Techno-economics of Algal Biodiesel

Abstract

Algal biodiesel production presents a possible carbon-neutral source of transportation fuel. Whilst algal biodiesel circumvents some of the issues arising from the use of crop- and waste–biomass-based fuels, the lack of commercial success raises questions regarding the feasibility of the process. Numerous economic and environmental impact assessments have produced highly variable results, predicting costs from as little as 0.42–72 USD L−1. A meta-analysis of these assessments reveals that areal productivity and provision of nutrients, as well as energy and water usage, are the key challenges to algal biodiesel production. A consideration of maximum achievable photosynthetic activity indicates that some scope exists for increasing areal productivity; hence, the factors influencing productivity are discussed in detail. Carbon dioxide supply may represent the single most important challenge to algal biodiesel, while recycling of other nutrients (specifically nitrogen and phosphate) is essential. Finally, a careful balance must be struck between energy and water consumption; this balance is primarily influenced by bioreactor design. It is unlikely that algal biodiesel will supply a substantial portion of the world’s transportation energy demand, but it may fill niche markets such as aviation fuel. Process economics are enhanced by integrating biodiesel production into a biorefinery, producing a suite of products.