The Seasteading Institute

Reply To: billswift wrote:I remember

[quote=billswift]

I remember reading about 20 years ago, that it took the manure of about 40 dairy cows to produce enough methane to cook for a family of 4, so it's not really practical as a primary energy source. On the other hand, a methane digester is an excellent liquid manure composter, if you primarily used it for that and just trapped the methane as a minor side product, that may be practical. You need to do something with the shit after all; and it works better as fertilizer if it has been composted first.

Methane digestion needs anaerobic conditions. Ordinary composting (garden composting and composting toilets) use aerobic conditions specifically to prevent formation of methane.

[/quote]

Mother Earth News has an old artical on a 1-cow digester. It uses a modified 55 gal drum and some rubber inner-tubes. It was sufficient to cook 1 meal, for 1 person, per day.

The Chinese Bio-gas digester, uses all animal wastes (people, pets, livestock) to produce methane for cooking and heating, along with fairly well processed sludge, for fertilizer. I would suggest adding an aerobic process, after the anaerobicsfor best safety and least complexity.

To increase the heat-value of the gas, it is necessary to remove the CO2. This has been achieved with a lime/water solution(hydrated lime/white-wash), which can be renewed by simply heating the solution to release the CO2. Alternately, the mixed gasses can be run through a multi-stage compressor and the CO2 precipitated out, making "Dry-Ice." Personally, I'd use the simpler method and release the CO2 into a greenhouse, until I decide I need the Dry-Ice, which could be used in old-fashioned ice-boxes and vented into the greenhouse...

Nice to have options, at any rate.

Later,

J.L..F.

If you can't swim with the big fish, stick to the reef