Algae Biodiesel: Oil from Algae
One of the newest and most innovative forms of alternative fuels in development today is algae based biofuel. Algae are one of the fastest growing and most adaptive organisms on the planet and researchers are developing ways of using algae to capture CO2 from the atmosphere and to output fuels that can meet our energy needs. Proponents hope that large scale production of algae based fuel can dramatically lessen our dependence on crude oil as well as capture immense quantities of CO2 in the process. Obviously this CO2 will be released again once the fuel is burned, but the system represents a cycle that is much more sustainable than the one currently practiced.
The process of producing algae is really quite simple. Algae are grown in either open-pond or closed-pond systems. Once the algae have been harvested, the lipids (oils) are extracted from the walls of the algae cells. There are different ways to extract oil from algae. The oil press is the simplest, most popular method because it extracts up to 75% of the oil from the algae being pressed.
Another process is called the hexane solvent method. In this method, the hexane solvent is combined with combined with the pressed algae, which then extracts up to 95% of oil from algae. First, the press squeezes the oil. Then, the leftover algae is mixed with hexane, filtered, and cleaned so as to ensure that no chemical is left in the oil.
A third process is known as the supercritical fluids method. This method extracts up to 100% of the oil from algae. Carbon dioxide behaves as the supercritical fluid—when a substance is pressurized and heated to change its composition into a liquid as well as a gas. The carbon dioxide is then mixed with the algae. Once combined, the carbon dioxide turns the algae into oil. The additional equipment and work needed in this method makes it a less popular option.
Once the oil has been extracted from the algae cells, it is refined using fatty acid chains in a process called transesterification. In this process, a catalyst such as sodium hydroxide is mixed in with an alcohol such as methanol. This creates a biodiesel fuel combined with glycerol. The mixture is then refined to remove the glycerol, leaving the final product: algae biodiesel fuel.
Algae biodiesel researchers are using a process studied in organic chemistry called transestrerification to discover efficient ways to make algae biodiesel fuel. In transesterification, an alcohol and an ester compound are mixed, and through the resulting reaction, a different type of alcohol and a different ester is created. An ester s a special type of chemical compound in which an acid has had one of its hydroxyl groups replaced by a molecule of oxygen. In this process, the oil that comes from the algae is altered into biodiesel through a specific chemical reaction.
Growing Algae for Biodiesel Use
The most natural way of growing algae for biodiesel production is through open-pond growth. Using ponds, algae can grow in hot, sunny areas of the world in order to produce a maximum amount of algae. Open-ponds provide the least invasive method of algae growth, however it has numerous drawbacks. Bad weather and contamination from strains of bacteria or other organisms can stunt algae growth. Furthermore, the water the algae grow in needs to be kept at a certain temperature, which can be difficult to maintain.
Vertical growth/closed loop production has been developed to produce algae faster and more efficiently than open growth ponds. With vertical growing, algae are placed in clear plastic bags, so they are exposed to sunlight on two sides. The bags are stacked high and protected from the rain by covers. With the extra sun exposure, the productivity rate of the algae is increased, increasing oil production as well. Furthermore, the algae are protected from contamination.
Closed-tank bioreactor plants are employed to increase the rates of oil production even further. These plants grow algae indoors within large, round drums which can grow algae under ideal conditions. The algae are manipulated to grow at maximum levels and can be harvested every day. This produces a high output of algae, which produces large amounts of oil for biodiesel. Closed bioreactor plants can be strategically placed near energy plants to capture excess carbon dioxide that otherwise would pollute the air.
Researchers are experimenting with a process called fermentation where algae are cultivated in closed containers and fed sugar in order to promote growth. In this method, all errors are eliminated because the growers are given the ability to control all the environmental factors. Algae biodiesel can be produced anywhere in the world through fermentation. However, researchers are trying to find a way to get enough sugar without creating problems.
The PROS and CONS of Algae Biodiesel
First, open-pond growing is a very risky process. Not only does the water temperature have to be exact, carbon dioxide has to be pumped into the ponds, creating a high risk of contamination. Biodiesel labs are currently solving this problem by using the closed bioreactor system in order to counteract these issues.
No real testing has been done on algae biodiesel and its effectiveness with actual cars. Companies are making deals with large oil companies to test and produce the algae, however, it is all still in the testing phase. There is only one algae biodiesel car on the streets: a Mercedes Benz E320. The company used algae biodiesel to fuel this car and drive it on the streets of Park City, Utah. No statistics were released on the car’s gas mileage or what kind of emissions it produced.
Under optimal conditions, algae can be grown in massive, almost limitless, amounts. Half of algae’s composition, by weight, is lipid oil. Algae can be converted to oil, refined into biodiesel and have its remaining material sold as high protein animal feed. Algae are a non-food crop which removes large amounts of carbon dioxide from the air, and it also grows extremely fast. Algae grows on water, thus it does not use valuable land for growth. Algae are a high energy dense crop which needs a large source of carbon dioxide to grow. Thus, algae can be set up near electric utilities looking to reduce their carbon emissions. Algae capture phosphorous and nitrogen from wastewater treatment facilities. If developers can get all the kinks worked out, algae has the potential to change the way we produce oil and deal with CO2 emissions with a single high energy organism.
Source: HowStuffWorksThis entry was posted by in Alternative Energy, Energy, Environment, Featured, To Learn and tagged algae, algae based fuel, algae biodiesel, algae biofuel, bioreactor, CO2, CO2 emissions, open pond, vertical growth.