Environmental Engineering Reference
In-Depth Information
Mortimer et al., 2003; Puppan, 2002; Booth et al., 2005; Bozbas, 2005).
Individual studies dif er in many respects however, making it dii cult to
generalize all aspects of environmental impacts of biodiesel. Using life-
cycle assessment of RME (rapeseed methyl ester) and conventional diesel,
Franke and Reinhardt (1998) present a comparative overview of the
environmental impacts of both these diesel fuels. Of the six environmental
impacts considered, three are shown to favour RME and the remaining
three to favour fossil fuel diesel. Although RME could have a potentially
lower greenhouse ef ect (CO
2
equivalents), low eco and human toxicity
(NO
x
) and lower resource demand (i nite energy), it is shown to have a
signii cant ozone depletion potential due to nitrous oxide (N
2
O) emissions.
Furthermore, potential eutrophication and acidii cation from the use of
fertilizers, pesticides and herbicides in rapeseed production adds to the
potential negative environmental impacts of biodiesel.
Franke and Reinhardt (1998) is one of the few studies that can be termed
'complete' life-cycle assessment in that they cover almost all aspects of the
life cycle of the products in question for both RME and conventional
diesel. As such, the results from the study also seem very balanced with
regard to which fuel is more ecologically sound. Nevertheless, the authors
conclude - 'under certain assumptions, RME has or can have an “overall”
ecological advantage against diesel oil' (Franke and Reinhardt, 1998,
p. 1032).
The carbon balance and ecological footprint of ethanol as a fuel were
analysed by Dias de Oliveira et al. (2005) for the examples of Brazil and
the United States. Controversially they conclude that using ethanol as a
substitute for petroleum is not environmentally sustainable when emis-
sions from agricultural inputs (in the case of sugarcane) and conversion (in
the case of maize) are taken into account. In contrast, a study on ethanol
from maize and biodiesel from soybeans showed that ethanol yields 25 per
cent more energy than that invested in its production and biodiesel yields
93 per cent more (Hill et al., 2006). The situation is further complicated by
the use of nitrogen fertilizers in biofuel production because N
2
O release
from fertilizer application signii cantly contributes towards GHG emis-
sions (Crutzen et al., 2007), though if nitrogen demand is reduced by using
second generation biofuel feedstocks such as grasses and woody coppice,
this problem is alleviated.
One of the major environmental impacts from the burning of fossil fuel
diesel comes from the emission of sulphur. Biodiesel, on the contrary, pro-
duces virtually zero sulphur emissions, making it much cleaner compared
with fossil fuel diesel (Puppan, 2002; Bozbas, 2005). With biodiesel, there
is also a signii cant reduction in other emissions, such as carbon monoxide,
hydrocarbons and soot (Puppan, 2002; Mortimer et al., 2003; Nwafor,
