Profitability and net greenhouse gas balances in pasture-based dairy systems: an exploratory case study of twelve South African farms

Using net greenhouse gas (GHG) balances from the DESTiny biogenic carbon model ( https://assetresearch.org.za/on-farm-carbon-capture-and-storage-capacity/ ) together with detailed farm financial accounts, this exploratory case study examines how profitability and net GHG balance co-vary on twelve pasture-based dairy farms in the Garden Route region of South Africa. Net GHG balances, the annual net flux of emissions and removals within the farm boundary, include enteric methane, manure, soil N₂O, emissions from on-farm energy use and purchased inputs, and net biogenic carbon fluxes. Eleven of the twelve farms achieved net GHG removals (a negative net GHG balance) and all farms were profitable, with mean net profits (before carbon valuation) of USD0.39 kg −1 fat- and protein-corrected milk (FPCM), USD6,331 ha −1 and USD2,105 LSU −1 , and mean net GHG balances of −0.95 kg CO₂e kg −1 FPCM, −14.4 t CO₂e ha −1 and −4.71 t CO₂e LSU −1 . Profit per hectare was negatively associated with net GHG per hectare (Spearman ρ = −0.70, p = 0.011), and this association remained when the only net-source farm was excluded (ρ = −0.66, p = 0.026). Associations per kg FPCM (ρ = −0.31) and per LSU (ρ = −0.34) were weak and not statistically significant. Valuing the net GHG balance at the South African carbon tax rate (R190, about USD25.7 t −1 CO₂e) strengthened all three associations, and at USD100 t −1 CO₂e the per-kg association became significant (ρ = −0.76, p = 0.004). Farms that combined high profit per hectare with large net removals typically had high forage yields, a large share of the forage area under no-tillage, moderate synthetic nitrogen use and a feed-sourcing strategy that balanced self-produced forage with purchased concentrates. The results are descriptive and specific to this sample, but they suggest that, once biogenic carbon removals are accounted for, land-efficient management in pasture-based dairy systems can go together with both profitability and larger net removals, and that valuing the modelled net GHG balance at a carbon price would reinforce this alignment at the product level. The net GHG balances are modelled annual flows, not measured changes in carbon stocks, and the carbon valuation is a hypothetical shadow price, not marketable carbon.