Improved Reaction Data Heat Up the Biofuels Harvest

Aug 06, 2008
Improved Reaction Data Heat Up the Biofuels Harvest
New NIST research results are a step toward more efficient production of cellulosic ethanol, a biofuel that can be made from corn-harvest leftovers—stalks, husks, leaves—and the inedible parts of other plants as well as a diverse array of abundant non-food plants such as switchgrass. Image: NREL photographer, Jim Yost

High food prices, concern over dwindling supplies of fossil fuels and the desire for clean, renewable energy have led many to seek ways to make ethanol out of cellulosic sources such as wood, hay and switchgrass. But today’s processes are notoriously inefficient.

In a new paper, researchers at the National Institute of Standards and Technology (NIST) have detailed some of the most fundamental processes involved in extracting sugars from biomass, the first step in producing ethanol by fermentation. Their findings should help engineers to improve their process designs in order to extract the maximum amount of fuel from a given measure of biomass.

Most of the ethanol produced in the United States is created by fermenting the sugars and starch found in corn. The capability to convert inedible plants and agricultural waste into usable sources for ethanol production will help to supplement alternatives to fossil fuels while reducing the diversion of food crops to energy uses.

Glucose can be extracted from two substances found in most plants: cellulose, the long molecule chains that comprise the cell walls of green plants, and its flimsier cell-wall counterpart, hemicellulose. The extracted glucose is then easily converted by fermentation to ethanol. NIST researchers, in collaboration with the National Renewable Energy Laboratory in Golden, Colo., have defined the theoretical limits of reactions important to cleaving, or breaking apart, cellulose and hemicellulose to produce glucose. They also determined that the energy needed to rupture these key bonds is a constant value for each molecular bond that is broken during the cleavage reactions.

According to Yadu Tewari, Brian Lang and Robert Goldberg, chemists at NIST and co-authors of the paper, cellulose and hemicellulose both present problems to would-be ethanol producers.

“Cellulose and hemicellulose are recalcitrant,” Goldberg says. “They don’t want to break down. It takes a long time for wood to rot. It even takes termites a long time to break wood down, and they’re pretty good at it. Ethanol producers face the same problem. Because of the way these molecules are arranged, it’s difficult to get access to the reactive centers in wood and other biomass. What we have done is to study some of the most basic reactions associated with the breakdown of these materials.”

With enzymes to speed the reactions, the team used calorimetry and chromatography to measure the thermodynamic property values of several reactions associated with the breakdown of cellulosic and hemicellulosic substances. Because process design and bioengineering benefit from the availability of these values, the data obtained in this investigation represent a “small but significant step toward maximizing the efficiency of biomass utilization,” Tewari says.

Citation: Y.B. Tewari, B.E. Lang, S.R. Decker and R.N. Goldberg. Thermodynamics of the hydrolysis reactions of 1,4-ß-D-xylobiose, 1,4-ß-D-xylotriose, D-cellobiose, and D-maltose. Journal of Chemical Thermodynamics. Available online at dx.doi.org/10.1016/j.jct.2008.05.015 .

Provided by NIST

Explore further: Scientists find clues to cancer drug failure

add to favorites email to friend print save as pdf

Related Stories

United Airlines won't accept rechargeable battery shipments

1 hour ago

Citing safety concerns, United Airlines on Monday became the second major U.S. airline to announce it will no longer accept bulk shipments of rechargeable batteries of the kind that power everything from smartphones to laptops ...

Recommended for you

What causes the sunlight flavour in milk?

12 hours ago

Most of us have tasted milk that has been left in the sun – it has a distinctive off-flavour. The reason is that milk and other dairy products turn rancid when exposed to light.

Scientists find clues to cancer drug failure

Mar 02, 2015

Cancer patients fear the possibility that one day their cells might start rendering many different chemotherapy regimens ineffective. This phenomenon, called multidrug resistance, leads to tumors that defy ...

Smart crystallization

Mar 02, 2015

A novel nucleating agent that builds on the concept of molecularly imprinted polymers (MIPs) could allow crystallographers access to proteins and other biological macromolecules that are usually reluctant ...

Supersonic electrons could produce future solar fuel

Mar 02, 2015

Researchers from institutions including Lund University have taken a step closer to producing solar fuel using artificial photosynthesis. In a new study, they have successfully tracked the electrons' rapid transit through ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.