Introduction 

Net zero carbon does not mean zero. For example, the Earth has used CO2 as an energy vector for 4 billion years by using non-fossil carbon as chemical fuel source and recycling the CO2 by-product using renewable (solar) energy through photosynthesis. They key to this success is that CO2 production and recycling are balanced in nature.

The problem is that, since the Industrial Revolution, energy production for heat, electricity, transport and manufacturing has operated as an almost exclusively linear economy using fossil fuel carbon as the fuel source and generating huge amounts of CO2 by-product. However, the scale, extreme environments (high temperature/pressure, reactive gases) and complexity of process chemistries, allied to the significant, long-standing industrial expertise is fossil fuel raw materials makes decarbonisation non-trivial.

Task 2 considers alternative carbon sources for fossil fuel carbon based either on waste and/or on “recent” which can displace “ancient” fossil fuel carbon in iron and steelmaking. This decarbonises the process because “recent” carbon arises from CO2 which has recently been removed from the atmosphere. In this way, any CO2 which is released does not add to atmospheric CO2 concentrations.

Outcomes

Zero carbon steelmaking is very unlikely because carbon is still required even for EAF remelting processes. However, net zero steelmaking whilst ambitious is theoretically possible. Task 2 initially focussed on reprocessing non-recyclable waste. But the scope has extended to other non-fossil fuel carbon and associated life cycle analysis. Task 2 also initially focussed on blast furnace ironmaking but has extended the scope to also consider slag recycling, the decarbonisation of sinter production, carbon within EAF processing and CO2 recycling. Whilst the manufacturing processes may differ, the central theme remains – i.e., if you input non-fossil fuel material and recycle the CO2 by-products, you achieve net zero.

Key parameters for non-fossil fuel carbon have been identified in comparison with the significant, long-term understanding related to fossil fuels (coke, coal, natural gas etc). A range of non-recyclable waste and fossil fuels have been studied in the context of different iron and steelmaking processes. Parameters include reaction rates, kinetics and thermodynamics for devolatilization, burn-out, gasification and in process reactions, in situ chemical speciation and reactivity and pilot scale simulation. Iron and steelmaking contexts studied include blast furnaces, iron oxide sintering, EAF simulation, along with circular economy/recycling. We have also assisted steelmakers with regulatory approvals and carbon manufacturing issues.

Impact

The risks to implementation are the same as they would be for the introduction of any new raw material into the process (e.g., composition, reactivity and side reactions). But these risks are exacerbated by potential additional technological changes to materials handling and the manufacturing processes themselves. These risks can be mitigated, and the impact generated by tests at increasing scale towards plant scale tests. Government support for full scale plant tests would help remove barriers to impact.

Next Steps

Energy is at the heart of all decarbonisation issues. It is the reason that fossil fuels or any alternative raw materials are used in any industrial process, and it will become, if anything, more important as we move, stepwise towards net zero. The next stages are to consider the de-fossilisation of carbon raw materials and the decarbonisation and recycling of exhaust gases but all within the quantum yield (i.e., energy in versus energy out) of these processes