Biomass-based solutions have been discussed as having the potential to replace fossil-based solutions in the iron and steel industry. To produce the biocarbon required in these processes, thermochemical treatment, pyrolysis, typically takes place. There are various ways to produce biocarbon, alongside other products, which are called pyrolysis oil and pyrolysis gas. These conversion methods can be divided into conventional and non-conventional methods. In this paper, those techniques and technologies to produce biocarbon are summarized and reviewed. Additionally, the effect of different process parameters and their effect on biocarbon yield and properties are summarized. The process parameters considered were final pyrolysis temperature, heating rate, reaction atmosphere, pressure, catalyst, use of binders, and particle size. Finally, the effect of different reactor configurations is discussed. Understanding the combination of these methods, technology parameters, and reactor configurations will help to produce biocarbon with the desired quality and highest yield possible.

There has been a rising interest in the iron and steel industry in replacing fossil-based carbon carriers in their processes because they are the main origin of the anthropogenic carbon emissions within the industry. The use of bio-based carbon carriers could be one solution to partly tackle this challenge. Conventionally, biocarbon is produced by pyrolysis with fixed heating rate, pyrolysis temperature, and retention time. Although the mechanisms behind the formation of biocarbon and the decomposition temperatures of the main compounds of biomass-based materials are known, this knowledge is rarely being utilized in the design of commercial pyrolysis reactors, even though the pyrolysis mechanism-based approach increases the biocarbon yield. In this study, the mechanistic pathway of carbonization of lignocellulosic biomass is taken into account to produce biocarbon with higher yield and quality than conventional pyrolysis with the same process time. Results show that when the process time is the same in both methods, segmented pyrolysis increases biocarbon yield up to 5.4% within a pyrolysis temperature range from 300 °C to 900 °C. Also, fixed carbon yield increased 1.5% in this temperature area. When using segmented pyrolysis, the most suitable pyrolysis temperature is 700 °C based on the characteristics of the produced biocarbon.

Understanding the suitability of various raw materials for biocarbon briquettes under industrially relevant conditions is essential to replace coke in metallurgical applications. Additionally, a deeper understanding of how different pyrolysis methods affect biocarbon briquette properties is required. In this study, biocarbon briquettes were produced using four different raw materials: garden waste, demolition wood, hemp, and lignin. The briquettes were subjected to two pyrolysis methods, conventional and segmented, both carried out at a final pyrolysis temperature of 600 °C. Key properties including compressive strength, electrical conductivity, and porosity were evaluated. Carbon conversions were assessed at 1100 °C in a mixture of CO/CO ₂ gases. The results show that both the choice of raw material and the pyrolysis method significantly influenced briquette performance. Among the raw materials studied, lignin-based biocarbon briquettes showed similar carbon conversion rates to coke, the final conversions after 15 min being 20% and 15% for biocarbon and coke, respectively. On the other hand, using segmented pyrolysis decreased the carbon conversion rate by 4.5% on average compared to conventional pyrolysis. The average compressive strength of the briquettes varied from 12.9 to 31.1 MPa, being similar to coke. Based on the results, the reactivity of biocarbon was successfully modified without compromising the mechanical properties of the biocarbon briquette. Graphical Abstract