Can earthworms increase inorganic carbon sequestration in an artificial system

Enhanced Silicate Weathering (ESW) is a promising Carbon Dioxide Removal (CDR) technology, but the factors that maximize its effectiveness remain unclear. Recent studies have shown that earthworms can amplify mineral weathering rates and increase inorganic carbon (IC) sequestration. Here, we test the capacity of earthworms to accelerate ESW rates by 1) identifying optimal conditions for earthworms in an environment composed of ground silicate rocks and organic substrate, and 2) determining to what extent earthworms can enhance IC sequestration. We conducted five rounds of two-month experiments in a climate chamber at 25°C, using two endogeic earthworm species, four rock flours in two grain sizes, two organic substrates, and two water irrigation rates at three frequencies in different combinations. Rock flours were used as single types or sizes, as well as mixtures. At the end of each round, we measured earthworm survival and activity, dissolved and solid IC, total alkalinity, pH, electrical conductivity, and major ions. Amongst all the factors considered, we found that mineral type and mineral grain size dominantly drove earthworm survival and activity. Following mineral type and grain size, earthworm species and density determined earthworm survival, while earthworm density and mixtures of mineral types and/or grain sizes impacted earthworm activity. Preliminary results suggest that earthworms increase mineral weathering rates and IC sequestration. We demonstrate that earthworms can thrive in a fully artificial system designed for accelerating ESW rates and can contribute to amplifying this process, with important implications for application of ESW in soils.