Cleaning Up Steel
And Other Materials Essential To Humanity
By Elizabeth Thomson for The Engine
Illustrations by Julie Carles
The cars we drive, the buildings we live in, the processing and storage of the food we consume — these and much more are dependent on steel. The material is essential to humanity.
And we make a lot of it. In 2018, the world produced some 1.8 billion metric tons. That’s enough to produce 43,100 copies of the Bird’s Nest stadium in China, the primary venue of the 2008 Summer Olympics. Plus, that demand is expected to grow as the Earth becomes more populated.
Steel is also responsible, however, for huge amounts of carbon dioxide, the most important of the greenhouse gases that are slowly warming our planet and changing its climate.
How huge?
Donald Sadoway, who has been a professor at MIT for 42 years, has created a new “country” to drive home the impact. “If you take the total carbon dioxide emissions of the world in 2018, and you break it down by country, the number one contributor is China,” says the professor of materials science and engineering. “Number two is the United States. And if I took the total carbon dioxide emissions from the world steel industry, and compared them to all other countries, steel would rank third. So you have China, the U.S., and what I call The Republic of Steel.”
In 2017, almost two tons of carbon dioxide were emitted for every ton of steel produced, making the industry responsible for “seven to nine percent of global direct emissions from the use of fossil fuels,” according to the World Steel Association. “That’s big. Big,” says Sadoway, who notes that “close behind are cement and chemicals.”
Bill Gates also recognizes the enormity of those numbers. “Whenever I hear an idea for what we can do to keep global warming in check … I always ask this question: ‘What’s your plan for steel?’,” he wrote in his GatesNotes blog on August 27, 2019. That question “opens the door to an important subject that deserves a lot more attention in any conversation about climate change. Making steel and other materials — such as cement, plastic, glass, aluminum, and paper — is the third biggest contributor of greenhouse gases, behind agriculture and making electricity.”
Fortunately, many companies and researchers are reimagining the industrial processes behind our most polluting materials. They range from a company near Boston that’s developing a way to make steel that replaces carbon dioxide emissions with oxygen, to MIT research on an electrically conducting cement with eco-friendly applications that could offset the material’s negative impacts.
Toward Cleaner Steel
The steel industry is well aware of its product’s impact on the environment and has been addressing the issue for some time. As a result, the North American industry in particular “has really made some significant gains over the last 30 years or so,” said Mark Thimons, Vice President for Sustainability at the American Iron and Steel Institute (AISI). Since 1990, he says, “there’s been a reduction in carbon dioxide emissions per ton of steel by about 37 percent.”
Those cuts are due in part to a trend toward automation and toward reducing the number of steps involved in making steel. For example, says Thimons, those steps “used to include a lot of re-heating of steel, and that’s been abandoned in large part in favor of continuous processing.”
Recycling is also an “important part of the sustainability story for steel,” Thimons says. More than 70 percent of the metal is recycled in the United States. And “any recycling improves the energy and emissions profile of the steel that’s produced.” Further, Thimons noted, unlike most other materials, steel can be continually recycled into other products without real loss of quality. A steel beam could become a car door or a vegetable can or a refrigerator, and vice versa.
The steel industry is also working toward future technologies that could make the steel making process more sustainable. Michael Sortwell is AISI’s Senior Director for Technology. Part of Sortwell’s job involves bringing together AISI members to discuss common challenges, which can then become research projects.
One example is research toward completely new ways of producing steel.
Since 2005, AISI has directed work toward a novel process called flash ironmaking.6 Because flash ironmaking “makes better use of our raw materials, it’s expected to minimize carbon dioxide emissions and reduce energy requirements,” says Sortwell. “It’s a pretty big deal, with the potential to offset and eventually replace the blast furnace and other iron-making processes.”
The project was a collaboration between the United States Department of Energy, AISI, Berry Metal Company, and the University of Utah. Last year the team finished tests of a lab-scale reactor, and “we now have a project plan to move forward with a pilot plant,” Sortwell says.
Molten Metal
A little north of Boston, another company is developing a new approach to the production of steel. Based on work began some 25 years ago by MIT’s Sadoway, Boston Metal is zapping a molten mixture of iron ore and other materials with electricity to create steel and other metals.
Unlike the conventional technology for making steel, the Boston Metal process — called molten oxide electrolysis — does not use the element at the root of steel’s carbon dioxide problems: carbon derived from coal. The principal byproduct of the new system? Oxygen, instead of CO2.
