Emission intensity

Jane Court, Richard Eckard, Ralph Behrendt and Graeme Anderson

Total greenhouse gas (GHG) emissions are measured in kilograms or tonnes of carbon dioxide equivalents (CO₂e). The main GHG on farms are carbon dioxide, methane and nitrous oxide. The CO₂e takes into account the different global warming potential of these gases.

An emission audit splits emissions into scope 1, 2 and 3. Scope 1 are all emissions produced on the farm (such as from livestock production); scope 2 covers emissions from energy use, and scope 3 are the emissions produced by inputs that come into the farm (such as feed supplements and fertilizers).

Methane emissions from livestock farms are driven by livestock numbers

Greenhouse gas (GHG) emissions from livestock farms are a numbers game. The more stock, the higher the GHG emissions, as the main source (>70%) is methane from digestion in the animal and breakdown of manure. How much animals eat is directly related to the amount of methane produced.

So the number and weight, or dry sheep equivalents/adult equivalents run on a farm are the primary driver of emissions. There are currently few cost-effective technologies for farmers to substantially reduce methane without reducing stock numbers, so research will be required to achieve significant reductions.

There is potential for some farmers to make significant reductions through carbon sequestration in trees and soil, but these will reach a plateau over time so provide temporary carbon solutions but other long term benefits.

Emission intensity (EI)

Emission intensity (EI) is estimated as total GHG in kilograms CO₂e divided by the units of product produced (as sold). For livestock the units of product can be measured in kilograms of liveweight (LWt) or wool sold from a farm. For example, this means EI is reported as kg CO₂e per kg LWt.

EI is a more useful measure for agriculture as it is a measure of efficiency of production rather than size. If farms were currently compared, or products sourced, on lowest total farm emissions, then small farms would be selected which would be a perverse outcome. Strategies that improve production efficiency will generally drive down emission intensity and improve profitability.

Emission intensity from livestock is the tonnes of CO₂e divided by the tonnes of product from the livestock

Farmers currently have more options to reduce this number than they do to reduce total emissions. As farm value chain targets are all EI based, incentives or demand for lower EI products is likely to increase.

Think of emissions intensity as a ratio (kg CO₂e/kg liveweight or wool). To reduce EI, you can either reduce total GHG emissions (for the same production), or increase total product produced (for the same emissions).

Either way, the ratio decreases. Greenhouse gas farm calculators, like the Melbourne University Sheep-Beef Greenhouse Accounting Framework (SB-GAF) and the MLA carbon calculator, generate an EI value for beef and sheep meat (as live weight LWt) and greasy wool. The EI can include sequestration in trees. For grain crops, the EI is a measure per tonne of grain and for dairy as emissions per kg milk solids.

Benchmarking

Emission intensity values allow for comparison and benchmarking between farms of different sizes. The emission intensity for beef, sheep meat and wool differ because of fundamental differences in the systems. It is therefore unhelpful to compare EI between products.

Potential improvements or reductions in EI will also depend on the local environment/climate. For example, high rainfall improved pastures may have more potential to reduce EI, due to quicker turn off times and higher fecundity associated with better pasture production. Sheep systems are typically more efficient with regards to EI as their emissions are divided over two products (wool and meat), plus have higher twinning, which generally results in lower emissions intensities for sheep meat than for beef.

Table 1 provides a common range of EI figures for beef, sheep and wool for southern Australia.

Table 1: Common emissions intensities for Australian beef and sheep production (based on calculations from SB-GAF calculators).

Allocation between products on farm and for meat and wool

If a farm produces several products e.g. beef, hay and grain, then total farm emissions will be spread across the enterprises to reflect the inputs used for each. As sheep produce meat and wool, emissions need to be allocated between the two.

This is done in emission calculators according to the protein required to produce each. Wool is always the larger number in terms of percentage protein – but wool and meat cannot be compared on their EI as they are quite different products.

Also, as fibre diameter (micron) is the main determinant of price and end product, and is negatively correlated to weight, efficiency of wool production is not recognised in the EI number.

Comparing EI from wool of similar fibre diameter would be a better way to compare farms. Note that if you have a shedding flock and there is no wool harvested, all emissions are allocated to meat production.

What practices reduce EI

Reducing EI can therefore be done by reducing the total emissions (without reducing the amount of product sold) or by increasing the amount (kg) of product sold from the same number/weight of animals. Because EI relates to efficiency of production, many strategies that reduce EI can lead to increased production and/or profitability.

Profitability and farm goals will be the main driver of making changes, but if EI also improves, this can be a bonus.

What else affects EI?

Total emissions and EI will vary from year to year on most farms. If the farm is in a build-up phase (and therefore do not sell many animals) or sell down (e.g. in a drought) then EI could be much higher or lower (respectively) than in a more normal or stable year.

If this is the case, this needs to be taken into consideration when looking at or comparing your EI numbers to other farms and within the farm over time. Looking at a year that is in a steady state or a 5-year average may be more useful. When making comparisons, ensure that scope 3 emissions are included in the EI and clarify whether sequestration is included, as both can have significant effects on the number.

Why is emissions intensity important?

With International Financial Reporting Standards now including climate-related disclosures, plus most agricultural value chain companies setting GHG targets, value chains are increasingly being required to account for their emissions. Some are also looking to promote low carbon products.

Australian farmers have continuously improved livestock productivity and efficiency to increase profitability and respond to climate and market variability. Many of these practices will directly reduce EI. As an example, a study in 2009 showed how methane per unit production had been trending downwards over the previous couple of decades in the beef industry, due to improvements in animal breeding, diet and management.

This article is an abridged form of a fact sheet produced as part of the MLA CN30 project.