One of Australia’s foremost soil carbon experts has significant concerns about the Coalition’s proposed funding of soil carbon initiatives, on which the Coalition is relying for more than 60% of its emissions abatement task between now and 2020.

Professor Alex McBratney, Pro-Dean of Sydney University’s Faculty of Agriculture Food & Natural Resources, has told Crikey that the $8-10 cost per tonne of CO2-equivalent on which the Coalition has based its figures is probably too low given the cost associated with sequestering soil carbon.  “It needs to be closer to $20-40 a tonne to be viable.”

Professor McBratney’s comments follow eminent scientist Peter Cosier’s criticism that farmers would be receiving more under the Government’s CPRS than under the Coalition’s plan.

However, Professor McBratney is very optimistic about the potential for sequestering soil carbon and believes the Coalition is being conservative on its long-term potential.

Soil carbon — increasing carbon levels in soil through no-till or lower-till cultivation methods, composting or adding biochar to soil —  has huge potential for biosequestration of carbon, locking carbon in soil for decades and, possibly, hundreds and thousands of years.  It has some heavyweight backers. James Lovelock, James Hansen, Tim Flannery and Ross Garnaut are just some of climate change icons that urged a serious effort on biosequestration.  Malcolm Turnbull began promoting soil carbon and particularly biochar early last year, and proposed that farmers be permitted to obtain credits under the CPRS for it on  an opt-in basis.  The Government later agreed to that and it now forms part of the revised, Turnbull-era CPRS Bill reintroduced into Parliament on Tuesday.

However, soil carbon has come under attack from left-wing environmental groups, who argue that its biosequestration potential is as yet unproven and that demand for products such as  biochar will see biosequestration competing with food production as biofuels have, leading to higher food prices.

Critics say there is insufficient peer-reviewed evidence of the long-term stability of soil carbon, and that there is some evidence that no-till and biochar use actually reduce soil carbon levels.  No-till cultivation also requires greater use of herbicides (and has been encouraged by agri-multinationals such as  Monsanto for the reason), or organic farming methods, which mean significantly more expensive food.

Biochar has come under greater scrutiny.  It is produced from biomass such as agricultural waste through a heating process that can also produce biofuels.  Very fine black carbon is susceptible to blowing or draining away — one Canadian study showed 25% loss in the process of transporting and spreading, including photos of clouds of black carbon — a particularly intensive greenhouse contributor — blowing away during spreading.  In many cases, composting the original waste material rather than turning it into biochar is more viable.  It is the production of biochar that critics believe has the potential to drive up food prices.

Soil carbon credits also have no value under current international carbon trading rules, although as Tony Abbott has noted, that’s a secondary issue if soil carbon delivers a genuine carbon sink — it removes CO2 from the atmosphere.

But while objections to biosequestration seem mainly confined to the hairshirt elements of the environmental movement, there is broader agreement that accurate measurement of soil carbon needs to be resolved before it can be viable.  The CSIRO last year started a multi-year project to address issues in soil carbon measurement and said yesterday much more research needed to be done.

Professor McBratney who has undertaken extensive work on the issue, believes these issues will take 2-3 years to resolve but says relatively accurate measurement of soil carbon levels can be obtained at reasonable cost and form the basis for paying farmers.  However, he proposes some caveats — a payments system should be based on whole units — such as an entire farm — so that total net carbon loss or gain can be monitored, and it should include all carbon — he says soils also contain non-organic carbonate carbon, which can be lost through irrigation and therefore any system must be on a “net carbon” basis.

He also suggests payment systems be based on relatively conservative verification systems, and if farmers want to be paid more, they pay for more accurate testing.  Soil carbon credits are available on the Chicago Climate Exchange, he says, but are worth less than $US1 due to the lack of independent verification and reliance on estimation rather than measurement.

Professor McBratney also proposed farmers be paid an ongoing, rather than one-off, payment as an incentive to maintain soil carbon levels.

He would prefer to see a market-based mechanism, and believes $8-10 “won’t cut it”.  “Increasing soil carbon levels requires greater production levels or addition of biomass.  Adding a tonne of carbon to soil requires about 100 kilograms of nitrogen, and that either has to be purchased  at about $1 per kilogram or produced via legumes, which need water.”  Professor McBratney thinks $20-40 a tonne is a more realistic but still conservative cost.

However, he says there is enormous potential for soil carbon sequestration and that Australia is probably the world leader with the most sophisticated public debate in the area.  “You’re not going to see anything for the next two or three years but by 2020, we should start to see a real difference. A reasonable aspiration is a 20% increase in soil carbon by 2020.”

That assumes our politicians managed to get the right incentives in place.