Scientists suggest changes to Australia’s soil carbon methodology

Beef Central, 29/09/2023
William Edge, Shutterstock

Australia’s plan to achieve net zero greenhouse gas emissions by 2050 relies heavily on carbon credits.

These credits are awarded to projects that avoid the release of greenhouse gases or remove and “sequester” (store) carbon so it’s no longer warming the atmosphere.

Farmers can be awarded credits for increasing soil carbon content. The federal government or companies can then purchase these credits to offset their carbon emissions.

These credits must represent genuine carbon sequestration if they are to mitigate climate change.

As Australian agricultural and soil scientists, we have serious concerns about the way credits are awarded for soil carbon sequestration under the Australian carbon credit unit scheme. There are four main issues with the method that must be addressed as a matter of urgency.

Soil organic carbon is the treasure beneath our feet (Food and Agriculture Organization of the United Nations)

Understanding the carbon cycle

Much like water, carbon cycles through the environment, moving between plants, the earth and the atmosphere.

Plants take in carbon dioxide from the atmosphere as they grow. The carbon is stored in the plant tissue. When plants die, or drop leaves, this carbon-rich organic matter enters the soil. Then it decomposes, releasing carbon dioxide back into the atmosphere.

When carbon inputs from plants exceed losses from the decomposition of organic matter, the amount of soil carbon increases. That means soil organic carbon is more likely to increase during good seasons when there’s plenty of rainfall available to support plant growth – such as during the recent three-year period of consecutive La Niña events.

Graphic illustrating how carbon cycles through agricultural systems
The carbon cycle.
Richard Eckard, University of Melbourne

Increases need to be due to management

The recent tranche of credits awarded to soil carbon projects raises similar concerns to those that have been raised by experts about credits awarded to trees. Namely, carbon credits are being awarded for changes associated with seasonal conditions (changes that would have happened anyway) rather than human actions.

The current soil carbon method awards credits when an increase in soil organic carbon is detected between two points in time. This is problematic because it can award credits to projects that report increases during relatively wet periods.

This is the case for projects sampled in 2021, directly after a period where conditions were unusually favourable for plant growth. That means credits were awarded for sequestration that had more to do with the weather than good management.

Where crediting occurs due to seasonal conditions, the scheme is not providing any true (additional) climate change mitigation.

Soil carbon can be lost

Where soil carbon losses are greater than inputs, soil carbon stocks decline and sequestered carbon is released back to the atmosphere. The emissions can be rapid and considerable.

Furthermore, modelling indicates it’s likely soil carbon could be lost under the warmer and drier conditions of future climates.

Where a project loses soil carbon, the legislation does not require excess credits to be returned. Rather, a scheme-wide buffer generated from all sequestration projects covers such losses.

This approach is inequitable because all projects share the same burden of maintaining the buffer, irrespective of the risk of reversal of individual projects.

Overinflated sequestration rates

Based on a comprehensive global analysis, the number of carbon credits generated by some Australian projects appears unrealistically high. The most likely reason for these large values is high rainfall, but the way the method works makes it impossible to know for sure because the impacts of management are not identified.

This is not the first time a soil carbon project has made unrealistic claims.

In addition, one project saw 44% of the increase in soil carbon at depths below 30cm. This is an issue because published studies show soil carbon changes in deeper soil are relatively small and happen slowly. We are concerned the reported changes may have more to do with the way they were calculated.

Currently, data used to calculate credits are not released by the scheme regulator so cannot be scientifically verified. The release of data under strict non-disclosure arrangements would allow scientists to assess the implementation of the method. This would provide confidence credits generated represent real climate change mitigation.

Increased transparency was a key recommendation of the Chubb Review of Australian Carbon Credit Units in 2022.

Contributing to our emissions targets?

Australia’s emissions are reported annually to the United Nations in the national greenhouse gas inventory. These annual inventories show progress towards our declared emissions reduction targets.

The current inventory method used to account for changes in soil carbon uses coarse regional-level statistics. Changes to practices at farm level, such as grazing management, are not detected and will not be reflected in our national greenhouse gas accounts. Further, Australia reports changes in soil carbon for the top 30cm of the soil only whereas carbon credits are also awarded for changes that occur deeper in the soil.

This means some soil carbon credits the Australian government purchases do not count toward our emissions targets. It calls into question the effectiveness of using taxpayer funds to purchase soil carbon credits as a policy tool.

Getting it right

To address the issues we have identified, the measurement-based soil carbon method needs to be revised to only credit increases due to management. For instance, the Verra scheme in the international voluntary carbon market uses a method that minimises crediting for increases associated with rainfall.

