Biorefining of marine macroalgal biomass for production of biofuel and commodity chemicals

Abstract

The large scale production of marine macroalgae, mainly for human consumption, has given rise to their consideration as a non-lignocellulosic feedstock for the production of renewable fuels. However, making biofuel economical from algal biomass requires the co-production of additional useful biochemical components that are unique to algae and that have a proven market value. A viable and sustainable biorefining technology that maximizes the utilisation of feedstock for the production of chemicals along with fuel is, therefore, indispensable. Here, we for the first time demonstrate a tractable integrated process that facilitates sequential extraction of the major components of red algal biomass as commodity products such as pigments, lipid, agar, minerals and energy dense substrate (cellulose). The computed yield data from small-scale biorefinery trials suggest that a ton of fresh biomass supplies several valuable extracts: 0.3–0.7 kg of R-phycoerythrin (R-PE), 0.1–0.3 kg of R-phycocyanin (R-PC), 1.2–4.8 kg of lipids, 28.4–94.4 kg of agar, 4.4–41.9 kg of cellulose and 3.1–3.6 kiloliters of mineral solution. The enzymatic hydrolysis and fermentation of cellulose thus obtained would yield 1.8–17.4 kg of ethanol. A distinct advantage of this process over direct extraction is the improved quality of agar (gel strength higher by 1.5–3 fold) without alkali and acid pretreatment of sample, the elimination of residue and the reduction by up to 85% in chemicals usage in cellulose extraction. The findings reported in this study forms the basis for starting new ocean-based bio-industries minimizing the dependence on the terrestrial resources for food, feed, energy and chemicals.