Due to the overwhelming response and interest in cultivating algae as a sustainable source of energy, several comprehensive techno-economic assessments have revealed the actual potential of this renewable source on a commercial scale (Amer et al., 2011; Davis et al., 2011; Delrue et al., 2012; Sun et al., 2011). Referring to Figure 12.3, the average biodie­sel selling prices for algae cultivated in an open pond and a closed photobioreactor are $2.97/L and $4.93/L, respectively, or 66% higher for algae cultivated in a closed photobioreactor compared to an open pond. Clearly, although the closed photobioreactor has the advantage of permitting a single strain culture and has high biomass productivity, this cultivation system is still considered expensive from the techno-economic point of view. On the other hand, algal biodiesel produced using the open pond system faces high economic competition from first — and second-generation biodiesel. The estimated biodiesel selling prices for biodiesel produced from soybean oil, jatropha oil, and waste frying oil were $1.35/L (Hu et al., 2008), $1.4/L (Wang et al., 2011), and $0.73/L (Araujo et al.,

2010) , respectively, which are much lower compared to algal biodiesel but very close to the selling price of petro-diesel at $1.2/L (McHenry, 2012). Although the biomass and lipids productivity of algae are superior to terrestrial oil-bearing crops, nevertheless the cultivation and downstream processing stages are much more complicated and consumed significant amounts of energy input. This result also indicates that the positive opportunity for using algal biomass to generate alternative fuel has been overclaimed, and thus ad­vanced improvements are needed to address the feasibility of utilizing this renewable feedstock for commercial use.