Microalgae are well recognized for their potential to contribute as an important energy source as well as to provide a renewable feedstock for commodity organic products. Their role as a renewable energy source has promise for both the pro­duction of liquid fuels, including diesel, gasoline, and jet fuels, and electricity generation. Routes to these energy sources include accumulation of algal oil for transesterification to biodiesel, fermentation to alcohols for inclusion in gasoline, production of hydrogen, anaerobic digestion to biogas, thermal processing to bio-oil, co-combustion, and gasification (Chisti and Yan, 2011).

The technical feasibility of algal biomass as a source of bioenergy has been demon­strated for a number of the products described above. Further evidence of the commer­cial interest in these products is demonstrated by both the R&D investment of leading energy companies, including Exxon, BP, Chevron, Shell, and Neste Oil (Norsker et al., 2011), as well as a number of start-up companies attempting commercialization of algal fuels (Table 9.1). However, it is recognized that these products remain expensive in comparison to petroleum-based products. Further, it is essential to understand the environmental benefits of these process routes objectively. Optimization of the product spectrum in terms of economic and environmental sustainability is best informed by a rigorous analytical approach that informs the key process targets for their improvement.

This chapter focuses on the economic and environmental impacts of the production of algal oil and biodiesel as primary products, owing to the comprehensive analysis of these routes. Processing of algal biomass to secondary products in a biorefinery approach is included to explore the potential of algal energy more completely. The alternative bioenergy products are not considered comprehensively here.

TABLE 9.1

Start-Up Companies for Algal Biofuels

Source: From Chisti and Yan (2011).