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Abstract
As the United States begins to move towards putting an
economic value on reducing greenhouse gas (GHG) emissions,
the need for improved accounting standards becomes
acute. Lifecycle analysis (LCA), which involves the systematic
collection and interpretation of material flow in all
relevant processes of a product, has become the accepted
procedure to use to determine greenhouse gas emissions of
products ranging from transportation fuels, to building materials,
to food production (Farrell et al., 2006; Hill et al., 2006;
Owen, 2004). The basic motivation of LCA is that, to conduct
a fair assessment of the environmental impacts of a product, it
is necessary to take into account all of the processes throughout
the product’s lifespan, including the extraction of raw
material, the manufacturing processes that convert raw material
into the product, and the utilization and disposal of the
product. For many products, including fossil fuels, a standard
LCA is generally all that is needed to understand greenhouse
gas emission implications.
Accounting procedures for biological-based products,
however, require additional considerations. Consider a country
that expands production of an agricultural feedstock to
produce biofuels. To understand how such an endeavor affects
GHG emissions requires analysis of the greenhouse gas
contents of all the inputs used to produce the feedstock as
well as the inputs used to create the fuel from the feedstock.
This is as far as most LCAs go. But expanded production of
the feedstock does not just magically happen. Either current
uses of the feedstock must be reduced to free up supply for
production of biofuels, or additional production must occur.
If current uses are reduced, then the greenhouse gas emissions
associated with the current use should be credited towards
the biofuels because they are no longer being emitted.
However, if an alternative product is used as a substitute for
the current use of the feedstock then the GHG implications of
increased production of the substitute should also be counted
as a debit. If current use is maintained, then the implications
of expanded production of the feedstock need to be accounted
for, including changes in crop acreage, production practices,
and whether new land is brought into production. And lastly,
if changes in land use in the biofuels-expanding region result
in changed land-use decisions in other regions, then the GHG
implications in these regions may have to be accounted for, depending
on the definition of system boundary in an analysis.
The need for accounting systems that take into account
changes in production systems has been recognized (Delucchi,
2004; Feehan and Peterson, 2004). In a recent report,
the Clean Air Task Force noted that “current lifecycle analyses
do not account for greenhouse gas emissions and other
global warming impacts that may be caused by changes in
land use; food, fuel, and materials markets (Lewis, 2007).”
Righelato and Spracklen (2007) showed that carbon changes
related to land use changes could outweigh the avoided emissions
through the substitution of petroleum fuel by biofuels.
The contribution of this chapter is two-fold: (i) to develop
the beginnings of a protocol for system-wide accounting
(SWA) systems that incorporates land use and other changes
not included in LCA, and (ii) to apply the protocol to a case
study of ethanol refined from Iowa corn. We will first lay out
the basics of LCA for corn ethanol and gasoline. This serves
as the beginning point for SWA because the components of
LCA results can be used in SWA. We then assess the GHG
impacts of ethanol from Iowa corn based on both types of accounting
systems.