Boston Metal & ArcelorMittal Take Different Routes To Green Steel

Manufacturing steel is an incredibly dirty business. Each tonne produced creates about 2 tonnes of carbon dioxide. As the industry produces about 2 billion tonnes of steel every year, a lot of CO2 is released into the atmosphere – in fact about 7% of all global emissions. This makes it important to find ways to make green steel to control global warming.

The problem is that the traditional way of making steel – heating iron in a blast furnace – has been around for centuries. It uses lots of energy both to heat the contents inside the furnace and also to convert coal into coke, which then reacts with iron ore and is converted into pig iron bars. Some of this energy comes from electricity, but much of it comes from burning methane, which is often incorrectly referred to as “natural gas”.

ArcelorMittal is one of the largest steelmakers in the world. It seeks to reduce carbon emissions from steel production by replacing green hydrogen with coke. This eliminates the significant emissions from coke production, but still requires huge amounts of electricity for the rest of the process.

RWE, one of the largest electricity producers in Germany, and ArcelorMittal signed an agreement memorandum this week. Under the agreement, they will work together to develop, build and operate offshore wind farms and hydrogen plants to provide the renewable energy and green hydrogen required to produce low-emission steels in Germany. The plan is to replace coal with wind power and green hydrogen as the main energy source in steel production at ArcelorMittal’s steel mills in Germany.

Reiner Blaschek, CEO of ArcelorMittal Germany, says: “ArcelorMittal Germany is undergoing a radical transition to ensure that we reach our goal of reducing CO2 emissions, which means that the energy used to produce steel The partnership we have announced with RWE today is important for a number of reasons, it will provide us with the renewable, affordable electricity and green hydrogen we need to produce low-emission steels, “while remaining competitive in a global market, it also provides vital security in the supply chain by integrating the supply of energy and hydrogen into our business.” The new offshore wind farms will be located in the North Sea.

Boston Metal skips The Green Hydrogen Step

Boston Metal is a spinoff of MIT in Woburn, Massachusetts. Unlike most steelmakers, it wants to skip the green hydrogen step and go straight to making carbon steel using what it calls the molten oxide electrolysis process, which uses electricity to separate oxygen from iron ore, a critical step in the steelmaking process. “The advantage we have is that it’s a one-step process that directly electrifies steel production,” Adam Rauwerdink, Boston Metal’s vice president of business development, told Canary media.

“You do not understand when you look around in your landscape where embedded and ingrained [steel] is in society, ”said Chathurika Gamage, head of climate intelligence at the nonprofit research organization RMI. “Everything we do, the buildings we are in – it gives structural stability, literally, to all these spaces.”

“Decarbonization of the iron and steel industry means basic decarbonization of the blast furnace,” said Zhiyuan Fan, a research fellow at the Center for Global Energy Policy at Columbia University. “If you fix the blast furnace [issue]half of your problem is gone. “

Fans’ team in Columbia last year published a study that compared several strategies for decarbonizing steel and found that electrification is the key to offsetting emissions. The more the process can benefit from clean electricity instead of burning coal and other fossil fuels, the easier it will be to reduce emissions. “We know how to decarbonize the grid better than we know how to decarbonize a blast furnace,” adds Fan.

“Ten or 20 years ago, the grid was not clean, so it made no sense, and there was no demand for a greener version of steel, but now both are available,” says Rauwerdink.

Lower the cost of manufacturing steel

Making something in a laboratory is all very nice, but being able to scale the technology to make millions of tons of green steel is something completely different. Boston Metal believes it has the answer.

Electrolysis has been an important part of aluminum production for over 100 years. Boston Metal’s molten oxide electrolysis process uses this technique on iron, which requires warmer temperatures. Aluminum electrolysis takes place at temperatures just below 1,000 degrees Celsius, while iron electrolysis requires about 1,600 ° C, a temperature much warmer than molten lava.

To begin with, the iron ore is melted with heat produced from electricity. Then it is located in a cell that is built almost like a giant battery. At the top, an anode provides electrical charge. At the bottom, a cathode receives the electric charge. In between, the charge flows through an electrolyte, which in this case is a scalding bath of molten materials. The electrolyte contains a number of elements bound to oxygen, including aluminum, silicon, and calcium.

According to Boston Metal, the process works even with low-quality iron ore, which is cheaper and more abundant than higher-quality ore that has fewer impurities. “Some of the other technologies that are being developed [to manufacture] green steel needs the super-premium qualities of ores, ”says Rauwerdink. “We can benefit from all the much more abundant qualities of ore, which is the key to cultivating the technology in the long run.”

