Page 37 - Materials Chemistry, Second Edition

Key Issues in Conducting Life Cycle Assessment 23

3.2.1 Direct Impacts
Land use and land-use change, in relation to biomass supply for bioenergy, are
characterized as having various input–output inventories, resulting in different
contributions to impact categories that affect different areas of protection. Relevant
impact categories include global warming, eutrophication, acidification, toxicity,
water use, and land use. These impacts are induced by input–output components
and activities in the agricultural chain including land transformation, cultivation of
energy crops, and removal of biomass residues from soil, as shown in Fig. 2.
Typical inventories include, for example, the use of fossil fuels in tractors for land
clearing, tillage, planting, and harvesting; the application of seeds, fertilizer, and
pesticides; and the use of water for irrigation. Important GHG emission species
related to agricultural activities are N 2 O and CH 4 in addition to CO 2 . Land-use-
related activities may directly affect the quality of land (natural environment) as an
area of protection. This quality in terms of ecosystem services include soil quality,
biomass productivity, and biodiversity (Mila i Canals et al. 2007). The charac-
terization of these land-use impact categories, however, is less developed
compared to other categories.

3.2.2 Indirect Impacts

In principle, indirect land use will have the same inventory components and
relevant impact categories as that of direct land use. Indirect land use refers to the
changes in land use that take place elsewhere as a consequence of the development
of bioenergy systems. In the LCA methodology, this indirect impact may have a
broader meaning, including any relevant effects to different chains, for example, if
large-scale bioenergy production affects food production chains. As an illustration,
if fertile land previously used for food crops (such as corn, soybeans, or palm) is
transformed to produce bioenergy, this could lead to farmers clearing wild lands
elsewhere in the world to meet the displaced demand for food crops (Tilman et al.
2009).
The paper by Searchinger et al. (2008) has pointed out the significant
contribution of indirect impacts on the LCA of bioenergy systems. The authors
argued that, based on a sustainability criterion, fuel oil is better than most biofuels.
There are two connected arguments put forth. First, biofuel development provoked
a rise in the price of food, leading to the stimulation and expansion of food
production. Second, the subsequent displacement of food production into new
areas of cultivation (indirect land-use change) resulted in a release of CO 2 into the
atmosphere. It holds biofuel production responsible for global climate change in
ways not measured by previous LCA studies (Harvey and Pilgrim 2011). The
above explanation on indirect impact changes the entire nature of LCA to one
which must be able to model global economic interaction (Sheehan 2009). In
addition to indirect land use, other types of indirect impacts may be needed to
properly assess the total GHG emissions implications of substituting biofuels for