As cellulosic ethanol becomes more and more a front-runner to help reduce the country’s “addiction to oil,” the high cost of producing it still stands as one of the major hurdles. But now, Baylor University researchers have identified about 40 different compounds created in the pre-treatment step when making cellulosic ethanol that could be responsible for restricting the fermenting process, which ultimately leads to higher production costs.
“We screened for 40 compounds, like phenols and organic acids, and they were all present,” said Dr. Kevin Chambliss, an assistant professor of chemistry at Baylor who is a co-lead investigator. “We chose these certain 40 compounds because they are believed to be inhibitory, but there could be more compounds involved.”
While conventional ethanol and cellulosic ethanol are essentially the same product, the two are made from different feedstocks. Conventional ethanol is produced from grains such as corn and wheat. Cellulosic ethanol is made from the non-food portion of many agricultural wastes. One of the more common wastes used is corn stover, which are the stalks and residue left over after harvest. Researchers said there has been a recent emphasis on learning more about cellulosic ethanol because agricultural wastes are mostly an untapped resource.
The research results mark the first time these 40 compounds have been quantitatively measured in different process streams. Researchers conducted the pre-treatment step on corn stover and poplar eight different ways, varying pH levels, temperature, salt concentrations and how long the batch is “cooked.”
Researchers said perhaps the most interesting finding is that as they varied the pre-treatment process, levels of compounds also changed. This means that it might not be necessary to totally remove an inhibitory compound.
“If you can identify a pre-treatment condition that maximizes sugar production, yet minimizes inhibitor production, that could increase efficiency better than just removing the compound,” said Dr. Peter van Walsum, an associate professor of environmental studies at Baylor and co-lead investigator.
Chambliss and van Walsum said they also came across some surprises. For instance, concentrations of certain compounds seemed to increase when temperatures were increased, but the concentration also increased at reduced temperatures when reactions were conducted for longer periods of time. They are still investigating why, exactly, this occurred.
Researchers will also test a softwood feedstock – douglas fir – in the coming months.
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