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A crane is used to move a garbage bin to the upper floors of a condo tower under construction, in Vancouver on Feb. 16.DARRYL DYCK/The Canadian Press

As world leaders head to Glasgow this weekend for the 26th United Nations Climate Change Conference, there is a welcome sense of rolling-up of sleeves and getting to work.

After half a decade of ambiguity and political stasis, and amid fast-rising fear that climate change has spiralled out of control, we are finally seeing Europe, the United States and China (to some extent) devoting more genuine policy energy and money to the hard goal of producing zero new carbon emissions by 2050.

Much of that goal is built around a basic assumption: that it’s possible to reach net-zero emissions if the largest economies are able to remove fossil fuels from transportation networks and electrical generation. Together, those sectors account for the majority of the world’s greenhouse emissions. The political assumption is that these, along with carbon pricing or taxes to shift the rest of the economy into more efficient sources, will be sufficient.

Which is hopeful, because those things are finally beginning to happen. A growing number of countries, including Canada, have agreed to end the sale of fossil-fuel automobiles after 2030. In others, shifting electrical production to non-emitting sources has moved from vague ambition to real policy.

But there is a large obstacle that we tend to miss. It’s what you might call a steel-reinforced concrete elephant in the room.

“There’s a simple formula – the idea is to decarbonize the electric sector and then to run everything on electricity that you possibly can. Doing those two things together gets you a long way, but definitely not all the way.”

So says Samantha Gross, a climate-policy expert at the Brookings Institution and a former head of the climate-policy office at the U.S. Department of Energy. She recently published a report on the neglected challenge of decarbonizing heavy industry. It found that this simple formula for cutting carbon emissions really does not work in three major industries: steel, chemicals and concrete.

Together, those industries account for perhaps 20 per cent of all carbon emissions. They produce large emissions of carbon dioxide not through the energy used in their production (that can often be electrified), but through the basic chemical reactions that bring them into existence. Turning iron ore and coke into steel, heating calcium carbonate until it becomes the raw material for cement, or producing bulk chemicals such as ammonia used for fertilizer are transformations that by their nature release large amounts of carbon.

There are technologies that could theoretically reduce this. Hydrogen direct reduction is a steelmaking process that eliminates the use of coke (a coal product that is high in carbon). Cement could possibly be made using materials other than limestone, and heated using hydrogen – assuming hydrogen itself is no longer made using natural gas, and assuming structural engineers come to view non-limestone concrete as a safe material.

All three industries have produced road maps to a zero-carbon production process by 2050. The international concrete industry’s plan is typical: Its biggest net-zero step comes from carbon capture and storage – that is, the expensive process of intercepting the gases produced in the manufacturing process and storing them underground. This approach is currently almost non-existent in cement or steel production, beyond a handful of very early pilot projects in wealthy countries. Environmental critics have pointed out that the rest of the savings seem to come from vague “efficiencies” that would be expensive if fully feasible.

But steel and especially cement are low-profit-margin, and generally more localized and fragmented, industries that can’t make big shifts easily. Faced with carbon pricing or taxes, they’re more likely to pass the costs to the consumer instead of reducing outputs. As the pandemic spike in the cost of construction materials showed us, builders will keep buying raw materials even at double the price.

This reality has led the environmental movement to approach the entire topic with one pointed question: Why not just reduce the amount of steel, concrete and bulk chemicals we use?

“I would give that a big fat ‘no,’” Ms. Gross says, “because we will need a lot of infrastructure to do a green transition – not just for mitigation, but for adaptation too. You need to build all these renewable energy facilities, you need to build dikes and levees and sea walls, things to protect us from the climate change that we’re definitely going to see.”

Getting to net zero by 2050, in other words, is best seen as a big, expensive global megaproject that is going to require vastly more cement and steel than we currently use – and that’s the optimistic scenario, the one where we do manage to prevent a climate disaster.

We need to recognize that part of that megaproject will have to involve governments directly helping these industries adopt new and expensive technologies, and fairly fast, because unlike the auto industry, they’re not going to find it profitable to do it on their own.

Building a green future, after all, counts for little if the building materials themselves are part of the problem.

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