Slag stones - the waste from iron ore, macro

Project nominated for the Excellence in sustainability Steelie Award 2021

In recent decades, we have seen increased steel production, which creates more coproducts, including slag. To minimise the environmental consequences caused by large volumes of slag, there is a growing need to better recycle these and other manufacturing co-products. As one way to recycle slag, the steel industry is developing new applications and encouraging businesses to upcycle them in various fields, such as construction and agriculture.

First, in an effort to upcycle steel slag, POSCO has developed “Slastics,” a composite material comprised of steel slag and plastic waste. As Slastics are remarkably durable and long-lasting, it has great potential for broad applications as building and engineering materials. Moreover, by replacing wood, plastic, and concrete, it may serve as the new material used to build green infrastructure. Compared to when plastics are incinerated, 99% of greenhouse gas (GHG) emissions are avoided when plastics are reused to produce
Slastics; this is equivalent to preventing 2.33 tonnes of CO2 for each tonne of recycled plastic.

The second effort POSCO made toward upcycling is silicate slag fertilisers that were made available to farming communities. The fertiliser contains 25-30% of soluble silicic acid that boosts photosynthesis in rice plants, which increases rice crop yield. Paddy fields treated with silicate fertiliser have proven to have “Negative Emissions,” owing to iron ions in slag that mitigate GHG emissions. Thus, silicate fertilisers contribute to national GHG reduction in the agricultural sector. Since 1974, 14 million tonnes of silicate fertilisers have been distributed to rice paddies to improve the crop yield and enhance quality. This translates into better profit for farmers.