[asa] Biofuels Not the "Green Bullet" Once Thought

Two recent studies in Science Express has expressed serious doubts whether
biofuels are a viable option for fighting anthropogenic climate change.

http://www.sciencemag.org/cgi/content/abstract/1151861

Most prior studies have found that substituting biofuels for gasoline will
> reduce greenhouse gases because biofuels sequester carbon through the
> growth of the feedstock. These analyses have failed to count the carbon
> emissions that occur as farmers worldwide respond to higher prices and
> convert forest and grassland to new cropland to replace the grain (or
> cropland) diverted to biofuels. Using a worldwide agricultural model to
> estimate emissions from land use change, we found that corn-based ethanol,
> instead of producing a 20% savings, nearly doubles greenhouse emissions over
> 30 years and increases greenhouse gases for 167 years. Biofuels from
> switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This
> result raises concerns about large biofuel mandates and highlights the
> value of using waste products.

http://www.sciencemag.org/cgi/content/abstract/1152747

Increasing energy use, climate change, and carbon dioxide (CO2) emissions
> from fossil fuels make switching to low-carbon fuels a high priority.
> Biofuels are a potential low-carbon energy source, but whether biofuels
> offer carbon savings depends on how they are produced. Converting
> rainforests, peatlands, savannas, or grasslands to produce food-based
> biofuels in Brazil, Southeast Asia, and the United States creates a
> 'biofuel carbon debt' by releasing 17 to 420 times more CO2 gas (GHG)
> reductions these biofuels provide by displacing fossil fuels. In contrast,
> biofuels made from waste biomass or from biomass grown on abandoned
> agricultural lands planted with perennials incur little or no carbon debt
> and offer immediate and sustained GHG advantages. than the annual
> greenhouse.

To be sure, every major (and minor) candidate for president had biofuels in
their platform and is a key provision in every piece of legislation to fight
anthropogenic climate change. The thinking went that since biofuels
naturally sequestered CO2 then this would be preferable to burning fossil
fuels. It could be used as a cheap pick up line to get votes particularly
Iowa Caucus votes. It's been widely known that ethanol from corn was on the
"bubble" in terms of being a net winner or loser. These two studies even put
all biofuels even so-called cellulosic biofuels in jeopardy for -- and this
is key -- *biofuels that are produced as normal agricultural crops*. From
the second paper:

Our results demonstrate that the net effect of biofuel production via
> clearing of carbon-rich habitats is to increase CO2 emissions for decades or
> centuries relative to fossil fuel use. Conversely, biofuels from perennials
> grown on *degraded farmland and from waste streams* would minimize habitat
> destruction, competition with food production, and carbon debts, all of
> which are associated with direct and indirect land clearing for biofuel
> production. [emphasis mine]

In order to make biofuels work would mean the politicians would have to
resist pandering to the farm vote (and even more difficult Archer Daniels
Midland). One of the ways this issue has been incorrectly framed is
so-called energy independence. According to these studies, of the current
methods of producing biofuels Brazilian sugar cane is the best. Having
American farmers grow so-called green crops simply is not a good idea. Sugar
cane ethanol produced on Cerrado sensu stricto takes ~17 years to pay the
carbon debt, while ethanol from corn produced on US Central grasslands has a
carbon debt repayment time of ~93 years and soybean diesel from converted
Amazonian rainforest has a repayment time of ~320 years.

Our analyses suggest that biofuels, if produced on converted land, could,
> for long periods of time, be much greater net emitters of greenhouse gases
> than the fossil fuels that they typically displace. All but two, sugarcane
> ethanol and soybean biodiesel on Cerrado, would generate greater GHG
> emissions for at least half a century, with several forms of biofuel
> production from land conversion doing so for centuries. At least for current
> or developing biofuel technologies, any strategy to reduce GHG emissions
> that causes land conversion from native ecosystems to cropland is likely to
> be counterproductive.

Finally, this whole issue really underscores the necessity of the government
not picking winners and losers. Many if not all of the climate change have
mandated biofuels rather than carbon targets. This was a mistake. There are
probably others that may be mistakes in the future, e.g. mandating nuclear
power. Let us engineers do our job. Give us a carbon target and we'll tell
you how to get there. In engineering speak, give us a requirements spec and
not a functional spec.

Rich Blinne (Member ASA)

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Received on Fri Feb 8 11:55:42 2008