A joint research team led by Professor Takeshi Sako at the Graduate School of Science and Technology Research (Energy System Section), Shizuoka University, announced on April 8, 2008, that it has developed a new technology for clean incineration of biomass waste. The method, studied by researchers from government, industry, and academia, treats biomass with high-temperature and high-pressure steam called "subcritical water," and then recovers heat from the combustion process and inorganic residue for further utilization. It's drawing attention as the world's first low-cost, clean incineration method to treat biomass waste.
In the system, livestock excrement is incinerated with air in the first reactor containing water in a subcritical state at around 400 degree Celsius and 10 megapascals (Mpa). Thermal energy generated from the combustion is recovered for further utilization, while the ammonia is decomposed in the second reactor filled with a catalyst. When one ton of livestock excrement is processed, which includes 0.8 tons of moisture, the thermal energy equivalent to that of 42 liters of heavy oil is gained, which equates to a reduction of approximately 34 kilograms of carbon dioxide emissions.
In Japan, biomass waste such as food waste, sewage sludge, livestock excrement, and agricultural waste amounts to 240 million tons each year, 75 million of which is left untapped. The new method can safely process perishable and bad-smelling biomass waste having a high water content, and completely decompose it into harmless water, carbon dioxide, nitrogen, and inorganic residue as materials for use as fertilizer. Besides these advantages, the recovered heat energy can be used for power generation and heating.
The researchers aim to achieve practical application of the technology in a few years and start selling plants with a processing capacity of one to five tons per day at an initial cost of about 100 to 200 million yen (U.S.$952,000-1,904,000). They are also trying to lower operational costs to make the system more affordable for local municipalities, organizations such as agricultural cooperatives, and other factories.
- Shizuoka University official site