A Review of Hydrothermal Liquefaction of Biomass for Biofuels Production with a Special Focus on the Effect of Process Parameters, Co-Solvents, and Extraction Solvents

Ankit Mathanker, Snehlata Das, Deepak Pudasainee, Monir Khan, Amit Kumar and Rajender Gupta
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Ankit Mathanker: Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 2R3, Canada
Snehlata Das: Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 2R3, Canada
Deepak Pudasainee: Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 2R3, Canada
Monir Khan: Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 2R3, Canada
Amit Kumar: Department of Mechanical Engineering, University of Alberta, Edmonton, AB T6G 2R3, Canada
Rajender Gupta: Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 2R3, Canada

Energies, 2021, vol. 14, issue 16, 1-60

Abstract: Hydrothermal liquefaction is one of the common thermochemical conversion methods adapted to convert high-water content biomass feedstocks to biofuels and many other valuable industrial chemicals. The hydrothermal process is broadly classified into carbonization, liquefaction, and gasification with hydrothermal liquefaction conducted in the intermediate temperature range of 250–374 °C and pressure of 4–25 MPa. Due to the ease of adaptability, there has been considerable research into the process on using various types of biomass feedstocks. Over the years, various solvents and co-solvents have been used as mediums of conversion, to promote easy decomposition of the lignocellulosic components in biomass. The product separation process, to obtain the final products, typically involves multiple extraction and evaporation steps, which greatly depend on the type of extractive solvents and process parameters. In general, the main aim of the hydrothermal process is to produce a primary product, such as bio-oil, biochar, gases, or industrial chemicals, such as adhesives, benzene, toluene, and xylene. All of the secondary products become part of the side streams. The optimum process parameters are obtained to improve the yield and quality of the primary products. A great deal of the process depends on understanding the underlined reaction chemistry during the process. Therefore, this article reviews the major works conducted in the field of hydrothermal liquefaction in order to understand the mechanism of lignocellulosic conversion, describing the concept of a batch and a continuous process with the most recent state-of-art technologies in the field. Further, the article provides detailed insight into the effects of various process parameters, co-solvents, and extraction solvents, and their effects on the products’ yield and quality. It also provides information about possible applications of products obtained through liquefaction. Lastly, it addresses gaps in research and provides suggestions for future studies.

Keywords: biomass; biofuels; bio-oil; bio-crude; char; hydrothermal liquefaction; hydrothermal processing; lignocellulosic biomass (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (4)

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