Decarbonizing Steel: Forging a New Road Forward
By Dylan Comfort • 10 min read
Despite its necessity in today’s world, steel production has lasting effects on the environment that cannot be ignored. The steelmaking process is very carbon intensive, with each ton of produced steel emitting 1.85 tons of carbon. Steel production alone accounts for 8% of global emissions and makes up the largest portion of industrial emissions. With demand for steel set to increase by 10% by 2050, the industry must address its environmental impact. To understand how carbon emissions can be reduced in the steel industry, it is necessary to comprehend the steel production process.
Steel Creation
Steel production can be separated into two main methods: blast furnace (BF)/blast oxygen furnace (BOF) and electric arc furnace (EAF), both of which are very carbon intensive. The BF/BOF production method creates the alloy from iron ore by removing oxygen from the ore, whereas the EAF process allows for recycled steel scrap to be refurbished into new material. EAFs can also use direct-reduced iron (DRI), a higher-quality metallic iron product relative to regular iron ore. A more in-depth explanation of each method will aid in understanding where change can be made.
Blast Furnace/Blast Oxygen Furnace
The top of the furnace is continuously fed with charge (iron ore, coke, and limestone)
A blast of hot air (pure oxygen in a BOF) into the furnace from the bottom
Coke provides additional heat, further increasing the temperature of the charge
Coke reacts with the oxygen from the hot air, creating the reducing agent (carbon monoxide). This chemical reaction removes oxygen from the ore
Limestone reacts with any impurities in the furnace, creating slag, which floats to the top of the furnace
Roughly every hour, the molten iron is sent on for further processing
The blast furnace process
Electric Arc Furnace
The charge door is opened and charge is put into the base of the furnace
An electric current jumps (arcs) between electrodes, producing high temperatures
The charge melts and the resulting chemical produces molten
Alloying materials (ex. chromium, cobalt, columbium) are added to create molten steel
The furnace is tipped, pouring out molten steel that will be refined and cast
The electric arc furnace process
Decarbonization Strategies
Just as there are two methods for the production of steel, decarbonization strategies can be put into two categories; one for each production method. Since carbon is essential in the BF/BOF process, there are currently only strategies that can be used to reduce emissions, whereas EAF can entirely eliminate emissions.
Blast Furnace/Blast Oxygen Furnace
Biomass Reductants
As mentioned in Step 3 of the BF manufacturing process, a reducing agent is needed to remove oxygen from the iron ore. Usually, this reducing agent is provided through the burning of fossil fuels. A proposed alternative to the current reducing agent is biomass, the renewable organic material that comes from recently living organisms. Using biomass as a reducing agent would be more cost-effective and emit fewer carbon emissions.
Carbon Capture and Usage
Carbon can potentially be captured and stored throughout the steelmaking process through the use of carbon capture and utilization/storage (CCUS) technologies. The captured carbon can be repurposed into renewable chemicals such as ammonia and bioethanol, which offer an alternative to traditional fossil fuels used to power vehicles, planes, and ships.
Electric Arc Furnace
Increased EAF Usage
With the EAF process already more environmentally friendly due to its use of recycled materials, increasing the share of steel supplied by EAFs will aid in the decarbonization of steel. EAFs' utilization of electricity allows the method to avoid emissions.
Increased DRI Usage in EAF
To allow the production of higher quality steel, DRI-based material (which already emits less than pure iron ore when used in the steelmaking process), can be used with recycled scrap steel. This addresses one of the large concerns about EAFs and their inability to produce high-quality steel with scrap metal alone.
DRI and EAF Using Hydrogen
This strategy combines both EAF strategies. With increased usage of DRI and EAFs, the key implementation is the removal of emissions in the DRI production process through the use of hydrogen. Hydrogen would be used as an alternative reducing agent for the most common reducing agents in DRI production: coal and natural gas. Making this change would make the entire EAF steelmaking process free of carbon emissions.
Challenges facing the decarbonization of steel
Supply of Renewable Energy
There will need to be an abundance of renewable energy to decarbonize the industry. With lots of electricity required to power EAF plants and incumbent plants attached to power grids with little capacity, a large supply of green energy will need to be implemented. Furthermore, the green hydrogen economy is in its infancy and will require significant resources to reach the scale needed to have a large impact on the decarbonization of steel.
Little Regulation
Current policies are expected to cause a slight decrease in carbon emissions from the steel industry, but not enough to significantly aid countries in reaching their Paris Agreement targets. Increased regulation can accelerate the decarbonization journey for the industry and countries as a whole.
Quality of Iron Ore
To create DRI, high-grade iron ore is required. Experts estimate that 66% of the world’s iron supply is not suitable for DRI-EAF production. This means that low-emitting technologies will need to be developed to work with low-quality iron ore.
Financing
Due to the capital-intensive nature of the steel industry, a large investment is needed to replace production assets. With the majority of the industry pursuing a cost leadership strategy, the investment in green technologies will need to come with little risk. This ties into the risks caused by little regulation, as government incentives could lead to increased investment and implementation in green production technologies.
Something Completely New: A Boston Metal Case Study
Boston Metal has developed an early-stage technology called Molten Oxide Electrolysis (MOE). The process uses electricity to separate chemical compounds and create a high-purity metal. This process has been found to work with low and medium-grade iron ore and emanates the need for fossil fuel-reducing agents.
Moving Forward
There is no question that the need to decarbonize the steel industry is rising. With consumers becoming more aware of the economic footprint of their products, the steel industry will be forced to adjust. Currently, there are some strategies that could be taken to market, such as carbon reduction strategies in the BF/BOF production process, the use of the EAF production method, and increased use of DRI. While the industry faces large challenges, there are companies coming up with innovative strategies every day to overcome the high emissions coming from one of the world’s most essential industries.
Sources:
https://www.ey.com/en_id/mining-metals/five-actions-to-improve-the-sustainability-of-steel
https://www.britannica.com/technology/steel
https://www.bostonmetal.com/green-steel-solution/
https://www.ft.com/content/3bcbcb60-037f-11e9-99df-6183d3002ee1
https://steelmuseum.org/steelmaking_exhibit_2016/electric_furnace.cfm
https://fathom.world/ammonia-methanol-101/
