Machine Design

Ethanol from trees?

Researchers at the SUNY College of Environmental Science and Forestry (ESF) have invented a method that may eventually let them synthesize ethanol from wood.

This process could one day make it possible to develop agricultural feedstocks for ethanol production.

The process is the work of Dr. Thomas E. Amidon, chair of the college's Faculty of Paper Science and Engineering. Amidon's process is a way of removing energy-rich sugars from wood. Once fermented, the sugar xylan can produce ethanol, which can be used in cars instead of, or in combination with, traditional gasoline.

Polysaccharide (sugar) cellulose is the most widely consumed component of woody plants. In the context of a paper mill, cellulose becomes pulp for use in making paper. The second largest component of hardwood trees is the polysaccharide xylan, which is primarily dissolved in the pulping process.

Although the energy factor is the focus of attention now, there is a second benefit to the process. In addition to extracting sugar, scientists can separate out the wood's acetic acid, which is used to manufacture polyvinyl acetate, a plastic used in many aspects of home construction. It is also used to make many other consumer products. The commercial value of acetic acid is nearly three times that of ethanol: 45 cents/lb as opposed to 18 cents/lb. One advantage to the process is it uses no harsh chemicals. "Water is my preferred solvent because if it gets loose in the world, the world knows how to deal with it," says Amidon.

The watery solution that remains after the chips are removed is then forced through a membrane that separates the sugars from the water. The acetic acid is removed the same way.

The work, while still in the testing phase, has received support from International Paper, the world's largest paper company, and from Lyonsdale Biomass, a wood-fueled energy producer.

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