“Our process uses electricity to go from a raw ore to a liquid metal,” says Adam Rauwerdink, the company’s vice president of business development. “The incumbent process starts with the same ore feedstock, but uses coal to form the reaction that frees the iron from the ore. So you get a lot of carbon dioxide.”
The overall process is not new. Aluminum is produced this way. But making aluminum isn’t as challenging. It takes place at significantly lower temperatures than those required for the electrolysis of iron ore, allowing reactors made of relatively low-cost materials that won’t melt or otherwise disrupt the process through undesired reactions.
Until about six years ago, there was no analogous set of materials for the production of steel via electrolysis. In particular, researchers could not find a suitable material for the anode of the reactor. Then Sadoway and colleagues solved the problem by identifying an inexpensive alloy of chromium and iron that could indeed withstand the extreme environment associated with molten temperatures hotter than lava (around 1,550°C, or ~ 3,000°F). “That was the breakthrough that really propelled Boston Metal,” Sadoway says.
The company, which was founded in 2012, is growing quickly. Last fall there were nine employees; now there are 30. A series of larger and larger electrolysis cells, or reactors, have replaced the lab-scale cell developed by Sadoway, which was the size of a coffee mug. That cell operated at currents of only a few amperes. By next spring, Boston Metal aims to have a cell that will be roughly the size of a school bus and run at 25,000 amperes.
“Once we’re confident we’ve got the design correct, we’ll go to 50,000 amperes, and that’s an industrial cell,” says Sadoway, who expects to reach that goal by the end of 2021. Early aluminum industrial cells ran at about 50,000 amperes; today’s aluminum factory runs at about 500,000.
Another way to reduce the environmental impact of steel and other metals is to create better versions that, for example, last longer, and so don’t have to be replaced as often. Modumetal, a company based in Seattle, is doing just that with a new class of materials known as nano laminated alloys. Think “metallic plywood,” says CEO Christina Lomasney.
Like Boston Metal, the Modumetal manufacturing process also uses electricity — rather than heat — to produce its products. In this case, however, a lower-temperature process (80–90°C) results in nanometer-thin layers of metal alloys that can be engineered to have a variety of important properties like better strength and resistance to corrosion. The company imparts those properties by modulating the electric field — hence the name Modumetal — as it passes through a proprietary mixture of materials where the reactions occur. “That’s our secret sauce,” Lomasney says.
The company’s principal product is a coating called NanoGalv. “In a corrosive environment, it lasts 30 times longer than conventional galvanized steel,” Lomasney says. Currently, the company has two licensed manufacturers, Tri-Star Fasteners of Singapore, and Rollstud of the United Kingdom and the United Arab Emirates. “Other licensees representing other parts of the world are coming online soon,” Lomasney says.
The Other Elephant
Tackling the carbon-dioxide emissions from the production of steel is key in the fight against global warming, but there’s another elephant in the room that must also be addressed: cement. The production of cement, the “glue” that binds together stone particles of different sizes to form concrete when mixed with water, is responsible for roughly eight percent of worldwide carbon-dioxide emissions.
Concrete, also like steel, is essential to society, and demand is growing. Behind water, it’s the most widely used material on Earth. By 2050, we are expected to use four times the amount produced in 1990.”
What can be done to cut the material’s emissions? Professor Franz-Josef Ulm, faculty director of the MIT Concrete Sustainability Hub, holds up a small glass jar containing a black slurry that he believes represents the future of the industry.
That black slurry is the first cement with a completely new function: It can conduct electricity. Coupled to photovoltaic cells on the roofs of buildings or along highways, concrete made with the material could one day lead to self-heating roads (no salt necessary for ice removal) and floors that warm on demand, cutting the significant carbon-dioxide emissions associated with home heating from fossil fuels.
“Right now, concrete is just there,” Ulm says. But new, valuable functions in addition to strength — like the electrical conductivity being developed at MIT — could offset its overall environmental impact. “That puts concrete in another league, because now it becomes part of the solution,” Ulm says.
Cutting concrete’s carbon footprint by giving the material completely new functions is still in the lab. But Ulm notes three other approaches in use today for tackling the problem. The first involves optimizing the existing industrial process for the production of cement.
A second approach for cutting cement’s emissions is to replace some of it with other materials. Several such supplementary cementitious materials already exist, including fly ash (a by-product of the coal industry) and silica fume (a byproduct from the production of silicon metal or ferrosilicon alloys).
