Israel's Complete Biogas Plant!
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[1] Insulated digestion chambers produce biogas.
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What turns farm waste into feed, fuel, and other useful products?
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Early last year, two of MOTHER's editors visited Israel as part of a solar tour sponsored by this magazine and Michigan's Jordan College. That Mideast nation, even though oil-poor, does receive an abundance of sunshine . . . which is widely used to supplement more conventional energy sources. But, while the Israeli people are maintaining their position in the vanguard of solar development, they are continuing to look into the potential of oth er alternative forms of power as well. In fact, the Kefar Gil'adi kibbutz—on Israel's northern frontier—incorporates what may very well be the largest thermophilic biogas generation system in the world!
Biogas (composed largely of methane, carbon dioxide, and a bit of water vapor) is processed from organic waste. Closely related to natural gas, the "scavenged" fuel can be used to power stoves, heaters, lamps, refrigerators, and internal combustion engines.
Israel's methane gas project has been an ongoing affair for nearly two years. Initial research was carried out on a 35-cubic-foot digester . . . then two 350-cubic-foot experimental plants were built. Finally, in August of 1979, the 7,063-cubic-foot biogas "factory" shown here was put into operation. Though it's not completed yet (the plant is actually a practical "working" research project), the system has been producing gas on a regular basis all through its "debugging" phase.
A SIMPLE PROCESS. . .
The people responsible for the success of the biogas project don't look at the plant as merely a source of energy . . . instead, they take a wholistic approach. The operation started with a 500-head cattle feedlot—where disposal of waste was a concern—and, in effect, converted that "problem" into usable energy . . . enough to replace about half a ton of fuel oil a day. That, of course, Is all well and good, but the researchers are also feeding the spent manure (after it's been "degassed") to fish being raised in the farm's breeding ponds . . . and then using the fish for human consumption!
Actually, the gas generation process isn't too complicated: Waste from the cattle shed is scraped into a concrete trench with a front-end loader and is taken—via conveyor belt—to a pit where it's mixed with water and thoroughly ground up by a mechanical macerator until the material is in the form of a homogeneous slurry ... which is particularly high in solids by normal biogas production standards.
At this point, the undigested mixture is pumped through a series of heat exchangers—where it's warmed to 131°F using methane-fed gas jets—and on into two insulated, steel digestion chambers totaling over 7,000 cubic feet in volume. (The use of two tanks rather than one makes the digestion process somewhat more flexible.) Each day, a small percentage of fresh manure material is added to the vessels to replace the slurry that has been digested .
