Greenhouse gas emissions profile for 1 tonne of wheat produced in Central Zone (East) New South Wales: a life cycle assessment approach

Life Cycle Assessment (LCA) has become an increasingly common approach across different industries, including agriculture, for environmental impact assessment. A single-issue LCA focusing on greenhouse gas emissions was conducted to determine the emissions profile and total carbon footprint of wheat produced in the Central Zone (East) of New South Wales. Greenhouse gas emissions (in carbon dioxide equivalents; CO₂-e) from all stages of the production process, both pre-farm and on-farm, were included. Total emissions were found to be 200 kg CO₂-e per t of wheat at the farm gate, based on a 3.5 t/ha grain yield. The relative contribution of greenhouse gas emissions from different components of the production system was determined, with most emissions (37%) coming from pre-farm production and transport of fertiliser (30%) and lime (7%) and from the nitrous oxide (N₂O) emitted from the nitrogenous fertiliser applied to the crop (26%). Other important emissions included the CO₂ emissions from the use of fertiliser and lime (15%) and the production, transport and use of diesel (16%). The relative importance of other minor emissions is also discussed. For a higher yielding crop (5.0 t/ha), total emissions were found to be 150 kg CO₂-e per t of wheat. This paper considers the effect of different management scenarios on the emissions profile and the effect of adopting a N₂O emissions factor, which is based on current New South Wales field research, rather than the current Australian National Greenhouse Accounts National Inventory Report default value. This LCA provides a template from which comparative farming systems LCA can be developed and provides data for the Australian Life Cycle Inventory.