Thermal Power Generation from Sewage Sludge

Japan's Electric Power Development Co., known as J-POWER, plans to start carrying out tests on power generation through combustion of coal mixed with sewage sludge at the Matsuura Thermal Power Station in Nagasaki Prefecture in August 2003. This will be the first attempt in Japan to use dried sewage sludge, or biosolids, as fuel at an electric utility thermal power plant.

Biosolids are made by blending waste cooking oil with sludge discharged from sewage treatment plants under reduced pressure and then heating the mixture to around 100 degrees Celsius. Through this process, the mixture turns into a granular coal-like fuel containing about five percent moisture, with a heating value of 21,000 to 25,000 kJ/kg (5,000 to 6,000 kcal/kg). Preliminary co-firing tests using a small test boiler have demonstrated that the mixture of coal and biosolids can be suitable as a fuel for coal-fired power plants. Under the tests that are to be conducted at the Matsuura power plant, coal mixed with an average of 0.07 percent biosolids (a maximum of one percent) will be burned as fuel. The tests are scheduled to start in late August, lasting for a year.

In Japan, a total of 75 million tonnes of sludge (two million tonnes on a dry basis) is generated by sewage treatment plants annually, accounting for about 18 percent of the total domestic industrial waste. Most local governments are disposing of sewage sludge by means of incineration, fusing, composting, or landfill. Of the sludge, no more than 60 percent is effectively used, and the remainder is buried in landfills.

If sewage sludge can be recycled as an alternative energy source (a biomass energy source) that can replace fossil fuel for coal-fired power plants, the sludge will be effectively and consistently used in the long term. This attempt is thus expected to contribute to establishing a recycling-based society and protecting the global environment.



Posted: 2003/09/27 11:51:58 AM
Japanese version