Replacing Coal Used in Steelmaking with Biocarbon from Hydrolysis Lignin -Techno-Economic Evaluation

Iron and steel industry is the second largest industrial emitter in the world after the cement industry. In 2017 Global crude steel production direct CO2 emissions of 2 billion tonnes represented 23.5% of industrial emissions in the world. Bio-reducing agents provide the possibility of achieving a rapid reduction in fossil CO2 emissions in the steel industry. Forest-sector residues can be converted by slow pyrolysis to biocarbon for reduction purposes, which can be an asset for both the forest and metal industry. This study focused on the evaluation of the production of biocarbon from hydrolysis lignin, a side-product from 2nd generation bioethanol process, a) produced in a stand-alone plant close to a steel mill and b) produced in a pulp and paper mill integrated plant. The conceptual level techno-economic analysis indicates that biocarbon made of hydrolysis lignin at an integrated pulp and paper mill site will provide the potential option for bio-based carbon production within the forest to metal value chain, providing a substantial source, at an annual potential of 44 k tonnes of biocarbon. Hydrolysis lignin could thus provide a significant biocarbon source for the pulverized coal injection (PCI) in the blast furnace, in addition to other bio-based side-streams (e.g. bark, wood/forest chips and sawdust). The economic feasibility will depend on emission trading, fossil coal price and on integration of the excess energy from pyrolysis and possibly available low-grade heat at the biocarbon production site.