Researchers find easier, lower-cost way to break down plants

Source: Amanda Peterka, E&E reporter • Posted: Thursday, January 9, 2014

Researchers at North Carolina State University say they’ve discovered a new way to break down plant materials, a development that could lower production costs for advanced biofuels.

Their method uses liquid salts to extract lignin — the tough parts of a plant that protect cell walls — from farm residues and grasses. Unlike in prevailing methods for breaking down plants, liquid salts can be used at lower temperatures and be almost fully recovered after the process.

“Finding inexpensive ways to remove lignin is one of the largest barriers to producing cost-effective biofuels,” said Ezinne Achinivu, a chemical and biomolecular engineering researcher at North Carolina State. “And our approach is very promising.”

The researchers manufactured the liquid salts, which are known as protic ionic liquids, by combining acetic acid — the main component of vinegar — with amines, which are derivatives of ammonia.

The protic ionic liquids were then added to stalks, leaves and other parts of the corn plant that are left on the field after harvest. The lignin in the plant materials dissolved into the liquid salt solution, leaving a sugar-rich material that is used in the production of cellulosic biofuel.

The researchers were able to separate the liquid salt-lignin mixture into its components, leaving the protic ionic liquids available for future use. The lignin is valuable to biofuel producers as a co-product that can be burned for power.

Achinivu said that the technique could be easily scaled up and is “likely to be both more energy-efficient and less expensive than existing biomass pretreatment techniques for removing lignin.” Existing techniques involve high heat and the buildup of residues that make it difficult to recover components for future use.

Research results are posted online and will be published this year in Green Chemistry, a journal of the Royal Society of Chemistry. The U.S. Air Force Office of Scientific Research funded the research.