Life Cycle Assessment of grain cropping

Abstract

Life cycle assessment (LCA) is a relatively recent framework that was developed to estimate the environmental impacts of industrial production processes and systems. The framework is now being applied to agricultural systems, including cropping systems, to identify opportunities for more environmentally-sustainable production. This purpose of this paper is to provide an overview of the application of LCA to grain cropping systems. Research at NSW DPI has focused on using LCA to estimate greenhouse gas (GHG) emissions from grain production systems for different regions of NSW as part of an industry-funded climate mitigation research program. The emission profiles suggest that GHG emissions in the systems modelled thus far are primarily the result of the production and application of synthetic N fertilizers, direct losses of nitrous oxide (N2O) via denitrification of soil mineral N and dissolution of lime. The emissions intensities of crops also differ between regions primarily due to rainfall patterns and soil type, the type of fertiliser used, levels of inputs and yields. LCA, however, can provide a more holistic view of environmental impacts by also estimating effects on indicators such as eutrophication, land-use change and ecological toxicity. The reporting of numerous indicators allows potential perverse impacts to be assessed from applications of potential mitigation strategies. For example, increasing the proportion of legumes in a cropping rotation may reduce GHG emissions for that land area. However, the action may also result in land-use change to maintain supply of products displaced by including legumes in the rotation. Emissions associated with this land-use change such as sequestration or emission of soil or biomass carbon, may also affect the overall environmental impact.