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Gober Gas Methane
Gobar Gas Methane Experiments in India
(From The Mother Earth News)

It's been a wild, exciting ride... but our blindly wasteful

squandering of the planet's fossil fuels will soon be a thing of the

past. In the United States alone (the worst example, perhaps, but

not really unusual among "modern" nations), every man,

woman and child consumes an average of three gallons of oil

each day. That's well over two hundred billion gallons a year.

If we continue burning off petroleum at only this rate -- which

isn't very likely since population is climbing and the big oil

companies remain chained to "sell-more-tomorrow" economics

-- experts predict the world will run out of refineable oil within

(are you ready for this?) n30 years.

So where does that leave us? Well, number one, we obviously

must get serious about population control and per capita

consumption of power and, number two, if we don't want to see

brownouts and rationing of the power we do use, we'd better

start looking around for ecologically-sound alternative sources

of energy.

And there are alternatives. One potent reservoir that's hardly

been tapped is methane gas.

Hundreds of millions of cubic feet of methane -- sometimes

called "swamp" or bio-gas -- are generated every year by the

de- composition of organic material. It's a near-twin of the

natural gas that big utility companies pump out of the ground

and which so many of us use for heating our homes and for

cooking. Instead of being harnessed like natural gas, however,

methane has traditionally been considered as merely a

dangerous nuisance that should be gotten rid of as fast as

possible. Only recently have a few thoughtful men begun to

regard methane as a potentially revolutionary source of

controllable energy.

One such man is Ram Bux Singh, director of the Gobar Gas

Research Station at Ajitmal in northern India. Although some

basic research into methane gas production was done in

Germany and England during World War II's fuel shortages, the

most active exploration of the gas's potential is being done today

in India.

And with good reason. Population pressure has practically

eliminated India's forests, causing desperate fuel shortages in

most rural areas. As a result, up to three-quarters of the

country's annual billion tons of manure (India has two cows for

every person) is burned for cooking or heating. This creates

enormous medical problems -- the drying dung is a dangerous

breeding place for flies and the acrid smoke is responsible for

widespread eye disease -- and deprives the country's soil of vital

organic nutrients contained in the manure.

The Gobar (Hindi for "cow dung") Gas Research Station --

established in 1960 as the latest of a long series of Indian

experimental projects dating back to the 1930's -- has

concentrated its efforts, as the name suggests, on generating

methane gas from cow manure. At the station, Ram Bux Singh

and his co- workers have designed and put into operation bio-gas

plants ranging in output from 100 to 9,000 cubic feet of methane

a day. They've installed heating coils, mechanical agitators and

filters in some of the generators and experimented with different

mixes of manure and vegetable wastes. Results of the project

have been meticulously documented and recorded.

Facts about gobar*

<http://ww2.green-trust.org:8383/2000/biofuel/methane.htm#go

bar> gas

Cow dung gas is 55-65% methane, 30-35% carbon di- oxide,

with some hydrogen, nitrogen and other traces. Its heat value is

about 600 B.T.U.'s per cubic foot.

A sample analyzed by the Gas Council Laboratory at Watson

House in England contained 68% methane, 31% carbon dioxide

and 1% nitrogen. It tested at 678 B.T.U.

This compares with natural gas's 80% methane, which yields a

B.T.U. value of about 1,000.

Gobar gas may be improved by filtering it through limewater

(to remove carbon dioxide), iron filings (to absorb corrosive

hydrogen sulphide) and calcium chloride (to extract water

vapor).

Cow dung slurry is composed of 1.8-2.4% nitrogen (N),

1.0-1.2/a phosphorus (P2O5), 0.6-0.8% potassium (K2O) and

from 50-75% organic humus.

About one cubic foot of gas may be generated from one pound

of cow manure at 75 F. This is enough gas to cook a day's meals

for 4-6 people.

About 225 cubic feet of gas equals one gallon of gasoline. The

manure produced by one cow in one year can be converted to

methane which is the equivalent of over 50 gallons of gasoline.

Gas engines require 18 cubic feet of methane per horse- power

per hour. *Hindi for "cow dung"

This comprehensive eleven-year-long research program has

yielded designs for five standardized, basic gobar plants that

operate efficiently under widely varying conditions with only

minor modifications (see construction details of 100 cubic foot

digester that accompany this article)... and a treasure trove of

specific, field-tested principles for methane gas production.

