Options for Energy from Algae at Wastewater Treatment Facilities

Abstract

The development of algae biofuels is a priority for the U.S. Department of Energy, Department of Defense, and many other organizations. Large-scale algae production facilities are already in the planning stage. Algal biomass harvested from wastewater treatment ponds can also potentially be used as a feedstock for renewable fuels such as biogas, biodiesel, bio-oil or synthesis gas. Despite the large number of algae-based treatment systems operating throughout the world, none are currently known to routinely produce a fuel product. Instead, at facilities that harvest their algae, the biomass is typically disposed of in the ponds. A major hurdle to taking advantage of this unused biomass resource is determining the suitability of various types of algae biofuel technologies. A great deal of scientific literature discusses the downstream processing of algal mass in large biorefinery-type settings. These large facilities closely resemble currently operational biodiesel plants, allowing researchers to build on lessons learned at functioning facilities and to conduct calculations based on empirical data. By most estimates, economies of scale dictate that these facilities must be large in order to process algae biomass economically. However, the vast majority of wastewater algae production takes place in smaller, distributed treatment facilities, leading to complications of biomass transport to centralized biomass-to-fuel plants. In the current paper, the algae biomass potential of a typical wastewater treatment pond system is compared with the scale of a large bioprocessing facility, and a variety of on-site alternatives are considered for the production of fuel from algae at wastewater treatment facilities.