank. The tank is placed on supports six-inches above the floor of this water-bath.
helpful is the experience of baking bread, or making wine or beer. Each of these skills is both skill and facts. There are some things that are facts. But your skill is worth more than the facts. "For bread to rise and for wine to ferment, the temperature conditions have to be, as we say, just right. This is true of the methane-process, and is another example of fermentation.
Methane-production happens by itself in old landfills, but we want more production from less input. As for good bread, heat supplied during the rising process needs to be just what bread wants and free of drafts. For maximum methane production, the best temperature needs to be spread evenly.
Written in South Africa some years ago, L. John Fry's book-Practical Building of Methane Power Plants- observed that pipes supplying heat to the slurry had to be hotter than good to get enough heat to the slurry inside. This caused two bad effects. The methane organisms in area of the pipe were cooked to the kill point. Such heating caused a crust to form on the heating pipe that caused the heat within the pipe to be insulated from the slurry.
Using pipes for the heat-transfer is not the way to go. But body warmth for
the process is essential, as is the right temperature for causing bread to
rise or beer to ferment. So next is "How best to heat the tank?"
The Key to Even Heating
In my book, The Do's & Don't's of Methane, the proposal to solve the problem
was a false-floor in the methane tank. This would separate the active
slurry from the water beneath; the warm water provides heat transfer to the
slurry above. The false-floor then acts as a double-boiler.The source of heat is below the slurry, providing heat at the very lowest
point. Because the heat transfer is spread over the entire lower surface,
there are no hot-spots that produce a kill temperature or crusting problem.
Thermosiphon Provides Effective Circulation :
Setting the tank in some sort of a water-bath was good. But the surprise in this design is how easily and how well the principal of thermosiphon worked for the heat transfer. The water heater provides heat from either a small gas-burner or solar-panel. This warm water moves up into the water bath, circulating so well that one would think there was a circulating-pump somewhere in the system. But there is no pump, just a closed-circuit of water moving by a heat differential. In the 18 inch deep water-bath, the hot pipe enters the bath at the mid point ( or nine inches above
the floor ). The return pipe at the opposite end of the bath is as low as
possible. With only a nine inch difference between the input and the return
pipes, the circulation is wonderful.
The reason for the input entering the bath at the midpoint is to provide as
much of a strata of warm water above the input as possible. And it works
amazingly well. The water bath heats the tank evenly... ( pic ? )
Above: The new metal tank methane digester on its trailer.Photo by Al Rutan
Page 18, 84 Home Power #40 • April / May 1994, Methane
...and effectively from the bottom up so that the working temperature within
the slurry is even and constant. This way of working the heating problem has been called the Rutan-Design. As I write, a new methane-display is being constructed. It consists of a new trailer ( a 16 foot car hauler ) fitted with metal tank three feet in diameter and ten feet long. The tank has three windows so that one can watch the methane activity within the tank. It will be heated with a solar collector, using some stored gas for backup. With the right kind of feeding and management, this size is large enough to provide the cooking and heating needs for an energy efficient homestead.
Al Rutan, POB 50, Liberty Center, IA 50145 NESEA ( pic ? )
3.6 inches wide x 4.8 inches high
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-no end-
Why consider it? For us who spent our youth
chopping wood to heat and cook at home, the idea of gas is paradise. The idea and the joy of turning a valve to have flame is amazing.
It is clean and uncomplicated. Clean? Yes, clean. There is no soot that
collects in a chimney from the burning of methane gas. Does it need to be
vented? if at all possible. The fumes from any type of combustion should be.
If the combustion is complete, what is produced is carbon dioxide and water-vapor. Yet combustion is not always as perfect as it could be.
the Indian government 40 years ago pushed the development of methane for
homes because people were going blind from burning cow dung for fuel. and pioneers also by buffalo chips. Burning raw manure is to be avoided.
methane tests also come from both India and China, big populations, big
pollution problems from waste, and big need for fuel.
At Home: home-made methane is one more way to provide access to energy, which adds quality to living. as electricity?, gas production means tending to living things, like a flock of chickens, a band of sheep, or milking goats. For much gas to grow, there needs to be a sensitivity to the special needs of the micro creatures that produce flammable gas as their waste. This means providing for their wants and ( don't laugh) giving them a measure of love. all living things: plants, animals, and people, require love in order to flourish. even to small creatures that can't be seen with the eye.
A person we know who had a methane system one day gave it a good kick as an experiment. The gas production stopped, and started slowly again only after some time had passed. have responsibility for the care of a colony of living things, so making gas to burn has a side folks may need to think of.
The blessings of gas are many. It is so easy to use. It is controllable.
It is easy to store. It can be used easy. It will even run a vacuum cleaner if you put the methane gas through a fuel-cell which will turn the gas directly into electricity. Plus, it is so clean! no soot, no creosote,
no ash, and no chopping. What more ask?
Making and Using Methane Gas: Methane is a natural gas. The reason it's called"natural" is because it occurs in nature everywhere. It can be the gas found in a swamp or marsh, the gas found in a coal mine, 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 thing is the same, CH-4.
We've heard that methane is odorless, and it is. Sewer gas we know is not.
So what is the difference? When the steps that make gas is working, there are other gases made at the same time. from micro-organisms feeding upon organic matter and producing gas as a waste product. Methane,which is odorless, is one of them. Hydrogen-sulfide, which is smelly, is another. hydrogen-sulfide is what gives us the sewer gas or "fart" smell.
