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

  • 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.