LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

GROUP 4, SESSION B: CROP PRODUCTION SYSTEMS 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
806
100. Environmental implications of using biomass versus fossil fuels
for energy production: the case of willow, an energy crop
Thu Lan T. Nguyen * , John E. Hermansen
Dept. of Agroecology, Aarhus University, Blichers Allé 20, Postbox 50, DK-8830 Tjele, Denmark, Corresponding
author. E-mail: ThuLan.ThiNguyen@agrsci.dk
Fossil fuel use for energy production is facing serious problems related to resource depletion and environmental
degradation, notably climate change. Biomass fuels e.g. wood waste, crop residues, energy crops, in
contrast, are considered renewable and carbon neutral. Unlike fossil fuels that take millions of years to be
available as an energy source, biomass can be regenerated relatively quickly through photosynthesis. Biomass
burning releases CO2 back to the atmosphere but this biogenic CO2 is not counted as contributing to
global warming. Apart from wood waste and crop residues, energy crops e.g. willow and miscanthus have
recently received large attention as a potential source of renewable energy. Whereas biomass is “carbon neutral”
when burned, the inputs used to produce it may be a source of CO2 and other GHG emissions.
Our research questions were: (1) What if the upstream impacts of energy production from biomass fuels, i.e.
those connected with biomass cultivation and distribution, are included?, (2) In addition to global warming
and non-renewable energy, what about other impact categories like acidification, eutrophication, ecotoxicity,
human toxicity, etc., and 3) How to account for trade-offs among different impact categories? A thorough
and comprehensive analysis is thus necessary to assess the sustainability of substituting biomass for fossil
fuels in energy production. The task is not only to include more impact categories than global warming and
non-renewable energy but also to perform the analysis at a more aggregated level, i.e., translating impacts in
different mid-point categories into a single unit so that they can be weighted and added together to give a
single score value.
In this paper, we present as a case study the results of an LCA study on electricity generation from willow
produced on arable land, in comparison with fossil fuels. Inventory data for the entire process from willow
cultivation to energy production were from Nielsen and Illerup (2003) and Uellendahl et al. (2008). Midpoint
impact categories considered were global warming, non-renewable energy, acidification, eutrophication,
respiratory inorganics, human toxicity, ecotoxicity, photochemical ozone and nature occupation. All midpoint
impacts were then translated into a single monetary unit. The LCIA method used was Stepwise 2006
(Weidema, 2009). For a verification of the monetarisation scheme used in the Stepwise2006 method versus
that used in previous studies, a sensitivity analysis was also performed.
The midpoint impact assessment shows that substitution of willow for fossil fuels would bring both environmental
benefits and costs. The substitution for coal offered environmental benefits in all impact categories
considered except for nature occupation and eutrophication. The substitution for natural gas reduced
impacts on human toxicity, ecotoxicity, global warming and non-renewable energy but increased nature occupation,
eutrophication, respiratory inorganics, acidification and photochemical ozone. The results at the
aggregated level show that energy production from willow scores better than from coal (0.11 vs. 0.12
EUR/kWh) but worse than from natural gas (0.11 vs. 0.06 EUR/kWh). Much of this inferior performance is
accounted for by the impact on nature occupation of biomass fuel crops; nature occupation is by far the main
contributor with a share of approx. 80% of the aggregated single score. Nature occupation thus remains a
major environmental hotspot for bioenergy development, stressing the importance of seeking improvements
in relation to this indicator in order for biomass fuels like energy crops to be a viable fuel source.
References
Nielsen, M., Illerup, J.B., 2003. Emissionsfaktorer og emissionsopgørelse for decentral kraftvarme, Eltra
PSO projekt 3141, Kortlægning af emissionsfaktorer fra decentral kraftvarme, Delrapport 6, Faglig rapport
fra DMU, nr. 442.
Uellendahl, H., Wang, G., Moller, H.B. et al., 2008. Energy balance and cost-benefit analysis of biogas production
from perennial energy crops pre-treated by wet oxidation. Water Sci Technol. 58, 1841-1847
Weidema, B.P., 2009. Using the budget constraint to monetarise impact assessment results. Ecological Economics
68, 1591-1598.