Iin the city of Woburn, Massachusetts, a suburb north of Boston, a cadre of white-coated engineers and scientists inspected a neat stack of brick-sized, gunmetal-colored steel ingots on a desk in a neon-lit laboratory room.
What they were looking at was a batch of steel made with an innovative manufacturing method, one such Boston Metal, a company that spun out of MIT a decade ago, hopes to dramatically transform the way the alloy has been made for centuries. By using electricity to separate iron from its ore, the company claims it can make steel without emitting carbon dioxide and offers a way to rid one of the world’s worst industries of greenhouse gas emissions.
Steel is an essential raw material for engineering and construction and with more than one of the most popular industrial materials in the world 2 trillion tons are produced annually. However, this abundance comes at a high cost to the environment. Accounts for steel production 7 to 11 percent of global greenhouse gas emissions, making it one of the largest industrial sources of air pollution. And because the production could rise this environmental pollution could increase by a third by 2050.
This represents a major challenge in overcoming the climate crisis. The United Nations says Significant reductions in industry CO2 emissions are essential to keep global warming below the 1.5 degree Celsius mark set in the 2015 Paris Climate Agreement. To achieve this, emissions from steel and other heavy industries must fall by 93 percent by 2050, they say estimates by the International Energy Agency.
With increasing pressure from governments and investors to reduce emissions, a number of steelmakers – including both large producers and start-ups – are experimenting with low-carbon technologies that use hydrogen or electricity instead of traditional high-carbon manufacturing. Some of these efforts are approaching commercial reality.
“We’re talking about a capital-intensive, risk-averse industry where disruptions are extremely rare,” said Chris Bataille, energy economist at IDDRI, a Paris-based research think tank. So he added: “It’s exciting” that so much is happening at once.
Still, experts agree that the transformation of a global industry that turned around $2.5 trillion in 2017 and employs more than 6 million people will require enormous effort. Aside from the practical obstacles to timely scaling novel processes to meet global climate goals, there are concerns about China, which produces more than half of the world’s steel and whose plans to decarbonize the steel sector remain vague.
“It’s certainly not an easy solution to decarbonize an industry like this,” Bataille said. “But there is no other choice. The future of the sector – and that of our climate – depends on it.”
Modern steelmaking includes several stages of production. Most commonly, iron ore is crushed and processed into sinter (a rough solid) or pellets. Separately, coal is baked and turned into coke. The ore and coke are then mixed with limestone and fed into a large blast furnace where an extremely hot air flow is introduced from below. The coke burns at high temperatures and the mixture produces liquid iron, known as pig iron or blast furnace iron. The molten material then enters an oxygen furnace where it is blown with pure oxygen through a water-cooled lance, forcing out carbon to leave crude steel as the end product.
This method, first patented by English engineer Henry Bessemer in the 1850s, produces carbon dioxide emissions in a number of ways. First, the chemical reactions in the blast furnace result in emissions as the carbon trapped in coke and limestone combines with the oxygen in the air to produce carbon dioxide as a by-product. In addition, fossil fuels are typically burned to heat the blast furnace and power sintering and pelleting plants and coke ovens, releasing carbon dioxide in the process.
Up to 70 percent of the world’s steel is produced and created in this way almost two tons of carbon dioxide for every ton of steel produced. That remaining 30 percent is produced almost exclusively by electric arc furnaces, which use an electric current to melt steel – mostly recycled scrap – and have significantly lower CO₂ emissions as blast furnaces.
However, not all future demand can be met this way due to limited scrap supply, said Jeffrey Rissman, an industry program director and head of modeling at San Francisco-based energy and climate policy firm Energy Innovation. With the right policies, recycling could meet up to 45 percent of global demand by 2050, he said. “The rest is satisfied by forging primary ore-based steel, which is where most of the emissions come from.”
“If the steel industry is serious about its climate commitments,” he added, “it needs to fundamentally transform the way the material is made — and pretty quickly.”
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