Perspectives of co-extraction of geothermal heat with the critical raw materials lithium and copper from sedimentary basin fluids on the example of the North German Basin

The co-extraction of critical raw materials (CRMs) and heat from geothermal fluids offers a promising approach to simultaneously address the increasing global demands for both, metals and energy. In brines from sedimentary basins, high concentrations of lithium and other CRMs such as copper, are emerging as an attractive complementary resource for mining, because these types of geological settings are ubiquitously occurring within the continental crust. In this contribution, we investigate the North German Basin as an example for an underexplored sedimentary reservoir, with lithium (and to a minor extend copper) serving as representative CRMs. We summarize the current state of knowledge and main perspectives that are relevant for co-extraction of CRMs and heat. We identified five key controlling factors: (1) the source and mobility of lithium in geothermal brines; (2) the feasibility of brine production from a low-permeability sandstone reservoir including exploitation, management, and sustainability of extraction by considering potential lithium co-production rates on the example of a well in the North German Basin; (3) thermal-hydraulic challenges in combined heat and lithium production; (4) suitable material selection to prevent severe corrosion and associated damages; and (5) environmental, social, governance aspects, as well as life cycle assessment of such co-production. In conclusion, the current data indicate that sedimentary basins fluids offer great potential for co-extraction of geothermal heat and critical raw materials (CRM) like Li and Cu, but at current state more demonstrators are needed to prove the technical and economic feasibility of CRM and heat co-extraction.