Energy from wood

US researchers have invented a method for removing energy-rich sugars from wood, a process that could help provide local feedstocks for ethanol production.

Researchers at the Syracuse, NY-based SUNY College of Environmental Science and Forestry (ESF) have invented a method for removing energy-rich sugars from wood, a process that could help provide local feedstocks for ethanol production.

The process for separating wood into its components was developed at ESF by Dr. Thomas E. Amidon, chair of the college’s Faculty of Paper Science and Engineering.

Chief among the components of wood is cellulose, a polysaccharide (sugar). 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.

“The real value in that sugar,” Amidon said, “was never exploited. Once fermented, the sugar xylan can produce ethanol, which can be used in cars instead of, or in combination with, traditional gasoline.”

In addition to extracting sugar from the wood, scientists can separate out the wood’s acetic acid, which is used primarily in manufacturing. A major use of acetic acid is the manufacturing of polyvinyl acetate, a plastic used in many aspects of home construction, and many other consumer products. The commercial value of acetic acid is nearly three times that of ethanol: 45 cents per pound as opposed to 18 cents per pound.

The process was developed in ESF’s Walters Hall, home to the Faculty of Paper Science and Engineering. In the process, ordinary wood chips are mixed with water and heated at high temperatures for a specified length of time. That time can be shortened if the chips are first subjected to biopulping, a process that allows natural wood-decaying fungi to munch through the lignin that binds the cellulose in the wood.

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-fuelled energy producer in Lyons Falls.

In addition, the ESF team has demonstrated the process for scientists from the National Renewable Energy Laboratory in Colorado.

The process is not choosy about which hardwood trees it uses. Maples work, but so do the willow biomass crops that are being developed by ESF researchers and their colleagues as a commercial crop for energy uses, such as at the Lyonsdale facility.

“If you consider the concept of removing sugars and acetic acid from willow biomass and then burning or gasifying what’s left over from that process, the economics of growing willow as an energy crop are significantly improved,” Amidon said.

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