To support revision of Australia’s scheme, scientists should be granted access to project data. Data could to be used to improve models in order to distinguish between climate and management effects. This would ensure the method is fit for purpose.

There also needs to be greater focus on monitoring changes in soil carbon. For a start, Australia’s Terrestrial Ecosystem Research Network should be extended to include agricultural land. This would provide data to increase transparency, independence and rigour of soil carbon estimates.

The revisions we propose would help ensure investment in carbon credits contributes to our national emissions reduction targets and addresses the urgent challenge of climate change.The Conversation

Aaron Simmons, Adjunct Senior Research Fellow, University of New England; Annette Cowie, Adjunct Professor, University of New England; Beverley Henry, Adjunct Associate Professor, Queensland University of Technology; Brian Wilson, Professor, University of New England; David Pannell, Director, Centre for Environmental Economics and Policy, The University of Western Australia; David Rowlings, Professor, Queensland University of Technology; Elaine Mitchell, Research Fellow, Queensland University of Technology; Matthew Tom Harrison, Associate Professor of Sustainable Agriculture, University of Tasmania; Peter Grace, Professor of Global Change, Queensland University of Technology; Raphael Viscarra Rossel, Professor of Soil & Landscape Science, Curtin University; Richard Eckard, Professor & Director, Primary Industries Climate Challenges Centre, The University of Melbourne, and Warwick Badgery, Research Leader Pastures an Rangelands, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.


Authors: Aaron Simmons, Annette Cowie, Beverley Henry,  Brian Wilson, David Pannell, David Rowlings, Elaine Mitchell, Matthew Tom Harrison, Peter Grace, Raphael Viscarra Rossel, Richard Eckard and Warwick Badgery.





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  1. George King, 03/10/2023

    I’m in full support and encourage anyone to manage their land in a way which increases soil carbon levels. The byproduct of this will be more stable environments, people and economics.

    Endorsement of Carbon as an environmental threat is flawed on every level. Mass symptom treating at a global level will most likely lead to increased carbon emissions whilst reducing resource availability, just as we are seeing in the renewable energy sector. If this madness gets imbedded into food production systems we will most likely see increased emissions and starvation.

    • Natalie Hick, 06/10/2023

      Conversely, if monetised, it will allow farmers and graziers to recoup their landscape improvement costs, focus on ag land regen and provide a longterm income stream additional to the production capacity improvements and yield improvements.
      All onfarm landscape remediation has a cost/benefit and a level of risk involved. I urge you to read the fine print in the methodologies to see how the processes and compliance have buffers and consideration for droughts and other adverse events in sequestration timelines…I have been involved in soil carbon for over 12 years now, and while the commentary on this site is mostly negative…don’t underestimate the value of the robust and well thought out the ERF, scientists and regulators have put into ensuring accuracy…Maybe read the Chubb review…then compare it to the rest of the world. Continual putting down of the carbon markets in Australia will cause emitting companies to go offshore to secure credits for their emissions obligations and Australia will be much worse off…especially graziers and farmers who have an unprecedented opportunity to have a win/win. Be careful what you wish for…..

      • Aaron Simmons, 09/10/2023

        Hi Natalie

        There can be no double-counting of credits. Farmers can sell credits or have low C products – not both. Australian farmers will need to think carefully about the economic benefits of selling credits v maintaining market access as demands for low C commodities increases. If they need to retain credits to reduce their own emissions then there will no additional income stream from generating credits.

  2. Jim Shovelton, 01/10/2023

    I have yet to be convinced about the integrity of soil carbon sequestration systems. At a basic level I could not find any data (it may be there) on the spatial variation of soil C that would inform the sampling intensity to achieve an acceptable accuracy – say +/- 10%?? – what is the assumed error factor in the methodology?. Nor does there appear to be any consideration of laboratory error. As there errors are additive, so it is quite possible that the errors result in an inflated value at the start of the period and a lower figure at the end of the monitoring despite there being no change in soil C.
    Given that the analysis of the long term topdressing trial at Hamilton PVI (at the end of 25 years,) demonstrated a trend but no statistical difference between treatments (pasture growth that resulted in 4 fold increase in stocking rate) does not bode well for measuring C increases over shorter periods.
    Further, increasing pasture production to improve soil carbon, (through expenditure on fertilizer) will inevitably mean more stock will be run to cover the cost of the fertilizer. One model I looked at suggested that the likely increase in soil C would not offset the increase in methane from the extra stock.

