Greenhouse Gas Removal in the Iron and Steel Industry

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This is a GGR Topic-specific proposalUp to 200 billion tonnes of slag may be produced over the next century as a by-product of the iron and steel industry, which could theoretically sequester up to 90 to 155 billion tonnes of CO2 through enhanced weathering. This proposal explores the exciting possibility of realising an economic greenhouse gas removal technology within an existing industry through the novel management of waste material. We will do this by exploring the internal chemistry of historic slag deposits to understand the long-term constraints on CO2 sequestration, and undertake field trials of CO2 injection into large controlled reactors. Iron and steel slags are a glass/semi-crystalline material rich in silicate and oxide minerals, which dissolve 4-5 orders of magnitude more rapidly compared to their naturally occurring counterparts. These wastes are found as large deposits at current and former steelworks, and represent a considerable environmental liability for producers. By accelerating the weathering of slag, it may be possible to reduce this environmental burden. It also offers a mechanism by which the CO2 intensive steel industry could begin to decarbonise, and ultimately become net negative, if combined with extensive emissions reduction at source.Previous research has demonstrated unintentional atmospheric CO2 sequestration over multiple decades in the drainage waters emerging from slag heaps, and small scale engineered systems have been proposed to carbonate slag under elevated temperatures and pressures. What remains unclear is the feasibility and efficacy of engineering approaches to accelerate ambient weathering to occur in a policy-relevant time period at a relevant scale. This research aims to bridge this gap by demonstrating how such engineering interventions can accelerate the natural weathering processes and provide a means for these industrial residues to act as a major atmospheric CO2 sink.