Algal biofuels present many advantages over fossil fuels with respect to their renewability, lower levels of CO2 emissions, biodegradability, and safety. However, at the projected cost of $7.50 per gallon after cultivation, harvesting, extraction, and conversion, algal biofuels are not currently economically viable. Calcium Oxide nanocrystals can be used to mitigate the cost of conversion by acting as the main catalyst in turning crude algal oil into biodiesel, a process known as transesterification. In transesterification, chemical catalysts, such as CaO nanocrystals, are added to mixtures of alcohol and crude bio-oil to promote the reaction which produces alkyl esters (biodiesel) and the byproduct glycerol. CaO nanocrystals are more widely available and commercially less expensive than traditional catalysts, and have also been evidenced to have a higher tolerance for low oil qualities. They also have the advantage of being heterogeneous catalysts, which means the catalysts and reactants are in different phases, allowing for extraction and reuse of the catalysts after reactions have taken place.
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While superior from an environmental and sustainability standpoint, algal biofuels are currently economically disadvantageous. Converting crude algal oil into biodiesel can be made less expensive by using CaO nanocrystals as the main chemical catalyst in the transesterification process, which causes alcohol additives to react with the extracted bio-oil, creating biodiesel that is able to be used as fuel. CaO nanocrystals are reusable, durable under poor oil conditions, and less expensive compared to traditional homogenous catalysts.
As a heterogeneous catalyst, CaO nanocrystals exist in a different state (solid) from the reactants in solution (liquid), making them easier to separate after the reaction has occurred. Since catalysts are neither consumed nor destroyed in reaction they are also reusable, making them an economically efficient additive. By decreasing costs of biodiesel transesterification through the use of CaO nanocrystals, alternative fuels can be viewed as a realisitic solution to the current energy crisis. CaO nanocrystals also exhibit low sensitivity to free fatty acids found in bio-oils, and do not corrode reaction vessels. Calcium Oxide in its nanocrystal form increases the number of reaction sites which subsequently increases the reactivity of the species, improving its performance as a catalyst.
Despite the sustainability benefits of algal biofuels, extensive cultivation of algae can negatively impact the environment. Enrichment of agricultural sites with nitrogen and phosphorous needed to promote algal growth may lead to the eutrophication of freshwater environments, decreasing the oxygen supply as the excess algae decomposes, resulting in dead zones of marine life.