For every tonne of steel produced in an integrated steelmaking plant, 400 to 500 kg of by-products are produced. The majority of these by-products are slags. These slags are not waste but a valuable resource.
The use of slags from iron and steel production as fertilisers and liming materials has been a long tradition in modern society. Slags from blast furnaces and basic oxygen furnaces have been approved fertilisers in Germany for more than 60 and 30 years, respectively. They have been used in all types of crop production and landscaping in the US since the 1920s. In Japan, slag silicate fertiliser has been used in rice cultivation for many years.
The slags contain useful elements like calcium, magnesium, aluminium, silicon, iron, sulphur, manganese and other
elements required in fertilisers. They are useful properties for plant nutrition and soil quality. Their alkaline properties also remedy soil acidity.
Farmers use slag fertilisers to maximise yields of cultivated crops and pasture. These nutritious materials are not only used in home vegetable gardens to improve soil texture and quality but also in greenhouses to make rich soil for plant beds and potting soil. They are used in parks and golf courses as well as land reclamation projects to correct soil acidity.
Moreover, calcium and magnesium in the slags have a better solubility than that of magnesium carbonate in natural limestone and dolomite. The use of these slags helps reduce natural resource exploitation and landfill.