Agriculture Reference
In-Depth Information
resulting increase in carbon dioxide emissions into the atmosphere. These carbon
dioxide emissions could be greater than those associated with fossil energy use. It is
important that policies be established to manage land use change so that practices
are sustainable.
g r e e n h o u s e g a s e m i is is i o n is
Increased use of corn and other grains is based on use of large quantities of nitrogen
fertilizer. Higher prices for grains may result in application of more fertilizer to exist-
ing and newly cultivated marginal lands to spur crop yield. Excessive application of
nitrogen fertilizer can result in release of nitrous oxide, one of the most potent GHGs,
on a molecule per molecule basis, 300 times more potent than carbon dioxide.
Although biofuel will address carbon dioxide emissions to the atmosphere,
increased production of corn and other crops requiring high rates of nitrogen fertil-
izer to achieve the high yields necessary to supply the massive amount of feedstock
needed to make biofuels a significant player in the energy game will increase the
potential for some of this nitrogen to enter the ecosystem as leachate or nitrous oxide
(Kim and Dale, 2005).
y i e L D s
Historically, average yields of commodity crops have steadily increased as a result of
genetic modification through conventional breeding and more recently through biotech-
nology. Expected future yield increases will allow even greater amounts of both food
and fuel to be grown on each unit of land area. In fact, the Billion Ton Vision (Perlack
et al., 2005) uses the assumption that grain crop yields will double in the 25-year time
frame of their analysis (through 2030). They also assumed that harvest index or grain-to-
stover ratio would remain constant for all grains except soybean. The outcome of these
assumptions is that crop biomass production will increase linearly with grain yield.
Others question the validity of the assumption that the rate of yield increase we have
experienced over the past 40 years can be maintained over the next 25 years (Cassman,
2007; Council for Agricultural Science and Technology [CAST] 2006).
r u r a L e C o n o m i C D e v e L o P m e n t
Because photosynthetic solar energy capture is low, biomass production, on the scale
needed to significantly contribute to the transportation fuel supply, will require large
land areas. This in turn means that its production and gathering of the biomass feed-
stock will be distributed and will provide jobs and income for residents over large
rural areas. This activity has potential to revitalize many economically depressed
regions and will as a result provide significant social benefits. In addition, because
cellulosic biomass tends to have low physical density as well as low energy density,
transportation of the raw feedstock will be expensive. On-farm and local community
preprocessing may be economically beneficial and even essential. These pretreat-
ment facilities will add value to the biomass feedstock and in so doing will create
additional jobs and enhanced rural community vitality.
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