Environ Exp Biol (2024) 22: 135–147

Hydrothermal liquefaction: exploring feedstock for sustainable biofuel production

Abstract

A number of technological strategies utilizing various types of biomass for the production of hydrocarbons have been put forth but their energy intensive methods are a concern for improved efficiency of biofuel production. Hydrothermal liquefaction (HTL) has emerged as a promising and feasible technology towards utilization of lignocellulosic biomass. The suitability of different biomass feedstock for HTL is intricately tied to their macromolecular composition and process parameters. The comprehensive analysis of feedstock for hydrothermal liquefaction (HTL) signal towards the immense potential of various biomass feedstock, such as corn stover, Miscanthus, pine biomass, Spirulina, sugarcane bagasse, rice bran etc. in contributing significantly to renewable energy production. The study emphasizes that the composition of biomass is critical in influencing bio-oil yield during the HTL process. Biomass components like cellulose, hemicellulose, and lignin, each play distinct roles in determining the efficiency of conversion. Specifically, feedstock with higher cellulose and hemicellulose content, such as Miscanthus and sugarcane bagasse, demonstrate superior bio-oil yields. The analysis of proximate factors affecting HTL efficiency reveals that moisture content, ash content and high heating value (HHV) are pivotal in optimizing the process. In addition to composition and physical characteristics, the article underscores the significance of growth conditions and nutrient utilization in cultivating biomass feedstock. Integrating HTL with biomass cultivation can create a sustainable, closed-loop system where nutrients from the HTL process are recycled back into cultivation. Biomass offers a renewable energy alternative, however it also poses challenges related to land use and potential competition with food production. Sustainable practices, such as utilizing agricultural and forestry residues and optimizing collection as well as storage processes, can alleviate some of these concerns. By optimizing feedstock selection, process parameters, and integrating sustainable practices, HTL can play a decisive role in advancing biofuel production and contributing to a more sustainable energy future. The interplay between biomass composition, processing efficiency, environmental impacts, and economic feasibility is essential for realizing the full potential of HTL technology in the bio-economy. The current analysis sheds light on the relationship of bio-oil yield with macromolecular components including cellulose, hemicellulose, and lignin as well as process parameters like ash content, moisture content, higher heating value, fixed carbon and volatiles. Focusing on process optimization, this study embodies a closer analysis of literature aimed at defining optimum strategies for enhancement of HTL.