Woody biomass — particularly wood chips — would be an ideal feedstock for producing carbonised biomass (biochar) with at least 65pc carbon content that could be used as a reductant in steelmaking to replace fossil fuels, delegates heard at the Argus Biomass conference in London last week.
"The main driver for us is to use [biochar] as a reductant, not for [process heat generation], so the driver is the carbon" content when defining the specifications of the biomass we can use, steelmaker ArcelorMittal's European buyer of biomass and alternative reductants,Steve Sirdey, said. Particle size distribution of biochar is another key specification, he said.
Biochar used in a blast furnace needs to have at least 65pc carbon content, with a minimum particle size distribution of 6mm corresponding to the correct size to fit existing grinding equipment. Steelmaking in an electric arc furnace requires at least 80pc carbon-intensive biochar, with a particle size at least 10mm for top charge and 3-5mm for injection, Sirdey said.
ArcelorMittal aims to replace up to 20pc of its fossil fuels injected today — pulverised coal injection in the blast furnace and anthracite in the electric arc furnace — without changing existing production processes, Sirdey said. "We can reach up to 2.8mn t/yr of [biochar consumption] with at least 65pc carbon content… If everything works well, ArcelorMittal is able to commit on long-term offtake contracts after all the… laboratory and other testing," he added.
As we are replacing coal, price will be another main criteria in deciding on how much fossil fuel to replace with biochar, Sirdey said.
"With the existing technology and the information we have, we think wood chips are the best feedstock at the moment in terms of chemical composition," Tata Steel's biomass and coal procurement manager, Frank van der Zon, said. Tata Steel would need to consume around 250,000 t/yr of biochar for its steelmaking unit in the Netherlands, which would require around 1.2mn-1.5mn t/yr of wood chip feedstock.
Steelmakers also have to consider whether to buy biochar or build on-site biochar production capacity. "Our goal is to be offtakers and commit to volumes. To meet decarbonisation targets, we believe that the biochar plant needs to be close to the feedstock," Sirdey said. ArcelorMittal commissioned the first of two 37,500 t/yr biochar producing units at its Torero plant in Ghent, Belgium, in December. The unit will use around 90,000 t/yr of waste wood as feedstock.
Unlike for power generation, the EU has not regulated the use of biomass by steelmakers or other hard-to-abate sectors, with companies following local regulations in the areas that they operate. But steelmakers are setting up a voluntary standard for the biomass to be certified for sustainability, with Tata Steel and ArcelorMittal aiming to consume only biomass that complies with EU renewable energy directive standards.
"We need to prove that biomass is the right feedstock… and have the responsibility to make sure that the feedstock is sustainably sourced," van der Zon said.
The majority of the steel industry's decarbonisation will be through technology change — switching to electrification with the electric arc furnace, which will reduce emissions by 70-80pc, van der Zon said. The remaining emissions are the hard-to-abate part, where using biomass to replace fossil fuels would help the sector to "become completely carbon neutral", he said.
