The Power of Poplar, the Biofuel Tree

But it seems that poplars, despite my parents’ insistence to the contrary, could turn out to be very useful someday. Since the first fuel shocks of the 1970s, Jon Johnson, currently a researcher at Washington State University, has been studying the near-ubiquitous tree, also known as cottonwood, as a biofuel resource to combat both high gasoline prices and global warming.

Poplars do exhibit some very desirable biocrop traits: they grow quickly, reaching maturity (70-80 feet high and 10 inches across) in six years. They’ve also shown the ability to grow in some fairly poor soils, and with minimal attention, and energy can be processed from them at cellulosic ethanol plants through a process that, not accounting for energy from fossil fuels, releases no additional carbon dioxide. 

Perhaps it’s this potential that has landed Johnson, along with partner firms ZeaChem and GreenWood Resources, a $583,000 federal grant for his continued study of the poplar tree as an energy source. “Wet chemistry is real expensive to analyze samples, and it takes months,” Johnson said. “It will run to $150 a sample, and you can see if you have only 100 samples, it is way beyond budget. The spectrography can be done in seconds, and it will give you a variety of readings.” Though methods such as these, Johnson and the two companies hope to find the most suitable poplar hybrids and extract energy from them.

While I like the use of this non-food crop for biolfuel research, I do have some reservations about the poplar project. The plants must still be cultivated on a large scale, requiring some form of mechanized agriculture.  This is especially pertinent considering that out every thousand plants grown, only “two or three might show hybrid vigor” and be grown to maturity. While it might not create the same footprint as the massively industrialized corn ethanol process, there’s still plenty of carbon involved the in the creation of poplar ethanol to be accounted for. 

Additionally, fully-grown trees are a tremendous carbon sink. Carbon impact reduction through reforestation is one of the few facets of global warming mitigation in which the US is currently a world leader.  Gains made in harvesting the plants for fuel now need to be weighed against the carbon reduction that the plant might account for over a lifespan that can reach upwards of 50 years.

Still, on many important fronts, poplars represent an exciting new potential biocrop, with a mature plantation yielding three times the ethanol per acre of an industrial corn crop.  Combined with a still-reduced carbon footprint, and with a very limited impact on the global food supply, poplar ethanol may yet play an important role in determining America’s green energy future. 

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Photo by Flickr user Dano