Recent development of hydrothermal liquefaction for algal biorefinery

• Published in: Renewable & sustainable energy reviews Vol. 121; p. 109707
• Main Authors: Gu, X., Martinez-Fernandez, J.S., Pang, N., Fu, X., Chen, S.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2020
• Subjects: Algal biofuels; Bioproducts; Hydrothermal liquefaction; Process development; Reaction pathways; Techno-economic analysis; Process development; Techno-economic analysis; Bioproducts; Reaction pathways; Hydrothermal liquefaction; Algal biofuels
• ISSN: 1364-0321; 1879-0690
• DOI: 10.1016/j.rser.2020.109707

Hydrothermal liquefaction (HTL) is considered as one of the most promising methods for converting algal biomass to bio-oil and other value-added chemicals. The conventional HTL process, however, is limited by its incapability of recovering high-value bioactive compounds that are desirable for enhancing overall process feasibility. The two-stage sequential hydrothermal liquefaction (SEQHTL) process was proposed as an alternative to overcome this limitation. SEQHTL operates at reduced temperature and pressure to facilitate production of co-products in addition to bio-oil. This article offers a comprehensive review of the SEQHTL process in comparison with conventional HTL. Main topics include: operation principles and targeting final products of HTL, reaction mechanisms of algal biomass in the HTL process, recent publications on algae-related HTL studies, features of the SEQHTL process, advantages of the SEQHTL process for production of high quality bio-oil as well as extraction of prospective high-value co-products that may be harvested from microalgae biomass, cost advantage of the SEQHTL process, challenges identified with techno-economic and life-cycle assessments, and suggested future HTL research and development in comparison with other conversion technologies. All these aspects collectively provide an overview of the SEQHTL technology. [Display omitted] •Performance of two-stage hydrothermal liquefaction process is critically reviewed.•Two-stage process enables co-product recovery along with algal bio-oil production.•Two-stage process leads to lower cost due to the reduced operating temperature.•Different algal conversion technologies are compared.•Challenges and development of algal hydrothermal liquefaction process are evaluated.