Is anyone using methane ?

[Chuck]

In looking at reducing dependence on fossil fuels, gas for heating and transportation (different types of gas...) I've been revisiting the concept of using methane. I'm building a new home and have been required to install a septic tank rather than use a composting toilet. I've been thinking this may be a mixed blessing/hassle. The tank has been in for a year and it's pretty obvious that it's producing methane, even with very limited weekend use. I'm wondering if it's worth trying to capture and use it.

The plans I've seen suggest it takes at least a cow's worth of manure to supply a small family's normal cooking use. I was wondering if anyone is producing and using methane from any source and how they might be doing it.

Thanks,

Chuck

[GaryGary]

Hi,

I know little about this, so others may have much better info.

What I have read about producing methane indicates that a septic tank does produce some methane, but its very inefficient.  This is mainly because good methane generators need to produce the right temperatures and the right flow of material through the generator.  A septic tank is poor at this -- each time it gets a dose of cold water, the methane production drops to near nothing.

I've collected a few links on methane production here:

http://www.builditsolar.com/Projects/BioFuel/biofuels.htm#Methane

The articles by Al Rutan are a good place to start if youv'e not read much about methane generators before.

The methane calculator (Biorealis) can give you some idea how much methane you can generate from based on how much and what kind of "stuff" you have to put in it.

Gary

[gale]

I have seen several Agricultural methane digesters.  The smallest I saw used the the manure from 100 cows, from this they were able to run a lp fired generator for several hours each day, selling the electricity back to the power company.  

A methane digestor being fed from a human family, I doubt could produce anything more than a few cubic feet per day, unless you were in like a landscaping business, were you have a large amount of organic feed material.

Structurally a septic tank could not work as a digestor with out major modification, the key being that methane production is anaerobic in nature, you must eliminate the oxygen, the big structures use plastic sheets, anchored and seal to prevent oxygen from gettting in and methane from escaping.  then when they reload, they pump all the methane out, reload, then pump all the air out, so that the plastic film is flush to the feed material, then the bacteria pruducing methane filling the plastic like a ballon.

[hvirtane]

It is much more than worth of nothing,

what you can produce by human manure.

For example in Nepal smallest

biogas systems are utilizing only

8 people human manure.

I've seen in India biogas systems

built to utilize the manure of one single cow,

capable of producing gas enough for

the cooking of a family.

I think that the main problem is how to

utilize the gas. In developing countries

the gas is mainly used for cooking.

You might try making a bigger system

and putting inside the digester other

suitable organic wastes, too.

- Hannu

[roddy]

there are several articles on methane use and production in old Home Power magazines. these are available as individual copies or you can buy the whole cdo-rom set pretty reasonably. As I recall the general concensus was that human manure won't make much of a differnece, but the "output" of a few cattle or horses is enough for cooking or maybe dwh or supplemental heat with little modification. They even tell how to modify lp/ng burners for methane and hydrogen burning in various articles.

roddyb

[hvirtane]

I forgot to mention

that it is really important

to keep the biogas digester

warm enough. About 29 C - 41 C degrees

is the good temperature.

You might experiment with

a solar heating system

to keep the biodigester warm.

I talked some time ago

with an old expert with

biogas systems. He told that

if you'll use the generated

biogas to keep the digester warm

(in Finnish conditions) you need

to burn about 10% of the gas.

So even that kind of heating system

will work.

Please read also:

http://www.drdo.org/labs/dls/drde/products/biodigester.htm

http://www.cipav.org.co/lrrd/lrrd10/1/anh101.htm

http://lists.ibiblio.org/pipermail/homestead/2005-October/005938.html

- Hannu

[Chuck]

Interesting comments guys, Thanks for the additional food for thought. I know a normal septic system is too cold and most plans I have include a way of stirring the waste. I think both of these can be addressed and incorporated into a septic system, Maybe I'll get some time to look into it further.

Many thanks.

Chuck