When these gases are trapped in the ground a long time, the smell clears,
leaving an odorless gas. The sewer gas smell can be removed easily from the
mixture by simply bubbling all the gas in calcium-carbonate, which is simple
barn-lime, this is called 'scrubbing' it becomes odorless. gas companies add odor as a safety measure so that our noses can smell"loose gas".
All these burnable gases are produced by anaerobic-organisms feeding upon
organic matter. anaerobic means they only live when no air is in the place
where they are working. They are the same organisms that cause us to have
stomach-intestine gas. Each time a warm-blooded animal shits, some of the gas-producing organisms are contained in the shit. This is why it can be said that methane is everywhere. Wherever air is removed from the decomposing process, the growth of methane and other gases can happen.
The micro-organisms that make gas are sensitive. they want body temperature
to work best. In people, that is 98.6°F. In a chicken or a pig the body
temperature is 103°F. So right around 100°F is the best. it can work at cooler, but as temp drops so the work slows.
People will sometimes ask, "Why can't I use the gas off my septic tank to
burn in a stove?" The septic tank changes temperature to much, the amount of
gas produced is minimal. Each time a toilet is flushed with cold water, the
tank goes into "shock." Each time some warm wash water from a bath or shower
flows into the tank, it works more until the next shot of cold water. those tanks are in the ground, which stays at a constant 50° to 55°F. The ground is a heat-sink, draining heat away from the tank. About all one gets from a septic tank, is enuff gas to make a stink. Because the temperatur cannot be kept at the working level, such tanks have to be pumped. The solids cannot be well digested and so keep building up.
Key Considerations: It is the idea of a tank which offers us the most best way of making methane. Liquid within a tank gives two things, 1.room to move, or transport and 2.no usable air. are needed for the-most growth.
(pic ? ) Slurry Level - Input - Slurry - Level - Input - Pipe - Output
Slurry - Level - Exit - Pipe- Exit Basin - Gas Line Out
METHANE TANK CONCEPT SKETCH
Some methane production occurs in such places as an ordinary barnyard
manure-pile. The center of the pile is without air and with the heat
made by the pile some methane gas grows. but this way is slow, A solid pile we would need would have to be, a small mountain.
In a tank, is much better. It is much easier to have the tank "just bubbling away" so that the gas collected in a short time is very much.How much gas do I need? how much material do I need to produce this amount of gas? how large must the tank be to produce and store this amount of gas? Gas is thought of in terms of cubic feet. a cubic-foot is a box 12x12x12 inches. How much gas is in the box may change if the pressure is hi or lo. when we are working with methane, we are talking about only ounces of pressure, just enough pressure to push the gas to the burner, = a stove, water heater, or refrigerator. For "home-made methane," our pressure regulator is not any more than a heavy rock on a gas-holding bag, or the weight of a solid yet expandable gas-holder floating in liquid. nothing difficult.
How Much Gas Does One Need? : To find the amount of gas needed, the average family of four burns around 200 cubic feet of gas a day. if adding chores of cooking, heating space and heating water. you can trim this by using ones that dont use much gas, such as flow-on-demand water heaters, and high-efficiency space heaters. or get a list from some family that uses gas, and see how much it is. then find how they could use gas better.
Processes of Gas: We say liquid provides transport. transport is two-.
1.we must transport the material to the tank. 2. is the transport of the micro-organisms to the material, or it to them, so that it can be digested by them. inside an animal it is called peristalsis. We copy this transport by very gently moving the contents within the tank from time to time.
The Tank: A simple paddle tool works best. Some sytems re-circulate some of
the gas to make movement, but not always well. Often inorganic-material is stirred from the bottom of the tank, such as sand and small rocks that hurt the living organisms. The best way is a slow-mixing action with a paddle of some sort. just to move the material very gently a few times each day.
The exclusion of air is important to make it work. even if we know
that water contains some air ( otherwise how could fish breathe? ) once the activity of gas-producing bacteria starts, even the air is mostly removed.
The tank must be closed so that new air is not able to enter. This is done
good-enuff by having both the fill-pipe and the exit-pipe reach below the
water line. So, air exposure to the tank is limited to the surface of the
water level in both the fill and exit pipes.
In the past much talk was on whether the tank should be vertical(up-down)or horozontal. It is agreed that when the tank is horizontal it works best. (Note the pic on pg. 25.)The reason is that the fill and exit pipes need to be spaced as far apart as possible. Then the material entering the tank has greater exposure to the activity within the tank before being moved near the exit pipe. The gentle stirring action needed, mixes up everything. Yet if
the new material is forced to "travel" some distance before reaching the
exit pipe, then the micro-organisms will have more time to feed upon it
before it is replaced by incoming material.
How big should the tank be? This is figrd by how much material you give to the tank on a daily basis, and also how much gas one wants.
Production Mixture:
The input for the tank needs to be a mixture of manure and carbon material.
Carbon material is mostly waste-vegetation, but it can't be just anything. It needs to be something that when soaked in water for a few days becomes very soft. The bacteria don't have any teeth. They have to "gum" it.
Hardness can be misleading. A carrot seems hard, but if soaked long enough
it turns to mush. Grass clippings, on the other hand, contain a quantity of
'lignin', that cellulose-fiber that makes wood very "woody." Anything with
a high content of lignin will not work well in a methane tank. Straw for the
most part is acceptable. Hay is not. Even newspaper works well.
Although newspaper at one point was wood, the lignin has been broken down
so that when the newspaper is soaked for a day or so, it turns to mush,
good stuff for our purposes. The bacteria want a mixture of 30 parts carbon
to 1 part nitrogen. Manure is nitrogen rich, about 15 parts carbon to 1
part nitrogen, to much, so manure needs more straight carbon material, such
as straw, paper, sawdust,(wood is high in carbon) The ratio 30-1 isn't to
important, but the 30-1 is the ideal. Potency:different animal manures make
different amounts of methane. Chicken-manure can be really hi. I seen as high a yield as 10 cubic feet of gas from each pound of naturally moist chicken manure when mixed with some finely ground spilled feed.
