## 1 Introduction  
Some strains of algae show promise as a sustainable source of biofuel due to their rapid growth, ability to grow on non-arable land, and high triacylglycerglycerol (TAG) content. TAGs can be easily converted to biodiesel, which is compatible with current fuel infrastructure [1]. Biodiesel has a higher energy density than ethanol, yet it is relatively non-toxic, biodegradable, and produces lower exhaust emissions than petroleum-based fuels, making it is one of the most attractive forms of alternative energy [2,3]. Additionally, when derived from plant sources such as algae, biodiesel has the potential of a near-neutral carbon footprint [4], though considerable work must be done in order to realize this goal in an economically and environmentally-feasible manner [5]. While algae are promising, there are technical challenges that currently make it prohibitively expensive as a source of fuel. Algae grow at dilute concentrations, generally less than 1 g/L [6], so it must be concentrated before it can be processed. Most concentration processes require pumping the dilute algal suspension and may involve other energy intensive steps such as centrifugation [7], compressors for dissolved air flotation, or else treatment of large volumes of water with chemicals (flocculation). Centrifugation, for example, could account for 30% of processing costs [8]. Once algae have been harvested, there are additional processing steps that often include lysis and drying of the algae followed by extraction with organic solvents to obtain the neutral lipids, primarily TAGs, that can then be converted to biodiesel [3]. Drying can be expensive but it facilitates the interaction between solvent and algae to improve extraction efficiency. However, the extraction solvent must be removed and recovered prior to conversion of lipids to biodiesel and there are attending questions about pollution of the air and contamination of the biomass with solvents. This is also considered a large part of the cost in processing algae [5]. Once the lipids have been isolated, they can be converted to biodiesel by either acid- or base-catalyzed transesterification, typically with methanol, to yield fatty acid methyl esters (FAMEs) and glycerol [9]. The transesterification reaction is sensitive to water [10, 11, 12, 13, 14] but this is not normally a problem since oils, such as would be obtained by hexane extraction, normally contain little water. When the entire processes is analyzed for cost and energy expenditure, some current projections suggest that the energy spent in the cultivation, harvest, and extraction of oil from algae could be greater than that gained from the product [5] along with the possibility of significant environmental impact [15]. It is generally agreed that for algae to be economically feasible, improvements in technology will be needed. Efforts to reduce cost and simplify processing of algal biomass to biofuel have led to studies of direct conversion of dry or even wet algal biomass to biodiesel. Previous studies have shown that algal lipids can be transesterified _in situ_ by adding reagents to a dried sample of algae [11, 16, 17, 18, 19]. One study examined a two-step procedure where the acyl groups of component lipids were hydrolyzed with base and then re-esterified in excess sulfuric acid/methanol [20]. This procedure gave greater amounts FAME than obtained by lipid extraction followed by transesterification. Another study showed that direct acid-catalyzed transesterification of wet biomass can produce FAME yields similar to that of dried biomass, although FAME compositions differed [11]. In this study we show that anion exchange resins such as Amberlite can concentrate and dewater algae (_i.e._, harvest algae) and then be eluted with 5% sulfuric acid/methanol reagent. The eluted algaeappear to dissolve in the sulfuric acid reagent and esterified fatty acids are converted to FAMEs (biodiesel).