Life-cycle assessment of eucalyptus short-rotation coppices for bioenergy production in Southern France
Résumé
Short rotation coppices (SRCs) are considered prime candidates for biomass production, yielding good-quality feedstock that is easy to harvest. Besides technical, social and economical aspects, environmental issues are important to take into account when developing SRCs. Here, we evaluated the environmental impacts of delivering 1 GJ of heat from eucalyptus SRC using life cycle assessment (LCA), based on management scenarios involving different rotations lengths, fertilizer input rates, stem densities and harvest methods. Compared to equivalent fossil chains, all eucalyptus scenarios achieved savings of fossil energy and greenhouse gas (GHG) emissions in the 80%-90% range, and had generally lower impacts, except for eutrophication. The 3-year rotation scenario was the most energy and GHG-intensive, while manual felling for the longer rotations resulted in 2-fold larger photochemical ozone impacts compared to the other scenarios. Transportation of wood chips and fertilization were the top two contributors to the impacts, the latter being more important with the shorter rotation lengths due to the evergreen character of eucalyptus. The possibility of including ecosystem carbon dynamics was also investigated, by translating the temporary sequestration of atmospheric CO2 in the above- and below-ground biomass of eucalyptus as CO2 savings using various published equivalence factors. This offset the life-cycle GHG emissions of heat provision from eucalyptus SRCs by 70 to 400%.
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