Hog manure usually yields about 4 cubic feet per wet pound. Cow manure
usually yields about 1 cubic foot of gas for each pound of fresh manure.
The reason there is such a difference is that much of the methane has already been released when the waste goes through the digestive system
of a ruminant. but There is usually so much cow manure, its still worth it.
Another thing happens also, the raw manure becomes aged and totally acceptable to be placed on growing things. green fresh manure is not.
Sizing the System:Having said that we need around 200 cubic feet of gas a day, we need to set about designing a system that...(jump to 112)
Gas Storage Tank: ...considerably over ordinary sheet metal. The acids within the mixture do not work rapidly on the tank, but they will eat it over an extended period of time. at first, I had an 250 gallon fuel-oil tank that I used for show-tell purposes. It lasted years. It finally rusted, but the metal was light-gauge to begin with, but the tank served well. Because oxygen is excluded in the process and the pH must be kept at neutral (7,0-15), the deterioration of the tank was not rapid.
And a milk bulk tank already has a mixing paddle. All access ports above the
water-line are to be sealed air tight for gas production and safety. The Gas Holder: Regarding a gas holder, one may use a solid vessel open at the top filled with liquid with another vessel open at the bottom placed in it.
The gas pushes the top up out of the liquid as the gas is produced (see illustration on pg. 27). The simplest type of gas-holder is an expandable bag. It can be something like a waterbed-mattress upon which a weight is placed to produce enough pressure to send the gas to the place for use, a burner or somethn. One may use simply a vinyl of some type, but the best type of material is a nylon fabric that is impregnated with vinyl, not laminated, which becomes durable. If this inflatable bag is placed inside
a "silo" or? , then its sure that the bag is not going to be punctured. The people who work with the nylon impregnated-vinyl ( one names is Herculite) seal it by a process of electro-statically welding it. Using an ordinary adhesive may not work because methane tends to dissolve a number of adhesives..end?
For Now: The process of making methane gas is simple, watch the basic needs of the process. They are: 1the right balance of material,
2the right temperature, and 3the exclusion of air. Give these three and the methane process is unavoidable. The trick is to be sensitive to the fine-tuning of each of these three. As we
continue with more methane articles in Home Power...?, we will do just that.
Access Author: Al Rutan, POB 289, Delano, MN 55328
112...will provide this. How much is 200 cubic feet? a bag that is six feet wide, six feet long and six feet high, and you're seeing a space of 200 cubic feet. If we say that a mix of manures will give 4 to 5 cubic feet of gas per pound of naturally wet manure we need about 40 pounds of manure a day.
We need even less manure if we use chicken waste. These 40 pounds are going to be mixed with some type of additional carbon material, to which water ( warm water if can) will be added to give us a "slurry." This will most likely be about 15 gallons of bulk. think of it as in three 5-gal. buckets. Size of the Tank: It is generally a rule of thumb that the size of the tank needs to be 40-times the size of daily input. This means that when 1/40th of the volume of the tank is entered at the input-end then 1.40th of the volume will exit the overflow-end simply by being displaced. Add some space at the top of the liquid for the gas to collect, so the tank should be about 50 times the size of daily input. (eating habit?)
Sewage plants that employ the methane process ( and many do ) like to have
a holding time of 90 days. In other words, to have the tank 90 times the size of the daily input. The purpose of this is to totally destroy any possible pathogens. That length of time within the tank does it. inspections by health departments around the country keep a check on such activity and find that the 90-day holding time accomplishes this goal. Within a 40-day holding period most of the pathogens are destroyed. Because we are not dealing mostly with human feces (although this material may be
used with animal waste) the longer holding time is not as needful.
Within a 40-day time span the greatest amount of gas is produced. In a
period longer than 40 days, the gas production begins to slow down very.
We need a tank that is 50-times the amount of the daily input of 15 gallons,
or a 750 gallon tank. so, a 1,000 gallon tank would be ideal to take
care of extra demand or additional material.
Tank Choice: A 1,000 gallon discarded milk bulk tank would be ideal. Because bulk tanks already have a system for cooling the tank, this system could be easily adapted for holding the temperature 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 an advantage because it would extend the life of the tank...end?
Home Power #27 • February / March 1992
The article in HP26? says that we need about 50 pounds of waste daily,
a mixture of manure and carbon material to feed the digester that will turn
this material into about 200 cubic feet of gas.
The focus of'this'article is just this problem. As anyone who has done any
kind of homesteading knows, there is a ... ( jump to ? )
More On Methane:...in the last issue of HP, the methane article praised the ease with which gas is used, merely turning a valve to have instant vapor fuel. It takes so little effort. If gas is so easy, how does fifty pounds of manure get pushed around without any effort? Aw...you caught me! I...
hard way and an easy way to do every job. Part of skill is to see how people can approach a task that is downright tedious, and by some clever spin, make it easier.
Easy is Better:This became a lesson of heart while living at Red Lodge, MT.
I was raising rabbits for market, lots of them, about 200 breeding does.
