Sustainability: Energy, Environment, Food, Economy

Researchers at DOE’s National Renewable Energy Laboratory (NREL) and ethanol producers are racing to come up with ways to make ethanol from cellulosic biomass that are cheaper and easier to produce than current methods. But they are hitting a wall. Cell walls in plants are making the production of cellulosic ethanol a challenge. So researchers are creating their own computer program to help model and break down the tiny fibers of cellulose — or fibrils — found in plant cells.

Cellulosic biomass contains sugars that are much harder to get at because the plants use these tougher plant cells as structure to hold up the plant. NREL’s Antti-Pekka Hynninen is part of a team creating their own computer program to help model and break down the cellulose fibrils found in plant cells.

“To reduce the cost of cellulosic ethanol we must understand how to break down the plant cells into the sugars needed to make ethanol,” NREL Researcher Antti-Pekka Hynninen said. “The cellulose fibrils of these plants are very long so we use computer modeling to see how we can break them apart.”

NREL researchers typically study cellulose fibrils that are 500 to 1,000 glucose units long and figure out the easiest way to bust them apart. However, these fibrils are too large to study using current computer models.

“Right now the technique is to consider each atom in each fiber, which is not practical using existing computers,” Principle Scientist Mark Nimlos said. “We need to group atoms into beads, or larger grains.”

Hynninen hopes to overcome the problem presented by such large molecules by building a simpler “coarse-grained” computer model of cellulose fibrils. In the new approach, multiple atoms (typically 3 to 7) are grouped into a single spherical bead. The coarse-grained model is then built up from these beads. The new model is expected to allow computer simulations that are 10 to 100 times faster.

Next steps for the program officially titled “Meso-Scale Computational Modeling of Polysaccharides in Plant Cell Walls” are to validate the model and publish the work done at NREL so this type of modeling can be used in other areas.
“I believe this same method could be used for other systems and they don’t have to be cellulosic or proteins — there’s a potential for many uses.” Hynninen said. — Heather Lammers