The firm claims to produce sustainable building materials from waste . Mineral gypsum extracted from polluted soil ; mixed with water to make cement . Over 100 houses built so far , each one saving estimated 100 tons of CO2 , says firm .
Mining firm claims to produce sustainable building materials from waste . Mineral gypsum extracted from polluted water ; mixed with cement to make bricks . Over 60 houses built so far , each one saving estimated three tons of CO2 , says firm .