Amount, availability, and potential use of rice straw (agricultural residue) biomass as an energy resource in Japan

This paper discusses the use of agricultural residue in Japan as an energy resource, based on the amounts produced and availability. The main agricultural residues in Japan are rice straw and rice husk. Based on a scenario wherein these residues are collected as is the rice product, we evaluate the size, cost, and CO2 emission for power generation. Rice residue has a production potential of 12 Mt-dry year−1, and 1.7 kt of rice straw is collected for each storage location. As this is too small an amount even for the smallest scale of power plant available, 2-month operation per year is assumed. Assuming a steam boiler and turbine with an efficiency of 7%, power generation from rice straw biomass can supply 3.8 billion(kW)h of electricity per year, or 0.47% of the total electricity demand in Japan. The electricity generated from this source costs as much as 25 JPY (kW h)−1 (0.21 US$ (kW h)−1, 1 US$=120 JPY), more than double the current price of electricity. With heat recovery at 80% efficiency, the simultaneous heat supplied via cogeneration reaches 10% of that supplied by heavy oil in Japan. Further cost incentives will be required if the rice residue utilization is to be introduced. It will also be important to develop effective technologies to achieve high efficiency even in small-scale processes. If Japanese technologies enable the effective use of agricultural residue abroad as a result of Japanese effort from the years after 2010, the resulting reduction of greenhouse gas emission can be counted under the framework of the Kyoto Protocol.