Fundamentals of combined Pyrogenic and Mineral Carbon Capture and Storage

• Applicant: Dr. Nikolas Hagemann
• Subject Area: Soil Sciences
• Term: from 2021 to 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467391808

To limit global warming, carbon dioxide removal (CDR) from the atmosphere is urgently needed at large scale. Two readily available and scalable negative emission technologies (NET) are enhanced silicate rock weathering (EW) and pyrogenic carbon capture and storage (PyCCS). In EW, volcanic silicate rock powder is applied to soil where it reacts with CO2 to bicarbonate, which may precipitate as carbonate through further reactions in the soil or may enter ground and surface waters via soil solution and be transported to the oceans. In PyCCS, CDR is performed by photosynthesis (biomass production) followed by the pyrolysis of biomass transforming the captured carbon into a recalcitrant solid form (biochar) that persists for centuries when applied to soil. The combination of both NETs, i.e., pyrogenic and mineral carbon capture and storage (PyMiCCS), could maximize the carbon sink potential per cultivated area of land and could synergistically unite their positive effects towards soil fertility. However, systematic research is needed to assess the influence of co-pyrolysis and co-application of silicate rock powder and biochar in regard to material properties, enhanced weathering and pyrolytic conversion rates, environmental risks, and the combined impact of biochar and EW on plant growth and soil fertility. Furthermore, the CDR dynamics of this combined carbon sink must be measured to allow the evaluation of PyMiCCS among other NETs. For this purpose, both blends of biochar and rock powder as well as co-pyrolysates of biomass and rock powder are produced experimentally at kilogram scale. These PyMiCCS materials are applied in column and greenhouse experiments. Weathering rates, nutrient leaching and plant growth are quantified. Both pristine and aged biochars are subject to spectro-microscopy to characterize the impact of rock powder on pyrogenic carbon speciation. On aged biochar, obtained from the greenhouse experiments, the impact of rock powder on the aging process is studied, especially the organic coating on biochar formed by sorption of water-soluble organic molecules that contribute to the capacity of biochar to retain soil nutrients. Based on these experimental data and a literature review, CDR dynamics of PyMiCCS sinks are described in order to enable carbon sink certification and to identify the potential role of PyMiCCS within the spectrum of NETs.

• DFG Programme: Research Grants