Algae Biofuel

CHEN 282 Project
Algal Biofuel
Introduction
Algal biofuel offers a great promise in replacing fossil fuel with algae, a renewable source, to produce biodiesel, as well as the production of useful byproducts (fertilizer and feedstock). Algae-based biodiesel or ethanols are considered third-generation biofuels. Algae can be easily grown and manipulated in order to produce large amounts withoutdisturbing any food sources or natural habitats. All algae need in order to grow are: land, water, CO2 or Sugars, Nutrients, and Electricity. There are over 100,000 different plantlike organisms that belong to the algae family. However, the type of algae best suited for biodiesel production is pond scum. One of the advantages of using algae to produce biodiesel is that through photosynthesis, thealgae pull carbon dioxide from the air and replace it with oxygen. This recycling of carbon dioxide ultimately helps reduce GHG emissions to the atmosphere. Biodiesel is produced by harvesting the algal biomass and extracting lipids from the algae’s cell walls. These lipids contain: triacylglyceride (TAG) and fatty acids (FA).
Methods
The algae biodiesel production is divided into several stepsshown in Figure 1. The process starts with the cultivation of algae in a water source that cannot be easily used for agriculture. The most common way to cultivate algae is through photosynthesis (the open pond method), using sunlight and CO2 as energy sources, this method ultimately helps reduce the Green House Gases emissions to the atmosphere. Other ways to cultivate algae is through verticalgrowth/ closed loop production and closed-tank bioreactors. Once the algae have grown and oil has accumulated, the algal biomass is harvested and dewatered. The next step will be the extraction of oil from the algae. There are different oil extraction methods available such as: the oil press method, the hexane solvent method, and the supercritical fluids method. With the oil press method up to 75%of the oil from the algae can be extracted, while the hexane solvent method (combined with pressing the algae) can extract up to 95% of the oil from algae. In contrast, the supercritical fluids method extracts up to 100% of oil from the algae, however this method is a less popular option because of the additional equipment and work.

Figure 1 : adapted from Daily Tech.http://www.dailytech.com/Military+Biofuel+Costs+Slashed+Thanks+to+Massive+Navy+Purchase/article23454.htm
Once the oil (or lipids) is extracted it is redefined using fatty acid chains. The transesterification process is to replace the glycerol to a simple alcohol, so as to produce methyl or ethyl esters of fatty acids. Transesterification of algal oil is usually done with ethanol and sodium ethanolate, which serves as thecatalyst. Ethanol reacts with the triglyceride (algae oil) to produce biodiesel combined with glycerol, which is the refined in order to remove the glycerol and the final product is the algae biodiesel fuel.

Figure 2: adapted from "Transesterification." Wikipedia. Wikimedia Foundation, 18 Apr. 2012. Web. 29 Apr. 2012. <http://en.wikipedia.org/wiki/Transesterification>.
There are a fewdrawbacks when high conversion of triacylglycerol (lipids) to their corresponding esters, a solution to these drawbacks is the use of biocatalysts (lipases) in transesterification of triacylglycerol. This approach, known as Enzymatic Conversion, has become increasingly attractive, but it hasn’t been demonstrated to large scales because of the lipases high prices and its short life. Recently it hasbeen used a solvent engineering method to enhance the lipase-catalyzed methanolysis of triacylglycerols for biodiesel production.
Results
Through the use of catalysts and after various chemical processes, it was able to transform the algae (S) to biodiesel (P). Biodiesel is our main product in this case; other high-value byproducts are produced as well such as: fertilizers, feedstock, and...