Reducing the Carbon Footprint of Dairy Cows
March 9, 2021
“With more environmental pressures on farmers and direct support likely to change in the future, it will more important than ever that farm businesses aim to be sustainable both economically and environmentally.” says Brian Finch, CAFRE Agri-Environment Adviser. One environmental issue on the horizon is climate change and how dairy farms can reduce their carbon footprint.
Robert Bryson from Loughbrickland is a member of one of CAFRE’s dairy business development groups and has carried out a carbon footprint for the dairy enterprise in 2018 as part of the Dairy-4-Future project. The farm consists of 210 Holsteins with an annual milk yield of 9600 litres from 2.5 tonnes of concentrate per cow. Robert’s dairy enterprise foot-print was calculated at 0.99 kg of CO2 equivalent per kg milk corrected to 4 % fat and 3.5 % protein which is well below the DAERA’s Farm Business Survey average of 1.24. Strategies used to increase milk production often cause greater emissions in total but a lower emission intensity (in other words lower emissions per litre).
Methane is the biggest GHG and is responsible for about 50% of emissions, so milking top performing healthy cows for as long as possible will help lower the footprint. Robert has a replacement rate of 22% and calving interval of 385 days. He aims to breed cows that will last at least four lactations. His average lifetime performance per cow is currently 40,000 litres as compared to the NI average of 23,000 litres.
Nitrous oxide is next biggest GHG on a dairy farm, with the main source from spreading slurry and fertiliser, accounting for about 30% of emissions on NI dairy farms. Nitrous oxide is about 300 times more potent than carbon dioxide. Robert has been using low emission slurry spreading and spreads the majority of slurry from late February to May. Fertiliser usage is kept to a minimum by spreading to crop requirements based on a soil analysis and by maintaining optimum soil pH.
Concentrates contribute approximately 10% of GHG emission from dairy farming. Robert targets his concentrate feeding by feeding to yield in the parlour only with silage easy fed ad-lib. Robert’s feed rate is currently 0.26 kg per litre. Robert aims to maximise his milk from forage (MFF) which stands at 3900 litres per cow which is above the benchmark average of 1960 litres. Robert aims to have all cows out by end of February for 2-3 hours grazing and out full time by end of March. Silage quality is paramount to maximise MFF.
The remainder of the emissions in form of carbon dioxide, are from electric and fuel use. About half the energy costs for dairy farmers are associated with milk cooling and heating water for cleaning and operating vacuum pumps. Electric use can be reduced by using a heat exchanger to recover the heat released from milk cooling. Using solar PV panels to heat the water could also be considered and using LED lighting which Robert has already installed.
Brian concludes that “in Northern Ireland there is a wide range of production systems, from total confinement to spring calving grass based systems. Studies have shown there is more emission intensity variability within a production system than between systems, perhaps as much as 30%. Maximising efficiency within a system is more important than the type of system used”.