The Exeter Soil Carbon Sequestration Lab (ExSEQ)): Advancing Quantification of Soil Carbon Dynamics and Climate Mitigation Potential

Understanding how land management influences soil carbon dynamics and greenhouse gas fluxes is essential for evaluating realistic carbon dioxide removal potential. However, soil carbon changes are difficult to detect against large background stocks, often requiring long-term field studies, and gains may be offset by increased emissions of other greenhouse gases, particularly nitrous oxide. Few land-based mitigation projects have the capacity to measure these processes in sufficient detail. Together, these limitations introduce considerable uncertainty when estimating the true climate benefit of soil-based approaches. Here we introduce the Exeter Soil Carbon Sequestration Lab (ExSEQ), which has been established to address these challenges. 

Central to the facility are two large-scale, environmentally controlled growth chambers at the University of Exeter. Temperature, light, CO₂, and humidity are precisely regulated, allowing crops to grow in soil under realistic yet highly controlled climatic conditions and a continuously ¹³CO₂-enriched atmosphere. We have successfully grown pasture species and arable crops through their full life cycles under continuous stable-carbon isotope labelling at 500‰. This level of enrichment allows accurate tracing of plant-derived carbon into soils and enables precise quantification of new soil organic matter formation, even when newly added carbon represents less than 0.5% of the total SOM pool. 

ExSEQ supports continuous, high-frequency measurement of CO₂, CH₄, and N₂O fluxes, together with isotopic characterisation of both gases and soil carbon. Fluxes are monitored without opening the chambers, preventing dilution of the isotopic signal and allowing simultaneous quantification of new SOM inputs, losses of existing soil carbon, and full greenhouse gas budgets to assess net climate mitigation outcomes. 

While no laboratory can fully replicate the complexity of field systems, ExSEQ operates at a realistic scale and enables rapid screening of potential interventions across contrasting soils, climates, and plant–soil systems. The facility offers considerable potential to advance understanding of the effects of different fertilisers, soil amendments (e.g. enhanced rock weathering, biochar, biostimulants), and management practices (e.g. tillage intensity, pasture sward biodiversity, grazing management). ExSEQ provides a highly adaptable experimental platform deployable across a wide range of land management scenarios and aims to promote collaboration across academic institutions and industry.