It’s also possible to create stronger cements by engineering the material’s structure at the molecular scale. “Then we can do more with less material,” Ulm says. This relatively new approach began around 2010 after Ulm and colleagues decoded the basic molecular structure of cement — essentially, its DNA. That breakthrough is also behind Ulm’s creation of the first cement with electrical conductivity. “Like many things in science, you come to [such discoveries] because you have understood something fundamentally new about a material,” Ulm says.
What about recycling? It’s important, but not as straightforward as for steel, for a few reasons. Old concrete that’s crushed can replace some of the particles, or aggregate, that make up about 70–85 percent of the material, but it can’t replace the key ingredient: cement. There have been studies toward recycling the cement, “but we have not yet succeeded,” Ulm says.
Further, recycled aggregate can’t be used in applications with strict quality standards because it could introduce impurities that affect the product. Bridges — which are meant to last for decades — are an example of such an application.
Finally, says Ulm, concrete is heavy. So even if you’re recycling for aggregate, you must consider the life-cycle costs of transportation. Because of these challenges, says Ulm, “the recycling of concrete is still in its infancy, with high potential for transformational impact through science-enabled engineering.”
CO2: Part of the Solution
Richard Riman remembers when he first came up with the idea that has since led to Solidia Technologies, a company in New Jersey that aims to lower concrete’s carbon footprint by 70 percent. “I was looking into my backyard in the early 2000s thinking about the carbon-dioxide problem when I thought, ‘Why don’t we just find ways to use CO2 in concrete and other materials, for we would then consume CO2 in very large quantities?’”
The Distinguished Professor at Rutgers University went on to found Solidia Technologies, applying that rationale — and his expertise in hydrothermal solidification technology — to cement. Working closely with co-inventor Vahit Atakan, who now serves as Solidia’s chief scientist, the result is several Rutgers patents for a technique licensed by Solidia that uses carbon dioxide to cure, or harden, the concrete, instead of water.
Rutgers University, Chris Stern, Co-Founder & CEO, Carbicrete
Finding a way to consume carbon dioxide in and of itself cuts the gas’s environmental footprint, but there is more. The technology also includes a cement manufacturing method that significantly reduces the amounts of CO2 released during cement production.
That’s because, for one, Solidia’s cement can be made at significantly lower temperatures than conventional cement. This reduces the amount of fuel needed, whose combustion to generate heat releases less CO2, Riman says. Further, the new cement requires less of cement’s key ingredient — calcium carbonate — whose decomposition during cement production also releases CO2. Taken together, along with its CO2 curing process, that’s why the company thinks it could have an outsized impact on carbon pollution.
To create concrete, Solidia mixes its cement with aggregate and a little water, then forms it into the desired shape. Add carbon dioxide, and the cement solidifies. “Under a controlled set of conditions, you can literally hear the material breathe in the CO2,” Riman says.
The new cement is composed of the same minerals already used in the industry — calcium carbonate and silica — they are just combined in a different ratio. And that means that the process can be quickly adopted by existing cement plants with no additional capital expenditures — a huge plus for cement manufacturers.
Among additional benefits, the “green” cement can be stockpiled
for future use, resulting in “a huge improvement to the business model,” Riman says. Conventional cement is not practical to store because it reacts and solidifies with water — even changes in humidity — resulting in unusable clumps. Solidia cement doesn’t react with water, only CO2. According to the company, the absence of a reaction with water can also save up to three trillion liters of freshwater each year.
In 2013, Solidia launched a pilot program with LafargeHolcim to supply EP Henry, a company that produces pavers, with Solidia cement. The product performance is excellent, as verified by third parties. In September of 2019, EP Henry became the first company in the world to sell pavers using Solidia cement.
Other companies are also looking at solving the carbon dioxide problem by using the material in new products. Carbicrete, a firm out of Montreal, believes it has found a way to create concrete blocks that are carbon negative, or result in a net removal of the gas from the atmosphere. In 2018, the company was named one of ten finalists in the NRG COSIA Carbon XPRIZE, a competition focused on finding ways to use carbon dioxide in valuable products. The winner, to be announced in fall 2020, will take home $20 million.
“The magic of Carbicrete is that we’re solving three different problems,” says CEO Chris Stern.
The company not only replaces cement — and its consequent emissions of carbon dioxide — but does so with steel slag, a waste material from the steel industry. The final coup? Carbicrete, which is based on research out of McGill University, creates its cement by reacting the steel slag with carbon dioxide.
