Circularity and decarbonization in steel plants: valorization of waste streams for bio-char production

Steel plants are large emitters of greenhouse gases due to their high-power demand and the necessity to include a carbon source in the production process, being steel an alloy of Fe and C; therefore, they fall into the hard-to-abate category. This thesis explores the feasibility and challenges of the substitution of electrical arc furnace (EAF) steel plants fossil coal by employing a carbonaceous man-made and renewable material called hydrochar, produced coupling waste streams with an innovative industrial process called Hydrothermal Carbonization (HTC). The findings of the study reveal mixed results: wastewater-grown microalgae char, even adopting more performing heterotrophic mode, is too costly, whereas the use of food waste and digestate proved more feasible and competitive. The work contributes valuable insight into advancing eco-friendly and economically sustainable alternatives to fossil source of carbon, paving the way for further investigation on the use of this material in the steel industry and beyond.