US scheme used by Australian farmers reveals the dangers of trading soil carbon to tackle climate change

Soil carbon is in the spotlight in Australia. A key plank in the Morrison government's technology-led emissions reduction policy, it involves changing farming techniques so soils store more carbon from the atmosphere.

Farmers can encourage and accelerate this process through methods that increase plant production, such as improving nutrient management or sowing permanent pastures. For each unit of atmospheric carbon they remove in this way, farmers can earn "carbon credits" to be sold in emissions trading markets.

But not all carbon credits are created equal. In one high-profile deal in January, an Australian farm sold soil carbon credits to Microsoft under a scheme based in the United States. We analysed the methodology behind the trade, and found some increases in soil carbon claimed under the scheme were far too optimistic.

It's just one of several problems raised by the sale of carbon credits offshore. If not addressed, the credibility of carbon trading will be undermined. Ultimately the climate - and the planet - will be the loser.