Steel has a fossil fuel problem, and it’s called the blast furnace.
Blast furnace (BF) technology has been central to steelmaking for hundreds of years. Today, blast furnaces produce around 90% of the world’s iron — a critical step in the steel production process. However, because blast furnace production is so carbon intensive, this step also emits the vast majority of overall steelmaking emissions.
The core issue is that blast furnace ironmaking depends on coke, a refined type of coal that acts both as a heat source and a chemical reductant. Coal therefore plays an inherent role in blast furnace operation.
Let’s run through the blast furnace production process to better understand why the technology can never be fully decarbonized.
Keep scrolling to learn about the BF process or click here to skip graphic.
Image credit: Doethion | Dreamstime.com
Blast furnace process emissions comparison
In most steelmaking configurations like BF-BOF, blast furnaces contribute more carbon emissions than any other unit in alternatives like scrap-fed electric arc furnace (EAF) or direct reduced iron (DRI)-EAF production. The blast furnace-basic oxygen furnace (BF-BOF) process, which uses coal as a reducing agent, produces enormous amounts of CO2 — around 2.2 tonnes of CO2/tonne of steel (t CO2/t steel) when including both scope 1 and scope 2 emissions.
Understanding categories of emissions for steel emission intensity calculations. (click to expand)
In calculating greenhouse gas emissions, analysts use three categories.
- Scope 1: “direct” emissions, resulting from onsite processes and fuel use during production at the plant
- Scope 2: resulting from purchased electricity and estimated using the approximate CO2 intensity of the grid supplying the power
- Scope 3: upstream and downstream emissions, e.g. embodied emissions from the purchased scrap steel used in production or downstream in the process
Steel emissions intensities typically include scope 1 and 2 emissions only.
In contrast, EAFs cut emissions dramatically when using recycled scrap, which is the dominant feedstock today. Considering scope 1 and 2 emissions, EAFs using scrap as the primary feedstock emit around 0.3 t CO2/t steel on average, whereas those using fossil gas-based DRI have higher carbon intensities of around 1.4 t CO2/t steel. For producing iron, the leading low-emissions alternative is DRI, particularly when paired with EAFs. Steel produced using fossil gas DRI still has a lower carbon intensity than BF-BOF, and hydrogen-based DRI powered by renewable electricity can bring emissions close to zero.
DRI-EAF offers the clearest proven and available pathway for decarbonizing primary steel production. This is something coal-based blast furnaces cannot achieve, even with retrofits.
The global blast furnace fleet is massive
But these furnaces have limited lifespans
Decarbonization of the steel industry rests on blast furnace phaseout. As these operating blast furnaces age, there is an opportunity to transition toward greener technology.
Despite the age of many of these units, most major steelmakers have not announced clear retirement plans for this capacity.
This is a critical junction in the steel industry. Reinvesting in old blast furnaces or building new blast furnaces risks locking in coal and threatens climate goals.
Relinings are the key decision point
Blast furnaces typically undergo a major relining project every 15–20 years, which involves capital-intensive upgrades to extend the life of the unit. These projects can cost hundreds of millions of dollars, or as much as 25-50% of the cost of a new blast furnace.
These investment decisions represent critical intervention points for the green steel transition, as reinvesting in these coal-based units locks in emissions for decades when that capital could instead be directed to lower-emission technologies.
China’s blast furnace fleet has an oversized impact
As the world’s largest blast furnace operator, the choices China makes will play a pivotal role in shaping not only its own decarbonization pathway but also global efforts to curb industrial emissions.
India leads on new blast furnace developments
While China operates the largest and youngest blast furnace fleet today, India is ramping up blast furnace capacity faster than any other country, with 142 mtpa under development.
Nearly 90% of these developments have not yet started construction, however, meaning they could still change course.
India’s trajectory therefore has the potential to shape the entire steel industry just as much as China’s. If blast furnace expansion plans are carried out, this could delay decarbonization of the industry around the world.
Altogether, the investment decisions these leaders make – both in building new blast furnaces and extending the lives of existing ones – will play a huge role in whether the sector can meet Net Zero goals.
Making steel doesn’t have to be so emissions intensive
Reducing global iron and steel emissions means addressing the blast furnace fleet: developing comprehensive phaseout plans for operating units and replacing new blast furnace projects with cleaner technologies. DRI-EAF is a commercially available alternative and offers a lower or even zero-emissions route for producing primary steel. Alongside emerging methods like molten oxide electrolysis and DRI-smelter-BOF, this means the industry has a clear path forward.
Without urgent action, the steel transition is at risk – but changing course is still possible. Prioritizing DRI over new blast furnace capacity enables continued steel production without locking in decades of coal-based emissions.
Explore more iron and steel data and blast furnace unit details in the Global Iron and Steel Tracker.