Cement Pollution | 25 Jun 2019

The production of cement is a cause of 7 % of global carbon dioxide emissions, more than what comes from all the trucks in the world.

Cement’s contribution to emissions is especially immense because of the chemical process required to make it.
A ton of cement yields at least half a ton of CO₂.
- Kilns are heated to more than 1,400 degrees Celsius, about four times hotter than a home oven set to the self-clean cycle.
- Inside the kiln, carbon trapped in the limestone combines with oxygen and is released as CO2, the most abundant greenhouse gas.
Alternatives to cement: Many cement makers are working to cut the amount of clinker (a key raw ingredient) in their cement, while some others are looking at substitutes including fly-ash, which comes from the chimneys of plants that burn coal, or slag from steel-making blast furnaces.
The high cost of the greener forms of cement makes it difficult for consumers to use it as an alternative such as geopolymer cement.
It can further make it difficult for policymakers to take greenhouse gases out of buildings, roads and bridges.

Geopolymer cement is made from aluminium and silicon.
The sources of aluminium in nature are not present as carbonates and therefore, when made active for use as cement, do not release vast quantities of CO₂.
The most readily available raw materials containing aluminium and silicon are fly ash and slag.
Brazil, for instance, is making rapid progress in the adoption of greener alternatives to traditional cement, as it has the availability of raw materials such as pozzolan, a type of siliceous and aluminous material that results in a product with the same technical properties as the traditional cement. Also, it has one of the lowest clinker contents in the world for its cement, below 70 % in the year 2014.