Genetically Engineered Trees as Biofuel Feedstock

[Now that corn ethanol has fallen out of favor politically, the bioenergy industry will be focusing more and more on forests.]

- by Alex Maragos, November 28, 2014, WLFI

[[{"type":"media","view_mode":"media_large","fid":"323","attributes":{"alt":"","class":"media-image","height":"480","style":"width: 330px; height: 392px; margin: 3px 10px; float: left;","width":"404"}}]]Ethanol made from corn already powers millions of cars and trucks on the road, but a group of researchers at Purdue University wants to make biofuel better. Since corn ethanol affects the food supply, this group creates fuel from something nobody eats — trees.

The quest to make better fuel involves several professors and students from the school’s chemical engineering and forestry departments. Every step of the process to make fuel from wood is carefully calculated and tested, starting with the type of tree the researchers need.

Poplar trees grow on three acres at the recently dedicated Richard G. Lugar Forestry Farm at Purdue. These trees are not rare, but this group is one of a kind. They were born in a lab by Purdue forestry professor Rick Meilan. He crossbred different strains to come up with the trees that would resist disease, grow fast and potentially produce the most fuel.

“We can genetically engineer it relatively easily,” Meilan said while walking among the nearly 2,000 poplars he planted. “Ten or 15 years from now we’ll be able to utilize these trees as a biomass source for making ethanol. So rather than relying exclusively on corn for making ethanol to use as a fuel, we’ll be able to use the sugars in the walls of these trees.”

Meilan sends tree samples to the chemical engineers, so they can be run through a custom made reactor. The reactor was built by a team of chemical engineers. In that reactor, which is slightly larger than a refrigerator, the team can create a small amount of fuel from the raw biomass.

“We all sat down and thought of the process — which if we could break down the biomass into smaller molecules at high temperature and immediately remove the oxygen, then we could collect liquid product which would be very valuable,” said professor Rakesh Agrawal. His team said it can take virtually any biomass and turn it into fuel, but poplar wood is among the best materials — along with switchgrass and corn stover, which is left over from the harvest.

“Give us any biomass, and we’ll give you the liquid,” said Agrawal.

The technology gives hopes to a burgeoning biofuel industry. The biggest barrier to widespread biofuel use continues to be cost, especially at a time when it is forced to compete with falling oil and gas prices. However, Purdue plows ahead with research in the field, which includes an agreement with the U.S. Navy bolstering its own green efforts.

That research is similar to this work, but aims to create jet fuel from biomass. As a result, that project is much more selective about which biomass it can use. Agrawal said the biggest difference with his project is the variety of plants he can turn into working fuel. Both projects, however, face significant challenges in making enough of the fuel to test. Still, there is plenty material to test that otherwise is going to little use.

“In the U.S., we can collect anywhere from half a billion to a billion tons of biomass every year,” Agrawal said. “If we can convert all of that biomass to liquid fuel, then that much less fossil fuel would be needed.”

Though burning the fuel would create greenhouse gases much the same as gasoline does, the ability to sidestep fossil fuels is the main attraction. A “closed loop” system, meaning totally renewable with no waste, is also what keeps Meilan hopeful about his work and this project.

“We’re [burning] the fossil fuels and releasing the carbon dioxide into the atmosphere,” said Meilan. “The nice thing about these trees — sure, we’re [burning] a product that’s made from these trees — but these trees can fix the carbon dioxide that’s emitted into the atmosphere back into biomass.”