Life cycle analyses

Dr Stewart Ledgard leads a team of researchers active in the new area of application of Life Cycle Assessment (LCA) to agricultural systems and products. The research focuses on determining the total resource use (energy, water, nutrients) and environmental emissions (affecting air and water quality) throughout the life cycle of a system or product.

In dairy systems, LCA accounts for extraction of all raw materials, production of all key inputs (e.g. electricity, fertiliser, brought-in feeds) and all components of the system including land used for growing replacement animals, external feeds and grazing-off animals. By accounting for all contributors to milk production, it enables valid comparison of farm systems that vary in intensity of production with varying levels of external farm inputs.

LCA has been used as a research tool to examine the eco-efficiency of different farm systems or inputs. For example, recent analyses have indicated that dairy farm systems based on the use of legumes in pastures that supply nitrogen via biological fixation of atmospheric N2 use 40% less fossil fuel and produce 10% less greenhouse gas than similar systems based on nitrogen-fertilised grass for equivalent milk production.

Analysis of the effects of intensification using maize silage showed a mix of eco-efficiency gains and losses. Total energy use per kilogram of milk increased with maize silage use, whereas results for greenhouse gas emissions and eutrophication potential per kilogram were variable.

Maize integration showed increases in these environmental indices in initial studies, but a reduction when it was associated with good management practices for optimum production.

Application of LCA in agricultural systems has had a dominant focus on determination of the carbon footprint or total greenhouse gas emissions per kilogram of milk produced. This was used in a joint project with Fonterra and MAF to determine the carbon footprint of milk production as well as the processing and transport to overseas markets.

Life cycle analyses - graph