Page 284 - Materials Chemistry, Second Edition

A Comparison of Life Cycle Assessment Studies 275

out that by using displacement approach, all four soybean-based fuels can achieve
a modest to significant reduction in well-to-wheel GHG emissions (64–174 %)
versus petroleum-based fuels. In this study, Huo and co-worker concluded that the
method used to calculate coproduct credits is a crucial issue in biofuel LCA that
should be carefully addressed and extensive efforts must be made to identify the
most reasonable approach for dealing with the coproducts of biofuel production
system. Finco et al. (2012) conducted an LCA study on rapeseed and reported a
56 % less CO 2 equivalent GHG emission from the rapeseed biodiesel than diesel.
However, this study does not include negative impact caused by land use partic-
ularly from the use of N fertilizer. N 2 O emissions, a by-product of N fertilization
in agriculture, as one responsible factor to enhanced GHG emissions compared to
consumption of fossil fuels (Crutzen et al. 2008) and can overrule the benefit of
biofuel. Halleux et al. (2008) conducted a detail comparative LCA between eth-
anol from sugar beet and methyl ester from rapeseed and concluded an advantage
of rapeseed over sugar beet biofuel in terms of total environment impact and GHG
emission. Table 1 is explaining the environmental potentiality of various feedstock
biofuels over reference fuel (i.e., mostly fossil diesel or fossil gasoline).
Result of Stucki et al. (2012) on LCA of biogas from different purchased
substrates and energy crops viz. sugar beet, fodder beet, beet residues, maize
silage, molasses, and glycerin shows that the environmental impacts of biogas
from purchased substrates are in the same range than those from liquid biofuels.
Chandrashekar et al. (2012) find 1.25 times negative global warming potential of
Pongamia pinnata compared to fossil fuel and Jatropha biodiesel, and nil acidi-
fication and eutrophication potential. However, variations in the LCA result are
also observed by the differences in selection of scope, system boundary, and other
phases of LCA (Table 1). These issues were reviewed in detailed by Reap et al.
(2008a, b) and Singh et al. (2010).
The life cycle stages can have harmful effects or benefits of different envi-
ronmental, economical, and social dimensions. Therefore, an assessment of the
complete fuel chains from different perspectives is of crucial importance in order
to achieve sustainable biofuels (Markevicius et al. 2010). Comprehensive LCA of
biofuels illustrating environmental benefits and impacts can be a tool for policy
decisions and for technology development.
Current disagreements about the performance of biofuels rest on different
approaches and assumptions used by the investigators (Farrell et al. 2006). The use
of different input data, functional units, allocation methods, reference systems and
other assumptions complicates comparisons of LCA bioenergy studies and
uncertainties and use of specific local factors for indirect effects (e.g., land-use
change and N-based soil emissions) may give rise to wide ranges of final results
(Cherubini and Strømman 2011). The system choice for comparing different
biofuels must be identical because different systems could results improper results,
e.g., the choice of passenger car, the efficiency and emissions of EURO V and
EURO III varied a lot, so different passenger car, bus, and other transportation
vehicles could not be identical to compare different biofuels. The system bound-
aries of different biofuels also need to be identical, as inclusion and exclusion of