Managing carbon in livestock systems: modelling options for net carbon balance (UNE/I&I NSW)

Summary

​The new carbon faming initiative (CFI) has raised a number of issues in regards to how producers may determine on-farm methane (CH4) and nitrous oxide (N2O) emissions. This project has modelled emissions of the green house gases (GHG) CH4 and N20 from lamb production and evaluated a 'do now' emissions management strategy across 50 years of variable climate (1961-2011). A measure of emissions intensity (kg CO2e/kg live weight) of lamb production on the Northern Tablelands of Australia for low and high productivity landscapes has been evaluated. The Sustainable Grazing Systems (SGS) pasture model and GrassGro have been used to perform 50 year simulations and FarmGas, an inventory calculator, was used to calculate emissions over a 1 year period. Differences between packages in growth and emissions estimates exist. SGS, over 50 years, estimated 15,330 vs. 8.410 kg CO2e/year of enteric CH4 emissions and 4.08 vs. 4.86 kg/kg emissions intensity for high and low productivity landscapes, respectively; and 10.39 vs. 3.42 t CO2e/ha/year of N2O for high and low productivity landscapes, respectively. GrassGro, over 50 years, estimated 24,154 vs. 11,510 kg CO2e/year of enteric CH4 and 8.53 vs. 9.50 kg /kg emissions intensity for high and low productivity landscapes, respectively. FarmGas, over 1 year, estimated 20,823 vs. 10,229 kg CO2e/year of enteric CH4 and 5.43 vs. 6.04 kg/kg emissions intensity for high and low productivity landscapes, respectively; and 3,267 vs. 1,584 kg CO2e/year of N2O for high and low productivity landscapes, respectively with a total intensity of 6.28 vs. 6.97 for high and low productivity landscapes, respectively. In conclusion, total emissions are higher for high productivity landscapes but in terms of intensity, high productivity landscapes produce less CH4 per product produced on more highly productive landscapes. This finding was consistent across all emissions calculators used, but the magnitude of emissions and of emission intensities varied with the calculator used.​