Biochar – not just fertiliser

The steel industry is one of the largest contributors to global greenhouse gas emissions. Turning iron ore into steel is an energy intensive process relying heavily on coal. BlueScope Steel in Wollongong received funding in 2022 from the Australian Renewable Energy Agency (ARENA) to investigate biochar as a partial substitute for coal in the blast furnace refining process. The biochar is ground and blended with crushed coal, and the mixture is blown into the blast furnace. The biochar-coal mixture provides heat and takes part in the reaction to remove oxygen from the iron ore.

In a collaboration between the University of Wollongong and the CSIRO, pilot trials were conducted at the University’s Bulk Materials Engineering Australia test facility to assess the compatibility of the biochar-coal blend with the pulverised coal injection plant. Here researchers found that biochar creates dust that takes longer to settle than coal, it holds up to 45% water by mass compared to about 15% for coal and was more difficult to grind to the required particle size. However, the biochar-coal blend did handle better than coal alone.

Finding large quantities of biochar could be problematic. The CSIRO have developed a self-sustaining pyrolysis process that can meet the demands of specific applications involved in metal production, requiring no external heat and can use a wide range of biomass feedstock.