Elin Hernebrant, Development Engineer and Ryan Robinson, Process Development Engineer at Höganäs
Höganäs, which is 50 percent owned by Lindéngruppen, is on a journey to become climate neutral by 2045. An important step towards this ambition would be to replace fossil coal with renewable biochar in its sponge iron production process, which is the company’s largest source of carbon dioxide emissions.
As with all industrial steel production, Höganäs currently uses fossil coal as a reducing agent to convert iron ore into sponge iron. However, the company has successfully conducted various small-scale tests involving climate-neutral biochar made from biomass.
“Replacing fossil coal with renewables is more complicated than it sounds,” says Ryan Robinson, Process Development Engineer at Höganäs. “Our fossil coal-based process has been developed over more than 100 years and small changes can have major consequences for both the process and product quality.”
But as the small-scale tests, both in the lab and in production, showed no effect on the quality of Höganäs’ sponge iron, the company is now planning full-scale tests with up to 20 percent biochar, which is expected to reduce Höganäs’ carbon dioxide emissions by around 13 percent.
Höganäs has secured a supplier of good quality biochar, but the biggest challenge of using biochar as a reducing agent is that it only has a quarter of the bulk density of fossil coal and is more reactive. “Density and reactivity are crucial to ensure a successful reduction process, so we have to adapt the physical properties of the biochar,” says Robinson.
As there are no suppliers of high-density biochar with low reactivity, Höganäs is building a provisional biochar pre-treatment plant, which will produce pellets with twice the density of untreated biochar. The plant should be operational after the summer 2021.
“Once our biochar pre-treatment facility is complete, we will be able to test the use of 20 percent biochar in our production,” says Elin Hernebrant, Development Engineer at Höganäs. “If all goes to plan, we will conduct these full-scale tests later in 2021 and it will verify if this proportion of biochar can be used permanently in our production to reduce emissions while maintaining high-quality sponge iron.”
“Replacing 20 percent of the fossil coal with biochar in our production would potentially reduce carbon dioxide emissions by 29,000 tonnes per year – if our full-scale tests are a success and we can permanently use this proportion of our biochar pellets in our sponge iron production,” says Robinson.
“Our use of biochar is innovative as metallurgy processes around the world have been optimised for fossil coal since the start of the industrial revolution,” says Magnus Pettersson, Energy Coordinator at Höganäs. “This is particularly true for our unique solid state reduction process that has specific demands for the carbon we use to produce a high-quality metallurgy grade powder.”
Magnus Pettersson, Energy Coordinator at Höganäs
“Permanently using 20 percent biochar would require investments in our process to maintain the properties and quality of our metal powder,” explains Pettersson. “But it would pave the way for us to further adjust our processes and the biochar to gradually increase the proportion of biochar we can use – to further reduce emissions towards our goal of carbon neutrality.”
“Our cooperation with the Luleå University of Technology in Sweden, which supports us in how we can optimise the biochar to our process, is essential for our work going forward,” says Robinson. “I believe we will be able to eventually achieve a 50 percent use of biochar in our production process based on our current technology, with the potential to further increase this proportion as knowledge and technologies advance.”
Another potential benefit of Höganäs’ large-scale use of biochar would be that it will stimulate the currently limited availability of biochar to the various industries interested in replacing fossil coal with renewable and low-carbon alternatives.
“As an early adopter of biochar on a large scale, we hope to stimulate greater biochar production for ourselves and for industry in general, which has the potential to bring about a significant de-carbonisation of society,” says Pettersson.
In early March 2021, the Swedish Energy Agency granted SEK 2.7 million to support Höganäs with their work to replace fossil coal with biochar. The contribution will partially fund the full-scale biochar testing and was granted on the grounds that the project has the potential to realise a significant carbon emission reduction.
