Life cycle assessment of greenhouse gas emissions from changes in cane-growing practices

The most effective practice changes for reducing life cycle greenhouse gas (GHG) emissions from sugarcane growing in Queensland were identified. GHG emission intensity per tonne harvested cane in three regions (Central, Burdekin and Wet Tropics) were calculated using the CaneLCA tool for a range of practice change scenarios relative to a current base case. As expected, more efficient use of nitrogen (N) was the biggest emissions saver, potentially increased further by enhanced efficiency fertilisers (EEF) if any associated reductions in N rates do not compromise yields. In cases where water application rates or pumping head pressures are high, improved irrigation efficiency could be a similarly significant source of emission savings. Modest reductions can confidently be achieved from the adoption of wider row spacings (which reduces both tractor and harvester fuel use) and reduced tillage (which reduces tractor fuel use). Varying the amounts of herbicides applied had little impact on GHG emissions. The scale of potential emissions reductions was considered relative to those that have already occurred. A retrospective analysis (for the Wet Tropics region) showed that emissions intensity has already declined by about 30% as side effect of best management practice adoption to date for water quality protection, which is likely reflected across the state. This study suggests that if all the assessed tried and tested practice changes were adopted to a conservative extent (not including N rate reduction with use of EEF) further emission reductions of 13-16% may be possible relative to current practices.