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Soil Carbon: Can We Have Our Cake and Eat it Too?

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A key part of the Australian Government’s Direct Action Plan to presumably reduce emissions is to encourage the sequestration of carbon in soil. Given that the government has ‘axed the tax’ and plans to scale back or abolish the Renewable Energy Target, soil carbon sequestration is a key part of Australia’s carbon abatement policy. Soil carbon sequestration offers the alluring possibility of reducing Australia’s emissions without ‘clobbering the economy’. Instead of penalising businesses for emitting carbon, the Australian Government, through the Emissions Reduction Fund, will provide direct incentives for businesses to be rewarded for reducing carbon. Farmers will be a key beneficiary by producing carbon credits that polluters can use to offset emissions. This will allow Australian industry and consumers to operating as we always have without the associated economic restructuring caused by de-carbonising our energy sector.

How does soil carbon sequestration work? Essentially, it is a process where plants draw in carbon from the atmosphere and store it in the soil. Plants need carbon to grow. In fact, soil scientists have been alarmed at the falling rates of soil carbon in Australia and what this means for agricultural productivity and flora biodiversity. The Food and Agriculture Organization estimates that agricultural land could sequester up to 10% of atmospheric carbon, or 20 Petagrams (Pg, equal to 1 billion metric tons). To put that into perspective, in 2008 China emitted 6.5 Pg, USA 5.8 Pg and Australia 0.4 Pg. In addition, soil carbon sequestration have valuable co-benefits in improving agricultural productivity and enhancing the resilience of farms to droughts and other extreme weather events. There are also environmental co-benefits from soil carbon sequestration, such as improving the land’s ability to retain water. Clearly, soil carbon sequestration could be a key tool to fight climate change, as well as other looming global issues such as food security and water scarcity.

Despite the potential, there are some concerns about using soil carbon sequestration. The first is the lack of permanence. That is, storing carbon in soils is not treated as a permanent reduction in carbon emissions unlike (for example), switching from coal-fired power stations to solar power. This is because soil carbon levels change in response to natural and human-induced events. The lack of permanence reduces the value of carbon credits generated from soil carbon sequestration relative to permanent carbon reductions. Lower value for the soil carbon sequestration would also reduce the incentive for both farmers and investors to implement these projects. For some farmers, this may not be an issue because the shorter duration of soil carbon sequestration carbon credits means they do not have to lock up their land on a permanent basis.

Another concern is the limited commercial return from soil carbon sequestration. Analysis by Melbourne University researchers indicated that carbon credit prices of $23/t would be insufficient for farmers to generate a profit from soil carbon sequestration. This is mostly because of the cost of nitrogen required to stabilise the carbon in the soil. That is, additional nitrogen-based fertilisers are required to keep carbon in the soil. The analysis did not include the yield bonus from storing carbon which may outweigh the additional cost of nitrogen inputs. However, the analysis also did not account for additional irrigation costs to maintain pastures. For soil carbon sequestration to financially break-even, farmers would need to be able to sell their carbon credits for at least $30/t. Given that the Australian Government is the main purchaser of carbon credits under Direct Action and would have at the maximum a budget of $2.55 billion over the life of the Emissions Reduction Fund, at the most the Government will be able to finance the abatement of 85,000,000 metric tons (0.085 Pg) of carbon. This is approximately 20% of 2008 emissions. However, this understates the recurring cost of investing in soil carbon sequestration due to the non-permanence of the carbon credits.

Generating carbon credits from soil carbon sequestration is unlikely to appeal to all farmers. The financial attractiveness of soil carbon sequestration is critical for the success of the current Australian carbon reduction strategy. Leaning on Australian farmers may be insufficient to get the job done. And, the axing of the carbon tax may have actually harm the viability of the ‘carrots only’ strategy of relying on carbon credits to provide incentives to farmers and other industries to reduce carbon emissions. Unfortunately, the repeal of the carbon tax removed a major source of demand for polluters to purchase any kind of carbon credits. So what may happen is that the Australian Government may become the only purchaser of carbon credits to offset national carbon emissions. This means the tax-payer will be ultimately paying for polluters’ carbon emissions. This would hardly be efficient and equitable for polluters to lean on taxpayers for essentially returning to a more carbon-intensive economy.


