Production of mallee biomass in Western Australia: Energy balance analysis

In Western Australia (WA), mallee eucalypts are being developed to provide woody crops for wheatbelt farmers as part of a strategy to tackle a range of conservation issues including dryland salinity. If mallee crops prove commercially viable, a considerable centrally harvested biomass supply could be available for conversion to renewable energy and other industrial products. This study presents a systematic analysis of overall energy balance of mallee biomass production in WA. Mallee biomass production achieves strong energy gain with an energy ratio (the ratio of total energy outputs and total nonrenewable energy inputs) of 41.7 and an energy productivity of 206.3 GJ/(ha year). This performance by a perennial woody crop is considerably better than that achievable by annual energy crops, i.e. canola (rapeseed) for biodiesel in the same region, where energy ratios are typically <7.0 and energy productivities are <40.0 GJ/(ha year). Almost 80% of total energy inputs during mallee biomass production occur in biomass harvest and transport, arising mainly from the use of fossil fuels. The energy balance analysis indicate that to further improve the energy ratio, strategies should be focused on the development and optimization of harvest and transport strategies and logistics, as well as the improvement of machinery fuel efficiency.