Ram Bux Singh has compiled much of this information into

two booklets, BIO-GAS PLANT and SOME EXPERIMENTS

WITH BIO-GAS. The set of two manuals is available Air Mail

for $5.00 from Ram Bux Singh, Gobar Gas Research Station,

Ajitmal, Etawah (U.P.), India. The following information has

been adapted, by permission, from the handbooks:

FERMENTATION
There are two kinds of organic decomposition: aerobic

(requiring oxygen) and anaerobic (in the absence of oxygen).

Any kind of organic material -- animal or vegetable -- may be

broken down by either process, but the end-products will be quite

different. Aerobic fermentation produces carbon di- oxide,

ammonia, small amounts of other gases, considerable heat and a

residue which can be used as fertilizer. Anaerobic decomposition

-- on the other hand -- creates combustible meth- ane, carbon

dioxide, hydrogen, traces of other gases, only a little heat and a

slurry which is superior in nitrogen content to the residue yielded

by aerobic fermentation.
Anaerobic decomposition takes place in two stages as certain

micro-organisms feed on organic materials. First, acid-

producing bacteria break the complex organic molecules down

into simpler sugars, alcohol, glycerol and peptides. Then -- and

only when these substances have accumulated in sufficient

quantities -- a second group of bacteria converts some of the

simpler molecules into methane. The methane-releasing

microorganisms are especially sensitive to environmental

conditions.

TEMPERATURE ACIDITY
The proper pH range for anaerobic fermentation is between

6.8 and 8.0 and an acidity either higher or lower than this will

hamper fermentation. The introduction of too much raw

material can cause excess acidity (a too-low pH reading) and the

gas-producing bacteria will not be able to digest the acids quickly

enough. Decomposition will stop until balance is restored by the

growth of more bacteria. If the pH grows too high (not enough

acid), fermentation will slow until the digestive process forms

enough acidic carbon dioxide to restore balance.

CARBON-NITROGEN RATIO
Although bacteria responsible for the anaerobic process

require both elements in order to live, they consume carbon

about 30 to 35 times faster than they use nitrogen. Other

conditions being favorable, then, anaerobic digestion will

proceed most rapidly when raw material fed into a gobar plant

contains a carbon-nitrogen ratio of 30-1. If the ratio is higher,

the nitrogen will be exhausted while there is still a supply of

carbon left. This causes some bacteria to die, releasing the

nitrogen in their cells and -- eventually -- restoring equilibrium.

Digestion proceeds slowly as this occurs. On the other hand, if

there is too much nitrogen, fermentation (which will stop when

the carbon is exhausted) will be incomplete and the "left over"

nitrogen will not be digested. This lowers the fertilizing value of

the slurry. Only the proper ratio of carbon to nitrogen will insure

conversion of all available carbon to methane and carbon

dioxide with minimum loss of available nitrogen.

PERCENTAGE OF SOLIDS
The anaerobic decay of organic matter proceeds best if the

raw material consists of about 7 to 9 percent solids. Fresh cow

manure can be brought down to approximately this consistency

by diluting it with an equal amount of water.

BASIC DESIGN
Central to the operation and common to all gobar plant

designs' is an enclosed tank called a digester. This is an airtight

tank which may be filled with raw organic waste and from which

the final slurry and generated gas may be drawn. Differences in

the design of these tanks are based primarily on the material to

be fed to the generator, the cycle of fermentation desired and the

temperatures under which the plant will operate.

Tanks designed for the digestion of liquid or suspended- solid

waste (such as cow manure) are usually filled and emptied with

pipes and pumps. Circulation through the digester may also be

achieved without pumps by allowing old slurry to overflow the

tank as fresh material is fed in by gravity. An advantage of the

gravity system is its ability to handle bits of chopped vegetable

matter which would clog pumps. This is quite desirable, since the

vegetable waste provides more carbon than the nitrogen-rich

animal manure.

CONTINUOUS FEEDING (LIQUIDS)
Complete anaerobic digestion of animal wastes, such as cow

manure, takes about fifty days at moderately warm

temperatures. Such matter -- if allowed to remain undisturbed

for the full period -- will produce more than a third of its total
gas

the first week, another quarter the second week and the

remainder during the final six weeks.

A more consistent and rapid rate of gas production may be

maintained by continuously feeding small amounts of waste into

the digester daily. The method has the additional advantage of

preserving a higher percentage of the nitrogen in the slurry for

effective fertilizer use.

If this continuous feeding system is used, care must be taken to

insure that the plant is large enough to accommodate all the

waste material that will be fed through in one fermentation

cycle. A two-stage digester -- in which the first tank produces the

bulk of the methane (up to 80%) while the second finishes the

digestion at a more leisurely rate -- is often the answer.

