The role of earthworms in enhanced mineral weathering: Understanding their impact on carbon dynamics and sustainable fertilisation - Thesis

[Geoengineering News]

https://research.wur.nl/en/publications/the-role-of-earthworms-in-enhanced-mineral-weathering-understandi/

Authors: Tullia Calogiuri

20 February 2026

Abstract

Actively removing carbon dioxide (CO₂) from the atmosphere is urgently needed, in addition to reducing emissions, to meet the Paris Agreement target of limiting global warming to 1.5°C. Carbon Dioxide Removal technologies, such as Enhanced Mineral Weathering (EMW), offer a promising solution by speeding up the natural breakdown of silicate rocks to store CO₂ as inorganic carbon. EMW can also improve organic carbon stabilisation and enhance plant fertilisation. This technique can be applied to soils using different rock types and grain sizes and has the potential to remove up to 4 gigatonnes of CO₂ per year. However, this remains below the approximately 10 gigatonnes required annually to meet climate goals. Although reactor-based EMW can increase efficiency, it is expensive and energy-intensive, leading to growing interest in bio-based systems that use soil organisms to enhance weathering in a more sustainable way. Earthworms are particularly promising because their digestion processes and soil mixing activities can potentially increase weathering rates.

This PhD research was part of the European Horizon2020 BAM project, which aimed to explore biologically enhanced EMW. The main objective of this thesis was to understand how earthworms influence carbon dynamics and plant fertilisation through mineral weathering. The two main research goals were: first, to identify optimal conditions for earthworm survival in artificial organo-mineral systems and to understand how earthworms affect carbon stabilisation and sequestration; second, to test whether earthworm-processed material could improve soil carbon sequestration and plant fertilisation in grasslands.

To achieve these goals, a controlled experimental setup was developed, consisting of 200 microcosms filled with an artificial organo-mineral mixture. This system allowed the manipulation of abiotic and biotic factors, such as watering frequency, rock type and size, organic matter type, and earthworm species and density. Results showed that the structure of the system strongly influenced earthworm survival and activity. Coarser grains and straw improved water flow and prevented low-oxygen conditions, creating better living conditions for earthworms.

This research also revealed that living and dead earthworms affected mineral weathering differently. Living earthworms had limited short-term effects on inorganic carbon sequestration but likely contributed more to organic carbon stabilisation through physical and chemical soil processes. In contrast, dead earthworms significantly enhanced carbon capture, mainly through increased microbial activity. Further experiments using carbon isotopes confirmed that dead earthworms promoted inorganic carbon formation over time, while both living and dead earthworms increased organic carbon stabilisation through different pathways.

In a greenhouse experiment, two organo-mineral mixtures, processed and unprocessed by earthworms, were applied to potassium-poor sandy soil sown with grass. Results showed that grass enhanced mineral weathering through respiration and nutrient uptake. Both mixtures improved grass growth and reduced potassium deficiency, although no significant difference was observed between them.

Finally, this thesis highlighted the need for standardised indicators to measure mineral weathering and carbon sequestration. It also introduced the concept of “dead earthworm-mediated stimulation” and discussed the complex feedback between plant growth and mineral weathering. Overall, the research emphasizes the importance of biological processes in developing effective carbon removal strategies.

Source: Wageningen University & Research