Life Cycle Assessment of Torrefied Algal Biomass

Abstract

Biomass from microalgae and its residues can be burned directly, however it cannot be directly utilized to replace coal in the industry for power generation. This is due to its lower heating value as compared to coal. To solve this issue, a thermochemical process known as torrefaction is used. This increases the heating value of microalgal biomass to approximately the same level of coal. However, in order to consider for a large-scale production, the likely environmental impact of the prospective industrial scale should be gauged. Therefore, this paper presents a life cycle assessment of the production of torrefied microalgal biomass. Secondary data from the literature are then obtained and analyzed using a commercially available life cycle assessment tool SimaPro 8.5.2. Upon grouping the environmental impacts to three damage category, Damage to Human Health resulted to be the highest in all the production stages with 66.6% as compared to damage to Resources (29.2%) and Ecosystems (4.22%). The production stages are also weighed and the result revealed that the cultivation stage accounts for the highest combined environmental impacts with 65.7%. Upon scrutinizing the cultivation stage, large burden came from the use of fertilizers and electricity. Therefore, cultivation using inorganic fertilizers should be lessened. The use of waste nutrients from industries can be considered (organic fertilizers). Although microalgae have the potential for carbon capture and the torrefied algal biomass and its residue as a replacement for coal, the production process into its conversion to solid fuel using the electricity requires a suitable approach. Identifying other sources of energy and new technology should be addressed to help reduce the energy demand.