The nickelNickel slagSlag cleaning process in an electric furnaceElectric furnace (EF) utilizes coke—a fossil carbon source—as a reductant to recover valuable metalsMetals from flash smeltingFlash smelting furnace slagSlag as an EF matteMatte via physical settling processes and chemical reduction. The process annually produces considerable amounts of direct fossil CO2 emissionsFossil CO2 emission reduction and depends on coking coal, a critical raw material in the European Union, which highlights the need for alternative and more sustainable reductants. In this study, biochar, a product derived from thermochemical conversion of biomass, was investigated in large laboratory-scale nickelNickel slagSlag reduction experiments with 100 g sample size. The experiments were conducted at 1350 °C and 1400 °C under inert N2-Ar gas atmosphere testingTesting 100% coke, 100% biochar and 50% / 50% biochar/coke mix. The reduction times were 10, 30, 60, 90 and 120 min, the samples were water-quenched or water-granulated and analyzed using SEM–EDSScanning Electron Microscopy–Energy Dispersive Spectroscopy (SEM-EDS) and LA-ICP-MSLA-ICP-MS. The slagSlag phase formed had homogeneous, glassy areas as well as heterogeneous areas with crystalline microstructure and was depleted of valuable metalsMetals as most of them deported to a heterogeneous matteMatte phase. To estimate the recovery possibilities of Ni and Co, matteMatte/slagSlag distribution coefficientsDistribution coefficient were calculated. The findings suggest that biochar is a promising alternative reductant to coke in the nickelNickel slagSlag cleaning process, as it either performed better than or equally well as coke for Ni and Co recovery.