Recent advances in thermochemical methods for the conversion of algal biomass to energy

• Published in: The Science of the total environment 2021-04, Vol.766, p.144608-144608, Article 144608
• Main Authors: Das, Pritam, V.P., Chandramohan, Mathimani, Thangavel, Pugazhendhi, Arivalagan
• Format: Article
• Language: English
• Subjects: Algal-biomass; Biofuels; Biomass; Gases; Gasification; Pyrolysis; Thermochemical methods; Torrefaction
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.144608

Thermochemical techniques are being operated for the complete conversion of diverse biomasses to biofuels. Among the feedstocks used for thermochemical processes, algae are the promising biomass sources owing to their advantages over other feedstocks such as biomass productivity, renewability and sustainability. Due to several advantages, algal biomass is considered as a source for third generation biofuel. This review work aims to provide a state-of-the-art on the most commonly used thermochemical methods namely torrefaction, pyrolysis, and gasification processes. Furthermore, the production of biofuels from algal biomass was comprehensively articulated. Different algal strains used in thermochemical techniques and their conditions of operation were compared and discussed. The yield and quality of solid (char), liquid (bio-oil) and gaseous (syngas) products obtained through thermochemical methods were reviewed and analysed to understand the efficacy of each technique. End product percentage, quality and advantages of the torrefaction, pyrolysis, and gasification were summarized. It is found that the biofuel produced from the torrefaction process was easy to store and deliver and had higher utilization efficiency. Among the existing thermochemical methods, the pyrolysis process was widely used for the complete conversion of algal biomass to bio-oil or char. This study also revealed that the gasification (supercritical) method was the most energy efficient process for conversion of wet algal biomass. The reactor used in the thermochemical process and its subprocess was also highlighted. This study revealed that the fixed bed reactor was suitable for small scale production whereas the fluidized bed reactor could be scaled up for industrial production. In addition to that environmental impacts of the products were also spotlighted. Finally, the perspectives and challenges of algal biomass to bioenergy conversion were addressed. [Display omitted] •A review is made on recent developments on thermochemical processes of algal strains.•The common methods torrefaction, pyrolysis, and gasification processes were extensively reviewed.•Different algal strains used in thermochemical methods and their conditions were compared and discussed.•The yield, quality of solid, liquid and gaseous products obtained through thermochemical methods were reviewed.•End product percentage, advantages and challenges of the torrefaction, pyrolysis, and gasification were summarized.