Current options to reduce greenhouse gas production and store more carbon on Northern Territory pastoral land

In the last decade, much research and policy development has focused on creating demonstrable, auditable, evidence-based ways either to reduce carbon emissions (mostly cattle burping and fires) or to increase carbon storage (sequestration) in the soil or vegetation. Meat and Livestock Australia has a goal for the beef cattle industry to become carbon neutral by 2030, which is not that far away. Businesses can sign up to use approved methodologies under the Emissions Reduction Fund (ERF) and be awarded carbon credits (which can be sold or traded) for demonstrable avoided emissions or additional carbon stored. There has been widespread uptake of land-based mitigation projects under the ERF (Figure 1).

But what methods are actually relevant to the Northern Territory (NT) cattle industry right now?

Reducing carbon emissions

Methane emissions by beef cattle

There are several theoretical ways to reduce methane emissions by cattle in the extensive grazing industry, although some are still the subject of ongoing research.

• Optimise herd productivity and reduce methane emissions intensity (emissions per kg live weight produced) by herd management and breeding.
• Improve pasture and diet quality through planting legumes.
• Feed additives, including seaweed.
• Use rumen interventions, such as enteric methane inhibitors.

So far, there has been no breakthrough in feed additives or enteric methane inhibitors technology applicable to the extensive rangeland scale relevant to NT pastoral operations. It is hoped that in the near future cattle feedlots could provide feed additives to reduce methane emissions, but this technology is yet to be trialled so there are no guarantees.

Methods to reduce cattle emissions approved under the ERF

• The Nitrate methodology supplements cattle with nitrate instead of urea to increase digestion and, therefore, intake of poor quality pastures. Theoretically, this can reduce methane emissions while still providing cattle with nitrogen to feed the rumen. However, when this methodology was tested in north Queensland there was the potential for stock poisoning and decreased animal production.

The reduction in methane emissions with nitrate supplementation is relatively modest, around 10%. The higher cost of nitrate compared to urea supplementation is a barrier to adoption and there are currently no delivery technologies suitable to extensive rangelands, although this is an area of ongoing research. Given these shortcomings, it is not surprising there are no projects contracted under this methodology anywhere in Australia.

• The Beef Cattle Herd Management methodology aims to increase livestock productivity and decrease methane emissions intensity (emissions per kg live weight produced), but not necessarily methane emissions in total. For example, a breeder herd with poor performance may contain many cows that are not producing calves but are still eating grass and producing methane. If the herd is culled so only productive breeders are retained, calf numbers can be maintained with fewer total animals and lower methane emissions per kg live weight produced.

Eligible activities also include supplement feeding, planting improved pastures, improving herd genetics, and adding water points and fences, as long as they contribute to decreased herd emissions intensity. This methodology is applicable to any herd that can be better managed for productivity. Profitability may also be enhanced through increasing herd productivity. There are fewer opportunities for well-managed high performing herds, because they are already implementing these activities. Four out of the 5 contracted herd management projects across Australia include NT cattle. The listed NT participants are AACo, Consolidated Pastoral Co., Corporate Carbon Co. and the Indigenous Land and Sea Corporation.

Greenhouse gases emitted by fire – Savanna Burning projects

Areas with frequent, extensive late dry season fires can be managed by implementing early dry season burns that are less intense and, therefore, produce less greenhouse gas emissions. This Savanna Burning methodology is widely applied in the NT with 25 approved Savanna Burning projects covering 165,767km² or 12% of the total NT land area.

The NT has 32% (25 out of 78) of the Savanna Burning projects contracted across Australia, covering 52% of this methodology by land area nationally. Land with a history of high fire frequency is the most suitable for Savanna Burning projects. Most of the current Savanna Burning projects are located in the Top End of the NT on Aboriginal and conservation lands.

An analysis of the fire frequency in the VRD found that fire frequency was highest on land that was ungrazed, regardless of land tenure, but that grazed land usually had low fire incidence. Ungrazed land types on pastoral leases and conservation, defence and Aboriginal land had the highest fire frequency. Pastoral leases with low productivity land types can have high fire frequencies suitable for Savanna Burning projects, but the project area would only be for those high fire frequency areas.

Only 5% of the total pastoral lease area in the NT has active Savanna Burning projects. After an initial strong uptake by the NT pastoral industry, contracts for 12 stations have since been voluntarily revoked (covering 50,126km², or 3.7% of the NT, and 5% of the NT pastoral lease area).

