Major construction firm Kajima Corp. announced Monday that it has succeeded in building a facility that can generate electricity directly from leftover food and other organic waste.
By using microscopic organisms and fuel cells, the facility, located at Kajima’s technical research institute in Tokyo, can decompose about 200 kg of organic garbage per day and generate 120 kw of electricity per hour, according to the company.
It is the world’s first such plant to produce electricity from garbage without burning it. Because the whole process bypasses incineration, no harmful vapors or substances such as dioxin are produced.
A beer factory in Chiba Prefecture uses fuel cells to generate electricity from organic waste water, but the Kajima facility is the first to use garbage, the Tokyo-based construction firm said.
Under the process developed by the company, garbage is mixed with water and sent to a grinder to be made into liquid form. The liquid is then sent to a tank filled with carbon fibers. When microorganisms break down the organic substances, gases emerge. About 65 percent of that gas is methane.
The methane is extracted and condensed, and the hydrogen ions in the gas react with oxygen in the fuel cells, generating electricity.
A fuel cell operates like a battery, but does not run down or require recharging. They produce electricity by combining hydrogen ions with oxygen atoms.
Kajima’s technology is likely to be used by local governments, commercial facilities and leisure facilities, where large amounts of garbage are produced.
Kajima hopes to build a large-scale electricity generating facility in fiscal 2000, the officials said.
According to the firm, 1 ton of garbage can create about 580 kw of electricity, which is the equivalent of that consumed by an average household in two months.
The company estimates that it will cost 250 million yen to construct a plant that can decompose 2.5 tons of garbage.
Garbage incineration costs about 30,000 yen, and ash disposal requires additional costs, but the newly developed system avoids those expenses altogether, it said.
The company has already commercialized a system in which methane is produced by fermenting garbage, and a shopping center in Akashi, Hyogo Prefecture, is using the methane produced as a source of heat, the officials said.
Toru Morioka, professor of environmental engineering at Osaka University, said, “It is an innovative technology toward creating a recycling society, and it is a technology eyeing the mid-21st century.”
“The developed system is compact and can also produce energy with stability and with high efficiency,” Morioka added.
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