Quantitative and mechanistic assessment of carbon cycling of enhanced weathering and algal biochar in Mediterranean agroecosystems: An Ecotron study

Enhanced rock weathering (ERW) and algal biochar have emerged as promising carbon dioxide removal (CDR) strategies in the past decades, with ERW gaining substantial attention in recent years. However, significant knowledge gaps persist regarding the mechanisms and carbon flux pathways that determine effective CDR in terrestrial ecosystems.

To systematically trace carbon (C) fluxes and deepen the mechanistic understanding of organic-inorganic carbon (OC-IC) interactions in soils, we initiated a multi-year lysimeter experiment in very large model systems/macrocosms (5 m², 1.5 m depth) within an advanced controlled environment facility for ecosystem research (Ecotron). This setup enables quantification and verification of effective carbon sequestration by ERW and algal biochar in Mediterranean agroecosystems.

This controlled experimental framework enables continuous, high-frequency, and precise monitoring of C and nitrogen (N) fluxes comparable to natural agroecosystems, complemented by corresponding field reference sites (INRAE UE DiaScope) in Southern France. Integration of biogeochemical C and N cycling data allows assessment of ecosystem functions (e.g., microbial diversity and abundance, soil invertebrate fauna) critical for evaluating these CDR strategies prior to large-scale deployment. In addition, by coupling ecosystem-level C and N budgets with micro-scale analysis using soil fractionation and advanced spectrometry techniques, we expect to further disentangle potential mechanistic interactions between IC and OC in these Mediterranean alkaline soils.

This presentation will report preliminary results on ecosystem-scale C and N fluxes (e.g., CO₂ and N₂O emissions, soil physicochemical properties, and leachate at multiple depths), with implications for understanding the effectiveness and environmental impacts of ERW and algal biochar deployment in Mediterranean alkaline soils.