Seventeen percent

In a modern gym the machines tell you how many calories you have burned. They estimate the effort you put in by combining the speed achieved and the power needed to move the mechanism.

Now suppose the machines overestimate your effort by 17%.

When you push hard at the end of the 30 minute run to blast past 500 calories on the readout, you actually only made it to 415. What should you do? Complain to the management of the gym or send a shirty email to the equipment manufacturers. Maybe boycott gyms.

It would be totally crazy to boycott the gym because then you would have an extra 415 calories in your system and, over time, a far less healthy heart and lungs. Even if the estimates of calories burnt are wrong you will always get the net benefit of 30 minutes of exercise.

Recently CSIRO scientists have published a research paper in the letters section of the journal Nature Climate Change that claims that because the soil models used in the Australian national greenhouse gas accounts do not account for soil erosion they overestimate the net carbon flux from cropland by up to 40% and overestimate the potential 100 year sink for carbon in soil by 17%.

The 40% is politically very significant. It implies that arable agriculture in Australia is not such a big emitter of greenhouse gases as was thought and this is very good news for both the national accounts and the farming sectors keen to protect their exempt status as emitters. This is especially handy in international negotiations.

The 17% implies that less carbon is stored in soils than the models predict because some of the extra carbon sequestered is blown or washed away. This means if a farmer is paid for 10 tCO2e at the direct action auction he will actually only sequester 8.3 tCO2e. He is overpaid.

The integrity of offset markets requires that, as far as possible, each tCO2e paid for is actually a tCO2e of avoided emission or sequestration. Over-crediting is a problem.

But, here is the thing. The uncertainty with soil carbon has meant that the methodologies for accounting it are onerous requiring lots of repeated measurement and only a limited number of acceptable abatement activities. So there are very few projects where farmers are paid to build soil carbon.

And this is like boycotting the gym because the machines give faulty readings. You lose the benefit of the exercise.


At Alloporus we build carbon accounting methodologies, undertake project feasibility and due diligence assessments, support project establishment, and provide data reporting and validation services — contact us for details

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