The organizations I'm connected with here in the Indian Himalayas do work on renewable energy, and we used to have The Complete Biogas Handbook by David House, but can't find the book anymore.
It's listed at over $100 on Amazon and ABE books now. A few months ago it was listed at $25 and we failed to snap it up. If anyone has a copy and would be willing to sell it for under $50 we'd be very grateful. I have a US address it can be sent to.
Complete-biogas-handbook.jpg
The Complete Biogas Handbook by David House
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.