Chapter 15 - Third-generation bioethanol: status, scope, and challenges

Abstract

Fossil fuel depletion due to burgeoning demand in the industrial and transportation sectors associated with the increasing concerns of greenhouse gas footprint and dwindling stock of fossil reserves has necessitated the exploration of sustainable, technically feasible, and environmentally sound energy alternatives. Biofuels from biomass are emerging as a promising alternative to fossil fuels. Among these, bioethanol stands out as viable fuel in the transportation sector due to the possibility of blending with gasoline with an opportunity to mitigate carbon footprint. Bioethanol from first- and second-generation feedstocks did not meet the expectations as they competed with either food or land and due to the requirement of a cost-intensive production process for removal of lignin. Bioethanol from algal biomass, the third-generation feedstock, regarded as a sustainable one, has gained worldwide attention due to its wide applicability to achieve biorefinery. In this context, the current chapter presents the scope of and challenges in bioethanol production of the third-generation feedstock. The chapter introduces the feedstock available in India followed by the bioethanol production processes, namely hydrolysis, enzyme saccharification, and fermentation technologies. The penultimate section highlights the scope for an economically viable approach through the adoption of an integrated biorefinery. The concluding section outlines the scope for process optimization for the successful commercialization of bioethanol with the value-added products from the macroalgal feedstock.