When we posted about several "green gas" mills being built in the UK, it was easy to get carried away with all the pretty mock-ups of high-tech looking biogas facilities.
Ultimately, however, the technology behind anaerobic biogas digesters is pretty darned simple.
At least, that's what the folks behind this fascinating Solar CITIES tutorial on building your own biogas digester would have us believe. Pointing out that this is basically just an artificial stomach, the tutorial asks us to think of a biogas digester as a baby, or perhaps a fire-breathing dragon:
Food goes in, and solid and liquid waste comes out. As does flammable gas. (I am not sure I'd want to light my baby's farts on fire, but I get their analogy.)
Much like The Urban Farming Guys tutorial on DIY biogas, the Solar CITIES folks are using an Intermediate Bulk Container (IBC), which can often be found used from many food processors and other industrial operations. Basically they then just have to measure and cut three different pipes—one for feeding, one for the gas outlet, and one for displaced liquid fertilizer—insert them into the tank at the appropriate spots through a universal seal, and then plumb them in and get rolling.
Yes, that's an abridged version of how this is done. But the whole video takes eight minutes, so you can see for yourself how simple it looks. Solar CITIES (or possibly Solar C³ities—both spellings are used on their website), by the way, is an international non-profit dedicated to creating "an open-source virtual Hackspace for Biogas Innoventors and Practitioners." Which seems like a worthwhile goal. Now I just need to convince my wife to fill the basement with a big tank of sludge and gas...
A big thanks, as always, to Permaculture Magazine where I found this particular gem.