To deal with the growing effects of a changing climate, we need to make our communities more resilient. Much of that takes the shape of renewed infrastructure. The irony? It’s pretty carbon-intensive to build new roads and bridges. How can we safeguard our cities against climate change, while not making a bad situation worse?
$120 billion in annual damages (and growing)
Right now, major storms, wildfires, floods, and other extreme weather events cause roughly $120 billion in damages every year. Depending on how climate change plays out (which largely depends on the pace at which we decarbonize), that figure could grow substantially by the end of the century. According to the White House Office of Management and Budget, one of the largest drivers is hurricanes, which could create an additional $94 billion in annual disaster response costs by 2100 (a fact that’s maybe a little too close to home for us Floridians).
With some climate effects already locked in, knowing how to rebuild greener is key. Lots of folks are focused on electrification and renewable energy — and that’s fantastic. But there’s a less glamorous side to the climate fight that can significantly drive down emissions: buildings and infrastructure (or, more specifically, the materials they’re made out of).
The downside? They’re just about the hardest thing to decarbonize.
Cement may be the glue holding our cities together, but it emits 2.3 billion tons of CO2 per year
Accounting for mass, cement is the most widely used material in the world. We need it for our buildings, our bridges, our roads. But it’s got a big climate problem. In fact, if the cement industry were a country, it would be the third largest emitter in the world. Why so? Two main reasons:
- High temperature. Traditionally, cement production requires incredibly elevated temperatures (something like 1400°C, or ~2550°F). It’s pretty hard to generate that kind of heat without burning fossil fuels.
- Lime production, one of the key ingredients in cement. To create lime, you have to break down limestone (a mixture of calcium, oxygen, and carbon) by adding heat. The carbon gets released, combines with oxygen in the air, and continues on into our atmosphere as CO2.
Some innovators are already working on the temperature issue. Take Heliogen, a California-based startup that is amplifying temperatures through mirror-enhanced sunlight (I can’t be the only one who thinks of a little kid frying ants with a magnifying glass here, can I?).
While the high temp issue seems solvable in the somewhat near term, making lime production less carbon-intensive will likely be a bit trickier. You could reduce the amount of lime in the end product, but that would decrease the material’s strength. How do we preserve needed strength while also driving down CO2 emissions? Like with other processes, the answer may lie in carbon capture and storage.
Steel isn’t any better, accounting for 7% of annual global emissions
Every single year, the world produces 1.8 billion tons of steel. By 2050, that demand is expected to reach roughly 2.5 billion tons. But steel production has a lot of the same issues as cement, namely that production requires incredibly high temperatures (necessitating fossil fuels). Traditional blast furnace processes also use coke (a higher heat-producing version of coal) as a reducing agent to create iron from its ore.
To stick with the goals of the Paris climate agreement, steel will need to reduce its carbon intensity from 1.85 tons of CO2 per metric ton to a miniscule-by-comparison 0.2 tons. It looks like we’ve got our work cut out for us.
Like with cement, some are already taking on the problem of high steel emissions. Startup Limelight Steel’s technology focuses on more sustainably converting iron ore, with 40% less energy and zero emissions. Another, Colorado-based Electra, has developed low temperature iron ore refinement using zero-carbon intermittent electricity (down to only 60°C instead of 1600°C!).
We have a path forward for sustainable cement and steel, but still a long way to go
So what do we do? It’s clear that decarbonization of these materials will be much more complicated and costly than something like generating more electricity from renewables. Right now, we don’t have any alternatives that could be effectively deployed at large scales to replace cement and steel. This is a process that will take time (possibly lots of it), as more and more options are discovered in the lab.
