Discipline: environment; Keywords: GHG, emission reduction, net zero, carbon sequestration, systems dynamic model, dairy production systems. 
Sustainability of the SA Dairy Industry has been a focus point of Milk SA for some time. This is supported in a dynamic strategic and commitment report, entitled: ‘Sustainability in the SA dairy Industry: A Status and Progress Report’. The report is structured according to the FAO-IDF Dairy ®Declaration of Rotterdam (DDoR) and the Dairy Sustainability Framework (DSF), which endorses the UN 2030 Agenda for Sustainable Development and provides guidelines for sustainable development. One of the central topics is carbon dioxide (CO2) emission reduction in the dairy sector, with commitment intentions towards achieving ‘net zero’ sooner rather than later.

In the dairy industry, apart from private initiatives, CO2 emission reduction is primarily driven by the research and development (R & D) programme of Milk SA. As with other international initiatives, much focus is given to methane reduction as a primary atmospheric polluter. However, in contrast to many global approaches where carbon sequestration is not taken into account, sequestration is included since it contributes significantly to mitigating CO2 equivalent atmospheric warming levels, so too is nitrous oxide (N2O). The approach is justified as it is well documented that carbon sequestration has 2-3 times the potential to reduce CO2 levels than methane emission reduction and the reduction in atmospheric N2O is crucial since its warming potential may be 300 times that of CO2, in addition to the pollutant being a significant ozone depleting gas.

In one of Milk SA’s R & D projects carbon balances are being calculated by making use of a purpose-built systems dynamic model using Vensim®. This model plans to incorporate plant, soil and cow (metabolic) variables which capture all emission, sequestration and sink based carbon, including that of electricity and transport. Provision will be made for calculations according to GWP100 or GWP* and differences in production systems utilising conventional (chemical-based) or regenerative methodologies, resources (e.g. monoculture vs multispecies), soil carbon levels and product output. The model in testing has proved to be robust and accurate while it also provides the opportunity to link the outcomes with the finances of the farm, which eventually will be consolidated in an app allowing every farmer to apply his/her own data. Calculations including all these variables from actual farm data of pasture-based production systems suggest that a number of farms are already at carbon net zero level, although the use of GWP100 or GWP* does have an influence on that outcome.