Biorefinery processes convert biomass into energy and chemicals. In New York, where wood is a plentiful, Shijie Liu, a professor of paper and bioprocess engineering at the SUNY College of Environmental Science and Forestry, has been working to optimize production of biofuels such as ethanol and butanol.
Ethanol is made by a late step in processing, when sugars present in wood are fermented. “It’s a mix of six sugars,” Liu says, including glucose, mannose, and xylose.
Liu has been exploring ways to separate these different sugars, because the efficiency of fermentation could be improved. At the same time, he realized that sugars themselves might be marketable end products.
“We’re looking at the five-carbon sugar xylose,” Liu says. (Glucose and the others are six-carbon sugars.) “They have market value and are used to make the sweetener xylitol.”
Xylitol is used in gum and candies. Xylitol is also used to make cookies in East Asia, but is not used widely in the US. Humans don’t digest five-carbon sugars well, so it’s a natural, low-calorie sweetener.
Liu has a $250,000 grant from the New York State Energy Research and Development Authority to develop a process to recover xylose from wood.
The process begins by extracting woody biomass such as sugar maple wood and willow, although Liu plans to try other sources, such as mixed hardwoods and agricultural residues such as corn stalks. Next, the material gets digested, separated, hydrolyzed to capture the sugars.
Liu points out a plot twist. In recent years, growing cereal grains as an energy source has been criticized for impinging on food production resources. “What we’re looking at is using wood, an energy crop, as the source of a food additive.”
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