Feeding and watering this number was a time-consuming chore. I made hoppers
for the hay and feed-pellets early on, but providing abundant water was a
drag. I upgraded from water dishes to water bottles with a valve. This was
an improvement in cutting down the labor. The big jump was to a system of
watering-valves fed by little plastic lines from a central tank with a float
valve to control both the water level and pressure on the water lines.
the water put into 200 little water bowls which were constantly being spilled or fouled with waste. In the other, water was supplied by a small pipeline with drinking valves in each cage. The result was the same, water to drink, but the effort needed was totally different.
The two situations accomplished the same effect, abundant fresh water.
Consider the Critters: To have a genuine sense of well-being in the work, the animals and the space must be happy. St. Francis of Assisi- the purpose of life is not income only, but income in a caring and respectful way.
animals with which we work and depend do have right to quality of life.
Page 7 , 45 Home Power #27 • February / March 1992
Alternative Fuels, Moving the Material While It's Warm:
It is manure itself. How can a person move it with the least effort? Manure-delivery-systems have been made for many critters, except the horse. there is no device more automatic than a scoop shovel for cleaning out a horse-stall.
If one DOES have animals, the shit has to go somewhere. So why not turn the waste into vapor fuel (methane) and compost.
When the waste comes out of an animal, its the right temp, body temperature. The sooner the waste is moved from the animal to the tank the better. If the waste loses heat, then the heat must be restored to have the methane digestive process work best.
How do we gather the manure to begin with? How do we gather it as soon as
possible after it leaves the animal and before it cools down?
There are two, One is gravity and the other is water. The hay is forked down to the animals below, using gravity. Animals, if they feel good about
themselves, they groom themselves and their friends.
Quality of Life: Death for an animal, or a person , is not the worst thing
that can happen. Quality of life while something is alive, be it plant,
animal or person, is of big importance. is a person is sensitive to
the quality of life of the living things around the homestead. Are the
animals feeling good, are they grooming?
Now, why make a point of this if we are talking about methane and manure?
On the one hand we want to collect waste with the least effort possible and do it as easy as possible. On the other hand, we need to have sense for the animals on which we depend. If the animal wanders about freely, it will be very difficult to collect its waste. On the other hand, if the animal is tightly caged or tied, its quality of life bad. So what's the answer?
Somewhere there is room. Chickens, for instance, do most of their shit while perched at night. Milk cows leave much in the gutter while being milked or held in the barn during the night. Hogs that are always caged don't have much of a life, if caged only for the night they will leave much waste.
Chickens need to peck and scratch. the area under the roost was wired so The chickens could not get to the manure to disturb it. Slatted floors are useful for both hogs and cattle if not asked to stand on them all day. In all these plans, animal must be happy with it.
Page 8 , Home Power #27 • February / March 1992 Do We Really Need Animals? We still need the family-mule to plow the garden, a few milk goats or sheep wisdom is in some kind of animal-support in our homesteading.
Farmers who drive to the store for their butter, milk, and eggs? Our great
grandparents would shake their heads!
Author: Al Rutan, the Methane Man, P O Box 289, Delano, MN 55328
Gravity Works for Free:gravity can be used for more tasks the better. The animals can walk up as well as down. If housing for animals can be above the digester, then this saves work. Water has long been used for
transport. Since the development of the flush-toilet, in the 1850's in
England by Mr. Crapper (no kidding...that really was his name!), we have been using water to move shit. but Using water has a problem. important: liquid or water, wants to release heat. When water is heated, it will not retain its heat. We say, "It cools down."
Water Must Be Warm:If we are going to use water for moving manure, and have it work well, we must learn that water cannot be allowed to stand around waiting for the waste. Warm water can and should be used to wash down a gathering-point below a slatted floor. The gathering point had better not be a holding pit in the ground because the whole thing will cool off to ground temperature. In a pit, the methane activity begins right away, so animals above a pit are breathing its unclean air. This is why holding-pits MUST have vents fans if they are under cage areas.
Think in Terms of Free Energy:How can warm-water work for us? every place is different, but think of all the ways of getting "free" heat-energy, solar, wind, whatever, and use it.
Daily washing down of a gathering area with warm pressurized water. will increase the force of the wash and use less water.
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Page 9 Home Power #28 • April / May 1992
M ?...old and mildew have been seen by everyone. Most people have seen the process of rotting. We know it is common in nature. Methane gas is just
as common, but not as seen. Anyone near a sewer-manhole or a plumbing-vent pipe can smell of the methane process in action.
im saying this to show the methane-process is not difficult to harness. as making a loaf of bread. If condition is there, results happen.
Third in a series by Al Rutan,the Methane Man, Al Rutan © Al Rutan 1992
The Methane:it is a biological-process that uses the waste of bacteria. we call the little critters bacteria, or "methogenic micro-organisms."
creatures :In the plans of the creator, they are bacteria, one of the very smallest forms of life. When men explore stars with telescopes that can separate colors, they look for the presence of methane gas.
If the gas is present, life is possible. For our purpose, we are going to
call them "bacteria." They are curious little critters. Their waste product burns. Not only does it burn, it burns very well. Combustion(heating them) produces only carbon-dioxide and water vapor. There is no ash, no soot, no tar, no dirt of any kind. It's a very true fuel.
Characteristics: it is made of carbon and hydrogen. Its chemical formula is CH-4. It has an octane rating of 110 and produces around 1,000 BTUs (British- Thermal- Units) of heat per cubic-foot of gas. Because most gas is invisible, it seems mysterious. If we think about our own chemistry for a minute, it won't seem so strange. We know that we breathe in oxygen and exhale carbon-dioxide. So we, ourselves, have gas-producing organisms.
Gas Makers:The part that is "strange" is that it burns. If mixed with enuff air, it burns very rapidly... explosion! In nature, some bacteria work with air because they need oxygen, and some work only with no air. The methane
bacteria are anaerobic ( no-air ). When exposed to air, they die.
