Biofuel from rice

An efficient method for producing biofuel and animal feed from the same rice crop on farms has been developed by Japanese researchers.

Called ‘solid-state fermentation’, it involves packing whole rice plants into bales and adding yeast and enzymes to generate ethanol. The fuel is then drained off, leaving the plant matter to be used as animal fodder - all without the need for off-site processing.

The method shows the practical potential of an alternative to fossil fuels that does not displace food production, which has happened with ‘first-generation’ biofuels such as corn and sugarcane-based ethanol.

The fermentation of non-food sources such as straw and wood, so-called ‘second-generation’ biofuels, has been promoted as a promising alternative, but also has its limitations.

“Generally, the bottlenecks in second-generation biofuel production include the need for large facilities, bulky material transport and complicated treatment processes, all of which are costly and consume a great deal of energy,” said Mitsuo Horita from the National Institute for Agro-Environmental Sciences in Japan.

“What we’ve now demonstrated is a complete and scaled-up system which shows its potential in a practical on-farm situation … our system simply builds upon traditional processes already used by farmers for producing silage for animal feed. It results in a high yield of ethanol while producing good quality feed, with zero waste.”

Although the system Horita and colleagues developed requires a relatively long six months for fermentation, no energy needs to be supplied.

A vacuum distiller facilitated the extraction of 86% of the ethanol that accumulated in each bale or up to 12.4 kg of pure ethanol per bale - 10 times more ethanol than would result from natural silage production.

The ethanol also contained no insoluble particles and could therefore be easily dehydrated and concentrated for use as automotive fuel.

The remaining bale material was comparable to normal silage for animal feed, containing a similar amount of lactic acid and sugars, and high crude protein content.

Further studies are required, but the research shows the potential for complementary food and biofuel production at a local level by individual farmers, providing sustainable biofuel production and circumventing issues related to land-use competition.

The research has been published in Biotechnology for Biofuels.