A comprehensive review on the similarity and disparity of torrefied biomass and coal properties

• Published in: Renewable & sustainable energy reviews 2024-07, Vol.199, p.114502, Article 114502
• Main Authors: Adeleke, Adekunle A., Ikubanni, Peter P., Emmanuel, Stephen S., Fajobi, Moses O., Nwachukwu, Praise, Adesibikan, Ademidun A., Odusote, Jamiu K., Adeyemi, Emmanuel O., Abioye, Oluwaseyi M., Okolie, Jude A.
• Format: Article
• Language: English
• Subjects: Coal; Grindability; Hydrophobic; Renewable energy; Torrefaction; Torrefied biomass
• ISSN: 1364-0321; 1879-0690
• DOI: 10.1016/j.rser.2024.114502

The use of coal for energy generation is facing serious scrutiny because of environmental concerns. As a result, there is a growing global interest in biomass, a renewable and readily available energy source. However, the utilization of biomass comes with significant drawbacks, including its heterogeneity, low bulk density, and calorific value. Biomass also has a low energy content, high moisture, poor grindability, and high volatile matter, which affect its handling, bulk transportation, and storage. Torrefaction technology has been employed in previous works to improve the properties of biomass for subsequent handling and transportation and for low-cost energy generation. Since coal is a promising precursor for energy generation, it is imperative to compare the physicochemical properties of coal with that of torrefied biomass. Therefore, this study aims to conduct a comprehensive comparison between various grades of coal and torrefied biomass. The review revealed that torrefied biomass could replace coal, as its properties are similar to those of coal, except for high-grade coals. The proximate and ultimate analyses of coals (lignite and bituminous) were found to be comparable to various torrefied biomass materials. The fuel ratio (0.5–2.0), and higher heating values (16,100–19,000 kJ/kg) of coal and torrefied biomass were within the range useful for coal-fired plants. Additionally, ash analyses, ash fusion temperature, hygroscopic tendency, functional group study, and microstructural comparison were reviewed in this study. The results from various studies have shown close similarities with only small disimilarities in the fuel properties between coal and torrefied biomass. Therefore, torrefied biomass is proposed as a complimentary feedstock to coal in various applications. [Display omitted] •The similarity and disparity between torrefied biomass and coal are discussed.•Proximate, ultimate, calorific, and FTIR analyses of torrefied biomass and coal were discussed.•Fuel ratio, ash content, and grindability values of torrefied biomass and coal were discussed.•Present grade of coal with similar properties to torrefied biomass and application in thermal plants.•Recommend partial or total replacement of coal with torrefied biomass in co-fired plants.