CLIMATE SPECTATOR: Abbott’s abatement black hole

The Coalition has a massive budget black hole from its Direct Action climate change policy. The entire costings hinge on estimates of abatement from soil carbon that are woefully researched.

Climate Spectator

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 per cent 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 two to 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 one billion tonnes per year cited by Garnaut 2011. 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 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), 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 that was posted on the Liberals’ website (now no longer available). 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 per cent of total topsoil per year. Carbon comprises just 1 per cent to 5 per cent of topsoil and it is this figure that may be increased by 1 per cent per year. This equates to about 0.5 to 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 Atlasand optimistically assuming adoption of improved practice on up to 50 per cent of those areas.

The sequestration rate estimates for improved practices are mainly from peer reviewed research trials in Australia and the US 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



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 per cent and state a figure of 20 to 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 million 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 per cent) of cleared lower rainfall agricultural land were planted to oil mallee (a coppicing tree crop) it could provide over 4 per cent of the nation’s electricity while reducing CO2 by at least 20 million tonnes, about 40 per cent 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. 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 40,000ha 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 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 two or three 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 greater than $400/tonne, equating to greater than $150/tonne CO2 sequestered. It costs about $200 per tonne CO2 (mainly in fertiliser costs) to sequester carbon by mulching high rainfall pastures.

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 three to eight times what is achievable by farmers. Add to this the problems that their costing is underestimated by at least 150 per cent and the DoCCEE reckons only one 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.

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