Environmental Engineering Reference
In-Depth Information
1200
5020
1150
Ethanol
1000
Biodiesel
800
585
600
506
483
401
400
213
158
170
140
200
110
59
0
FIGure 11.31
Potential biofuel yields of first-, second-, and third-generation feedstocks. (From U.N.
Food and Agriculture Organization,
The State of Food and Agriculture
, 2008. Available at http://www.fao.
org/docrep/011/i0100e/i0100e00.htm; Fulton, L.,
Biodiesel: Technology Perspectives.
Geneva UNCTAD
Conference, 2006 and Chisti, Y.,
Biotechnol Adv
, 25, 294-306, 2007; ORNL,
Biofuels from
Switchgrass:
Greener Energy Pastures
, Oak Ridge National Laboratory, available at http://bioenergy.ornl.gov/papers/misc/
switgrs.html, 2005
.
)
be used to produce 2.6 times more ethanol per acre than corn (Heaton et al. 2008). High-yield micro-
algae strains have been estimated to only require 1-2.5% of arable land in the United States to meet
half of the nation's transportation fuel demand, whereas corn and soybeans would require several
times more than the current arable land area to meet the same target (Chisti 2007).
A 2005 joint analysis by the U.S. Department of Energy (DOE) and U.S. Department of
Agriculture (USDA) known as the Billion Ton Study projected that 1.3 billion tons of biomass
could be produced annually in the United States by 2030 (USDOE/USDA 2005). The sources and
amounts of biomass projected to be available in 2030 for a high-yield scenario (where agriculture
yields were 70% greater than the moderate yield increase scenario) are shown in Figure 11.32.
According to the study, three-quarters of the biomass would come from agricultural sources. The
analysis of forestry stocks excluded areas without roads and environmentally sensitive habitats. In
the agriculture sector, it was assumed that corn, wheat, and small grain crop yields would increase
by 50%; that 75% of crop residues were recoverable; and that 55 million acres of land could be
devoted to perennial bioenergy crop production.
In Brazil, sugarcane was cultivated on 7.8 million hectares in 2009, and an estimated 34 million
hectares of pastureland could be targeted for sugarcane expansion (USDA/FAS 2010). In Asia and
Africa, jatropha is a biodiesel crop of interest because it can grow on marginal land and does not
require large amounts of water or fertilizer. In order to satisfy biofuel/petroleum blending targets in
India, jatropha may occupy upwards of 11-13 million hectares (USDA/FAS 2011). Land use consid-
erations will likely play an important role in national agriculture plans.
11.4.2 l
ifE
-c
yclE
ghg E
miSSionS
Converting forested land to other uses releases CO
2
that was removed from the atmosphere. Tropical
deforestation throughout the 1990s accounted for approximately 20% of anthropogenic GHG emis-
sions (Gullison et al. 2007). Globally, many countries have established short-term national targets or
mandates for biofuel consumption (Peterson 2008). As biofuel production increases, where will the
additional crops be grown? Land-use change is an important component of the biofuels discussion,
