The potential of anaerobically digested crops to supply New Zealand rural fuel requirements

Increased concern over greenhouse gas (GHG) emissions and a stable source of transport fuel for New Zealand (NZ) has prompted interest in alternative sources of transport fuel. Approximately 50% of NZ’s GHG emissions come from the agriculture sector. There is little that can be done in the near future about GHG emissions from livestock, but one area that could be readily improved is the use of fossil fuels in agriculture.

This paper reports on the potential for anaerobically digested crops to supply NZ’s rural fuel requirements. The computer model APSIM was used to simulate biomass production on summer dry arable land in 12 different regions of New Zealand. The crops simulated were sorghum followed by winter wheat for the northern half of the North Island, and lucerne for the remainder of NZ. The potential yields generated by APSIM were then reduced by 25% to allow for below optimum crop husbandry.

Modelling indicated the biogas potential from only 5% of the summer dry arable land in NZ to be ~830 Mm3 CH4/yr. This gave a net yield of 580 Mm3 CH4/yr, once internal energy consumption was subtracted. This amount of energy equates to more than twice the amount of diesel fuel used by the Agriculture Sector in 2010. This level of gas production would be an important new addition to the rural economy.