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. This study evaluates the life cycle greenhouse gas (GHG) emissions during mallee biomass production in WA. The life cycle GHG emissions analysis exhaustively accounts for all activities and processes which may involve direct or indirect GHG emissions. Our results show that total GHG emission during mallee biomass production is 364.7 kg CO2-e per hectare per year, equivalent to 19.0 kg CO2-e per green tonne mallee biomass. Total GHG sequestrated by above-ground mallee biomass is 19394.4 kg CO2-e per hectare per year (i.e., 1010.1 kg CO2-e per green tonne mallee biomass). Non-renewable GHG emissions during the full life cycle of biomass production is less than 2% of the GHG sequestrated by above-ground mallee biomass, indicating mallee biomass production in WA is almost carbon natural. It is also important to note that ~65% of total non-renewable GHG emissions during mallee biomass production occur in harvest and transport, arising mainly from the use of fossil fuels. GHG emissions from soil due to the use of fertilisers also contribute to ~20% of the total non-renewable GHG emissions during the full life cycle. If mallee biomass is used to substitute for fossil fuels in energy generation, the biomass produced per hectare per year leads to ~19 tonnes CO2-e avoided, providing great potential for GHG reduction.