Greenhouse Gas Removal in the Iron and Steel Industry

This is a GGR Topic-specific proposal

Up 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.

Accelerated weathering of slag has exciting potential as a new option for climate change mitigation, with far reaching impact into climate change policy, waste management, environmental regulation, carbon infrastructure, energy production, mineral extraction, and land use.

Economic Impact: The economic impact of climate change mitigation technologies is the relative contribution of preventing the potential 5- 20% (e.g. Stern Review) economic reduction the economy due to climate change ($135-540 billion per year on current economy figures). Even if a technology were only able to contribute to mitigating a small fraction of this cost, the value could still be in multi-billions per year. To realise these big-picture economic impacts, the project will 1) demonstrate the technology at a pilot scale and create a robust assessment of larger operation, 2) address key uncertainties about environmental impact, 3) identify a road map for future research, and 4) work with industrial partners to identify intellectual property and market value specific to slag weathering.

Societal impact: Progress in shifting to a low carbon economy has important society impacts. Storage of carbon as alkalinity raises issues of environmental impact, global governance, and public perception. We will work closely with the Understanding Risk Group at Cardiff University to spin out projects that question public perception of this technology, the necessary conditions for a social license to operate. Presently, the London Convention/Protocol is being amended to consider ocean carbon storage, for which the PI was invited to supply evidence in 2015, and the results of this project will directly inform subsequent considerations. Questions of governance and policy will be explored further with collaborators (e.g. through existing collaborations with Oxford University). The results of this project will be disseminated widely through trade/popular publications, our website, a series of short online videos, and as a presentation at Cardiff's regular public lectures. We will work with local authorities who manage the environmental liability of the steel industry (see LoS from Redcar and Cleveland Council) to recognise the remediation co-benefits of accelerated weathering of slag.

Training and People: The project will develop the research group of an Early Career Scientist. The PDRA will receive training and skills that combine exploration and experimental geochemistry with engineering (carbonate system chemistry, reactor modelling, and techno-economic analysis). They will have access to the extensive staff training programme at Cardiff University, close contact with expertise in the School of Earth and Ocean Sciences, and additional external training will be completed as needed. The PI will attend a Residential Communication and Media skills training at the Royal Society. Finally, the knowledge associated with the project will be integrated into teaching in the school as part of student projects (+5-10 per year) and lecture courses (90 students per year).