Sustainability opportunities through small scale rice husk generators

Rice cultivation is widespread in the world, covering about 1% of the planet's surface and involving about a fifth of the world population. During the processing of rice, its husk (the outer part of the grain) is produced as a by-product. The use of this organic waste varies depending on the country and farmers’ traditions: in the best cases, rice husk is used as a fertilizer or for feeding animals; on the contrary, most of the times it is burned in open air or abandoned and left to ferment, which is not an environmentally sustainable behavior. In some cases, however, the farmers delivers the paddy rice to the rice mill for processing, together with the husk. This opens the door to the exploitation of rice husk as a fuel: indeed rice husk can be used for fuelling gasifiers for electric power generation. A literature review showed that there are two typical sizes of gasification plants fuelled with rice husk: small, with less than 100 kW power, and large, well over one megawatt power. The first are mainly spread in India while the latter are reported in Thailand, Vietnam and Malaysia. The purpose of this work is to set an appropriate assessment of the sustainability of medium-sized plants in China. In particular, we show which factors should be considered in assessing the economic sustainability and which techno-economic variables are crucial. Finally, we also present the major environmental and social benefits that could result from a greater diffusion of medium-sized rice husk power plants in rural communities.