Natural Gas and Sewage Gas:
What is the difference between natural gas and sewage gas? none.
Natural gas sold by the utilities is 90%, or better, methane. It has been
made in the ground over years of time and in most is almost pure methane because the ground has purified or "scrubbed" the gas. The only difference of gas made in the earth and gas made in sewage-plants is less time.
Home Power #28 • April / May 1992
( pic )1 ? 2 345 6 7 8 9 10 11 12 13 14 0 Acidic, Alkaline , The pH Scale
( pic ) a healthy digester, Neutral Alternative Fuels
Speeding up the action makes several gases, lots of carbon-dioxide. In a sewage-plant the mixture is about 70% methane and 30% carbon-dioxide, with trace amounts of hydrogen-sulfide. The carbon-dioxide departs from "natural gas" over time. The product,with the carbon dioxide, is called "biogas."
really, all natural gas is "biogas",all of it was from something that was,at one time, living. but "biogas" is produced in shorter time, and from things that were living recently. and made to process faster.
How Does it All Happen?:There are two breeds of anaerobic(no-air)bacteria that work together in two steps to make methane. The first is "acid-forming." they feed upon raw organic material. They produce no methane, only carbon-dioxide and some acids and "food" for the second bacteria.
The "food" consists of simple sugars, simple alcohols and peptides.
( see info on 'turning cellulose-material, plants, into sugar + alcohol )
The next, bacteria#2, feed upon this simpler food and produce methane. so now you see, when organic-material is placed in a container where no air is, both carbon-dioxide and methane are produced.
Need for Balance: bacteria#2 (methanogenic micro-organisms) need the food provided by the acid-forming bacteria#1, but they also need a balanced place to work. If the right balance between acid and base (alkaline) is not, the methane micro-organisms are in trouble and no methane is produced. they must have a pH of 7 to 8.5 in order to be normally active. What Does pH Mean?
bla bla bla, pH is "the negative logarithm of the effective hydrogen-ion concentration... used in expressing both acidity and alkalinity on a scale of 0 to 14 with 7 as neutral. Numbers less than 7 represent increasing acidity, numbers greater than 7 represent increasing alkalinity."
So pH means % of hydrogen, or proportion of hydrogen to the hydroxide-ion in a given material. It's a negative-log of hydrogen-ion concentration, so a pH of 7 means concentration is 10 - 7. bla bla bla Aren't you glad you asked?
Anyway, it's important info for keeping the digester healthy and happy.
The best pH for digestion is from 7.5 to 8.5.
How to Get a Reading:How does one measure pH? This is the easy part. Chemical supply houses and even most drug stores sell rolls of paper (called litmus paper) and/or little plastic strips that turn color when dipped in solution to tell you what the pH is. There is a slightly different color for each of the different pH numbers. You tear off a piece of the litmus paper about 1 1/2 inches long and dip it into a little of the slurry. The paper will start to change color within seconds. When compared to the color scale on the container, you can tell right away what the pH of the slurry is.
Why the Process May slow:
Generally if there's a problem, it's that the slurry is too acidic
(pH below 7). If there is a lot of new, raw, green material placed in the
digester, the acid forming bacteria have a party. The methane bacteria
are so disturbed by the high-acid concentration, they simply can't work.
Then it can take a long time for the methane-process to get to normal.
This generally occurs only in the beginning with start up or if too-much new
material is added at one time. ( like eating to much, acid-stomach )
If a measured amount of new material ( no more than 1/40th of the total liquid volume of the tank ) is added, then the new material is dilute enough not to upset the balance. But at first start-up, there is a lack of micro-organisms, and a moving to more acidity.
now you see why some early books on making-methane say start-up time can be from three weeks to three months. This is if you are beginning with all "new" material without the help of some already partially digested slurry.
A three-month start would stop almost anyone from trying to do it.
Home Power #28 • April / May 1992Alternative Fuels
Starting Up: Partly-digested slurry is kind of like sourdough starter. It has large populations of the right kind of micro-organisms to digest raw material and make methane. You can start from scratch, but it's faster if you can get some activity that's already established.
When I started a small digester in 1976, I seeded it with some slurry from
the St. Cloud, Minnesota, sewage-plant. The plant engineer told me at the
time that the plant was so overloaded with wastes from a local meat packing
house that the digester was just "going through the motions" and really not
working properly. I took some of the slurry anyway. Why not ? It was free
and I needed 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 carbon-dioxide, it didn't burn.
The pig manure , with the slurry from the St. Cloud plant was just too much raw material to feed to the digester. So there was a lot of carbon-dioxide and acid. The acid-forming bacteria were having a feast.
I mentioned the problem to friend with whom I was working at the time. He
said, "I make a lot of wine at home. Every once in a while I have the same
problem. When I do I add a little baking soda. ( cure for acid-stomach )
It straightens out the condition right away. The nice thing is it doesn't
leave an after taste. In your case that isn't a problem!"
I tried the baking soda: Within three days I had methane on the way. a few weeks later, I told this to the group. Baking soda was'my'discovery for correcting the pH in digesters, sewage-plants used large amounts of ammonia.
soda helps digestion of sludge and makes more burnable methane gas. and may act as a vitamin for bacteria. keeps your digester sweet and happy. Just add a little at a time until the pH is just right. Keep adding it periodically if the pH keeps dropping until the acid-forming bacteria do not over-acid. Don't be fooled if a lot of gas starts coming. The baking soda itself will produce some carbon-dioxide gas.