Another of the advantages of electrolysis of molten oxide compared to direct reduction of iron is its efficiency. By interrupting the hydrogen step, MOE puts energy directly into steel production and removes temporary phases where energy can be lost. MOE requires higher temperatures than hydrogen-based production, which erodes the benefits, but even when you consider it, MOE still ends up being more efficient.

Fan, the expert in green steel at Columbia, estimates that producing green steel using green hydrogen requires at least 30% more energy than MOE – and possibly as much as 50% to 60% more. “By skipping the different processes, you can actually achieve a lot of efficiency improvements,” he says.

The road to scale

A commercial plant can produce millions of tons of steel a year. In continuous operation, Boston Metal’s first demonstration cell will produce less than 100 tons of steel per year, so the company has a long way to go. “It’s just about assembling these cells, and so the proof lies in the pudding of how much it can scale,” Gamage from RMI said.

Scale is important in the steel industry, but it is also to be able to use capital-heavy systems that have already been built. Green hydrogen has a leg up on this front because it is compatible with the direct reduction of the iron process already used on a commercial scale with natural gas. It is relatively easy to replace natural gas with hydrogen. That is why large steel producers such as SSAB and ArcelorMittal have focused on green hydrogen for their immediate plans.

“We’re on the clock here,” Fan said. “If we want to decarbonize fully by 2050, we have to think about replacing the production unit within the next 10 years or 20. If the MOE is not commercially available at that time, it just went past the window.”

Boston Metal is working on a larger demonstration cell at its headquarters in Woburn, Massachusetts, which will be able to produce hundreds of tons of steel a year. Once it perfects the design, multiple cells can be built in the same plant and then potentially lined up in the hundreds, a design common to aluminum smelters.

“Because it’s a modular technology, the road to scaling will be pretty fast,” says Rauwerdink. “It’s like having a wind turbine and demonstrating five turbines, and then when that’s successful, build 100 or 200 for a commercial plant. It’s the same approach for us. We then do not have to go back and redesign a cell that is 100 times larger. “

The need for electricity without emissions

Boston Metal’s technology will need electricity generated from low – carbon sources to make a dent in steelmaking’s carbon emissions. “The future of steelmaking really depends on pure electrification,” Gamage said.

Steelmaking equipment tends to be in constant operation for several months at a time, and changing the chemical composition of metal naturally requires a lot of energy, so if the process is electrified, it will need a huge amount of electricity. Boston Metal says their technology uses 4 megawatt-hours of electricity to produce 1 ton of steel. That’s enough to run the average American home for more than four months.

According to Columbia’s research into decarbonisation of steel, replacing all the world’s blast furnaces with MOE manufacturing processes will require an amount of electricity equivalent to almost 20% of global electricity consumption in 2018. This means that the steel industry would become one of the largest users of electricity on the planet.

But replacing all steel production with hydrogen-driven direct reduction of iron may require even more electricity. This means that there is no way to deal with the climate impacts of steel without installing a huge amount of clean electricity production, other than ensuring that the grid is ready to reliably move around all the extra electricity.

“You’ll have to strengthen the network at a speed that utilities and network operators have not planned for,” said Thomas Koch Blank, senior rector of RMI’s Breakthrough Technology Program. And that would have to be done on a “10- to 15-year timeline.”

Sometimes the development of new decarbonisation technology is judged to be in conflict with the implementation of established solutions such as renewable energy, but in many circumstances these challenges are one and the same. Green steel is a good example.

“For us or for green hydrogen, you need clean electricity,” Rauwerdink said, “so all the work that goes into cleaning up the power grid enables solutions like ours.”

As the demand for green steel grows, more solutions will be needed to satisfy the world’s appetite for steel without overloading the atmosphere or the electricity grid. Koch Blank emphasizes that both electrolysis of molten oxide and hydrogen-driven direct reduction of iron hold promise for decarbonization of the steel industry and are worth pursuing. “Ultimately, I would be surprised if there is not enough space in the market for both technologies,” he said.


Green hydrogen has received a lot of attention in the press recently because it promises ways to reduce carbon emissions from industrial processes such as steel and cement production. But it is completely dependent on access to clean, reliable and affordable electricity. The road to emission-free building materials is clear, but getting there will require a major rethinking of renewable energy and how it will be distributed by the electricity grid in each country.


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