The following You Tube clip is suitable for small scale off-grid bio-gas production. The same principles can be applied to larger scale bio-digesters.
The IBC tote feeding a storage bag for cooking gas is what I looked at. it seems doable with plant and animal waste. I can use the liquid outflow as fertilizer. Just be careful what you put in it.
Gas production largely depends on what you're feeding it. Done right the digester will produce 5 PSI on its own. that is a lot of pressure on a plastic tank. The early versions of this a fellow used chicken and pig manure and hay and drove his car on it. However, It should be noted that methane Gas is one of the hottest there are, so the engine run on this should have stellate valves. The slurry needs to be agitated from time to time and you vent needs to be large enough to expel the solids, just like poo.
Motor Scooter runs fine on the untempered hooch I distill. And with a little tempering it ain't half bad to drink. I have a methane reclaimer and it just is not worth the effort at this time to feed it. Now the Poultry Barns, Hog Barns and Feedlots on the other hand have the concentrated volume to benefit from them.
It's a wonder that they let people still do this because methane is a powerful greenhouse gas, and open composting is bound to be outlawed too someday. Who would have thought that the Peace Corps, missionaries, and hippies would do anything bad for the environment...
You are quite correct about Methane being a powerful greenhouse gas: cow shit, poultry shit, pig shit and horse shit et al which as it breaks down, produces much methane, IS a significant green house gas... https://gml.noaa.gov/education/info_activities/pdfs/CTA_the_methane_cycle.pdf Better to break down methane produced by human animal husbandry and agriculture by burning the resultant methane, and producing CO2 and water vapour, which is less deleterous to the biosphere than methane...also, using bio digested methane, is a useful alternative to burning coal , oil and natural gas safely sequestered in stable geological substrates. Methane is the immediate greenhouse gas threar...CO2 is the longer term greenhouse threat...better to convert methane to CO2 than burn fossil fuel CO2, if one is concerned about greenhouse gas saturation.