The Nature Of Heat:Heat is a need for methane-production. In warm countys the process works with little help. In cold climate, making methane work is a challenge. like dirt,heat stratifies into layers, in air or water.
Heated fluids are less dense and tend to rise. This natural thermal
stratification in liquid is the very reason why the thermal-syphon principle in water-heaters works so well. It was this very fact which suggested a digester design with a false-floor containing only water. The bottom, the lowest point of the "working" tank, could be heated by a thermosyphon action from some heat source such as solar, or even a little of the gas itself.
( pic ) CUTAWAY SIDE VIEW , 30 INCH SERVICE DOME, 8 INCH FILL PIPE
GATE, VALVE , SOLAR ,HEATER INPUT, VIEW WINDOW 12 BY 18 INCHES
FLOOR BETWEEN SLURRY AND SOLAR HEATED WATER , 41.5 FEET LONG
SUPPORT PIERS, SOLAR HEATER OUTLET, TANK DRAIN, 4 INCH DRAIN WITH 12 INCH DIP GATE, VALVE, BAFFLE PLATE , SPILL-OVER , DAM WALL , GAS LINE
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The heat from the lowest part of this "double boiler" design would rise
through the slurry so that the very bottom of the "working" tank could more
easily be kept at the desired temperature in the entire digesting area. Such
a tank would most easily be constructed of fiberglass. It could be virtually
any size. Next time we'll think about the barriers to the transfer of heat,
( insulation ) a critical key to any successful operation. This brings us to the question of whether the operation is a net energy producer or an energy consumer. Author: Al Rutan, POB 289, Delano, MN 55328
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Temperature is critical to the success of any methane operation if it is to
be considered an energy system. If the main concern is waste-management
and not energy-production, then a net energy loss is not a major goal. If the intent is to produce energy, a net energy gain from the process is everything. Even More On Methane, Al Rutan, the Methane Man, ©1992 Al Rutan
Body Heat:Methane activity, in one of its natural situations, is found in the digestive tract of warm blooded animals, people included. For people, the normal body temperature is 98.6° F. In a chicken or pig it is 103° F. So right at 100° F is the ideal working temperature for the methane process.
To maintain this temperature outside an animal is a problem if the ambient
temperature is cool or cold. ( so make your methane right on/in the cow ? )
Sewage Plants ? Energy Producers
There were several methane farm operations launched in the upper midwest. All of them are now out of business. On the other hand, sewage plants of medium size still commonly use the process to treat toilet waste and destroy pathogens, but in each instance they consume much more energy during the cold part of the year than they produce. The toilet water flowing into each sewage plant is cold. It would be exceedingly difficult for sewage plants to be anything but energy-users rather than producers at any time except in the hottest part of the summer.
a persons verdict at the end of the methane studies were always the same:
"It's possible, but it isn't practical. It takes more energy to run the
system than the system can provide." In harnessing methane as an energy
system, it is important to conserve heat in the process of producing gas.
A few years ago a new sewage plant was built in Minnesota to at 17 million dollars. I asked the engineer, "Did you insulate the tank?" He said, "Oh yes. The old one used to actually freeze on the 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's right, but it never gets warm either." This sewage plant burned $750
thousand a year in fuel oil to keep the digester at 100° F. It costs big
bucks to flush the toilet in St. Cloud.MN
Capturing Warmth: Heat has to be considered as something that is very slippery. Conserving heat requires understanding insulation. there are many types of insulation available now that did not exist a few decades back.
But there's a general lack of understanding of insulating properties of common building materials such as wood, metal, and concrete. I recommend Movable Insulation, published by the Rodale Press in 1980.Anyone familiar with insulation knows that if it gets wet, it is no longer insulation. Some "closed cell" insulating such as urethane, styrofoam, and polyethylene-foam are more impervious to moisture than cellulose or fiberglass insulation. Closed cell materials can break-down if moisture-under-pressure is present.
Styrofoam on the outside of foundations is a frost-barrier for basements. Soil-pressure and moisture can cause styrofoam to be less than "bone dry" and so loose much of its insulating ability.
Situating the Tank: i say that the tank be insulated as possible. Insulation should be below the flow-line of material entering the tank, but should not be buried in the dirt, regardless of the insulation. The temperature of the ground several feet below the surface stays quite constant at 50° F – 55° F.
To the methane tank, the earth is a "heat sink", a cool mass always ready to
absorb its heat. The best way to fight this heat sink is to insulate the tank and build it above the ground. (like god did a cow ) Another good reason for a free-standing tank is access to the grit trap at the bottom.
A free-standing tank should be covered with six to eight inches of high
quality insulation. Various people have asked if a buried tank would work.
I can't say that it won't, but I've never seen any that work in a cold
climate, and I have seen several that don't.
Restoring Warmth:When feces leaves the body, the waste is at exactly the right temperature for working within the methane digester. Whatever heat is lost in the interval between leaving the animal and entering the digester has to be restored. If the heat needed is lots, there needs to be a heat source available with an abundance of "free" energy, such as solar or wind.
Relation to Fermentation: The methane-process is a type of fermentation. Most folks have baked bread or made homebrew beer or wine at one time. after yeast dough is kneaded, it is put in a warm place free of draft and allowed
to rise. A draft could produce cooling. The yeast organisms feed upon the
mixture's sugar. This produces carbon dioxide bubbles, which cause the dough
to rise. similar activity is within the methane tank. The methane organisms
feed upon simple sugars, alcohols, and peptides produced by acid forming
bacteria. Methane gas, CH-4 , is the result.
