Chemical Engineering World

Algae

Algae are a form of "simple," photosynthetic, and aquatic organisms. The most complex forms of algae are commonly called "seaweed," though algae range in size and complexity from unicellular forms to this more advanced form. They are called "simple" because they lack many complex features found in land plants. The most useful feature of algae for our purposes is that algae produce significant quantities of natural oils. In fact, there are estimates that the yield from algae can be 200 times greater than that from a comparable area of other sources of conventional vegetable oils.

Algal Oils

Oil from algae is quite similar to oils produced by conventional oil crops and oilseeds. Chemists generally do not speak of oil, which is a common word for a vaguely defined group of chemicals. Biological "oils," or lipids, are chemicals called triglycerides, composed of a central glycerol unit with three fatty acids attached. Chemically, biological lipids are similar to petroleum to the extent that both groups of chemicals are based on carbon and hydrogen.

The main problem with using biological lipids as fuels is the fact that lipids are much more viscous (or resistant to "flowing," in layman's terms) than the refined petrochemicals which make up gasoline, diesel fuel, kerosene, and other petroleum-based fuels. As a result, unrefined lipids will not be completely burned off in an engine, and leftover product which did not burn can accumulate in the engine.

Biodiesel from Algae Oil

The process of making biodiesel from oil is all about lowering the viscosity of oil by removing the glycerol; the process of converting algal oils is the same as that with any conventional vegetable oils. Chemists refer to this process as "transesterification," which in the case of biodiesel means splitting the triglycerides, separating the glycerol, which will settle, and converting the fatty acids into a solution of methyl esters, called biodiesel. This is done by mixing the biological oil with sodium methoxide.

Cultivating Algae

Algae can be cultivated at home using a device known as a "photobioreactor," or a bioreactor which includes a source of light. A basic reactor can be made from clear plastic tubes or plastic bottles or a plastic container of some sort. Algae need water, carbon dioxide, and light to grow; the reactor will contain water into which has been placed a culture of algae. Depending on the type of reactor chosen, algae can be cultivated continuously or in batches. The light source can be an LED, a phosphorescent bulb, or natural sunlight.

Getting Oil from the Algae

The making of biodiesel involves a number of separation processes, even more so in the case of biodiesel from algae: separating the algae from the solution, separating the oil from the algae, and separating the glycerol from the biodiesel after the reaction is complete. All of these separation processes can be done simply with a centrifuge.

Conclusions

While even biodiesel isn't quite a free lunch, getting biodiesel from algae can bring you one step closer. The product you get from algae-produced biodiesel is equivalent to that you get from other oils and the conversion of algal oil is the same as the conversion of any other oil; the algae are simply a renewable source of oil. Algae are quite safe, being commonly used in commercial products including food.