Emissions and abatement

The challenge for agriculture

The Australian Government plans to reduce greenhouse gas emissions in Australia via putting a price on carbon emissions and by other direct measures such as the Carbon Farming Initiative and renewable energy targets.

The challenge for Australian agriculture is two-fold:

1. There are competing policy objectives between food security and emissions reduction. As a major supplier of food for the international markets, Australia has an important role in contributing to world food security. Unlike energy, there is no alternative mechanism for producing food and the need for protein will ensure that the grazing industries play an ongoing role in global food supply. Population is expected to increase by 50% by 2050. It is hard to reconcile the need to increase food supplies with the need to reduce global emissions, including from agriculture. Targeting agriculture to reduce emissions per unit of product (emission intensity) is one option for resolving the conflicting needs for increasing agricultural production to meet increasing population growth, while also demonstrating emissions reduction per unit of product.
   
2. It is hard to imagine Australia meeting its longer term target (an 80% reduction in emissions by 2050) if agriculture (currently 16%) is not included in the emissions reduction process. Pressure from other sectors to include agriculture will be intense. The Government has flagged that despite being omitted from any current plans to price carbon pollution, agriculture will have to find ways to reduce emissions. In addition, the Government is moving to implement the Carbon Farming Initiative to give landholders access to carbon markets for any emission reduction activities they undertake

Back to top

Emission sources on dairy farms

Dairy farms have several significant emission sources. If we use as an example, a 330 cow farm that grazes pasture but with a high level of supplementation (56% of the diet as grazed pasture, and 44% as grain), the farm will have total emissions of approximately 2,120 tonnes of CO2e per year. This will consist of about 55% as methane and 18% as nitrous oxide (the so-called on-farm emissions) plus about 18% as embedded emissions in farm inputs (bought in feed, fertiliser and chemicals) and about 8% from on-farm energy use.

Methane production in the rumen of dairy cows is strongly associated with the digestion of forages, so high energy supplements (eg grain), or the use of fully mixed rations reduces methane per litre of milk. As a result, there is roughly 30% difference in emissions intensity between the two extremes of dairy systems – fully pasture fed (~17.5 t CO2-e/t milk solids) or fully lot fed (~12.5 t CO2-e/t milk solids).

Under current plans, carbon accounting, farmers are only accountable for the on-farm emissions (ie methane and nitrous oxide). The embedded emissions in farm inputs are accountable at the point of manufacture, or for bought in feeds, on the farm that produced the feed. Energy use (electricity and fuel) is accountable by the energy generator or the fuel refiner. If there is a price on carbon emissions, that price will be paid by the input providers and added to the price of dairy inputs.

Back to top

Possible abatement strategies

Dairy Australia and partners have been working hard to understand the abatement options for reducing farm emissions. Some ‘possibilities’ are listed below, but until there are clearer policy signals from government around a price on carbon emissions and the Carbon Farming Initiative, advocating one over another is not possible – even then, individual farm situations and options will vary. There has been no attempt in the list below to differentiate possibilities that are currently available from those that are yet to be developed, nor between possibilities that might or will not be available for support via the Carbon Farming Initiative. In addition, the possible strategies below should be read in conjunction with the information in “What should dairy farmers do now? (link) which concludes (among other things) that dairy farmers should focus on current efficiency and profitability rather than directly targeting emissions reductions. 

Herd

• Reduce herd size to minimise total emissions
• Reduce the number of unproductive animals to increase efficiency
• Extended lactations reduces the number of dry cows
• Animal breeding for lower emissions
• Higher feed conversion efficiency to reduce emissions per litre of milk
• Extended longevity in the herd reduces replacement rates
• Balanced crude protein in the diet to reduce urinary N and nitrous oxide emissions
• Rumen manipulation to reduce the abundance of methane producing microbes

Feed 

• Higher levels of grain feeding reduce emissions per litre of milk
• Feeding fats, oils and condensed tannins reduces methane production
• Maximising diet digestibility reduces methane production
• Balancing energy and protein contents minimises nitrous oxide emissions from urine
• Pasture breeding may offer improvements in feed quality and in rumen methane or urinary N production

Soil

• Improving drainage reduces the possibility for nitrous oxide production;
• Improving irrigation – similar to improving drainage by reducing waterlogging;
• Reduce grazing on wet soils when urine patches will be most likely to emit nitrous oxide;
• Nitrification inhibitors (on fertiliser, fed to cows, or applied to pastures as a spray) can reduce soil N loss as nitrous oxide; 
• Fertiliser management (rates, timing and type) – urea is less likely to produce nitrous oxide, while the timing needs to avoid waterlogged soils;
• Effluent management – as with fertiliser management.
  

At present the best advice to dairy farmers is to follow current best practice for soil, pasture, fertiliser and herd management as this will minimise greenhouse gas emissions per litre of milk. If Government plans to force down farm emissions become clear, more definitive examinations of how dairy farmers should act to reduce emissions will be explored through current R&D channels.

How these strategies can be applied to reduce methane and nitrous oxide emissions on dairy farms can be explored through the DGAS calculator.

Other abatement options include:

Methane digesters

Some large dairy farms and feedlots may produce sufficient manure from dairy effluent to make biogas generation from methane an option.

Reduce on-farm CO2

Though not counted as ‘farm emissions’, there is scope for more efficient energy use on some farms, with associated cost savings.

Reduce pre-farm embedded emissions

Not ‘farm emissions’ for accounting purposes and representing a very mixed bag. If increased grain feeding and/or increased nitrogen use (pasture quality) is a strategy for reducing methane, then more off-farm inputs, with a higher overall level of embedded emissions will be needed on dairy farms. On the other hand, production/manufacturing efficiencies in other industries could reduce the embedded emissions in farm inputs.

Back to top

References and resources

Christie, K; Rawnsley, R; Donaghy. (2008) Whole farm systems analysis of greenhouse gas emission abatement strategies for dairy farms. Final report to Dairy Australia on the investigation and analysis into greenhouse gas abatement strategies, modelling and decision tools for the Australian dairy industry.

Eckard, R. Greenhouse gas research, mitigation options & policy developments for agriculture. 4 page fact sheet

 

Back to top