I've was asked if the digestion process within the tank doesn't produce some
heat, such as the heat produced in a compost pile. It probably does. Because
the metabolic-activity is so diluted and spread out within the tank, the heat available is less than the desired temperature.
Awareness is Essential:You'll need to know how hot the tank is, day to day, season to season. install sensors both inside the tank and outside the
tank. Record temperature both inside and outside the tank over a period of
time. Then you will know how well the tank is retaining heat, at what
rate the temperature drops when no heat is added, and how much energy is
needed to raise the temperature. If this is done, then a reliable figur can be made of how much gas is needed to maintain working temperature if "free" heat is not available.
Producing methane gas is easy. The keeping of heatdetermines whether a methane system will "work" or not. Of all the systems I've seen that failed, the reason was improper handling of heat.
Birdy, birdy, in the sky. why did you do that in my eye ? I'm a big boy now
so I wont cry, but im sure glad 'cows' cant fly.
Care and Feeding of your Methane Digester:
I work with a mixture of manure and vegetation. Sometimes the question is
asked: can't one use just vegetation to produce methane? It can be done
because motherly Nature does. as Swamp-gas burning over a marsh.
Because the methane-bacteria is one of many things of the digestive tract, every time there is a fresh deposit, there is fresh input of the micro-biological organisms needed.How Much Gas Can I Get?:
There is many mixes of mater you can feed a methane digester. What happens when we eat? Some of it stirs us and some of it passes on as waste. manure, all of it, but the water, are the "total solids", and the part digestible to bacteria is "volatile solids". what is and what isn't for gas production have been gathered over years. Each say that there is other changes when dealing with animals, what they are eating, how they are housed.
the clearest is by New Alchemy Institute in California. in 1973 Their figures are as to what I've experienced.
The numbers run like this: a cow drops 52 lbs. of shit a day, 10 pounds are solids, the rest being water. Of the 10 pounds of solids, 80% or 8 lbs. are volatile, can be turned into gas. A horse produces 36 pounds of a day, of which 5.5 lbs. are volatile solids. A pig produces 7.5 lbs., of which 0.4 pounds are volatile solids. A person produces 0.5 pounds of shit a day, of which 0.13 pounds is volatile solid. Chickens produce 0.3 pounds a day which 0.06 pounds is a volatile solid. good information, but still doesn't tell us how much gas to expect. an "expert" would say"It all depends..." All manure contains a degree of nitrogen, but because nitrogen exists in so many chemical forms in nature ( ammonia (NH3), nitrates (NO3),proteins, etc. ) it's difficult to test the total amount of nitrogen in a given material. ( dont eat alot of beans )Why Nitrogen?:
The process wants one-part nitrogen to every 30-parts of carbon. Manure is
nitrogen-rich, 15 parts carbon for each one-part nitrogen, so all the studies show that gas production is increased by adding carbon-material ( plants, wood ) along with the manure. The nitrogen proportion may be even higher in animal waste if urine is included with the feces because urination is the principle way an animal rids itself of excess nitrogen.
example: straight chicken manure will produce only five cubic feet of gas for each pound of manure, but chicken manure mixed with paper pulp will
produce eight cubic feet of gas for each pound of manure used. My experience
was an amazing ten-cubic-feet of gas for each pound of chicken manure
when the manure contained some ground-feed that had been spilled.
Cow manure will produce only 1.5 cubic feet of gas per pound, but cow manure
mixed with grass clippings will produce 4.5 cubic feet of gas per pound of
manure. The Nature of Biogas:
Assume that we have a gas-producing system and it's making gas nicely and
filling the gas holder. What do we actually have? It's important to under-
stand that it isn't all methane. A proportion of it is carbon dioxide,
produced by the acid forming bacteria, which doesn't burn. This fact isn't
seen because if one ignites the end of a hose coming from the gas holder, there is a blue flame.
The fact that is important to know is: if we had pure methane we would have
a hotter flame, about 1000 BTU (British Thermal Unit) for each cubic foot of
gas. With carbon dioxide in it, we have 600 BTU for each cubic foot of gas.
The ingredients of the gas in our gas-holder will be: CH-4 methane: 54 , 70%
CO-2 carbon dioxide: 27 , 45% N2 nitrogen: 0.5 , 3%
H2 hydrogen: 1 , 10% CO carbon monoxide: 0.1%
O2 oxygen: 0.1% H2S hydrogen sulfide: traces
What if we could separate out the methane and dump the carbon-dioxide?. but look, Motherly Nature has made it very easy to do that, because these gases all have different specific-gravity weights.
How to Get Pure Methane:
The specific-gravity of methane is about half 0.55 as to air, so it rises, so does hydrogen. Carbon-dioxide is twice 2.00 the weight of air. Within a tall gas container, if the gases are allowed to settle, they will naturally separate themselves, the flammable gases rise to the top.
This fact says that a good design should have a petcock at the bottom of
a vertical gas holder. Use it to remove the carbon dioxide below. plants or trees growing around it will welcome a fresh sniff of carbon-dioxide.
Next time: safety aspects needed in working with homemade-gas.
Author: Al Rutan, the Methane Man, POB 289, Delano, MN 55328 ph.612-860-3998
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Home Power #40 • April / May 1994 <--- !
Methane More on Methane , Al Rutan the Methane Man ©1994 Al Rutan
Two years have passed since i wrote of methane in these pages.
