Pig Manure as an Energy Source Final Processing Facilities Are Full Farewell to Dioxins

			Reducing waste is crucial for an environmentally aware society, yet human endeavor is virtually impossible without generating waste products—hence utilizing these waste products effectively is of growing importance, whereas disposal was the only option in the past. Utilizing recycled industrial waste is one of the key technologies of the 21st century.
			One of Sumitomo Metals’ corporate missions is ensuring that it does not leave a mountain of waste for the next generation to deal with. The company is close to commercializing a system that processes ASR, said to be the most challenging industrial waste product to dispose of.

Pig Manure as an Energy Source

In a village about 100km northwest of Tokyo, a couple runs a farm with 500 pigs. In 2004, equipment such as fuel cells, a methane engine generator, and a gas holding tank that appeared to have little connection with pig farming were brought onto the farm to set up a trial facility to produce methane gas from pig manure for use as an energy source. How does the system work? Pigsties use sawdust for bedding, which absorbs feces and urine. The bedding is removed and placed in a machine that separates leftover food and fur mixed in with the manure to prevent blockages and breakdown of equipment, as well as to extract the separated fluid, which is easily broken down by bacteria, as the raw material for methane fermentation. Using only the separated fluid minimizes the required capacity of the concrete fermentation vat, thus saving on construction costs. The digestive fluid produced in the separation and fermentation processes can be sprayed as liquid fertilizer, but this farm does not have enough pasture land to spray. Thus, it is converted into solid fertilizer in a fermentation house, and can then be sold. The separated fluid is stored in the fermentation vat, which contains methane bacteria at 36°C, for 20-30 days. Methane gas is produced in this fermentation process, which is then dehumidified and put through biodesulferization and dry-type desulferization systems to reduce the sulfur concentration of the gas (sulfur hydrogen sulfide) from around 2,000 ppm to 1-10 ppm. This is stored in a gas holding tank and used for power generation with a 1 kw-class fuel cell and 5 kw-class methane engine generator. The cogeneration system also comes with a gas boiler, which means biogas can be burned directly. Power generated from the 2.6 tons of pig manure produced per day totals 141.5 kw—equivalent to the daily electric power consumption of 14 average households.

Pigs are delightful animals, but looking after 500 of them is hard work— especially when you consider that they produce 2.6 tons of manure per day that has to be removed.

Twenty Years of Solid Research Finally Bear Fruit

A hothouse used for composting solids remaining after the separation of solid and liquid wastes. Electricity generated with biogas produced by methane fermentation is used to regulate the temperature inside, and the resulting compost is an important revenue source for pig farmers. Meidensha Corporation developed this system, which it is testing with the New Energy and Industrial Technology Development Organization (NEDO). Meidensha has been researching waste disposal and energy-related themes for many years, and has delivered systems that produce methane gas and compost from livestock manure to more than 10 locations in the 1980s. The world was still suffering the after-effects of the two oil crises, and the system commanded attention as an alternative energy source to petroleum. However, interest faded after crude oil prices stabilized, and the company did not supply any more of these systems. Nonetheless, Meidensha continued with its research, because its engineers were convinced that the day would come when the system would be needed again. Almost 20 years later, their prediction has been borne out. Against the background of an increasingly serious global environmental and energy crisis, there has been a resurgence of interest in a system that effectively utilizes livestock manure—whose disposal can be a major problem—to produce energy. The enforcement of new regulations on manure disposal was another contributing factor, explains Professional Engineer and Manager of Meidensha’s Product Planning Section, Yoshiaki Arai, who has been involved in developing the system from the beginning: “From November 2004, when the Law on Promoting Proper Management and Use of Livestock Excreta came into force, it became illegal to store livestock manure in open-air stacks or uncovered pits because of the risk to the environment and to public health. It is a tough law that charges offenders a maximum ¥500,000 (close to US$5,000) fine, and consequently, manure disposal has become a real headache for farmers.”

	Village Without Electricity Lights Up
	Running and maintaining the system is costly for farmers—a pressing problem especially for the small farmer, whose economic and human resources are limited. About half of Japan’s pig farmers are small operations with 500 or fewer animals. Meidensha thus developed a trouble-free system based on a simple process that was easy to use on small farms. “Farmers have no choice but to pay a certain amount for manure disposal, but the disposal process of this system generates energy like gas or electricity, and the farm can also sell the compost produced. With the obvious environmental benefits on top of that, we think the system offers many advantages to farmers. Our next challenge is to reduce costs still further,” says Arai. Meidensha is also running a trial at a pig farm in the same locality as the system with around 1,000 animals, although these trial systems use micro-turbines instead of fuel cells. Overseas, the company is running trials at a beef farm in Cambodia with around 1,000 animals. The farm is in a district with no central electricity service, and the company has delighted local residents by supplying electricity generated by biogas to 120 local households and farms. Cattle produce 10 to 20 times more manure than pigs, which means far more electricity is generated. Arai says the company is receiving inquiries from overseas as well as across Japan, and anticipates growth in global demand in the years ahead.	Yoshiaki Arai, Professional Engineer and Manager of Product Planning Section, Meidensha