BATCH FEEDING (SOLIDS)
Bio-gas plants may be designed to digest vegetable wastes

alone but, since plant matter will not flow easily through pipes,

it's best to operate such a digester on a single-batch basis. With

this method the tank is opened completely, old slurry removed

and fresh material added. The tank is then resealed.

Depending on the fermenting material and temperature, gas

production from a batch-feeding will begin after two to four

weeks, gradually increase to a maximum output and then fall off

after about three or four months. It's best, therefore, to use two

or more batch digesters in combination so that at least one will

always be producing gas.

Because the carbon-nitrogen ratio of some vegetable matter is

much higher than that of animal wastes, some nitrogen

(preferably of organic origin) usually must be added to the

cellulose digested this way. On the other hand, vegetable waste

produces -- pound for pound -- about seven times more gas than

animal waste, so proportionally less must be digested to maintain

equal gas production.

AGITATION
Some means of mixing the slurry in a digester is always

desirable, though not absolutely essential. If left alone, the slurry

tends to settle out in layers and its surface may be covered with a

hard scum which hinders the release of gas.

This is a greater problem with vegetable matter than with

manure, since the animal waste has a somewhat greater

tendency to remain suspended in water and, thus, in intimate

contact with the gas-releasing bacteria. Continuous feeding also

helps, since fresh material entering the tank always induces some

movement in the slurry.

TEMPERATURE CONTROL
Although it's relatively easy to hold the temperature of a

digester at ideal operating levels by shading a gobar plant

located in a hot region, maintaining the same ideal temperature

in a cold climate is somewhat more difficult.

The first and most obvious provision, of course, is insulating

the tank with a two or three-foot thick layer of straw or similar

material that is, in turn, protected with a waterproof seal. If this

proves insufficient, the addition of heating coils must be

considered.

When hot water is regulated by a thermostat and circulated

through coils built into a digester, the fermenting process may be

kept at an efficient gas producing temperature quite easily. In

fact, circulation only for a couple of hours in the morning and

again in the evening should be sufficient in most climates. It is

especially interesting to note that using a portion of the gas

generated to heat the water is entirely feasible... the resulting

enormously-increased rate of gas production more than

compensates for the gas thus burned.

GAS COLLECTION
Gas is collected inside an anaerobic digester tank in an

inverted drum. The walls of this upside down drum extend down

into the slurry, forming a "cap" which both seals in the gas and

is free to rise and fall as more or less gas is generated.

The drum's weight provides the pressure which forces the gas

to its point of use through a small valve in the top of the cap.

Drums on larger plants must be counter-weighted to keep them

from exerting too much pressure on the slurry. Care must also be

taken to insure that such a cap is not counter-weighted to less

than atmospheric pressure, since this would allow air to travel

backwards through the exhaust line into the digester with two

results: destruction of the anaerobic conditions inside the tank

and possible destruction of you by an explosion of the

methane-oxygen mixture.

The radius of an inverted drum should never be less than three

inches smaller than the radius of the tank in which it floats, so

that minimal slurry is exposed to the air and maximum gas is

captured.

ABOVE vs BELOW GROUND DIGESTERS
Gobar tanks built above ground must be made of steel to

withstand the pressure of the slurry and it's simpler and less

expensive to construct underground methane plants. It's also

easier to gravity-feed a tank built at least partially beneath the

earth's surface. On the other hand, above-surface models are

easier to maintain and, if painted black, may be partially heated

by solar radiation.

These brief excerpts from Ram Bux Singh's books should

make it obvious that methane gas production from manure and

vegetable waste is no armchair visionary's dream. It's being

done right now and over 2,600 gobar plants are currently

operating in India alone.

Here, in the U.S. our more than four hundred million cattle,

pigs and chickens produce over two billion tons of manure a

year... enough to spread four feet deep over an area of five

hundred square miles! This valuable natural resource can be

used to generate both combustible gas -- thus relieving part of

our reliance on fossil fuels -- and a fertilizer richer in nitrogen

than raw manure.

Instead of contributing mightily to our water pollution crisis as

feedlot runoff, this bountiful end-product of animal life could be

turned to our advantage... as an economical and

ecologically-sound power source!

(These instructions are for an underground, single-stage,

double-chamber plant designed to digest 100 pounds of manure

every 24 hours -- five cows' worth -- but may be scaled upward

to construct a plant capable of producing 500 feet of gas a day).

