making biogas

thought i would issue a 'lets just say question'. what if methane became more valuable than gold- now lets say i have a 20 acres field, in which i was able to plant a crop; what should i plant in this field in order to produce the most methane in my biogas digester, ? what plant would give me the most methane per acre?

baked beans ??

Consider not just yield, but cost. I suggest grass. There is some good data available on grass digesters in Ireland that may be of interest. Throw a few cows on the pasture and you'll have a good mix, and meat or dairy to boot.

thanks for the idea Marcos, are you talking ordinary yard grass? so the cow eats some for the grass and poops, i cut some of the grass and jam it it in the digester, along with some of the cow poop; bobs your crazy uncle, and you have lots of methane right?? is the cow poop just to get some good bacteria to start the process?

I've seen a couple of articles using Jerusalem artichokes as feed stock for both ethanol and biogass.

Simple answer -- whatever makes the most biomass.

The chemical reaction in a biodigester is C6H12O6 ----> 3CH4 + 3CO2.

Or if you want to put it into words, every molecule of carbohydrate breaks down into equal parts methane and carbon dioxide. So to get more methane, you have to have more biomass going in.

What's that you say? Biomass is more than carbohydrate, there's protein and fats, and besides there's different types of carbohydrate and.....

In the famous words of W. C. Fields, "go away kid, you bother me". There's too many other things to do in life than to take inventory of all the chemical reactions going on in a biodigester. The one reaction above describes 97% of everything you need to know about your bioreactor. So whatever biomass you can shove into the bioreactor, give it a little time and you will get your methane.

handy farmer wrote:thanks for the idea Marcos, are you talking ordinary yard grass? so the cow eats some for the grass and poops, i cut some of the grass and jam it it in the digester, along with some of the cow poop; bobs your crazy uncle, and you have lots of methane right?? is the cow poop just to get some good bacteria to start the process?

Please note that this is not my area of expertise, but yes I'm talking ordinary yard grass. However, some strains are better than others. The cow poop is good for innoculation and also as a feed stock. There are many grass digesters in operation today making methane fuel gas (including the cows themselves).