Poplars as Biofuel — But at What Cost?

poplartree1.jpgIt seems like poplar trees can do everything these days. In addition to naturally absorbing carbon dioxide for us, they’ve been genetically modified to remediate soil. Now, the New York Times reports that North Carolina State researchers have created a poplar variety with 50 percent less lignin, which could make them suitable feedstock for the commercial production of cellulosic ethanol.
Cellulosic ethanol is made by knocking down plants’ cell walls and turning the resulting rubble into sugars, which are then turned into fuel. Depending on the chemicals present in the plant, that process can be harder (i.e. more expensive, less green) or easier. More of the enzyme amylase, for example, makes the process easier. Lignin, which makes cell walls stronger, makes the process harder.
There’s little doubt that less lignin would make the cellulosic process easier, but from a lifecycle perspective, it raises serious questions. Here’s why: Lignin exists in trees to help protect them from pests and fungal infection. If you reduce the amount of lignin, you leave the trees more exposed, which could mean they would need to be grown in greenhouses or administered additional pesticides.

As the NYT quoted a Canadian wood science professor as saying, “Nature would have selected for lower-lignin trees if they could survive.”
On the other hand, the article points out that because so few field tests have taken place, it’s hard to know how lower-lignin trees will respond to real conditions.
A startup is also featured in the article, South Carolina’s Arborgen. A $60 million joint venture created back in 2000 by Rubicon Industries, MeadWestvaco (MWV) and International Paper (IP), the company wants, and for now appears, to be the leader in genetically modified trees. Its first products will be transgenic eucalyptus trees, engineered to have about 10 percent less lignin.
All efforts to grow GM trees at scale will face fierce opposition from the anti-GMO crowd. While the main opposition to transgenic plants is centered in Europe, trees’ long life and symbolic importance could mean that the introduction of their transgenic versions would face a tough climate, even in North America. Thus far, the only commercial-scale GM tree-planting occurred several years ago in China. And, true to form, they were also poplars.