    I firmly believe that the development of the Soil C story was a political fix that avoided the Government of the day addressing the hard issues of GHC emisssion reduction. We need to address methane, but the rest of industry needs to reduce their emissions and not assume that agriculture will be the saviour

    • Natalie Hick, 06/10/2023

      Every business that does sequestration calcs have various buffers and variance thresholds….ring them up and ask them…that is what i do and most are forthcoming with what you are querying. There is also ample allowance for laboratory error…again, ring the labs and ask them what their processes are for outlier samples. Sampling plans have additional sampling points which ensure extra cores in case there are sample problems. Read the sampling protocols, it is all freely available.
      Top dressing is not allowed in soil carbon methodology for additionality, so therefore there is no comparison to the example that you gave…topdressing only affects the top 10cms of soil, and is disregarded in the soil methodology…the sampling process is clearly available, just google the soil method and sampling protocols.
      Soil cores are mostly done to 1 metre or more, the national soils data base only accounts for the top 30 cms, so of course rudimentary calcs give a perverse outcome…that is why the companies doing sequestration projections are a better bet to talk to.
      Fertiliser is not able to be used as an additionality activity, therefore this is negated completely.
      Methane emissions are well documented to be reduced when ruminants are managed in regenerative systems. My clients undertaking carbon projects are in carbon positive positions (we measure their emissions footprints regularly to ensure their emissions balance) Livestock systems are the least emittive of any ag commodity…so the methane scare mongering is just that…scare mongering…hence the methane abatement method for livestock is only feasible on 200 000 head or more…as the abatement is minuscule. Look up on the ERF register the low number of Methane Abatement projects being undertaken.
      Soil holds the most carbon of any terrestial eco-system on the planet…it is the cheapest and easiest to replace on a national scale…historical records show that carbon levels have been greatly reduced since industrial agriculture was introduced…therefore, it makes sense that it is also the best way to draw down carbon from the atmosphere and put it back where it comes from…carbon below 30cms is recalcitrant…and is not susceptable to bushfires and adverse weather etc….deep rooted perennial plants ensure that it goes well below 30cms…their are thousands of research papers done on this aspect. The length of project ensures that the long term sequestration is ensured and mitigated…we know that there will be a drought every 5 years or so…there is contingency to pause projects while droughts are evolving…and 25 years ensures a balance of good and bad seasons.
      Agriculture is and can be the saviour…reducing emissions alone will not get rid of the carbon in the atmosphere…emissions reduction only slows the inevitable. Not sure why you want to shut down the only real opportunity for farmers and graziers, in both financial outcomes and being able to be the real champions of climate change. Since i have been involved in the soil carbon game, successive governments have ping ponged carbon for their own benefit…don’t confuse real outcomes on ground with the political banter and negative commentary. My experience is that both sides of government are addressing the GHG emissions seriously…it is the bureaucrats and scientists with an agenda who are the causative agents for the flux that is happening currently. Meanwhile, farmers and graziers keep on improving their lot….with the hope that they can make a positive difference for themselves and the environment….my hope is that they make some money out of it as well.

      • Aaron Simmons, 09/10/2023

        Hi Natalie

        Topdressing is allowed as an activity under the method we discuss in our article. Sequestering soil carbon can provide climate change mitigation, if it is truly additional and only the portion of abatement that is the result of management is credited.

  3. Angus Hobson, 01/10/2023

    As I’ve said elsewhere…if we’re not careful, ACCUs will end up being agriculture’s bitcoin – with values that oscillate faster than the rate at which carbon disappears in a drought.

    • Natalie Hick, 06/10/2023

      I get this question often…is carbon just another bubble and when will it all fall over?….May i direct you to the collapse of the carbon markets around the world which started around 2009…
      Yes, they have been going that long….I was studying carbon internationally from about 2011 and so watched it happen in real time…google this: and you can read about what happened over a decade ago now.

      So the rebuild of credit markets is off the back of collapses years ago…and have been fortified with underpinning rigour, checks and balances.

      The chances of global collapse are way less than 10 years ago…when it was proper frontiers and high risk odds. Most of the market failures are related to dodgy project development and flimsy international methods…so don’t confuse good, solid method development and the positioning of the Australian credit market evolved from overseas experiences.
      Read the Chubb review to get some clarity on how the industry faired last year.

  4. David Corr, 30/09/2023

    Excellent article!

  5. Jack Twyford, 30/09/2023

    About time that peer reviewed scientific comment on soil carbon is countering many of the nonsense conclusive statements that get air time in the media. Congratulations but you’ll need a lot of good luck in getting your position across.
    Jack Twyford. Msc Agriculture; Bsc Agriculture (Uni Sydney 1970).

    • Natalie Hick, 06/10/2023

      Would love to see the peer reviewed papers written by the scientists in this article regarding the latest science relating to soil carbon and their citations etc. I am also interested in their latest real time trial results and how they have come to the conclusions and commentary in this article.