Increasing carbon storage

Other carbon methodologies aim to grow plants to take carbon dioxide out of the air, known as carbon sequestration. Above-ground carbon sequestration includes both live and dead trees and shrubs. Carbon farming below ground includes carbon stored in the soil due to the growth of roots and soil microbes, and incorporation of above-ground plant litter into the soil.

Savanna Burning sequestration

The 2018 Savanna Burning sequestration and emissions avoidance methodology also accounts for additional storage of above-ground dead vegetation with lower fire frequency. It requires a longer contracted period (25 to 100 years). There is only one project contracted under this methodology in Australia so far, on an Aboriginal-owned pastoral lease in Cape York, Queensland.

A further Savanna Burning methodology that takes into account the additional carbon stored in live vegetation due to milder fire regime is currently in development.

Other carbon farming sequestration methodologies

The remaining Carbon Farming methods are not yet used in the NT. They include all methods relating to increasing above-ground sequestration by letting trees regrow, planting trees, or not clearing trees, and soil carbon sequestration.

The methodologies not yet applied in the NT include:

• vegetation methodologies
• reforestation
• avoided deforestation
• avoided clearing of native regrowth
• human-induced regeneration of even aged native regrowth
• permanent environmental plantings of native species
• plantation forestry
• new farm forestry native plantations
• native forest from managed regrowth
• soil carbon sequestration by:
  • altering stocking rates, grazing duration and intensity
  • planting permanent pastures on former cropland that has depleted soil carbon
  • fertilising the soil to increase soil carbon potential.

The low proportion of the NT that has been cleared or cropped explains the lack of relevance and uptake of many of these methodologies in the NT.

What about soil carbon?

Soil carbon potential is quite low over much of the NT due to low soil fertility and or rainfall. However, even on more productive soil types, studies have found that soil carbon storage is naturally low in northern Australian grazed systems.

A review of soil carbon research on grazed lands across the NT and Queensland found there were no consistent soil carbon changes with different grazing land management or land condition. It was difficult to predict both the direction and magnitude of soil carbon changes based on land condition and management. This means that soil sequestration methods are relatively risky for landholders seeking a financial return on a changed management practice. The research was not able to demonstrate that improved land condition had much effect on soil carbon. The poorest land condition D tended to have lower soil carbon than A and B condition on grazed lands, but C condition land often had similar or higher soil carbon. For example, areas of C condition near water points in the Barkly Mitchell grasslands sometimes had higher soil carbon despite almost no pasture growth, due to cattle dung being incorporated into the soil. This represents the redistribution of carbon from the paddock to near the water point, rather than a net gain in soil carbon across the paddock.

What’s good for soil carbon isn’t necessarily good for grazing. Changes in pasture composition and woody thickening that are undesirable for grazing can be benign or positive for soil carbon. Low palatability perennial grasses have similar soil carbon as palatable perennial grasses. In the Wambiana grazing trial, soil carbon was highest with woody thickening at the expense of pasture availability for livestock production.

While it is often claimed that cell grazing can increase soil carbon, they found the opposite on buffel pastures at Douglas Daly Research Farm. Cell grazing resulted in lower soil carbon storage than continuous grazing when grazed at the same average stocking rates. In Mitchell grasslands at Toorak, Queensland, soil carbon decreased with higher continuous stocking rates. It is likely that as long as the stocking rate is appropriate, the impact of how the landscape is grazed (continuous vs. rotational) is less important for soil carbon.

At the long-term fire experiment at Kidman Springs, there was a slight trend for lower soil carbon with more frequent and early-burnt fire. This might be because frequent and early fire leads to less herbage and tree litter inputs into the soil. Researchers estimate that it may take up to 50 years for fire treatments to have detectable effects on soil carbon.

The department is currently collaborating with the University of Queensland to research the effect of fire and grazing on soil biological crusts and how much nitrogen and carbon is fixed into the soil at the Kidman Springs fire experiment and the Wambiana grazing trial (QDAF).

Summary

The greenhouse gas mitigation methods currently being implemented by the NT pastoral industry are the Savanna Burning methodology and the Herd Management methodology. A silver bullet to reduce methane emissions by cattle in extensive pastoral operations is still not available. Small gains can be made by improving pasture quality and herd efficiency and, where relevant, reducing late dry season fire.