Items

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  A marginal abatement cost curve for climate change mitigation by additional carbon storage in French agricultural land

  Following the Paris agreement in 2015, the European Union (EU) set a carbon neutrality objective by 2050, and so did France. The French agricultural sector can contribute as a carbon sink through carbon storage in biomass and soil, in addition to reducing GHG emissions. The objective of this study is to quantitatively assess the additional storage potential and cost of a set of eight carbon-storing practices. The impacts of these agricultural practices on soil organic carbon storage and crop production are assessed at a very fine spatial scale, using crop and grassland models. The associated area base, GHG budget, and implementation costs are assessed and aggregated at the region level. The economic model BANCO uses this information to derive the marginal abatement cost curve for France and identify the combination of carbon storing practices that minimizes the total cost of achieving a given national net GHG mitigation target. We find that a substantial amount of carbon, 36.2 to 52.9 MtCO2e yr−1, can be stored in soil and biomass for reasonable carbon prices of 55 and 250 € tCO2e−1, respectively (corresponding to current and 2030 French carbon value for climate action), mainly by developing agroforestry and hedges, generalising cover crops, and introducing or extending temporary grasslands in crop sequences. This finding questions the 3–5 times lower target of 10 MtCO2e.yr−1 retained for the agricultural carbon sink by the French climate neutrality strategy. Overall, this would decrease total French GHG emissions by 9.2–13.8%, respectively (reference year 2019).
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  The misconception of soil organic carbon sequestration notion: when do we achieve climate benefit?

  Soil organic carbon (SOC) sequestration is a key function of natural and semi-natural ecosystems. Restoring this property in terrestrial ecosystems has become central to the EU's climate change mitigation and adaptation strategies. However, SOC sequestration is a widely misunderstood concept. The different methodological approaches used to investigate and compare SOC stock under sustainable agricultural practices play a key role in reinforcing misconceptions about this complex process. This commentary paper aims not only to provide a clear definition of SOC sequestration, but also to interpret the results that can be obtained for SOC stock change estimation using the SOC stock difference and the pair comparison methods, as well as to identify the soil carbon-related processes that achieve climate mitigation. SOC sequestration can be defined as the progressive increase in a site's SOC stock compared to pre-intervention via a net depletion and transfer of atmospheric CO2 into the soil, where it is retained as soil organic matter (SOM), by plants, plant residues or other organic solids such as the material derived from the organic fraction of farming solid waste, which can be used as a fertilizer (e.g., manure, compost, biochar, digestate), and that is produced or derived from that land-unit. To date the most appropriate way to determine if a land unit's soil is a sink or rather a source of atmospheric CO2 is to implement the SOC stock difference method, provided the non-occurrence of carbon exchange between ecosystems.
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  A marginal abatement cost curve for climate change mitigation by additional carbon storage in French agricultural land

  Following the Paris agreement in 2015, the European Union (EU) set a carbon neutrality objective by 2050, and so did France. The French agricultural sector can contribute as a carbon sink through carbon storage in biomass and soil, in addition to reducing GHG emissions. The objective of this study is to quantitatively assess the additional storage potential and cost of a set of eight carbon-storing practices. The impacts of these agricultural practices on soil organic carbon storage and crop production are assessed at a very fine spatial scale, using crop and grassland models. The associated area base, GHG budget, and implementation costs are assessed and aggregated at the region level. The economic model BANCO uses this information to derive the marginal abatement cost curve for France and identify the combination of carbon storing practices that minimizes the total cost of achieving a given national net GHG mitigation target. We find that a substantial amount of carbon, 36.2 to 52.9 MtCO2e yr−1, can be stored in soil and biomass for reasonable carbon prices of 55 and 250 € tCO2e−1, respectively (corresponding to current and 2030 French carbon value for climate action), mainly by developing agroforestry and hedges, generalising cover crops, and introducing or extending temporary grasslands in crop sequences. This finding questions the 3–5 times lower target of 10 MtCO2e.yr−1 retained for the agricultural carbon sink by the French climate neutrality strategy. Overall, this would decrease total French GHG emissions by 9.2–13.8%, respectively (reference year 2019).