It was here at the Sekem farm and science school outside of Cairo Egypt that Thomas Culhane, Hanna Fathy and Solar CITIES intern Mike Rimoin deployed their invention of the open-source solar heated 3 IBC Solar CITIES Biodigester, perhaps the first use of IBCs for biogas in the world. Culhane felt it necessary to build a biogas system out of IBCs because he had just won a National Geographic Emerging Explorer's Blackstone Ranch Innovation Challenge Grant with Dr. Katey Walter Anthony from the University of Fairbanks in Alaska and had to come up with a small scale biogas system that would work in cold weather conditions. The open ARTI India systems they had been building in Cairo wouldn't work outside in the cold (they would lose heat too quickly) nor indoors (they would create odors and release methane). Meanwhile, typical cylindrical water tanks were either unavailable in Alaska or far too expensive to be feasible.
Culhane and Fathy, passing discarded International Bulk Containers on the roadside in Cairo, wondered if they couldn't make effective digesters from these types of tanks. With a little bit of research Culhane found that they could be found in almost every country in the world (they are, after all, INTERNATIONAL bulk containers!).
The problem they faced was that unlike the ARTI design, which uses a telescoping tank to hold the gas, the IBC has no storage possibility. Facing this challenge made Culhane come up with the idea of using 3 IBCs -- one as digestor, one to hold the gas, and one to create displacement water pressure to force the gas to the kitchen or generator.
As it turned out, it would be easier to produce the gas in an IBC but store it in a typical ARTI, as they did in 2012 at Mercy College and 2014 in Kibbutz Lotan (the digestor can be indoors and the floating storage outdoors) or to use the IBC as digester and store the gas in a large PVC bag and use a pump to create pressure. But for situations where IBCs are the ONLY tanks available and there are no bags or gas pumps, the 3 IBC system works rather well, and there is currently one operating in the favelas of Sao Paulo, built by the late permaculturist Paulo Mellett.
Culhane, Fathy and Rimoin tried three different variants of the system -- one was a traditional ARTI system with black plastic irrigation pipe surrounding it, connected to a solar hot water system (also made with black plastic irrigation pipe as heat exchanger rather than copper). The second was an IBC connected to an ARTI. The third was the 3 IBC system for places like Alaska where cylindrical water tanks for gas collection were not an option.
Based on these experiments Solar CITIES was able to choose different options for different conditions around the world.Event date: Tuesday, 12 May, 2009