Standard ethanol production is based on the extraction of sugars from the starch in biomass through fermentation, resulting in both ethanol and a highly viscous residue, which can contain non-extracted cellulose sugars.

Currently, researchers throughout the world are attempting to develop processes to cost-effectively extract cellulosic sugars, which would both increase the yield of ethanol production from typical feedstocks and allow a wider variety of biomass, such as forestry waste and grasses. This research also hopes to alleviate concerns about competition between food and energy crops.

However, a research microbiologist from the United States Department of Agriculture (USDA)Paul Weimer has a different view.

Weimar claims fermentation residue may be more valuable than the ethanol that can be processed from its cellulose.

“A lot of people want to do the same thing with biomass material that we've been doing with corn,” said Weimer.

“They want to hit it with enzymes to break it down into sugars, and ferment those sugars into ethanol.”

According to Weimar, the enzymes required to break down cellulose are very expensive, and requires the biomass to undergo costly pre-treatment to increase ethanol yields.

Weimar investigated the properties of the fermentation residue from ethanol and determined the organisms used to convert biomass do their job by sticking to the cellulose fibres with a glue-like substance called a glycocalyx.

“Because glycocalyx works so effectively at holding organisms to cellulose material, we found that we couldn't get the glue off of the fibres without destroying the glue. So, we took the entire fermentation mixture – the glue, plus the bacteria, plus the rest of the cellulosic biomass – and used it as an adhesive,” he said.

Working with USDA Forest Products Lab adhesive scientist Chuck Frihart, Weimar has tested the residue’s adhesive properties and believes it can be blended with phenol formaldehyde (PF), a petroleum-based adhesive widely used in the production of plywood.

Bio-based adhesives are commonly limited by poor performance in wet conditions, but Weimar’s research has indicated that a 50:50 blend of the ethanol residue with PF can overcome this obstacle, turning the ethanol by-product into a commodity and reducing the amount of petroleum used in some glue products.

Weimar said there were still a few obstacles facing bio-based adhesives: the residue needs to be thinned out to make it easier to apply, ramping up the glue production process to commercial levels, and further research into other bio-based glue blends.

The bio-based glue has the potential to drastically change the economics of ethanol production using feedstocks such as switchgrass or alfalfa, which are much less efficient than the US corn-ethanol industry.

“The PF that the fermentation process would partially replace sells for considerably more than ethanol, and the fermentation would still generate ethanol on the side," Weimar said.