Eric Verrecchia (Honorary Professor at the Institute of Earth Surface Dynamics at the Faculty of Geosciences and Environment of Lausanne)
Imagine buying a house without anyone checking the foundations. That’s essentially what agricultural “carbon credits” offer. The principle seems appealing: a farmer adopts better practices, their soil stores more organic carbon, and CO2 emitting companies buy “credits” from them to offset their emissions. A recent scientific study scrutinized the ten major international protocols used to calculate these credits. Conclusion: it arrived at a disappointing result. Some protocols don’t even bother to measure the organic carbon in the soil initially, preferring to use regional average values. As a result, the error can reach a factor of 2.5 before evaluating anything. Others simply ignore agricultural practices known for their impact on soil organic carbon, such as cover crops or crop rotation diversity. In short: credits are given based on values that haven’t been truly measured.
And what about when the protocol actually relies on on-site verification that the organic carbon is buried properly? Unsurprisingly, the situation isn’t much better. The methods used, the tools, the depth of sampling, the number of samples taken, all vary from one protocol to another, sometimes in proportions that significantly skew the results. As if these shortcomings weren’t enough, the details of these measures often remain secret, making independent verification impossible. Meanwhile, the companies buying these credits, often dearly, emit with the good conscience of those who believe they have paid their debt. This study does not claim that the idea of agricultural carbon credits is inherently bad; encouraging organic carbon storage in soils remains a relevant practice, not only from a “climate” perspective. But it warns: without common, rigorous, and transparent, scientifically-based rules, these credits often reduce today to empty promises. In conclusion, thanks to this type of study, we can only once again observe the extent of the gap between the apparent sophistication of these carbon markets and the scientific fragility that underlies them. But does this observation really remain an isolated case in climate policies proposed?
* Dupla, X., Bonvin, E., Deluz, C., Lugassy, L., Verrecchia, E., Baveye, P. C., Grand, S., & Boivin, P. (2024). Are soil carbon credits empty promises? Shortcomings of current soil carbon quantification methodologies and improvement avenues. Soil Use and Management, 40, e13092. https://doi.org/10.1111/sum.13092. The article is freely accessible.
