Study states biofuel benefits overestimated
June 11, 2012 - A commentary published in GCB Bioenergy reveals that calculations of greenhouse gas emissions from bioenergy production are neglecting crucial information that has led to the overestimation of the benefits of biofuels compared to fossil fuels.
June 11, 2012 By EurekAlert
June 11, 2012 – Two scientists are challenging the currently accepted norms of biofuel production. A commentary published in GCB Bioenergy
reveals that calculations of greenhouse gas (GHGs) emissions from
bioenergy production are neglecting crucial information that has led to
the overestimation of the benefits of biofuels compared to fossil fuels.
The critique extends to the Life Cycle Analysis models of bioenergy
production. Life Cycle Analysis (LCA) is a technique used to measure and
compile all factors relating to the production, usage, and disposal of a
fuel or product. The authors conclude that LCAs are overestimating the
positive aspects of biofuel use versus fossil fuel use by omitting the
emission of CO2 by vehicles that use ethanol and biodiesel even when
there is no valid justification.
Proponents of bioenergy argue that analyses should always ignore
this CO2 because plants grown for biofuel absorb and therefore offset
the same amount of carbon that is emitted by refining and combusting the
fuel. The commentary critiques this method by arguing that doing so
double counts the carbon absorbed by plants when the bioenergy crops are
grown on land already used for crop production or already growing other
plants because the bioenergy does not necessarily result in additional
carbon absorption. Biofuels can only reduce greenhouse gases if they
result in additional plant growth, or if they in effect generate
additional useable biomass by capturing waste material that would
otherwise decompose anyway.
The overestimation of bioenergy LCAs becomes increasingly magnified
when the omission of CO2 is combined with the underestimation of
nitrogen emissions from fertilizer application. According to lead author
Dr. Keith Smith, from the University of Edinburgh, "Emissions of N2O
from the soil make a large contribution to the global warming associated
with crop production because each kilogram of N2O emitted to the
atmosphere has about the same effect as 300kg of CO2." He notes that
several current LCAs underestimate the percentage of nitrogen fertilizer
application that is actually emitted to the atmosphere as a GHG. The
authors claim that the observed increase in atmospheric N2O shows that
this percentage is in reality nearly double the values used in the LCAs,
which greatly changes their outcome.
Since results of the LCAs have been widely utilized, Searchinger and
Smith conclude that the overall development and research of alternative
fuels has been heading in the wrong direction. "The best opportunity to
make beneficial biofuels is to use waste material or to focus on
relatively wet but highly degraded land," notes Dr. Smith. If bioenergy
crops are produced on degraded land, less GHGs will be emitted and more
will be stored. There are additional benefits: this method will not
compete with crop production for food, textiles, and other products.
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