“Carbon dioxide is generally not very reactive, but it’s reactive with steel slag,” Stern says. The end result: “We’re permanently sequestering about a kilogram of CO2 in each standard 18-kilogram concrete block we produce,” which means the company’s entire manufacturing process is carbon negative. Stern notes that a private consulting company has confirmed that conclusion.
The company is currently building a pilot plant to demonstrate the technology at scale. “We have to show that we can do this in the proper manner and at the cost model that we expect,” says Stern.
In September 2019, a team led by Professor Yet-Ming Chiang of MIT reported “a new way of manufacturing [cement] that could eliminate [its greenhouse gas] emissions altogether, and could even make some other useful products in the process,” according to MIT News.
Key to the work is an electrochemical process that uses electricity from renewable energy sources rather than fossil fuels to produce the cement. The new process also produces carbon dioxide, but in a pure, concentrated stream that could be captured and used for other applications like oil recovery. The CO2 emitted by conventional cement plants is contaminated with a variety of materials that make recycling the gas impractical.
Carbon Upcycling Technologies (CUT), a five-year-old startup in Calgary, aims to make CO2 green, according to its website. “We’re using the pollution of today to create the materials of tomorrow,” says CEO and Founder Apoorv Sinha.
CUT combines carbon dioxide with cheaply available feedstocks to create a portfolio of nanoparticle additives that can make a variety of products stronger or more efficient. “We’ve been vetted for over 10 different industries, from concrete and plastic to solar panels and pharmaceuticals,” says Madison Savilow, business development coordinator for the company.
In 2017, CUT became the youngest carbon utilization company to generate revenue with the sale of its first product, a coating for concrete that protects against corrosion. Another one of its products reacts carbon dioxide with fly ash, a byproduct of burning coal, to replace 20 percent of the cement in concrete. That increases the compressive strength of the concrete by some 30 percent over concrete made with conventional fly ash products, says Savilow.
CUT has won or is a finalist in several competitions. For example, like Carbicrete, it is among the 10 finalists in the NRG COSIA Carbon XPRIZE. As part of that competition, the company is scaling up its production capacity. “Right now we can produce one ton of our powders a day,” Savilow says. “Our next reactor for the XPRIZE will be capable of seven tons a day.”
At the Nanoscale
Shreya Dave points to thin sheets of material that range from a shimmery gold to a mottled brown and tan resembling bark. Those sheets represent a new filtration system that could significantly cut the energy use — and resulting greenhouse gas emissions — from the production of thousands of everyday products, from yogurt to plastic and fertilizers, not to mention many chemicals.
Dave, who is CEO of Via Separations, a startup in Somerville, Mass., notes that some 12 percent of all energy consumed in the U.S. is used to separate different compounds from one another in purification processes. “That’s roughly equivalent to the gasoline in all the cars and trucks in the United States per year,” she says.
Today most of those separations happen in a process Dave likens to cooking pasta. But rather than boiling the pasta in water then pouring the mixture through a strainer, industries boil off all the water to get at the pasta at the bottom of the pot. “We are working on creating a strainer at the molecular scale,” she says, noting that the conversion to filtration could cut 90 percent of the energy consumed by those heat-based separation processes.
Filtration is not new. The water industry uses it for desalination. However, water filters don’t work well for a variety of other applications like food processing or making paper, chemicals, and drugs. The Via Separations filter is based on a membrane developed by Dave and colleagues when Dave was a graduate student at MIT. “We take graphite — that’s pencil lead — and explode it in a controlled chemical reaction that results in atomically thin flakes. Then we put them back together in the form of a thin flat sheet.”
Those sheets are then stacked together, but minuscule spaces — pores — are stratified throughout, allowing passageways through the material. Each pore is only about one nanometer in diameter; contrast that to a human hair, which is about 75,000 nanometers wide. In a final step, the sheets are rolled up like carpet to be inserted into an existing filtration machine.
“So far, we’ve scaled up three orders of magnitude from the amount of material we made in the lab.” The ultimate goal, says Dave, is to create sheets of material that are cheaper than what you’d pay for flooring at a hardware store. “The target for us is a few dollars a square foot. And we think we can achieve that.”
Syzygy Plasmonics aims to dramatically reduce, and in many cases virtually eliminate, the carbon-dioxide emissions from chemical plants with a completely new type of reactor powered by light rather than the heat that comes from burning fossil fuels. “Our approach is a wild leap away from what is being done today,” says Syzygy (siz-uh-jee) CEO Trevor Best.
