As also pointed out in Chap. 1, estimates have been made of the maximum efficiency for the conversion of incident sunlight into biomass by algae. These vary between

5.5 and 11.6% (Heaton et al. 2008b; Vasudevan and Briggs 2008). Several authors have suggested that algal transport biofuels can beat terrestrial transport biofuels in the conversion of solar energy to transport biofuel by at least one order of magnitude (e. g. Chisti 2007; Chisti 2008a; Groom et al. 2008; Nowak 2008; Li et al. 2008). Here we will survey the suggestions that have been made for producing transport biofuels from algae and aquatic macrophytes and what is known about the solar energy conversion efficiency of such biofuels.