Dig a hole 13 feet deep and 12 feet in diameter, cutting away

trenches for the inlet and outlet pipes to angle down through.

In the center of the hole, pour a slab of concrete six inches

thick and six feet in diameter. The composition of the concrete

should be 1 part cement, 4 parts sand and 8 parts of 1" stone

aggregate.

The digester will be built on this base from 1:2:4 concrete

using 1/2" aggregate. The floor and walls will be 3" thick, giving

an inside diameter of 5'6". The walls will be 16' high and

reinforced with eight 3/8" machine steel vertical rods and 15

horizontal rings of the same material.

Inlet and outlet pipes of 4" galvanized iron should be

positioned before pouring the walls so that the pipes are

positioned 1-1/2' above the digester floor and in from the walls.

This is so that when the dividing wall is built across the center of

the digester, each pipe will be centered in its chamber. The

concrete must be tightly packed around the pipes to prevent

leakage.

Another wall of brick or concrete will be built three feet

outside the digester wall and to the same height (i.e. four feet

above ground level). This space will be filled with an insulating

material: straw, sawdust, shavings, etc.

Provide some means of descending into this space -- perhaps

rungs of machine steel rod extending from the digester wall to

the brick retaining wall -- in case it should ever become

necessary to empty the insulation. Seal the top of this area to

prevent water from getting in, and leave bare earth in the

bottom for drainage.

Bisecting the digester will be a wall of 4" reinforced concrete

eight feet high, at the top of which an iron support structure with

a guide pipe for the gas collector will be placed. This structure is

made of angle iron and the guide pipe is eight feet of 3"

galvanized iron pipe. The structure will be set in the digester

walls and solidly fixed atop the chamber-dividing wall. The pipe

must be in the exact center of the digester, allowing the gas

collector to descend into the slurry when empty and rise to

ground level when full. This requires 4' of vertical travel, thus the

top eight feet of the digester are left for the gas collector while

the bottom eight feet contain the dividing wall.

The gas collector is a roofed cylinder five feet in diameter and

four feet high constructed of 12-gauge machine steel sheeting. It

is braced internally with angle irons fitted at different heights so

that when the collector is rotated around its guide pipe the scum

on the surface of the slurry will be broken. The cylinder will first

be riveted, welded, tested for leaks by filling with water and

finish-welded. After all leaks are sealed it should be given two

coats of enamel paint inside and out. The top will be covered

with an insulating material.

The top of the gas collector is also fitted with a 1" tap and

valve, and to this is connected a flexible pipe leading to your gas

appliances. Inside the tap a piece of wire mesh is attached to

serve as a flame arrester. The actual capacity of the gas holder is

less than 100 cubic feet, but if the gas is being used regularly

there's no need to make it larger.

The mixing tank is a cylinder 2'4" in diameter and two feet

high. Its floor is one foot above ground level to provide hydraulic

head to feed the plant. The inlet pipe opening is flush with the

bottom of the mixing tank and is covered with a coarse screen to

prevent large pieces of waste from being ingested. The tank may

be built of bricks or concrete and is about 8-1/2 cubic feet in

volume, sufficient for the daily charge of waste matter.

The discharge pit should be large enough to accommodate all

the spent slurry that is expected to accumulate at a time. It's

made of bricks or concrete and the discharge end of the outlet

pipe should be just even with ground level.

An earth walkway at least three feet wide and level with the

top of the plant should be raised outside the brick wall for

support and additional insulation.

Approximate cost of materials for this plant in the United

States is $400.

Guest

In article <1180401820.201833.161210@i13g2000prf.googlegroups.com>,
nitai777@yahoo.com (Servitor) wrote:

Stephen Temple · Guest

srawlings@cix.compulink.co.uk wrote:

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In article <135o8dbtfct7hbc@corp.supernews.com>, usenet@jftemple.co.uk
(Stephen Temple) wrote:

Stephen Temple · Guest

srawlings@cix.compulink.co.uk wrote:

Tim Lamb · Guest

In message <135q5383h62hl65@corp.supernews.com>, Stephen Temple
<usenet@jftemple.co.uk> writes

Stephen Temple · Guest

Tim Lamb wrote:

Tim Lamb · Guest

In message <135qdg7okf1ucd5@corp.supernews.com>, Stephen Temple
<usenet@jftemple.co.uk> writes

AJH · Guest

On Tue, 29 May 2007 13:50:51 +0100, Stephen Temple
<usenet@jftemple.co.uk> wrote: