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15.3 Results
15.3.1 CF, WF, and EF per Unit Amount
15.3.1.1 Carbon Footprint
Table 15.5 and Fig. 15.3 summarize the net life-cycle GHG emissions from biofuels
derived from different biomass sources. Within the same type of biofuel such as
corn ethanol, different studies report different values depending on the researcher,
production system, and accounting boundary. Until 2005, most of the studies on
corn ethanol showed a corn ethanol CF slightly larger than that of gasoline, but studies after 2006 have demonstrated a 20  % or even greater GHG reduction by
Table 15.5 Life-cycle GHG emissions excluding those due to changes in land usage
Year
Net GHG
emissions
(g-CO2/MJ) Notes
Source
Reference
Gasoline
94.0
a
Gasoline
92.0
b
Gasoline (Japan)
81.7
c, d
Diesel
82.3
e
Corn ethanol
Marland and
Turhollow
1991
f
Lorenz and Morris
1995
f
Wang
2001 71.0
a
Graboski
2002 99.0
a
Shapouri et al.
2002
f
Patzek
2004 121.0
a
Shapouri et al.
2004 61.0
a
Pimentel et al.
2005 116.0
a
de Oliveira et al.
2005 98.0
a
Kim and Dale
2005
f
Farrell et al.
2006 87.0
a
Hill et al.
2006 84.9
e
Fargione et al.
2008 78.3
g
Serchinger et al.
2008 74.0
b
Toyota Motor
Corporation and
Mizuho Information
and Research Institute
2008 81.4
Maximum case
h
54.0
Minimum case
h
EU directive 2009/28/
EC
2009 43.0
Community
produced (natural
gas as process fuel
in CHP plant)
i
(continued)
O. Saito