At the bottom of this page (link), we have information about and links to free plans for four common types of hot-weather biogas digesters. Happy building!
But… you should know that those digesters were all designed for tropical places, not for the U.S. They won’t produce much biogas at night or in the cooler weather of the U.S., sorry to say.
Of course, biogas ‘just happens’— we don’t have to do anything to make this natural and most ancient of all biological processes work. As a testament, you can see that this lovely fuel will accumulate even under the ice in frozen lakes. The problem is that biogas produced in near-freezing conditions (even in slightly-less-than-shirtsleeve weather), is produced very s-l-o-w-l-y. (Want more numbers on this? Hey! We’ve got a spreadsheet for you!)
Biogas likes to be warm. For the biogas process, “warm” means “at or very near the body temperature of a mammal.” (For a cow, that’s 105°F.) Otherwise, the biology operates at a sleepy pace, and the fact is that there is no spot anywhere in the Continental U.S. where it is warm enough year ‘round that biogas can be produced at a good rate 24/7/365.
So if you want to make biogas in the U.S.— and you expect your digester to be outside, where all good digesters should be— you must have a digester that is well-insulated, and properly heated.
…And as you might suspect, we have such a digester. It’s called “[The_Cube]”, and you can read more about it just here.
Four hot weather or tropical Digesters
As promised above, here are some pages that give a lot of information about tropical-climate biogas digesters. These work! (If you live in Manila.):
- Introduction to these digesters…
- 55-gallon-drum digester (only useful for experiments)
- ARTI-type digester (good, but wastes biogas)
- Underground masonry/concrete digester (world’s most common type)
- Plastic bag digester (world’s cheapest digester!)