Environmental Engineering Reference
In-Depth Information
100
98
Tailpipe emissions
Fuel and feedstock transport
Fuel production
International land use change, mean
Domestic land use change
Net international agriculture (w/o land use change)
Net domestic agriculture (w/o land use change)
Net life-cycle GHG emissions
97
90
80
79
70
60
50
42
40
38
30
29
27
20
14
10
9
7
0
-10
-10
-20
-29
-30
-40
-50
FIGure 11.33
Life-cycle GHG results of biofuels that qualify under the EISA 2007 Renewable Fuel
Standard as modeled by the EPA.
One of the most-debated features of the Renewable Fuel Standard final rule, as published by
the EPA, is the inclusion of indirect land-use change GHG emissions. The EPA's model of indirect
land-use change used improved techniques since Searchinger et al. (2008) to include a more com-
prehensive inventory of the lands that would be affected. Figure 11.33 shows the life-cycle GHG
emissions in the year 2022 of Renewable Fuel Standard qualifying biofuel production pathways, as
determined by the EPA's peer-reviewed model (EPA 2010). Note the magnitude of GHGs attributed
to indirect land-use change relative to total emissions in Figure 11.33.
11.4.3 l
ifE
-c
yclE
l
and
-u
SE
m
EtricS
The life-cycle land area requirements of several electricity sources, including biomass, are shown in
Figure 11.34 (Spitzley and Keoleian 2005). The results presented in the figure considered acquisi-
tion of the input fuel, material acquisition and distribution, use, and end of life for different energy
systems per kilowatt-hour of electricity generated. The time period of land use was also considered.
For example, the biomass systems use a relatively large amount of land the entire time they are in
production, whereas the natural gas mining operation may have a relatively small surface footprint,
and the land may be restored once the natural gas has been extracted. However, this figure does not
account for the quality of the utilized land. Biomass may be grown on marginal farmlands, fallow
