What is the impact of the cost on concrete

Why concrete is harmful to the climate

Cement, water, sand and gravel form the basis of the world of the 21st century. The mixture is known as concrete. After a few hours of waiting, this mixture is used to create an artificial stone for dams, bridges, high-rise buildings and much more. For the climate, however, the miracle substance is a big problem, because around 700 kilograms of the greenhouse gas carbon dioxide are released into the air when one ton of cement is produced.

Apart from water, no other substance on earth is used as widely as cement, which makes concrete rock hard. And that adds up to immense amounts of greenhouse gas. Every year twelve cubic kilometers of concrete are produced worldwide, enough to cover the urban area of ​​Berlin evenly more than 13 meters high. The cement industry blows six percent of global carbon dioxide emissions into the air.

Strictly speaking, that's not that much: Other areas will have to tackle even bigger chunks in the energy transition. However, it is particularly difficult to stop the cement industry from releasing greenhouse gases: "Only a third of the carbon dioxide emissions come from the energy sector, but the majority comes from a chemical reaction in which limestone releases the greenhouse gas," explains Frank Winnefeld, who is in of the Eidgenössische Materialprüfungs- und Forschungsanstalt (Empa) in Dübendorf near Zurich deals with sustainable cement.

Window dressing with plastic waste

This means that proven climate protection solutions do not work here. When heating, you simply replace the oil or gas burner with a heat pump powered by green electricity or the diesel engine in the car with an electric drive in order to avoid most of the carbon dioxide emissions. In contrast, a rotary kiln fired with green hydrogen solves at best a third of the problem when burning cement.

»Only a third of carbon dioxide emissions come from the energy sector. Most of the rest comes from a chemical reaction «(Frank Winnefeld)

With this part of the problem, something has already happened in the past few decades. "In the past, natural gas or petroleum products were burned, but today the cement industry has already replaced 60 to 70 percent of these fuels with alternatives such as shredded plastics and old tires," explains Björn Siebert, who researches concrete at the Technical University of Cologne (TH Köln).

The only difference is that industry has replaced expensive crude oil or natural gas with inexpensive plastic waste that had to be disposed of anyway. However, this has practically not reduced carbon dioxide emissions. If you replace the previous energy suppliers with microwave heating or hydrogen, which in turn were generated with green energy from solar or wind energy systems, the situation looks better.