A conference presentation by our head of science, Jens Hammes, at the 3rd International Conference on Negative CO2 Emissions, 2024 in Oxford.

Abstract:

Enhanced weathering (EW) boosts the natural process of chemical rock weathering and is a promising strategy for substantial carbon dioxide removal (CDR). Large-scale deployment of EW is, however, hindered by the challenge of directly measuring the net achieved CDR. Monitoring, reporting and verification (MRV) of CDR achieved through EW will likely hinge on site-specific model calculations. Development of such models in turn requires numerous real life EW data sets from various environments to train and calibrate them.

Indoor mesocosm experiments are closed systems that represent realistic EW environments. Compared to open field settings, they allow more straightforward data collection as well as speeding up the EW process by optimising climatic conditions. In our large-scale greenhouse study, we created ca. 100 mesocosm experiments (each replicated 4 times) with Lolium perenne kept at temperatures consistently exceeding 20°C and irrigation rates equivalent to 2000 mm/a. A range of different treatments resulted from the combination of 16 soils (pH 4.5 to 7.5; clayey loam to sand; CEC 3-18 meq/100g; SOC 0.5-7%) with (ultra)mafic rocks and alkaline industrial wastes (11 different feedstock materials in total).

Our goal is to test various potential MRV approaches on short timescales and assess the CDR effects from different combinations of soils and EW materials. We carry out continuous CO2 monitoring and regularly sample soil, leachate water and biomass for a series of chemical analyses (pH, EC, alkalinity, cations, anions, heavy metals, …). Over 18 months, we expect to see distinct signals in our measurements between different treatments which can be used to derive a CDR effect calculation. Our preliminary results already revealed a much greater variation in CDR effect than expected from addition of the same rock dust to different soils. 

Thanks to the conference organizers CO2RE co2re.org for sharing the video with us and giving us the permission to share it.