Identifying opportunities to reduce greenhouse gas emissions from agricultural production: A Life Cycle Assessment approach

The use of Life Cycle Assessment (LCA) to determine environmental impacts of agricultural production is increasing, especially to determine greenhouse gas emissions. We have undertaken LCAs of wheat production in Central Zone (East) NSW (Figure 1) and cotton production at Narrabri NSW (Figure 2) and found the emissions profiles to be dominated by the production and use of synthetic nitrogenous fertilisers, at 67% of the emissions profile for wheat and 68% for cotton. When we studied the effect of replacing these fertilisers with biologically fixed N, emissions from a legume-based system were found to be 39% of those from a non-legume system (Table 1). Other factors which greatly influence calculated emissions are yield and choice of direct nitrous oxide emissions factor. We are primarily taking a regional approach to LCA and accommodating variability within regions. As it is not possible to build case-study scale LCAs across all farms in NSW, robust regional-scale LCAs provide a basis for advising producers on potential emissions reductions. Also, by showing inter- and intra-regional variability they provide a stronger platform for testing national policies, than coarser-scale studies.