25 Oktober 2006

Ethanol by-product being researched as an adhesive

Paul Weimer, a research microbiologist at the USDA’s Agricultural Research Service Dairy Forage Research Center and an associate professor at the University of Wisconsin-Madison, believes the fermentation leftovers from producing cellulosic ethanol may be valuable as a wood glue.

The glue-like substance, called glycocalyx, results from organisms sticking to cellulose fibers during the biomass-to-ethanol process. The organisms take the place of the yeast used in the traditional corn-to-ethanol process.

It was while doing parallel research into a bacterium that produces a fiber-degrading enzyme within the digestive organs of livestock animals that it first occurred to Weimer and his research team that they might be onto something.

After fermentation, the glycocalyx worked so effectively at holding organisms to cellulose material that Weimer found he couldn’t get the glue off of the fibers without destroying the glue, he said. So he took the entire fermentation mixture—consisting of the glue, the bacteria and the remaining cellulosic biomass—and used it as an adhesive to make plywood.

“We were aware that biobased adhesives, when you get them wet, the material tends to fall apart,” Weimer said. “Here is an organism that grows in a liquid environment, and we thought maybe it makes a good adhesive.”

Unfortunately, Weimer found that when used as a stand-alone product, the glue did fall apart when it got wet. However, when mixed with a commonly used petroleum-based resin—another adhesive substance—it was able to replace up to three-fourths of the resin and still have the same holding strength.

There are additional benefits if cellulosic ethanol is produced using the bacteria with fiber-degrading enzymes, according to Weimer. There would be no need to purchase costly enzymes, all processes could be done within one reactor (consolidated bioprocessing), the inhibitors generated by yeast and the liquid waste stream would be eliminated, and there would be no need for pretreatment. Ultimately, all these factors would reduce the cost of production of both the ethanol and the glue by-product, Weimer said.

Although the glue has potential, it has a number of hurdles before it can be used mainstream, he added. The No. 1 problem is the extreme viscosity of the substance. It does not pass through a glue gun easily and would have to be more easily applied to be practical for commercial use. Secondly, a much larger scale of production is needed. Finally, formulations that incorporate the bio-based glue into other types of adhesive mixtures must be developed.

The project is still in the basic research and development phase. Weimer and his research team have sent in applications for funding to keep pushing the project forward, but the speed of development of the glue largely depends on what happens with the production of cellulosic ethanol, Weimer said. Millions of dollars are being invested in the research of consolidated bioprocessing. With the attractive added value Weimer’s glue could provide, consolidated bioprocessing could be realized in a matter of a few years rather than a few decades, he said.

(Cf. news of Sept. 28, 2006.)

Source: Ethanolproducer Oct. 18, 2006.

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