  1. Andrew Hope says:

    By practising regenerative grazing coupled with an Holistic land management program, will greatly increase the productivity of the grasslands, greatly increasing both carbon sequestration and water retention of the soil without the cost of purchased fertiliser.

    • arthurchha says:

      Yes, that’s true for some systems. But as the University of Melbourne article points out, to stabilise the carbon in the soil you may need to add more nitrogen. I think this is more of a problem in Australia because soils here are generally nutrient-deficient. So, the eventual benefit-cost depends on whether or not on a net basis you reduce or increase your nitrogen inputs.

      • Andrew Hope says:

        I understand the problems of poor soils, my own grazing program was developed in Zimbabwe on Kalahari soils, as the foliage increases in volume, more atmospheric nitrogen is fixed by native legumes, and dissolved nitrogen stored in the higher soil moisture content, used by the other grasses and forbes. The native and introduced African forages in Australia respond readily to high density grazing as developed by Johann Zietsman and adopted by the Savory charities, the rapid defoliation/trampling combined with a suitably long rest period allows the plants to develop a deep rooting system bringing up deep seated nutrients, any further deficiencies will not affect adapted plants, but will need to be subsidised as supplements in any livestock in the ecosystem.
        The use of highly efficient artificial fertilisers restricts the development of deep roots, and short cuts the nutrient cycle, and to some degree, the water cycle as well as the deeper root systems facilitate better rain infiltration.

        • arthurchha says:

          That’s interesting. So can all pasture grasses fix atmospheric nitrogen? I’m not sure if that was taken account of in the Melbourne University article. That may reduce the need for bringing in nitrogen inputs. Thanks for pointing that out.

          • Andrew Hope says:

            It is mainly legumes that actually fix atmospheric nitrogen, grasses and non legume forbes utilise nitrogen dissolved by rain from the atmosphere, then it is stored as nutrients within the plant ready to be recycled through grazing wild and domestic animals. Nitrogen dissolved in rain water is unstable and has a limited period during which it is available to grasses and forbes after which it returns to the atmosphere, a high level of foliage cover, with increasing deeper rooting will utilise this nitrogen more rapidly and store as part of the plant structure. Trials in Africa, USA, Australia and South America show that a high density grazing system tailored for the specific ecosystem, is the only affordable and sustainable way to restore grasslands with the associated improvements in carbon and soil water storage. Try to get an on line copy of “Man Cattle and Veld” by Johann Zietsman, and any you tub talks by Alan Savory.

          • arthurchha says:

            Thanks for the tip. Does that mean livestock will graze on legumes rather than grasses? Or will there be some form of rotation?

  2. Earthwrecker says:

    Looks like a good proposal for more research in retension of carbon in soil. If the carbon sequestration can increase the productivity for the landowners, what is the political gain to the politician is an interesting question?

    Can you get any funding for this research?

    • arthurchha says:

      Well, the current Australian government is pushing soil carbon sequestration. Politically, it would appeal to their rural constituency so there is a clear gain there. As for funding, I think there could be demand for carbon measurement services. But I’m not sure there would be large adoption given the cost of soil carbon sequestration for the farmer. Of course, storing carbon in soils has productivity benefits so farmers may do this anyway to improve their soil.

  3. Andrew Hope says:

    It is essential that the herded stock eats as wide a variety of available plants to keep a healthy balance,and feed the soils, different plants play different roles in both nutrient storage, and available nutrients for the stock, so a wide variety as found in natural grasslands is essential, as opposed to the monocultures in planted pastures. The stock needs to be herded in such a way that they graze and trample the plants quickly, and move on so that the grazed portion of the grassland has the opportunity to have a long rest to maximise plant recovery, and soil health.

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