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17 October 2022


It’s generally assumed that cutting emissions from the industrial sector will be one of the hardest tasks.

If humans were to build a modern civilisation from scratch today, there would be no way around making use of cement and steel. However, we would prefer not to use the primitive methods of making those materials. And, fortunately, a series of innovations in recent years are likely to make that dream possible.

For thousands of years, cement and steel have been made in largely the same way. Take ore from mines and burn it up in a coal-fired furnace. In the process, generate huge amounts of greenhouse-gas emissions and plenty of mining waste.

As the urgency to cut emissions grows, policymakers have focused on cleaning up the electric grid, transport, and even agriculture. There’s not been a lot of focus on the industrial sector that is responsible for more than 20% of annual emissions of planet-warming gases, with cement and steel accounting for the vast majority.

It’s generally assumed that cutting emissions from the industrial sector will be one of the hardest tasks. Cement and steel “have not been the subject of significant scientific study,” says Eric Toone of Breakthrough Energy Ventures.

Given that cement and steel plants can last for 50 years or more, consultants brought in to deal with the emissions problem have often concluded that expensive carbon capture and storage technologies will have to be used. That narrative is starting to change.

Over the past few years a series of innovations are enabling the use of clean electricity to make cement and steel instead. The result is typically: no greenhouse-gas emissions, lower energy use, lower waste production, and often no fire at all.

Consider the example of Electra, a Colorado-based startup that has developed a new way of making emissions-free iron. The ironmaking process accounts for 90% of steel’s emissions, and Electra makes iron at merely 60 degrees Celsius — or temperatures cooler than coffee — instead of 1,600C inside a coal-fired furnace.

“What’s super interesting about low-temperature production is that it’s not just making the process green, it’s requiring less energy,” says Patricia Wexler, co-founder of Starlight Ventures. These technologies are now “less of a scientific challenge, and more of an implementation challenge.”

Another example is that of Chement, an Illinois-based startup that has invented a way of making cement at room temperature. While the chemistry is such that, even without burning coal, the process produces carbon dioxide, it does so as a pure gas. That way the costs of capture are only a small fraction compared to trapping those emissions from existing cement kilns.

“Day in and day out, we take materials and transform those materials,” says Venkat Viswanathan, an associate professor at Carnegie Mellon University and co-founder of Chement. “Usually that transformation is done at high temperature with heat generated by fossil fuels. But now we can do that with electricity at low temperature.”

There are other ideas that still rely on high temperature but get rid of coal. For the past decade, Boston Metal has been developing a method to turn iron ore to iron using electricity. It does so by melting the ore at 1,400C and then passing huge amounts of electricity through it. If the electricity comes from carbon-free sources, the iron it produces is emissions-free too.

Another example is that of Sublime Systems, a Boston-based startup that makes cement in two steps. Both steps can use carbon-free electricity, but one of the steps requires heating the material to 1 400C. Just like Chement, the chemical process inevitably releases carbon dioxide, but as a pure gas it can be captured and buried underground more cheaply.

“If the momentum we have currently stays in place, which I believe it will because of geopolitical and institutional forces, then in five years we’ll start to see major commitments to redo the way we manufacture things,” says Wexler.

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