Managing carbon in livestock systems: modelling options for net carbon balance (synthesis report)

Summary

​CFI methodologies for reducing CO2-e from methane and nitrous oxide and for storing soil carbon require a standardised, simple to use and consistent (accurate) protocol upon which to base the accounting method.
​In the RELRP program six demonstration sites were established to measure or estimate aspects of livestock production systems that should reasonably be expected to contribute data to a carbon balance sheet for each site. These sites covered different geographical regions and production systems. Different processes for collecting on-ground data were used, some measured inputs and outputs required for modelling, others used historical data provided by producers or the state agency responsible for the site / district in which the site was located.
At the two sites where measured, methane emissions approximated modelled estimates. At the one site where measured Nitrous Oxide emissions were less than those predicted by a model.
Where calculation methods were compared side by side at the same site, there were model differences in methane and nitrous oxide emissions. Where the biophysical models and FarmGas calculator were compared side by side they provided similar estimates of methane emissions. 
The data requirements for the biophysical models were extensive. Even for the calculators, the assumptions made, based on historical data, were extensive and unlikely to be challenged based on data collected on farm.
We recommend that a simple emissions calculator be developed, based on sensitivity analysis of the factors affecting on-farm greenhouse gas emissions. We also recommend that data on methane and nitrous oxide emissions over a range of enterprises be measured along with sufficient data to enable biophysical models to be run. This would provide the confidence that modelled / calculated estimates were related to observed rates of emission and underpin the development of future accounting systems.