**7. Techno-economic analysis and life cycle assessment**

A complete techno-econoic analysis for the microbial biodiesel production is difficult, especially considering that most of the technologies are still in the early research stage. Initial investment into microalgal biofuels has mostly failed and several early start-up companies have closed. Different versions of economic analysis for microalgae biofuel production have been published recently, and Table 4 lists an analysis conducted by Seed Science Ltd, sporsored by the British Columbia Innovation Council in Canada.

Table 4 shows that although photobioreactor has a higher cell concentration and utilizes CO2, its cost to produce lipid is the highest of all methods. Heterotrophic fermentation, however, appears to be the most economically feasible route to produce microbial biodiesel. Techno-economic analyses may vary from different research group, but their conclusions are similar. The biomass and oil generated from heterotrophic fermentation are more close to current fossile fuel cost. Heterotrophic fermentation relies less on local climate conditions and can be carried out in close fermentors, which may facilitate their commercialization.

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More effective, cost-efficient, and environmentally sound fermentation means to produce lipids are urgently needed, as well as adaptation of the fermentation cells to utilize lignocellulosic biomass. It is also widely indicated that currently microalgal biofuel systems are dependent on the production of coproducts (e.g., biochar, pigments, and nutriceuticals) for profitability. Considering the large scale of biofuel production, the market of the valuable byproducts will be the primary concern.


\*Assumes that the algae cake is sold to an ethanol producer for its carbohydrate content

Table 4. Cost comparison among different microalagae cultivation methods (Alabi. 2009)
