Biogas Power Generators

i made a five gallon AD last summer. On average it produced .5 cubic foot a day at slightly over 3" WC. Or 1.5 cubic feet @ 1 atmosphere.

I learned there's two approaches to ADs:

One where there is an abundant supply of manure. Manure being mostly bacteria and very little of the feedstock that has fed the bacteria to this point. So there's a need to replenish the bacteria frequently. (more bacteria not so much feedstock)

Another approach is to essentially create an animal gut. (This is the type i made) With a seed supply of a given manure, feed this "seed" bacteria with the same thing the live animal would consume. There needs to be a pre-fermenting process to the feedstock, that first breaks down the feedstock to help in the digestion. (i started with cattle manure and fed the digestor grass clippings)

Both systems need heat. Remember most living body temps are around or just under 100F. This temp. is where the bacteria are used to living and thriving. So AD are more viable in warmer climates, where heat is free. It's quite easy to make the methane. But like any system, there needs to be a measurement of input vs. output. BTUs/Watts/Horsepower all easily converted back and forth. For my climate, especially in winter, it took too much energy input as heat for the methane output. I didn't see any advantage to scaling up either.

As a side note i did also store, compress, filter and burn the methane in a 50cc moped engine. You really gain an appreciation for denser, liquid fuels when you compute what it takes to run a 50cc engine @ 2000rpm for 10 minutes. Even at a 10 to 1 fuel to air mixture. There's no substitute for BTUs/Watts/HP.

look for landfill gas engines,both Cumins and caterpillar are manufacturers of this engine ,you need to furnish chemical combination of Biogas you intend to use and most of all much depends on Calorific value of your Biogas for selecting the landfill gas engine available.if you contact either of the engine manufacturers application engineers they will help you.

crm

Landfill gas is not quite the same as biogas, so the applicability of these engines to biogas would be suspect. Biogases generally have hydrogen as a component, while landfill gases do not have hydrogen as characterized. Therefore the consideration of hydrogen in the design of the Generator combustor is critical for biogases.

Hello MultiTech

Not sure from your post whether you're trying to improve efficiency of biogas generation from the waste, or of biogas into electricity.

If it's the latter, there's a company in Austria called Gembacher who make gas engines/alternator sets. They quote efficiencies in the 43% range, this is from heat in the biogas to electrical power output, which I think is highly impressive.

Don't know how small you need or whether they make them small enough, but worth contacting.

Cheers.........Codey

http://www.manuremanagement.cornell.edu/

Look here for case studies of AD and generators.

The purity of the methane can be purified using a C02 extraction system from Mitton Valve. link www.mittonvalve.com

Biogas contains hydrogen: do you know how exactly this Mitton Valve system will react to the presence of hydrogen?

The valve is custom designed to handle whatever materials need to pass through it.

They also have a Hydrogen generating valve as well.

MM

If you are trying to improve gas production, there is a product on the market, usually called "Septic Helper", which I have used both to improve digestion in septic tanks and in a mulch digester that worked quite well. I am not sure what sort of bacteria this is. Also, living in a warm climate makes a difference, as others have noted...

Save your money; let 1/2lb of thawed hamburger set out for about 2hrs then add a thumb nail size portion of yeast, roll and drop into AD. Presto!

Much discussion of this has gone on in the Sustainable Energy Blog. Certainly the suggestions in this thread seem experienced and credible. You may want to check with CR4 member Chtank for he has collected a wealth of knowledge on this subject.

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