Emissions in dairy
How do dairy farms contribute to greenhouse gas emissions?
Agriculture accounts for approximately 16% of Australia's total greenhouse gas emissions, with direct on farm emissions from dairy farms contributing about 19% of this, (or about 3% of total national emissions).
Each individual dairy farm will have a different emissions profile depending upon their farm system. Approximately 60 to 70% of a typical dairy farm's emissions arise from methane produced by the rumination of cows. Nitrous oxide arising from dung and urine contributes about 10%, while energy and indirect losses from wet soils contribute a similar amount. The contribution from the production of electricity used on farm is also about 10%.
Knowing how much each of the various sources of your on farm emissions contributes to the total farm emission is important to help determine where and how to invest your time and effort to reduce them. The Dairy Greenhouse Gas abatement strategies calculator can help to determine your farms emissions. The DEC Climate Change team can assist in providing information on dairy farm emissions.
Can I reduce my emissions and if so, how?
The implementation of any emission trading scheme or carbon pollution reduction scheme would impact upon dairy farms, however there are many opportunities for dairy farmers to reduce their total net emissions or emissions per unit of production now.
Reductions in emissions can be achieved either by
- directly reducing the total tonnage of greenhouse gasses produced, or
- reducing the amount emitted per unit of production (ie the amount of greenhouse gases emitted per kilogram of milk solids produced). Note that this could potentially lead to a net increase of greenhouse gases produced in total if milk production increases.
A net reduction of emissions can be achieved by the use of feed additives and rumen modifiers to reduce enteric methane or nitrogen inhibitors to reduce nitrous oxide losses from dung, urine and soil.
Some of the strategies to reduce emissions from the major sources of on farm greenhouse gases are also in line with best management practices and can also provide a positive productivity benefit, such as
- Better targeted and timing of fertiliser applications to reduce nitrogen losses,
- Balancing the feed rations for cows to ensure correct energy, protein and fibre ratios to maintain a well functioning rumen,
- Ensuring stock are adequately fed to achieve genetic merit and optimum milk production levels.
These improvements in farm management can also lead to improved productivity and profitability, although they may result in increased carrying capacity or milk production. This could potentially increase the total amount of on farm greenhouse gases produced, but reduce the greenhouse gases per unit of production (ie per litre of milk or kg of milk solids).
Emissions can also be offset by "locking" carbon up in various forms such as tree plantings, which can also provide additional benefits such as shade and shelter.
What does soil carbon mean?
Soils contain carbon in the form of decaying organisms or plant matter, humus, or as charcoal resulting from burning. Each of these forms of carbon build up and decline at differing rates, dependant upon the type of production system, management practices, rainfall and soil type.
Research is currently under way to investigate how soil carbon may contribute to a carbon offset market. Raising the carbon levels in soil can potentially store (or sequester) carbon and have positive soil health benefits, however soil carbon can be difficult and costly to increase, particularly if already starting with high levels.
Increasing the net soil carbon may be difficult to achieve on dairy farms as many already have high levels, and the potential to increase these over current levels may be limited. Also soil carbon can be easily lost through management practices such as cultivation or due to drought.