That starts with size. Today’s chemical plants are enormous structures with lots of smokestacks. In comparison, the photoreactor at the heart of the Syzygy plan is magnitudes smaller. As a result, Best expects that the company’s first commercial photoreactor “will be about the size of a milk jug.” Several would be linked together to produce chemicals in quantity, but the overall plant would still be pretty small. For that and other reasons, says Best, “we envision small-scale point-of-use manufacturing centers that can be put on-site at a customer’s location.”
Other benefits: because the system is powered by LED lights, it operates at a temperature “very similar to your oven,” Best says. In contrast, a common reaction today for producing hydrogen — one of Syzygy’s target markets — runs at 1,500ºF. The system also does its work under much lower pressures. Taken together, that means the structure containing the reactor can be constructed using materials like aluminum, glass, or plastic, as compared to expensive alloys.
The breakthrough behind Syzygy is based on more than two decades of research at Rice University by Professors Naomi Hollis and Peter Nordlander. Both work in the field of nanophotonics, or the interaction of light with nanoscale structures. The two created what they call an antenna reactor, a hybrid structure that brings together two disparate materials. The first is a material that’s “extremely good at harvesting light and turning it into a usable form of energy,” Best says. That’s the antenna. The second is a traditional catalyst, or material that is very good at performing chemical reactions.
Although Syzygy is only about two years old, the company has already shown that the technology works for more than a dozen different chemical reactions at the lab scale.
More recently, the company has successfully scaled up a smaller number of these reactions into a bench-scale, single-cell photoreactor that “represents a world’s first in this arena,” Best said. Thanks to a successful funding round co-led by The Engine, the company aims to build a full-scale multi-cell photoreactor system in the early 2020s.
Challenges Remain
Radical innovations in the production of steel, concrete, and other materials are under development. Some are slowly moving into the marketplace. “But the market is a cruel arbiter,” says MIT’s Sadoway. “Nobody pays a premium for [something that’s] green. So you’ve got to make a product that’s as good as what’s being made by the incumbent today and is competitive in price.”
And according to a CNBC story about an analysis of corporate earnings profiles focused on steel, clean technologies for that industry won’t come online until the 2030s, and the resulting steel would be 20–30 percent more expensive.
That said, while acknowledging the latter statistic, SSAB, the largest steel sheet manufacturer in Scandinavia, and collaborators are proceeding with their own approach toward fossil-free steel. A pre-feasibility study for the project, dubbed HYBRIT, expects that factors such as increasing costs for CO2 emissions and lower costs for renewable energy will eventually make clean steel competitive with that produced through traditional processes.
What about concrete? Says MIT’s Ulm of that industry, “they’re under enormous pressure to reduce their environmental footprint.” And in the United States, “it’s just a matter of time until legislation is passed that taxes carbon-dioxide emissions, which will give the industry an additional economic incentive to cut those emissions and push forward with transformational innovations.”
Another challenge to getting innovative technologies into the marketplace is getting them included in industry spec sheets, or the accepted guidelines that set safety and performance standards. “The spec represents a barrier to entry for any technology,” says Modumetal’s Lomasney. “We’re selling into industries that have very mature procurement and supply chains and are not used to change or this level of innovation.”
Says Savilow of Carbon Upcycling Technologies, “talk to any materials company, and I guarantee that if they haven’t yet had their break into the spec sheets, that’s what they’re working towards.”
Finally, many of these technologies will only make sense with an abundant supply of renewable energy to run the reactions involved. “Otherwise you’re simply shifting the source of pollution,” Sadoway says.
Hope for the Future
Climate change is in the news almost every day; witness the worldwide demonstrations that prefaced a United Nations summit in September 2019. “But you’re not seeing as much about climate solutions,” says CUT’s Savilow. Yet “there are many technologies and materials out there that are ready.” Carbicrete’s Stern would agree. “There are a lot of solutions; they just have to be implemented. We have to stop thinking about a magic bullet and just start doing something today.”
Bill Gates is also hopeful. In the conclusion to his blog about plans for dealing with climate change, he wrote: “I’m optimistic about all these areas of innovation — especially if we couple progress in these areas with smart public policies. Companies need the right incentives to phase out old polluting factories and adopt these new approaches. If all of these pieces come together, we will have a climate-friendly plan for steel, as well as cement, plastic, and the other materials that make modern life possible.”
Best, of Syzygy, notes that “the problems [related to climate change] that we have to overcome over the next few decades are enormous, and very intimidating. But I’m getting more hopeful for the future the more I work in this area. Not just because of our own technology, but because so many other people in other companies are joining in the fight with us.”+
