New research identifies important influences on the energy and
environmental performance of biofuels made from agricultural crops.
Type of land use change, type of biofuel crop and the by-products
from the conversion process all influence performance.

The benefits of introducing biofuels in the transport
sector or as feedstock in the chemical industry are widely debated.
Research has produced contradictory results in terms of greenhouse
gas (GHG) reductions, energy efficiency, impact on biodiversity and
water pollution. There is also debate on the socio-economic
benefits, especially for developing countries.

The study analysed the energy and environmental
performance of six different agricultural crops: wheat, sugar beet,
rapeseed, crops for livestock, maize and willow. It considered two
possible direct land use changes: one from unfertilised grassland
and the other from land producing wheat for food without the
removal of straw. The biofuel production was assumed to take place
in northern Europe with current cultivation practices and
state-of-the-art technologies.

The researchers also considered whether to account for the
impacts of indirect land use change caused by biofuel crop
production, i.e. displacement of food and feed crop production to
areas not used for cultivation previously. Some other studies have
suggested that emissions from indirect land use change could
completely offset the benefits of using biofuels.

The researchers argue that, ideally, it should therefore
be included in environmental assessments of biofuels, but they were
not satisfied with the reliability of any existing methodologies
for its calculation, so did not include indirect land use change in
this study.

Energy performance was based on the ratio of energy
output, that is the energy produced by biofuels, to energy input,
such as energy needed for fuel, fertilisers and electricity to grow
and process crops. Environmental performance considered GHG
emissions during the life cycle of production and the impact on
eutrophication.

The energy output/input ratio of the different biofuel
production systems varied from the worst performer of 1.3 for
ethanol from grain, when by-products are excluded, to the best
performer of 11 for methanol from willow. Although willow does not
have the highest energy output (this comes from sugar beet and
wheat), it has a very low energy input giving it the best energy
balance.

The variation amongst systems also depends on the
efficiency of the crop-to-fuel conversion process and the
by-products. For example, the tops and leaves from sugar beet and
straw from wheat contribute to the energy output of the biofuel
production process.

If the best energy performer, willow,
replaced fossil vehicle fuels, the reduction in GHG emissions would
be approximately 80 to 85 per cent if the land used was previously
unfertilised grassland.

The environmental performance of biofuels from
agricultural crops depends a great deal on land use change, i.e.
what the land was used for before the biofuel crops were
grown.

If the best energy performer, willow, replaced fossil
vehicle fuels, the reduction in GHG emissions would be
approximately 80 to 85 per cent if the land used was previously
unfertilised grassland. Eutrophication impacts depend on the crop
type. Biofuels based on sugar beet, livestock crops and willow
contribute roughly 2-3 times less than biofuels based on
wheat.

The research highlighted several issues that could affect
the analysis but which could contribute to improved sustainability
assessments. As mentioned, indirect land use changes were not
included. Also, only two types of land use change were considered.
If peat soils are used to grow biofuel crops, then CO₂
emissions from the soil could be 10-20 times higher.

Nevertheless, the research has identified important
factors affecting the energy and environmental performance of
biofuels made from agricultural crops.

Source:Börjesson,
P. & Tufvesson, L.M. (2011) Agricultural crop-based biofuels -
resource efficiency and environmental performance including direct
land use changes. Journal of Cleaner Production.
19:108-120.