Carbon Calculators - Western Australian example farms

Page last updated: Wednesday, 27 March 2024 - 11:35am

Please note: This content may be out of date and is currently under review.

Dairy Cattle

Carbon Calculators – Western Australian Dairy farm example

Summary

A carbon account of an example Western Australian dairy farm was established using the D-GAF tool to assess the emissions from this farm. The data for this example was established from industry professional consultation . The example dairy farm is a 415 milking cow operation, producing on average 22 L/day/head. This is a non-irrigated production system, with 350 ha of improved pasture. Fertiliser applications included a total of 89 tonnes of Urea, and a total of 141 kg N/ha applied. 175 tonnes of lime was also applied.

Table 1 – Livestock numbers, weights and milk production

 

Milking Cows

Heifers >1

Heifers <1

Dairy Bulls>1

Dairy Bulls<1

 

Livestock Numbers

415

60

120

0

5

head

Liveweight

600

420

180

0

750

kg/head

Milk Production

22.3

NA

NA

NA

NA

L/day/head

Carbon Account Results

The largest percentage of CO2-eproduced was from enteric methane (60%), followed by the collective pre-farm scope 3 emissions (15%) then manure (12%).  The emissions intensity for milk solids was 13.87 t CO2-e/t MS/farm/year. The lowest contributing factors included electricity, fuel, herbicides and pesticides, and atmospheric deposition (1-2%) (figure 1). Most emissions emitted were methane, followed by carbon dioxide and nitrous oxide. The methane and nitrous oxide were predominantly produced from scope 1 emissions, where the carbon dioxide emissions were mainly produced from scope 3 emissions (figure 2).

Figure 1 – South West Dairy Example Farm emissions breakdown  (% tCO2e/farm)
Figure 1 – South West Dairy Example Farm emissions breakdown  (% t CO2e/farm)
Figure 2 - South West Dairy Example Farm greenhouse gas breakdown between gas type and scope
Figure 2 - South West Dairy Example Farm greenhouse gas breakdown between gas type and scope.

Enteric methane was the largest contributor to total farm emissions (60%). The largest factor influencing the production of methane is animal numbers, as numbers increase, particularly milking cows, the enteric methane will also increase. The amount of feed consumed influences the methane produced. Milking cows produced the largest daily methane yield (0.412-0.444 kg CH4/head/day), followed by the dairy bulls <1 year (0.236 kg CH4/head/day). The increase in methane produced by the milking cows, also aligned with the increase in feed consumption and milk production seen in spring. As liveweight increases there is also an increase methane produced by the animal.

Carbon sources of emissions such as lime, fuel and urea were reasonably small contributors to total emissions. Lime contributed 3% to the overall emissions, currently a small contributor due to the quantity of lime applied (figure 1). If the amount of lime needed increased, this would also be reflected in the emissions. Fuel and urea contributed to 2% of emissions independently. 7% of emissions emitted were due to fertiliser applications, including both nitrogen fertilisers and urea (figure 1). However, of the scope 1 fertiliser emission outputs, urea CO2 contributed 20% more t CO2-e/farm compared to direct fertiliser N2O emissions.

Two of the key influences on emissions from agricultural soils include leaching and runoff, and urine and dug deposited during grazing. Leaching and runoff contributed to 4% of the total emissions (figure 1). This is the leaching of organic nitrogen, and subsequent denitrification in rivers and estuaries. Leaching of nitrogen in soils includes both leaching of nitrogen from manure and fertiliser. In this example the emissions have been produced predominantly from fertilisers.

Manure represents 12% of the total emissions produced. Most of these emissions are present as methane from manure management strategies. While the anaerobic lagoon contributed to a smaller fraction of the manure management strategies implemented (table 2), the methane produced was much higher compared to the other manure management strategies. Urine and dung nitrous oxide emissions which were deposited during grazing contributed to almost a quarter of the total t CO2-e/farm manure emissions.

  Table 2 – Manure management

 

Pasture

Anaerobic Lagoon

Sump and Dispersal

Drain to Paddocks

Solid Storage

 

Manure management for milking cows

87.5

7.5

2.5

0

2.5

% of all excreta

Manure management for other dairy cows

100

0

0

0

0

% of all excreta

Options to reduce emissions in Dairy:

The largest challenge now is reducing the enteric methane emitted from the animal directly. The key ways to do this currently include improving livestock efficiencies, and reducing the emissions intensity. Other options such as feed supplements are potentially effective ways to reduce methane emitted by the animal, however these are not currently on the market, and will require extra expense for the farmer.

Animal genetics are the longest lasting and permanent options for reducing enteric methane. Changing genetics requires further research and it will take longer time periods to achieve.

The other large on farm emission is around manure management. These emissions are primarily from methane, but also include nitrous oxide. Measures to reduce GHG emissions from manure include stockpile aeration and composting which reducing methane emissions or adding urease inhibitors to manure stockpiles can reduce nitrous oxide emissions; urease inhibitors are chemical additives that stop or reduce the rate that urea is converted to nitrous oxide.

To reduce emissions from livestock urine some options include breeding for improved nitrogen efficiency, using forages with higher energy-to-protein ratios, and balancing high protein forages with high energy supplements.

There are a few other options to reduce, sequester or mitigate carbon emissions. These include, but are not limited to:

  • Sequester carbon by planting trees or encouraging remnant vegetation regrowth
  • Shift to renewable alternative energy sources
  • Reduce inputs
  • Improve livestock efficiencies by changing feed regimes, feed efficiencies such as increasing the improving the use of legumes in the system.
  • Use improved genetics to produce less methane,
  • Feed animals supplements that will mitigate methane mitigation
  • Prevent soil erosion by wind and water, and general improvement of soil characteristics (claying and liming)