DIY: hot tubs and biogas production, oh my.

A bunch of information re: small scale biogas (methane) production courtesy of Journey To Forever.

Methane Digesters for Fuel Gas and Fertilizer
Nepal Biogas Plant -- Construction Manual

Lots of other resources available in the Journey To Forever Biofuels Library.

Also found a few hot tub plans :)

BUILD A HOT TUB! Mother Earth News, Issue # 62 - March/April 1980
How to build a hot tub Steward Community Woodland
Our woodland wood fired hot tub Steward Community Woodland