Two University of Illinois (UI) scientists have developed an economical, environmentally friendly and component recycling way of pretreating Miscanthus.  The Miscanthus plant is often pointed to as a leading raw material solution to produce ethanol and escape the corn ethanol controversy as food vs. fuel.

Giant Miscanthus Nearly Ready to Harvest. Click image for the largest view.  Image Credit: Wikipedia.

Giant Miscanthus Nearly Ready to Harvest. Click image for the largest view. Image Credit: Wikipedia.

The UI team offers some impressive results, saying their data shows promise for the separation of hemicellulose and lignin and for the preservation of cellulose. They were able to remove up to 58 percent of lignin and 91 percent of hemicellulose and preserved 90 to 99 percent of cellulose.

Hao Feng, a University of Illinois professor of food science and human nutrition who also has extensive research experience with biofuels explains, “We pretreat the biomass with switchable butadiene sulfone in the presence of water to break down the plant cell wall, which consists of cellulose, hemicellulose and lignin, the source of biofuels and value-added products.”

Feng’s new technique is a green alternative to current industry practices because the butadiene sulfone can be recovered at potentially high yields since the solvent’s decomposition gases are also the raw materials for its production. That means that butadiene sulfone can be recycled and re-used after a pretreatment.

The chemistry isn’t a new rare thing – Feng notes the commercial availability for both production and recovery of this chemical should allow for a transfer of these operations into a cellulosic ethanol plant.  Butadiene sulfone, commonly called Sulfolene is readily available and used in oil refining.

The technology compares to current chemical pretreatment process using relatively harsh conditions to break down the tough structure of grass and other biomass followed by enzymes used to release the sugars that are converted to fuels through a fermentation process, Feng explains.  “These chemicals not only produce compounds that are toxic to fermenting microorganisms, they often result in byproducts that have negative environmental impact,” he says.

J. Atilio de Frias, co-author of the study and a doctoral student in the Feng’s laboratory explains the importance of the development with, “Pretreatment is the most expensive step in the production of biofuels and chemicals from lignocellulosic biomass.”

That is just so.

According to de Frias, butadiene sulfone has the unique ability to “switch” in equilibrium to 1,3-butadiene and sulfur dioxide at relatively low temperatures, forming sulfurous acid in the presence of water.

Using this relatively inexpensive and recoverable chemical to pretreat biomass in one step under mild conditions is definitely a step in the right direction, he says.

de Frias explains further, “At temperatures ranging from 90º to 110º C, the sulfurous acid hydrolyzes hemicellulose. Then butadiene sulfone helps to solubilize lignin with most of the cellulose preserved for downstream enzymatic hydrolysis.”  The pretreatment period runs 6 to up to 30 hours.

The scientists say their data shows promise for the separation of hemicellulose and lignin and for the preservation of cellulose.  Removing up to 58% of lignin, 91% of hemicellulose and preserving 90 to 99% of the cellulose is going to be noticed in the ethanol business.  The team demonstrated that after pretreatment process all of the butadiene sulfone can be decomposed into 1,3-butadiene and sulfur dioxide enabling potential solvent reformation and separation from the solubilized xylan derivatives and lignin.

Carefully engineered the process could run quite inexpensively.

Feng says this is the first time this solvent has been successfully used as a pretreatment in biofuel production. “We look forward to its testing and adoption by biofuel manufacturers that are working with Miscanthus and other biomass crops,” he said.

Feng and de Frias’ paper has been published the Green Chemistry journal of the Royal Chemical Society.


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