img

FIGURE 4-1 Resource requirements of algal biodiesel production.
NOTE: WWTPs denote municipal wastewater treatment plants. CAFOs are concentrated animal feeding operations.

produce alternative biofuels in an economically, environmentally, and socially sustainable way would have to be carefully considered (McKone et al., 2011). This chapter focuses on the current sustainability knowledge of the water, nutrient, land, and energy requirements of algal biofuels at all steps in the photoautotrophic algae-based production process (Figure 4-1). Where relevant data are available, quantitative case studies for at least two potential pathways for algal biofuel production are presented in this Chapter. In addition, potential assessment indicators are provided when appropriate, and current knowledge and data gaps are identified for each of the four resource requirement categories.

Major new advancements in the current knowledge base will require multi-hectare scale demonstration facilities to be built and maintained in operation for a period of time sufficient to allow detailed real-time analyses of the key variables required for commercial success (Campbell et al., 2011). Moreover, commercial-scale demonstrations will be necessary to assess and to improve algal biofuel technologies and their integration with the existing energy infrastructure (Sagar and van der Zwaan, 2006; Katzer, 2010). Innovations that result in reduced resource use along the entire algal biofuel supply chain will remove some of the existing barriers to the development of large-scale, sustainable, and economically viable algal biofuel enterprises. In addition, improvements in algal productivity and biofuel yield will help to reduce resource requirements per unit of algal biofuel produced.

4.1 WATER

Water provides the essential physical environment in which cultivated algae grow and reproduce (Murphy and Allen, 2011). It also acts as a thermal regulator and provides a



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement