The Coalition still intends to repeal Labor’s carbon price and Clean Energy Future. Their alternative is ‘Direct Action’, more aptly named ‘soil magic’ as its budget costings critically depend on getting 60% of its emission reductions through increasing the amounts of carbon in agricultural soils.
I explained in a previous Climate Spectator article why the cheap Chicago Climate Exchange soil offsets scheme on which it is modelled, failed spectacularly. In short, the verification, measurement, protection and creation of soil carbon offsets to internationally acceptable standards is fraught with difficulties. It would cost 2 -20 times more than the $10 per tonne CO2 claimed by the Liberals. But there is another question: “Can anywhere near the claimed 85 million tonnes CO2 be sequestered in Australian agriculture soils each year?
The Coalition probably got excited about ‘potential’ CO2 sequestration estimates of over 1 billion tonnes per year cited by Garnaut 2011 (13). But this relates to total capacity of soil to take up carbon and would only be attainable if all of the agricultural land was planted back to woody vegetation, which of course will never happen. NSW DPI 2008 (17) stated that 18 million tonnes of CO2 sequestration / year is ‘attainable’ for NSW soils alone. This figure is also meaningless because it (like Garnaut’s figure) does not take into account cost, land use constraints, compliance requirements and likely farmer uptake.
At the other end of the spectrum of estimates are those complied by the Department of Climate Change (DCCEE, 2011) (11), for likely adoption of carbon farming under the Government’s current Carbon Farming Initiative. Taking into account cost and likely farmer adoption, they estimate one million tonnes of CO2 per year may be sequestered in soils at a carbon price of $33/tonne.
The Coalition’s claims are also based on a second miscalculation, contained in an article posted on the Liberals’ website. It states “If you increase soil carbon by one per cent …. that equates to taking 50 tonnes of CO2 out of the atmosphere.” Problem is that that soil carbon can’t be increased by 1% of total topsoil per year. Carbon comprises just 1% to 5% of topsoil and it is this figure that may be increased by 1% per year. This equates to about 0.5 – 2.5 tonnes, which is closer to the scientifically measured figures.
In the table below I have taken an inventory approach, using agricultural land areas from the Australian Natural Resources Atlas (2) and optimistically assuming adoption of improved practice on up to 50% of those areas.
The sequestration rate estimates for improved practices are mainly from peer reviewed research trials in Australia and the US (2) and range from 0.4 tonnes of CO2 per hectare per year for US rangelands, 0.9 for improved dry land cropping practices, 1.6 for improved grazing practices and 3.0 for conversion of cropping to best practice grazing. I have estimated 2 tonnes for bio char and 3 for sugar cane trash retention. The figure of 1.5 tonnes CO2 / ha year for oil mallee is from my own field measurements and DoCCEE’s FullCAM software. In reality, changes in soil carbon are highly variable according to soil type and carbon losses caused by fire, drought, cultivation and erosion events.
Author’s estimates of maximum achievable soil carbon credits from Australian agricultural land
Land use category /
Total area (million ha)
Carbon farming practice
Assumed area of improved practice (ha)
Indicative soil C uptake
(t CO2 /ha/yr)
Measur-able / verifiable?
Indicative C price to cover cost $/tCO2
100 year covenant acceptable?
Indicative soil carbon credits / offsets (tCO2/yr)
Kyoto-compliant carbon credits
Dry land agriculture
Woody biomass crops
(10% of area)
High rainfall land > 600 mm (11 m)
Perennial pastures; rotational grazing (50%)
Bio-char/ mulch crops (30%)
Trash retention (40%)
Grazing control (30%)
Agricultural land (47m)
Tree planting (1.5%, marginal land)
Non-compliant, unmeasured offsets
Rangeland native grass and mulga (200m)
Destocking to <20% current rates
Dry land cropping
Minimal tillage and stubble retention (40%)
Liberals’ ‘Green corridors’ of trees
Summing my estimates in the table, about 21 million tonnes of compliant CO2 credits per year could be created in agricultural soils. It’s a ‘ballpark’ estimate with many uncertainties so I’ll allow plus or minus 50% and state a figure of 20-30 million tonnes, most of which would cost $25 or more per tonne.
Other possible avenues for soil carbon sequestration would not be eligible for compliant soil carbon credits. About 100 m tonnes of CO2 per year may be taken up in destocked rangelands, which would not be measurable for at least 20 years, if at all. Up to 9 million tonnes/ year may be sequestered by stubble retention in dry land cropping but this is already common practice and would not be deemed ‘additional’.
The most economic carbon farming enterprise would be commercial biomass crops for bio-energy, fuels and bio-char. If 4 million hectares (10%) of cleared lower rainfall agricultural land were planted to oil mallee (a coppicing tree crop) it could provide over 4% of the nation’s electricity while reducing CO2 by at least 20 million tonnes, about 40% of this being soil sequestration:
--Carbon fixation in the in the soil and roots of harvested oil mallee plantations (8 mt)
--Displacement of coal fired power generation (at least 8 mt)
--Charcoal to displace coke or for use as a soil ameliorant (up to 5 mt)
Oil mallee for energy would be viable with the average existing RECS price ($38/MWh) plus a carbon price of at least $25 per t CO2 (18). Unfortunately, this strategy is not part of the Coalition’s Direct Action plan and in any case would not be viable under their plan to remove the carbon price.
The Liberals’ only mention of tree planting in their policy is ‘Green Corridors”, amounting to about 40,000 ha of trees which could sequester about 0.1 million tCO2/year.
Destocking 200 million hectares of overgrazed rangelands (mulga and tussock grasslands) is the only strategy that may achieve 85 m t CO2 sequestration per year, but it would be next to impossible to measure the carbon storage. CSIRO Land and Water, 2010 (8) states: “It is impossible to design a trading scheme involving increasing soil or ecosystem C stocks in the Australian rangelands within the next few years that will effectively and quantitatively ensure decreased net emission of greenhouse gases to the atmosphere. If the objective is considered worth pursuing relative to alternative surer approaches, then a massive research agenda over the next 2 or 3 decades is needed to establish the requisite information base”. Destocking rangelands is not mentioned in the Coalition strategy and it would be interesting to see the reaction of their pastoralist supporters and the scientific community if they were to proceed with it.
Mulch cropping and bio char application are often touted as super carbon fixation solutions but both are exceedingly expensive. The market cost of bio char would be >$400/ tonne, equating to >$ 150 / tonne CO2 sequestered (18). It costs about $200 per tonne CO2 (mainly in fertilizer costs) to sequester carbon by mulching high rainfall pastures (15).
In summary, the Coalition’s claims as to the amount of CO2 that could be removed from the atmosphere by creating compliant soil carbon credits are grossly overstated. Their claimed 85 million tonnes is 3-8 times what is achievable by farmers. Add to this the problems that their costing is underestimated by at least 150% and the DoCCEE reckons only 1 million tonnes of CO2 credits will actually be created by farmers at a price of $33/ tonne. The Coalition’s soil carbon strategy is either deliberately deceptive, woefully researched or both.
Ben Rose is a Western Australian land management scientist with several years experience in carbon sequestration analysis including soil sampling and testing. He wrote chapter 20 of the book, “The Biochar Revolution, Transforming Agriculture and the Environment.
1.Australian Government Department of Climate Change and Energy Efficiency, 2011. Carbon Farming Initiative Preliminary estimates of abatement, Discussion Paper
2.Australian Natural Resources Atlas http://www.anra.gov.au/topics/agriculture/sheep-wool/region-high-rainfall-zone.html
3.Australian Soil Carbon Accreditation Scheme (ASCAS) http://www.amazingcarbon.com/What are Soil Credits.pdf
4.Bathgate A and Clayton H, 2010. Farm economic analysis of Sustainable Farms management scenarios http://fennerschool-research.anu.edu.au/sustfarms/downloads/SustFarms_Economic Scenario Analysis.pdf
5.Carson, J. 2011: ‘How much Carbon Can Soil Store?’; ‘Carbon Storage and the Esperance Sand Plain’. http://soilquality.org.au/factsheets
6.Chan, KY and McCoy, D. 2008. Soil carbon storage potential under perennial pastures in the mid-north coast of New South Wales, Australia.
7.Cotching, WE, 2009. Tasmanian Inst. of Agricultural Research. Quantifying Soil Carbon Storage in the Farm Carbon Story
8.CSIRO Land and Water, 2010 (Sanderman et al). Soil Carbon Sequestration Potential: A Review for Australian Agriculture. http://www.csiro.au/Portals/Publications/Research--Reports/~/media/CSIROau/Flagships/Sustainable Agriculture Flagship/SoilCarbonSequestrationPotential_SAF_PDF Standard.pdf
9.CSIRO, 2009. An Analysis of Greenhouse Gas Mitigation and Carbon Biosequestration Opportunities for Rural Land Use. http://www.csiro.au/files/files/prdz.pdf
10.CSIRO, 2011. Modelling Sustainable Management of Northern Australian Livestock Enterprises. MacLeod, N et al presentation for 9th international Rangelands Congress
11.Department of Climate Change and Energy Efficiency (DCCEE). 2011 Carbon Farming Initiative Preliminary estimates of abatement Discussion Paperhttp://www.climatechange.gov.au/~/media/publications/carbon-farming-initative/CFI-Preliminary-estimates-of-abatement.pdf
12. Department of Climate Change and Energy Efficiency (DCCEE). 2011. Carbon Farming Initiative Preliminary estimates of abatement Discussion Paper http://www.climatechange.gov.au/~/media/publications/carbon-farming-initative/CFI-Preliminary- estimates-of-abatement.pdf
13.Garnaut, R. 2011. Climate Change Review Update Paper #4 Transforming Rural Land Use.
14.Liberal Party, 2012. The Coalition's Direct Action Policy form Environment and Climate Change executive summary. http://www.liberal.org.au/~/media/Files/Policies
15.McKenzie Soil Management Pty. Ltd, 2010 Soil Carbon Sequestration under Pasture in Southern Australia. Report for Dairy Australia http://www.parliament.vic.gov.au/images/stories/committees/enrc/soil_carbon_sequestration/submission/Gippsland_Dairy.pdf
16.Mickelson and Co. Frequently Asked Questions about CCX Conservation and Grassland Soil Carbon Offsets. http://www.mickco.com/ClassLibrary/Page/Information/DataInstances/30/Files/88/No-Till_FAQ.pdf
17.NSW DPI Science & Research Technical paper, Sept 2008 by Chan, KY et al. Scoping Paper: Soil Organic Carbon Sequestration Potential for Agriculture in NSW.
18.Rose, BJ, 2010. Ch. 20 in Taylor, R. “The Biochar Revolution, Transforming Agriculture and the Environment”.
19.Umbers, A, 2008. Carbon in Australian Cropping Soils – We need to be realistic. GRDC/DAFF Sustainable Industries Initiative Project
20.Wikipedia, 2011. Chicago Climate Exchange. http://en.wikipedia.org/wiki/Chicago_Climate_Exchange
21.Dept. of Climate Change and Energy Efficiency, 2005. National Carbon Accounting Toolbox Full Carbon Accounting Model (FullCAM)
22.CSIRO, 2011. The buried cost of soil carbon credits. http://www.csiro.au/Organisation-Structure/Divisions/Plant-Industry/The-buried-cost-of-soil-carbon-credits.aspx