During his recently delivered inaugural address, Professor Charles Siyasiya of the Department of Materials Science and Metallurgical Engineering at the University of Pretoria (UP) focused on the benefits and shortfalls of ‘green steel’, which makes use of more sustainable production methods and emits 90% less CO₂ than that of traditional steelmaking, thus offering hope for a less carbon-intensive world.

“Traditional steelmaking contributes to 10% of global CO₂ emissions and it is clear that we have reached the limit of efforts to reverse its carbon-intensive effects,” Prof Siyasiya said during his address, titled ‘Advances in steel design and processing to curb greenhouse emissions’. “Green steel is the answer.”

While the amount of energy used per tonne of traditional steel has decreased by more than 60% over the past 40 years, progress has stalled; each tonne of steel now accounts for two tonnes of CO₂.

“There have been no significant improvements over the past 20 years, and it appears we have reached the point of diminishing marginal returns,” Prof Siyasiya said.

As a result, CO₂ emissions in the steel industry are a serious sustainability concern.

While energy usage per tonne of traditional steel is lower than it was four decades ago, the world is producing much more steel – some 2 billion tonnes a year in total – and therefore more emissions. In China, the largest steel producer, annual carbon emissions in tonnes soared by 1 000% between 1980 and 2020, rising from 190 to 1 900 megatonnes a year, Prof Siyasiya pointed out. If emissions from steel continue at their current rate, global warming would be exacerbated. By dramatically cutting traditional steelmaking emissions, green steel would help to curb global temperature increases.

“Hence the need to make steel differently, in a more sustainable way, in line with Sustainable Development Goal 13 [Climate Action],” Prof Siyasiya said. “A 90% reduction in CO₂ emissions from green steel will contribute towards a 1.5ºC increase in global temperature projection by 2050 instead of an increase of 3ºC degrees or more,” he added, referring to climatological studies that show carbon emission pathways to 2050. “Green steel offers hope.”

That said, the transition to near-zero carbon emissions comes with its own challenges.

Prof Wynand Steyn, Dean: Faculty of EBIT; Prof Charles Siyasiya and Prof Loretta Feris, Vice-Principal: Academic

“Green steels don’t come free; there is a catch – energy,” said Prof Siyasiya, explaining that taking the hydrogen route requires about 30% more energy per tonne of steel.

Only clean and renewable energy may be used in the making of green steel, which means only green hydrogen – which is produced from water using solar energy or wind turbines – may be used. This would call for massive investments in solar and wind energy.

On top of that, green steelmaking still makes use of some carbon, albeit only a fraction of that used in traditional steelmaking.

“For green steel, carbon is required to lower the melting point of iron, reduce the risk of iron fines catching fire by oxidation and to act as an alloying element,” Prof Siyasiya explained.

There are also challenges around the production, storage and transport of green hydrogen.  Furthermore, the elephant in the room is what to do with existing steelmaking infrastructure and machinery.

“How can it be repurposed?” Prof Siyasiya asked.

He concluded that while green steel has its challenges, these must be viewed as opportunities for innovation.

“The involvement of all stakeholders, including researchers, government, non-governmental institutions and industry is critical.”

Solutions that often seem simple may turn out to be highly complex, added Prof Wynand Steyn, Dean of UP’s Faculty of Engineering, Built Environment and Information Technology, in his closing remarks, during which he acknowledged Prof Siyasiya’s inaugural address. “This is why we develop new knowledge,” he said. “Steel is important. It makes life possible. Green steel makes life sustainable.”