Can steel slag help to save the world?

Humans produce a lot of waste. Practically every facet of production and manufacturing in our modern world generates some sort of waste product. In the steelmaking industry, it’s slag. This by-product is formed as the iron oxide reacts with carbon. It’s been increasingly used in making concrete and in road construction.

British Scientists are now looking at ways to use the steel industry’s waste to capture carbon dioxide in the atmosphere.

Turning Waste into Wonder

The industrial revolution left a deep mark on our world, and for Britain in particular, it changed its landscape dramatically. A once blooming countryside is now peppered with centuries-old piles of slag leftover from abandoned steel mills. Landscaping these slag piles into the environment has been a slow process and major effort from local authorities over the past few decades. One of which has been turned into a lovely parkland area for residents to play, cycle or walk their dogs.

As an alternative to landscaping slag piles, Dr Phil Renforth from Cardiff University’s School of Earth and Ocean Sciences is testing the feasibility of using iron and steel slag deposits to eliminate carbon dioxide from the atmosphere. Formative research conducted by Dr Renforth has shown that carbon dioxide in the atmosphere is soaked up by material inside slag heaps. The three-year project will be conducted across England and Wales and involves making more industrial waste piles.

On this, Dr Renforth said to The Observer, “the aim is not to use old slag heaps to remove carbon dioxide from the atmosphere, but to carry out trials that will show how we can extract carbon dioxide from the atmosphere by pumping air through newly created slag heaps”.

Scientific Approach

Dr Renforth will conduct his testing in two stages. The first will see Renforth’s team drill into one of the historic slag piles to evaluate what’s been happening to its chemical composition and processes over the years as its gathered rainwater and absorbed carbon dioxide. The second stage involves creating their own mini-heap (around the size of a skip bin) and experiment with its chemistry to optimise its ability to gather carbon dioxide from the atmosphere. Dr Renforth is hoping these slag-pile sequestrators could then be used as models of larger mechanisms that would successfully reduce overall carbon levels.

With the global slag production estimated at 500 million tonnes a year, there is a large opportunity to use the slag to remove carbon. “Our calculations suggest that we might produce between 100bn and 200bn tonnes of slag cumulatively by the end of this century,” said Dr Renforth. “That has the potential to remove 50-100bn tonnes of carbon from the atmosphere, we believe.”

Finding ways to suck carbon dioxide out of the environment is of vital importance, especially when trying to achieve global warming stabilisation and limiting climate change. “We are going to have think about ways of not just limiting carbon emissions but of actually removing greenhouse gases from the atmosphere and it may well be that technology based on slag leftovers from the steel industry could play a key role,” added Dr Renforth.

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