      • Aaron Simmons, 09/10/2023

        Hi Natalie

        All of our research papers on soil organic carbon can be found in our google scholar profile. And there are more to published so keep your eye on our profiles to get an understanding of SOC dynamics in Australia.

  6. John Bavea, 30/09/2023

    Could not the same concerns be expressed, for tree carbon albeit a longer cycle. Flood, fire and/or oxidation?

  7. Peter F Dunn, 29/09/2023

    With no disrespect whatsoever to the wonderfully dedicated Australian scientists involved, this admission and intention is so genuine, it is painful.
    Taking a lighter approach to make a point, is the awarding of CCCU (Chinese Carbon Credit Units) under the same level of scrutiny and qualification???
    (Happy to stand corrected, but there is probably no such thing as a CCCU.)
    Are Chinese farmers expected to play their part in offsetting the increasing emissions of their homeland, which is massively increasing fossil fuel use without credible challenge from the UN or green advocates in Australia and other lower emitting countries?
    By comparison, if truthful and realistic assessments are made, Australian farmers are already doing more than a fair share of the required effort.
    The raw material production, smelting and processing, and then the manufacture, transport and installation of renewable energy units (end of life removal and disposal not included here, as is not the installation, maintenance and removal of the huge power transmission infrastructures) is far more worthy of examination than farming practices.
    Universities seem to have forgotten that the humble taxpayer, who provides all of the legislative framework, and some of the funding, within which and with which they operate, is entitled to have a return in their investment. These humble taxpayers, who include a million or more involved directly and indirectly in rural industries, are entitled to have some university research lean towards their interests and livelihoods.
    Not an unreasonable entitlement.
    So, to put it bluntly, chasing uncertain climate trivia in order that it can be taken up by Australian farmers, when the major emitters are exploiting our stupidity, is not a return on investment for our humble taxpayers.

    • Natalie Hick, 06/10/2023

      Have a look at this article:
      China have a long way to go, but at least they are doing something…no doubt they will do it bigger than other countries, as they have to…they have a huge emissions footprint.
      There are many articles that show emissions disclosures for china and other countries.
      Agree that Australian farmers are doing their fair share…and they need to be acknowledged and applauded for the innovation and common sense that they are responding with.
      Unfortunately, being at the coal face every day, i get the brunt of the continuous negative sentiment. It does stymie progress and opportunity when constantly getting bombarded with how bad the Australian carbon markets are.
      The overzealous use of the precautionary principle ensures funds are wasted on literature reviews and other rear view mirror research.
      Yes farmers are entitled to progressive and contemporary science which is happening all over the world…particularly when the co-benefits create uplift on multiple fronts…carbon, production, financial and eco-system regen are not out of the realm of possibility.
      Major emittors will go away, (overseas)…as the generation of credits in Australia is being obfuscated by slow project development and uptake…for all the reason i have stated already.

    • Garrey Sellars, 02/10/2023

      to Peter F Dunn
      nothing more to say you got it

    • Rory McGuire, 30/09/2023

      Peter, I think the researchers were making the point that Australian taxpayers have been paying out good money, whenever the government buys these ACCUs without, in many cases, anything useful being achieved; no carbon is being sequestered long-term in the soil. In other words the taxpayers are being ripped off. This has been an obvious problem for years and the Chubb report was far too polite. The fact the government will not release its calculations adds further weight to the suggestion that the scheme is partly fraudulent, at least according to reputable scientific reasoning. The researchers have done the agricultural industry a service by publishing this, even though it presents some unpleasant truths.

      • Natalie Hick, 06/10/2023

        Have a look at this CER quarterly report:
        It shows who are buying credits…the voluntary market is growing all the time.
        Government purchases of credits was done to underpin market fundamentals and now voluntary purchases are fast catching up…the safe guard mechanism has helped as well.
        Voluntary markets are also being established alongside the regulated market and i am loving having alternative options for my clients to access if and when they need.
        Would love to see your results that say that soil carbon is not being sequestered over the long term…that goes against all public and proprietary research all around the world currently…amazing that you have access to such data.
        I am also interested in the calculations that you talk about the government not releasing as well…could you post on here what you mean by this please…so that we can all review it. Thanks.

        • Aaron Simmons, 09/10/2023

          Hi Natalie

          We can access the underlying calculations within the methodology, they are publicly available. However, we cannot access the data from the project that was used in the calculations to better understand what changed over time to generate the credits. Is the method working as it should? We have no idea because the audit only make sure the calculations were done correctly, not that the calculations are correctly assessing carbon stock changes.

          Soil organic carbon is not being sequestered in Australian agricultural systems. It has been well documented that SOC has been lost, particularly in our cropping systems. Projections suggest that SOC will be lost as Australia becomes hotter and drier.

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