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  5. 3. Improving bioethanol purity

Natural Energy

3. Improving bioethanol purity

Improving bioethanol purity

Bioethanol as a petroleum fuel alternative

Bioethanol is a fuel derived from plant resources such as sugar cane and corn. Bioethanol can be mixed with gasoline as an alternative vehicle fuel, thereby reducing consumption of fossil fuels such as petroleum. Bioethanol also helps to reduce CO2 emissions. Brazil has been one of the strongest adopters of bioethanol fuels, followed by Europe and the United States. In Japan, bioethanol production using domestically sourced resources is underway in Hokkaido, Niigata and Osaka, with widescale adoption of bioethanol fuel expected in the near future.

Dehydration at the final stage of bioethanol production

Input materials such as sugar cane have a high water content, and must be distilled to about 95% concentrate in order to produce fermented ethanol at 10% concentration.
Ethanol must have a purity of at least 99.5% to be used as a fuel. Dehydration is used to boost the purity further.

Bioethanol fuel production

Hitachi Zosen's dehydration system delivers world-class purity

Dehydration can be achieved in a variety of different ways. Hitachi Zosen has developed a zeolite membrane dehydration system based on the low-energy membrane separation process.
The zeolite membrane has microscopic pores measuring approximately 4 angstrom (1 angstrom = 0.00000001 cm) through which only water molecules are able to pass, leaving the ethanol on the other side.
The dehydration system developed by Hitachi Zosen employs a combination of azeotropic distillation and adsorption to reduce energy consumption by 20% - 30% relative to other dehydration systems. It is also more than twice as fast as conventional membrane dehydration, delivering a significant boost to the overall efficiency of bioethanol production.
Hitachi Zosen’s zeolite membrane dehydration system was chosen for Japan’s largest bioethanol production plan at Tokachi in Hokkaido prefecture (annual production capacity 15,000 kl), which was completed in 2009.

Zeolite membrane separation (dehydration)

Producing bioethanol from non-food resources

Bioethanol is promoted as a solution to global warming, but increasing demand for sugar cane and corn for bioethanol production may have the unintended effect of pushing up food prices and even causing food shortages.
Manufacturers and researchers are now starting to explore ways to produce bioethanol from non-food resources such as lumber waste, rice straw and kitchen scraps.