MAGNEX and PILCCU in Finland: deployment of CO2 mineralisation in circular economies

Abstract

Two ongoing projects in Finland, MAGNEX (Viable magnesium ecosystem: exploiting Mg from magnesium silicates with carbon capture and utilization) and PILCCU (Piloting of ÅA CCU) aim at using CO2 mineralisation technology for the overlapping purposes of large-scale CO2 emissions mitigation and bringing several valuable material streams into circular economies, including construction. Of central importance are magnesium-based materials, such as magnesium carbonate hydrate (MCH), besides (amorphous) silica and several metallic species. On top of revenues from these, CO2 emissions mitigation lowers the financial penalty from CO2 emission rights under for example the European ETS. The ÅA process routes are stepwise processes based on extraction of magnesium (and other species) from serpentinite-containing mining tailings from Finland, followed by precipitation of metallic species, carbonation using a CO2 containing gas-stream (no separate capture step needed) and recovery of solvent salt, respectively. Several separation steps involve (ion-selective) membrane electrodialysis. Besides ongoing mapping and characterisation of Finnish rock resources as tailings or other side-streams at metal and mineral mines in Finland, the projects address public acceptance, legislation and other non-technical issues related to large-scale roll-out of this type of CCU technology.For the use of the solids, magnesium-based cement binders and plaster-like recipes are investigated as well as applications for the (amorphous) silica and other residues, including the use of MCH for cyclic thermal energy storage (TES). Special focus is on accelerating the carbonation step and the final outcome of MCH production, considering pressure (including supercritical CO2 levels), and the role of recoverable catalysts and other additives. The work receives funding from the Academy of Finland (2022-2025) and from Business Finland plus industry partners (2022-2024), respectively.