Analytical models to assess the potential of waste-based industrial plants in the energy transition: an application to the steelmaking sector

Human activities, such as fossil fuel combustion and deforestation, have led to increased greenhouse gas emissions and global warming. To mitigate these effects, countries have pledged to limit global warming to 1.5°C and achieve carbon neutrality by 2050. This requires a transition to renewable energy sources, including photovoltaic panels, wind turbines, hydrogen, and biomethane. While progress has been made in the context of the energy transition, additional actions are required to reach the goal of reducing greenhouse gas emissions to net-zero. The steelmaking sector is particularly challenging to decarbonise due to its reliance on fossil fuels. However, the so-called secondary route, which involves melting recycled steel scrap in an electric arc furnace, offers a real decarbonisation potential. This route can be supported by the production of direct reduced iron, which can be produced using hydrogen instead of natural gas. Waste valorisation, which involves converting waste into energy or other valuable products, can also play a role in the energy transition. Waste valorisation plants can indeed produce both electricity, hydrogen, and biomethane. However, current waste valorisation assessment methods lack consideration of their role in the ongoing energy transition. Consistent with these gaps, the present work aims to develop analytical models to evaluate waste valorisation plants' economic and environmental performance within the context of the energy transition. A cost and investment analysis carried out with respect to three waste-to-energy plants allowed to identify gasification as the best option to support the current energy transition, due to its high electricity output despite high operational costs. The application of the environmental analytical models developed to compare different waste valorisation alternatives from the anaerobic digestion of waste, showed that biomethane production is better than electricity production, while hydrogen production is better than biomethane production. Moreover, the application of an environmental analytical model to the EU 2020 and 2030 scenarios showed that waste-based hydrogen production routes offer significant decarbonization potential. An economic model moreover showed that the secondary steelmaking route, supported by direct reduced iron production, prove to be profitable despite cost and carbon pricing fluctuations. An environmental analytical model allowed to find that national energy mixes play a crucial role in enabling sector decarbonization. Finally, it was found that waste-based hydrogen routes can accelerate decarbonization in steelmaking, enabling low-emission steel production even before large-scale electrolyzer installation becomes viable. These findings underscore the importance of incorporating energy transition considerations into waste valorisation assessments to optimize resource utilization and advance sustainable energy solutions.