HomePower.com issues 26, 27, 28, and 30 described the basics of methane
production from animal shit. I told of a low-pressure storage tank, tank
insulation, pH balance, animal treatment, and heat retention. I'd like to
share some new information I have learned since then. Some things worked and
other things didn't, but all facts whether positive or negative are part of
the mastering process. Today, my methane show-tell is better. I am removing the plastic tank used as a digestion-vessel last year, to use a metal tank. Why the change? reasons:First, the problems:Bonding Difficulties, a vapor-tight seal between the fill and overflow-pipes and the tank. The plastic tank didn't cost much to get. But experience has shown that it was not a
good choice. The tank material is polyethylene and the pipes are PVC plastic. you can weld polyethylene with heat and produce a bond easy. and I tried to make a vapor -tight seal with various types of glues and epoxies, which worked with some success.
But the tank was often moved from one place to annother. The sloshing in the tank caused pipes to break the bond with the tank. next reason:the plastic tank is too short; the tank is three feet in diameter and only five feet long. The best for a tank is three to five times as long as the diameter. This rule-of-thumb became useful when new material was moved into the tank
at the fill pipe. What came out the overflow was still bubbling, working.
Slurry Still Working:The supposed "waste" or "spent" bucket wasn't spent at all, but continued to be active after it had been forced out of the tank. A short tank is truly an better design. The fill-pipes and overflow-pipes were too close together. Also, the fill and overflow pipes should not be in line with each other. One should be at either the right or left side of center and the pipe at the opposite end of the tank should be on the other side of center. It doesn't make any difference to which side of center the pipes are placed. But it's important that the pipes at the ends of the tank not be in line with each other.
placement of pipes also provides the best position for the stirring-tool. On the plastic tank, the stirring-tool was tall with a crank at the top. After a short time, this was a poor design for a stirring device. The seal at the top is difficult to keep vapor-tight. If the bearings for the stirring-tool are below the water-line, then leakage is only moisture, but not vapor.
When the Tank Gets "Cranky":
Also a bearing-point at the bottom end of the shaft was missing. so it had to "float". With the resistance of the material within the tank, the pressure on one-bearing at the crank end of the shaft bent the tanks cover
as the crank was turned.
Ideas that Worked - the Heat Bath:
That's the bad news. So what's the good news? The water-bath for providing
heat to the tank. this would be an effective way to move heat from x? to the tank. and it worked even better than planned. Heat is supplied from a two foot square hot-water box placed below the level of the water bath. Placing the source of hot water under the water-bath allows the water to circulate itself, thermosiphon: hot water rises in a closed-circle of water. The connecting-pipes are two inches in diameter, one for supplying warm water and another for the return of the cooler water. The pipes from the hot water box connect to an 18 inch deep metal water bath underneath the tank. The tank is placed on supports six-inches above the floor of this water-bath.
helpful is the experience of baking bread, or making wine or beer. Each of these skills is both skill and facts. There are some things that are facts. But your skill is worth more than the facts. "For bread to rise and for wine to ferment, the temperature conditions have to be, as we say, just right. This is true of the methane-process, and is another example of fermentation.
Methane-production happens by itself in old landfills, but we want more production from less input. As for good bread, heat supplied during the rising process needs to be just what bread wants and free of drafts. For maximum methane production, the best temperature needs to be spread evenly.
Written in South Africa some years ago, L. John Fry's book-Practical Building of Methane Power Plants- observed that pipes supplying heat to the slurry had to be hotter than good to get enough heat to the slurry inside. This caused two bad effects. The methane organisms in area of the pipe were cooked to the kill point. Such heating caused a crust to form on the heating pipe that caused the heat within the pipe to be insulated from the slurry.
Using pipes for the heat-transfer is not the way to go. But body warmth for
the process is essential, as is the right temperature for causing bread to
rise or beer to ferment. So next is "How best to heat the tank?"
The Key to Even Heating
In my book, The Do's & Don't's of Methane, the proposal to solve the problem
was a false-floor in the methane tank. This would separate the active
slurry from the water beneath; the warm water provides heat transfer to the
slurry above. The false-floor then acts as a double-boiler.The source of heat is below the slurry, providing heat at the very lowest
point. Because the heat transfer is spread over the entire lower surface,
there are no hot-spots that produce a kill temperature or crusting problem.
Thermosiphon Provides Effective Circulation :
Setting the tank in some sort of a water-bath was good. But the surprise in this design is how easily and how well the principal of thermosiphon worked for the heat transfer. The water heater provides heat from either a small gas-burner or solar-panel. This warm water moves up into the water bath, circulating so well that one would think there was a circulating-pump somewhere in the system. But there is no pump, just a closed-circuit of water moving by a heat differential. In the 18 inch deep water-bath, the hot pipe enters the bath at the mid point ( or nine inches above
the floor ). The return pipe at the opposite end of the bath is as low as
possible. With only a nine inch difference between the input and the return
pipes, the circulation is wonderful.
The reason for the input entering the bath at the midpoint is to provide as
much of a strata of warm water above the input as possible. And it works
amazingly well. The water bath heats the tank evenly... ( pic ? )
Above: The new metal tank methane digester on its trailer.Photo by Al Rutan
Page 18, 84 Home Power #40 • April / May 1994, Methane
...and effectively from the bottom up so that the working temperature within
the slurry is even and constant. This way of working the heating problem has been called the Rutan-Design. As I write, a new methane-display is being constructed. It consists of a new trailer ( a 16 foot car hauler ) fitted with metal tank three feet in diameter and ten feet long. The tank has three windows so that one can watch the methane activity within the tank. It will be heated with a solar collector, using some stored gas for backup. With the right kind of feeding and management, this size is large enough to provide the cooking and heating needs for an energy efficient homestead.
Al Rutan, POB 50, Liberty Center, IA 50145 NESEA ( pic ? )
3.6 inches wide x 4.8 inches high
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