Cement is the Source of About 8% of the World's Carbon Dioxide Emissions (bbc.com)

Concrete is the most widely used man-made material in existence. It is second only to water as the most-consumed resource on the planet. But, while cement -- the key ingredient in concrete -- has shaped much of our built environment, it also has a massive carbon footprint. From a report: Cement is the source of about 8% of the world's carbon dioxide (CO2) emissions, according to think tank Chatham House. If the cement industry were a country, it would be the third largest emitter in the world -- behind China and the US. It contributes more CO2 than aviation fuel (2.5%) and is not far behind the global agriculture business (12%). Cement industry leaders were in Poland for the UN's climate change conference -- COP24 -- to discuss ways of meeting the requirements of the Paris Agreement on climate change. To do this, annual emissions from cement will need to fall by at least 16% by 2030.

Comments

Solved problem

[SuperKendall]

Concrete contributing to CO2 has been known for a while - that is why at this point there are a lot of solutions to that problem, including concrete variants that sequester or even absorb CO2.

Notice how old some of the results in that search are...

If CO2 is really a problem, local governments will seek to adopt some of those ideas.

Well known...

[apoc.famine]

Not sure how this is suddenly news. It's been called out since the very first IPCC report, and known long before that.

This is part of why nuclear power and hydroelectric power aren't exactly green. Far better than fossil fuels, sure, but much worse than an equivalent solar or wind farms in terms of CO2 release. The amount of concrete used in both nuclear plants and hydroelectric dams is massive. It dwarfs the pads for solar panels and wind turbines.

But like everything, it's complicated. Turns out that over decades, concrete actually absorbs a large amount of CO2. It seems to be close to half that released when making it. If carbon capture could be used during production, over its lifetime, concrete could become carbon negative. And alkali-activated cements seem to be on the horizon, taking industrial CO2 byproducts and making them into concrete-like structures.

Re:Well known...

[Solandri]

The amount of concrete used in both nuclear plants and hydroelectric dams is massive. It dwarfs the pads for solar panels and wind turbines.

Actually I did the calculations on this a few years back. Per GWh of energy generated, wind turbines use roughly an order of magnitude more concrete (and steel) than nuclear plants. You have to understand that wind turbines very rarely operate at full capacity like a nuclear reactor does. The actual electricity production of nuclear plants averages about 90% of their nameplate capacity. For onshore wind it's about 25%. So to generate the same amount of power over the course of a year as a single 1 GW nuclear reactor requires about 2500 1.5 MW wind turbines (3.6 GW capacity). And the steel and concrete for that many turbines far exceeds the requirements for the single nuclear plant. It also drives up the maintenance cost for wind far above that for nuclear, even with all the regulations covering nuclear. (In fact most of the wind-related deaths are due to maintenance personnel falling from turbines.)

Re:Well known...

[Areyoukiddingme]

How exactly does concrete produce CO2? Is it an essential part of production - or merely a result of heating in furnaces traditionally powered with coal?

It is an essential part of production of Portland cement, the most common cement in use worldwide. The CO2 is cooked out of limestone, resulting in calcium silicate, the constituent molecules of clinker.

Ancient Roman cement does not seem to be primarily calcium silicate, though studies are ongoing. The manufacturing process has been lost to history, and there was quite a bit of variance in the formula over the centuries it was made.

Remember...

[Thelasko]

Concrete is made with cement and aggregate. Cement is not the same as concrete. The two are not interchangeable.

Re:That's a trade I'm willing to make.

[Chas]

There are several ways to fix it.
There are ways to replace the portland cement.
There's also ways to SEQUESTER CO2 in concrete as well.
There are also forms of concrete that actually ABSORB CO2.

Re:That's a trade I'm willing to make.

[Rei]

wall thickness is not to protect rebar. commercial building codes specify 1.5" from rebar edge to concrete surface for bar size #2-#6 typically (with almost no exceptions) and 3" for earth exposed rebar (up to #6 or 5/8" dia rebar

You just contradicted yourself there. That minimum 1,5" / 3" is to protect the passivation layer on the steel (whether you realize that or not). The thicker the layer, the longer that carbonation takes. In ideal conditions, carbonation depth (in mm) progresses at a rate roughly: (-3,59 + 9 * W/B) * sqrt(t) where W/B is the water/binder ratio and t is time. However, a number of factors can significantly accelerate carbonation, so large margins need to be allowed for.