Emission factors and carbon emissions of methane from enteric fermentation of cattle produced under different management systems in South Africa

Production of livestock is important for sustainability of human nutrition and overall livelihoods. Demand for livestock products is increasing due to the growing global human population. Cattle production plays an important role in South Africa's socio-economics and largely benefits from vast rangelands available for grazing. Similarly, cattle and their management are significant emitters of greenhouse gases. Quantification of past cattle emissions in the country is, however, affected by unreliable activity data and emission factors. This study therefore aims to calculate emission factors for methane (CH4) produced by cattle during enteric fermentation and the related historical CH4 carbon emissions. The emission factors are developed for each cattle subcategory and management system. Feeding practices are collated from the survey conducted in 2015 and the literature. Dairy cattle have the highest emission factors, followed by subsistence beef and commercial beef cattle. However, the large population of commercial beef cattle results in the highest total emissions by category whilst dairy cattle are the smallest producers of CH4. Of the total CH4 emissions from enteric fermentation of 0.87 million tonnes in 2018, commercial beef cattle contributed 48% while subsistence beef cattle and dairy cattle accounted for 36% and 17% respectively. Declining population particularly of commercial beef cattle results in a reduction in emissions with time. Trends of implied emission factors and emissions per energy-corrected milk and animal carcass weight for beef cattle show that cattle production efficiencies are improving in South Africa. Despite relatively lower meat prices for beef compared to poultry, poultry consumption in the country is higher than that of beef and is still growing. This pattern will out-market beef consumption and ultimately cause the emissions to decline.