Building environmentally friendly houses from industrial waste

A South African coal mining company is cleaning up the industrial waste they have thrown out into the environment, turning them into materials to build cheap and environmentally friendly houses.

Over the past few years, AngloAmerican - one of the world's largest mining companies, has purified the contaminated water due to its coal mining operations in the city of Emalahleni, South Africa.

The new building material AngloAmerican created by mixing by-products called plaster with cement, creates cheap bricks for building houses.'We have built 62 houses. Each house needs about 8 tons of plaster, but currently we are separating more than 200 tons of this substance from waste water every day , 'said Peter Gunther, head of sustainable development, the unit behind this initiative of AngloAmerican, said.

Gypsum is a basic mineral of calcium and sulfur, not toxic and soluble in water, but becomes harder and more adherent when it is heated and dried. In addition, because plaster is very malleable when wet, its current most popular application is to use as plaster powder, to help smooth the surface of cement walls. Gunther believes this new tile has many advantages such as stiffer, soundproofing and better insulation than heavy-duty cement bricks that are commonly used in Emalahleni. But the most important thing for Emalahleni, one of the fastest growing cities in South Africa, is that gypsum bricks have little impact on the environment due to the very low cement content.

According to statistics from the organization of Sustainable Cement Initiative, about 5% of man-made CO2 emissions originate from chemicals and heating processes related to cement production. In addition, the cement manufacturing industry also requires a large amount of raw materials. Meanwhile, Gunther insisted that new bricks with very little cement reduced the average 3 tons of CO ₂ emissions on each built house.

In Emalahleni, the city is in serious shortage of housing, AngloAmerican aims to provide housing for the entire local workforce, with about 400 homes made of new materials built in 2012. But is plaster really the ideal material? Andrew Bloodworth, head of the mineral department at the British Geological Survey, said that gypsum is indeed insulated very well and can be very strong only when it is always in a dry state.'I have never heard plaster used to make bricks because it can disintegrate in water. I really want to know how plaster can be used to make bricks' , Bloodworth wondered. However, Gunther insists that the new brick is completely waterproof because part of it is cement. 'This tile has been rigorously tested by the South African Bureau of Standards and passed without problems' , Gunther added.