Fill ‘er up with switchgrass
Here’s your weekly Science Matters column by David Suzuki with Faisal Moola.
Not long ago, the question at the pump was always, “regular or
unleaded?” Today, leaded gasoline isn’t even an option in most
developed countries. And with the need to drastically reduce our
consumption of fossil fuels, the question of the future just might be
“switchgrass or algae?”
Of course, I’m being somewhat facetious. In their raw form you
couldn’t run your car on either. However both organisms have the
potential to be made into biofuels such as ethanol or biodiesel. And
that, if done in a careful and sustainable way, could greatly reduce
the greenhouse gas emissions that cause global warming.
However, in spite of some of the hoopla about biofuels, there are
still many obstacles to overcome. Yes, you can already get ethanol
mixed with your gasoline or biodiesel mixed with your regular diesel in
many North American cities. In fact, in countries like Brazil, gasoline
is always blended with at least 20 per cent ethanol and you can easily
get 100 per cent ethanol for your car. So far, so good. But these
biofuels have problems too.
As I discussed in a column last fall, a widespread adoption of
biofuels, such as biodiesel and ethanol could cause serious damage to
the environment and provide few benefits if the crop used to make the
fuel isn’t chosen carefully. Corn, for example, is the largest source
of ethanol in the United States, but it is a poor choice for fuel
because if you do a life-cycle analysis (looking at all the energy
needed to make the stuff), the energy obtained from corn-based ethanol
is only marginally better or worse than the energy you get out of it.
Plus, corn is heavily reliant on fertilizers and pesticides.
Thankfully, there are plenty of other options. Canola does better in
a lifecycle analysis, for example, and sugar cane – which is where
Brazil gets its ethanol from – better still. However, sugar cane
requires a hot climate and there are concerns that displacing Brazilian
subsistence farmers to grow sugar cane will push them into slashing and
burning the rainforest for cropland. So all biofuels still have an
environmental, economic or social cost. If these fuels are to be
sustainable, such costs need to be minimized.
One promising biofuel that scores well in preliminary studies is
cellulosic ethanol made from switchgrass. According to results of a
recent study published in the prestigious journal Proceedings of the
National Academy of Sciences, switchgrass grown and managed for biofuel
can produce 500 per cent more renewable energy than the energy it needs
to be grown and processed.
For the study, researchers conducted field trials (the first for
switchgrass) over five years on 10 farms in the Midwestern United
States. Looking at all the production and management information from
each farm, they were able to estimate greenhouse gas emissions and net
energy inputs to outputs. After a life-cycle analysis, the results were
very positive: greenhouse gas emissions from switchgrass-derived
cellulosic ethanol on the farms were 94 per cent lower than if the
energy had come from gasoline.
Another benefit of switchgrass, and part of the reason for its
success in the trials, is that it is a native prairie grass that grows
on agriculturally marginal land. This means that fewer chemical inputs
are required to maintain the crop and makes it less likely that growing
large crops of switchgrass would take away land that would otherwise be
used for food production.
Biofuels have the potential to help reduce pollution and global warming
emissions, as well as the regional conflicts caused by our dependence
on fossil fuels. But choosing the right fuel crop for the right
geographic area is critical, as is making sure that all social and
environmental factors are considered. If we can overcome those hurdles,
you can look for more biofuels made from waste wood, used vegetable
oil, and yes, even algae, at our pumps in the future.
Take David Suzuki’s Nature Challenge and learn more at www.davidsuzuki.org.