Producing Biofuels from Woody Plants With No Waste

Dr. Ratna Sharma-Shivappa helped develop a new way to free the carbohydrates from the lignin in some forms of biomass.
Researchers at North Carolina State University have developed a more efficient technique for producing biofuels from woody plants that significantly reduces the waste that results from conventional biofuel production techniques.

“The technique could open the door to making lignin-rich plant matter a commercially viable feedstock for biofuels, curtailing biofuel’s reliance on staple food crops,” says Dr. Ratna Sharma-Shivappa, associate professor of biological and agricultural engineering.

Traditionally, to make ethanol, butanol, or other biofuels, producers have used corn, beets, or other plant matter that is high in starches or simple sugars. However, these crops are also significant staple foods.

Other forms of biomass – such as switchgrass or inedible corn stalks – can also be used to make biofuels, but they pose their own problem. Their energy potential is locked away inside the plant’s lignin – the woody, protective material that provides each plant’s structural support. Breaking down that lignin to reach the plant’s component carbohydrates is an essential first step toward making biofuels.

At present, researchers exploring how to create biofuels from lignin treat the plant matter with harsh chemicals that break it down into a carbohydrate-rich substance and a liquid waste stream. These carbohydrates are then exposed to enzymes that turn the carbohydrates into sugars that can be fermented to make ethanol or butanol. This technique often results in a significant portion of the plant’s carbohydrates being siphoned off with the liquid waste stream.

By exposing the plant matter to gaseous ozone, with very little moisture, the NC State researchers are able to produce a carbohydrate-rich solid with no solid or liquid waste. Sharma-Shivappa notes that the process itself is more expensive than using a bath of harsh chemicals to free the carbohydrates, but is ultimately more cost-effective because it makes more efficient use of the plant matter.

“Our eventual goal is to use this technique for any type of feedstock, to produce any biofuel or biochemical that can use these sugars,” Sharma-Shivappa says.

(North Carolina State University)

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