ABSTRACT
Algae have been recommended as a fuel source for more than a century, most notably during world wars (McHugh, 2003). They were also the subject of increased attention after the oil crisis in the 1970s with the last major research programmes from that era ending in the 1980s (Sheehan et al., 1998). Algae are of interest again today as a renewable, carbon-neutral source of energy — or more correctly a source with potentially better greenhouse gas performance than other sources through their ability to capture CO2 (Bruton et al., 2009; FAO, 2010a). As with other non-food biomass (known as second- or third-generation biofuel feedstocks), marine and freshwater biomass is attractive because it is thought it will not impact on food prices in the way that first-generation feedstocks (based on agricultural crops) are projected to do. Algae are also considered to promise higher productivity, lower greenhouse gas profles and better sustainability than 1st generation feedstocks (de Schamphelaire and Verstraete, 2009; Clarens et al., 2010). This review will show some of these perceptions are ill-founded and that major impediments to the use of algal resources as commercial sources of biogas remain to be overcome.
