UK breakthrough could slash emissions from cement

[FloatingFatMan]

Quote

Scientists say they've found a way to recycle cement from demolished concrete buildings.

Cement is the modern world's most common construction material, but it is also a huge source of planet-warming gas emissions.

That is because of the chemical reactions when you heat limestone to high temperatures by burning fossil fuels.

Recycling cement would massively reduce its carbon footprint. Researchers say that if they switched to electric-powered furnaces, and used renewable energy like wind and solar rather than fossil fuels, that could mean no greenhouse gases would be released at all.

And that would be a big deal. Cement forms the foundation of the modern economy, both literally and metaphorically.

It is what binds the sand and aggregate in concrete together, and concrete is the most widely used material on the planet after water.

It is also a major driver of climate change. If cement was a country, it would be the third biggest source of emissions after China and the US, responsible for 7.5% of human-made CO2.

The problem is the material’s uniquely polluting chemistry.

It is made by heating limestone to up 1600 Celsius in giant kilns powered by fossil fuels.

Those emissions are just the start. The heat is used to drive carbon dioxide from the limestone, leaving a residue of cement.

Add both these sources of pollution together and it is estimated that about a tonne of carbon dioxide is produced for every tonne of cement.

The team of scientists, from Cambridge University, has found a neat way to sidestep those emissions.

It exploits the fact that you can reactivate used cement by exposing it to high temperatures again.

The chemistry is well-established, and it has been done at scale in cement kilns.

https://www.bbc.co.uk/news/articles/cxee01m5yero

This is pretty damn cool and I hope the full scale test reaps the same results! This would be a massive step towards reducing emissions.

[Astra.Xtreme]

I didn't know that cement generally wasn't recycled.  I've seen some cases where an old building is demolished, the cement ground up with a machine, and then trucked off to be presumably used again.  Maybe that's not the norm, but it makes sense that it should.

I do work in the steel industry, and many of the US steel mills purely make steel from recycled scrap.  It's something north of 70% of all US steel is made from scrap metal, and 90% of the steel making byproduct is also recycled.  Some mills have baghouses to scrub the air output, but they need to do way better.
The biggest issue is the furnaces.  A lot of the mills are old and use blast furnaces, which create a lot of pollution.  I imagine cement plants are probably the same way.  Upgrading a blast furnace to an electric arc furnace is a huge expense, but it has to be done.

As the article mentions, electric furnaces open the door to renewable energy sources.  The steel industry is starting to adopt hydrogen technology.  I also just heard of a new process called molten oxide electrolysis (MOE), which only has oxygen as a byproduct.  I'm sure that can be used in other processes than just steel.
There's a long ways to go, but these new discoveries are promising.

https://news.mit.edu/2024/mit-spinout-boston-metal-makes-steel-with-electricity-0522