Hiroshima to pioneer Japanese bio-coal

Hiroshima bio-coal plant converts treated sewage sludge via torrefaction, a mild pyrolysis, into dense renewable fuel for J-Power, enabling coal co-firing, lower CO2 emissions, higher energy density, and efficient biomass-to-energy supply chains.

Japanese coal mining has been on the decline since the 1980s. Poor quality, limited domestic availability, difficult mining conditions, and cheap imports have driven coal mining underground.

However, with the world trending toward green energy, Japan might have a chance to up domestic coal production again, as utilities like TEPCO wood-waste co-firing explore blended fuels, and the city of Hiroshima is taking a step in that direction.

The city of Hiroshima has awarded Electric Power Development Company Limited J-Power a contract to construct a grassroot bio-coal production facility adjacent to a neighboring sewage treatment center. According to project plans, treated raw sewage sludge will be transported to the bio-coal production facility to be dried and undergo torrefaction, which is a mild form of pyrolysis. J-Power began releasing bid documents this month and plans to begin construction later in the year.

Once complete and operational in the next fourth quarter, the US $107 million bio-coal facility is anticipated to produce 4,490 tonnes of burnable fuel bio-coal annually to be sold to J-Power as utilities pilot low-emissions coal plants across Japan.

Bio-coal is very similar to charcoal and is a much more efficient fuel source than straight biomass, having almost twice the energy output of sawdust pellets. The torrefaction process, in which collected biomass is heated and compressed, allows for a greater fuel quality and provides a bio-coal that has the same equivalent energy output as fossil coal. Fossil coal burning plants are a huge source of CO2 emissions; however, emissions could be greatly reduced through the use of bio-coal, while advances in coal gasification also contribute to lower emissions, which meets renewable fuel and CO2 emissions standards.

Biomass to energy via torrefaction is 80 more efficient than converting biomass to bio-fuels like ethanol, according to some studies. Using torrefaction is highly resource-efficient during the torrefaction process, 10 of the original biomass' energy is lost.

However, that 10, which is composed of volatile matter, is recycled to provide heating during the process itself. The resulting material can be further densified into briquettes or pellets to be used in various markets, including power generation with new boiler technology integration, steel production, and decentralized heating.

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