A central issue when assessing the mitigation potential of carbon farming practices is the non-permanence of carbon sequestered in the soil, which may produce that efforts to enhance soil organic carbon pools in the short term end up generating increased emissions from land use in the future. In particular, the role of non-permanence in the cost-effectiveness of agricultural carbon sequestration as a tool to meet current and future EU climate policy targets had not been explored so far. This topic was addressed by MARVIC partner Katarina Elofsson (Aarhus University) in an article recently published in the journal Environmental Modeling & Assessment.
In the study, authors Addisu Dilnessa, Katarina Elofsson, Arezoo Taghizadeh-Toosi and Torbjörn Jansson developed a dynamic and spatially disaggregated cost-effectiveness model, used to compare the minimum costs of meeting annual national and EU level targets for either carbon sequestration or greenhouse gas (GHG) emissions reductions across 26 EU countries from 2020 to 2050. In all cases, non-permanence was accounted for, and the 4p1000 target was considered, which requires that sequestration should equal at least 0.4% of the soil carbon stock. In particular, three measures were assessed: reductions in straw supply for bioenergy production, reductions in grain harvesting, and cultivation of catch crops, all of them contributing to carbon sequestration by increasing the volume of biomass that can be incorporated in the soil.
Importantly, findings indicate that carbon sequestration in agricultural soils has the potential to mitigate approximately 38 million tonnes of carbon dioxide equivalents annually from 2020 to 2050 at a marginal cost of approximately 64 € per tonne. In turn, emission targets are about 2.5 times more expensive than the corresponding sequestration targets, with a marginal cost of about 183 € per tonne. In addition, the results show that national targets are about 2.6 times more costly than the corresponding EU targets, and that the shadow prices vary substantially across EU member countries, suggesting that cost savings can be achieved by reallocating efforts between countries.
As the authors point out, there are still many questions that remain unanswered, but this publication is a critical step to fill current knowledge gaps regarding the role of non-permanence in carbon sequestration and its cost-effectiveness. By addressing these questions, strategies that balance policies with food production needs can be developed, leading to environmentally and economically sustainable solutions.
