DAIRY FARM GREENHOUSE GAS (GHG) EMISSIONS VERSUS THE GLOBAL BASELINE AND GHG TARGETS FOR THE SA INDUSTRY.

Discipline: environment; Key words: greenhouse gas emissions, global baseline, milk yield, target, non-cow associated factors.

The Dairy Sustainability framework (DSF) of the IDF proposed that the Baseline for the global dairy sector should be set at the FAO (2013) figure of 2.9 CO2 eq per kg of fat and protein corrected milk (FPCM). It is accepted that different countries will vary substantially as GHG emissions are influenced by milk yield, feeding practices and efficiency of production. Thus, the figure for some developed country industries is as low as 1.6 CO2 eq per kg FPCM, whereas the figure of Sub-Saharan Africa is 9.0 CO2 eq per kg FPCM. The question is what is the most probable figure for South Africa and how do we compare with the suggested baseline? To calculate this research in the country and elsewhere has been consulted, which is summarized below:

Methane scenarios* of cows in milk as affected by level of milk production using SA developed calculations (Reference: Reference: C.J.L. du Toit, H.H. Meissner & W.A. van Niekerk, 2013. Direct methane and nitrous oxide emissions of South African dairy and beef cattle. S.Afr. J. Anim. Sci. 43, 320-339.).

Milk production/lactation (litres) 3150 5520 6900 8280

Methane emission/cow/year (kg) 132 152 161 168

Methane emission (g/kg milk/day) 34.5 22.6 19.1 16.7

Kg CO2 eq/kg milk/day 1.05 0.69 0.58 0.51

*The scenarios reflect direct methane emissions from enteric fermentation and manure, so do the conversion to CO2 eq. They do not include other associated CO2 sources on farm such as energy and fuel use, and waste management as in a life cycle assessment (LCA).

Comments:

Methane emissions are more in cows producing more milk because they eat more, but the relationship with milk yield is not linear because the ration progressively contains more concentrates which produce less methane per unit than roughages, and the increase in intake is also not linear.
As a result of 1, methane emission per kg milk decreases sharply with increasing milk yield. In terms of quotas, this also implies that with increased milk yields per cow, a smaller dairy herd can be managed and even more reductions in methane emissions.
It is of course not only cows in milk which produce methane, but also dry cows and heifers. An approximate correction to the figure of kg CO2 eq per kg milk per day on a herd basis will increase the figure to respectively 1.50, 0.98, 0.83 and 0.73.

Comparisons where other CO2 sources were included:

Kristensen et al (2011) calculated about 1.24 kg CO2eq per kg milk for a milk production of 8200 litres, which is based on a Lifecycle Analysis (LCA), including manure, electricity, fuel and fertilizer.

Galloway et al (2018) at Woodlands calculated about 1.49 kg CO2eq per kg Energy Corrected Milk (ECM) for an ECM production of 6680, also with inclusion of other sources of CO2 emissions.

Note the significant influence of non-cow associated factors on the CO2 emissions of the farm

Approximation to National average (2017):

Assumptions: Total milk production: 3 100 million litres

Total cows: 615 000

Total herd: 978 000

Milk per cow per year: 5600 litres

Calculations: Methane emission/cow/year = 154 kg

Methane emission (g/kg milk/day) = 21.6 [0.66kg CO2eq/kg milk/day]

CO2eq per kg milk per herd per day = 0.94

If the non-herd associated factors are included the herd figure may increase to 2.2 to 2.5 CO2 eq per kg FPCM per day.

This figure is already below the suggested Global Baseline. However, as the average milk yield per year of the national herd is a mere 5600 litres, we should set a target of 7500 to 8000 litres per year and 1.5 to 2.0 CO2 eq per kg FPCM per day.