A Review of Seaweed Pre-Treatment Methods for Enhanced Biofuel Production by Anaerobic Digestion or Fermentation

Abstract

Macroalgae represent a potential biomass source for the production of bioethanol or biogas. Their use, however, is limited by several factors including, but not restricted to, their continuous supply for processing, and low biofuel yields. This review examines recent pre-treatment processes that have been used to improve the yields of either biogas or bioethanol from macroalgae. Factors that can influence hydrolysis efficiency and, consequently, biofuel yields, are highly affected by macroalgal composition, including content of salts, heavy metals, and polyphenols, structural make-up, as well as polysaccharide composition and relative content of carbohydrates. Other factors that can influence biofuel yield include the method of storage and preservation.

Sargassum Inundations in Turks and Caicos: Methane Potential and Proximate, Ultimate, Lipid, Amino Acid, Metal and Metalloid Analyses

“…The theoretical methane potential was calculated from the elemental analysis using the 'Buswell equation' [57,58] and also from the protein, lipid and carbohydrate (including and excluding fibre) content using the method of Heaven et al [56]. The ratio of the MP to the theoretical methane yields, expressed as a percentage, has been termed the biodegradability index (BI) [59,60].…”

A Brief Review of Anaerobic Digestion of Algae for Bioenergy

“…Both micro and macroalgal biomass may require pre-treatment before AD in order to break the cell wall structure to allow the microorganisms access to the organic components of the algae. Maneein et al [42] have recently reviewed the pre-treatment of seaweed for fermentation and AD.…”

“…Dietary fibre content, which usually refers to indigestible carbohydrate content, is around 40% (%DW) in the brown seaweed Sargassum muticum. Increasing surface area for microbial attack by reducing the size of the biomass should be done to increase biomethane yield but chemical attack/pre-treatment, for example, thermochemical hydrolysis of the biomass (3% sulfuric acid, 121 • C, 45 min) is often required [42,181]. Future work could target the effect of different commercially available enzymes on seaweed pre-treatment or the development of a more specific enzymatic cocktail that could efficiently breakdown the seaweed polysaccharides achieving maximum substrate hydrolysis yields.…”

“…Pechsiri et al [41]) also found an EROI of up to 2.6 for combined biogas and fertiliser production from large-scale cultivation of seaweed. Starch and ulvan are typical of green seaweeds (colour-coded green), and the polymeric polysaccharides carrageenan and agar are characteristic of red seaweeds (colour-coded red) [42].…”

“…Laminarin, fucoidan, and alginate are typical of brown seaweed (colour-coded brown). Starch and ulvan are typical of green seaweeds (colour-coded green), and the polymeric polysaccharides carrageenan and agar are characteristic of red seaweeds (colour-coded red) [42].…”