Algae Biodeisel

Algae Biodiesel Engineering: Extracting Oil from Algae

How can we get oil from algae? It's like getting juice from an orange -- with an additional chemical reaction thrown in. Algae are grown in either open-pond or closed-pond systems, which we'll discuss later. Once the algae are harvested, the lipids, or oils, are extracted from the walls of the algae cells.

There are a few different ways to extract the oil from algae. The oil press is the simplest and most popular method. It's similar to the concept of the olive press. It can extract up to 75 percent of the oil from the algae being pressed.

Basically a two-part process, the hexane solvent method (combined with pressing the algae) extracts up to 95 percent of oil from algae. First, the press squeezes out the oil. Then, leftover algae is mixed with hexane, filtered and cleaned so there's no chemical left in the oil.

The supercritical fluids method extracts up to 100 percent of the oil from algae. Carbon dioxide acts as the supercritical fluid -- when a substance is pressurized and heated to change its composition into a liquid as well as a gas. At this point, carbon dioxide is mixed with the algae. When they're combined, the carbon dioxide turns the algae completely into oil. The additional equipment and work make this method a less popular option.

Once the oil's extracted, it's refined using fatty acid chains in a process called transesterification. Here, a catalyst such as sodium hydroxide is mixed in with an alcohol such as methanol. This creates a biodiesel fuel combined with a glycerol. The mixture is refined to remove the glycerol. The final product is algae biodiesel fuel.

The process of extracting oil from the algae is universal, but companies producing algae biodiesel are using diverse methods to grow enough algae to produce large amounts of oil.

Now, we'll learn how they do it.

How Algae Biodiesel Works: A Bioreactor System

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Growing Algae for Biodiesel Use

So, we've talked about the chemical process that takes algae and turns it into biodiesel fuel. The real question, and one which many companies all over the globe are trying to answer, is how can we produce enough to meet the demand for biodiesel?

The most natural method of growing algae for biodiesel production is through open-pondgrowing. Using open ponds, we can grow algae in hot, sunny areas of the world to get maximum production. While this is the least invasive of all the growing techniques, it has some drawbacks. Bad weather can stunt algae growth, as can contamination from strains of bacteria or other outside organisms. The water in which the algae grow also has to be kept at a certain temperature, which can be difficult to maintain.

How Algae Biodiesel Works: Bioreactor Process

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Vertical growth/closed loop production has been developed by biofuel companies to produce algae faster and more efficiently than open pond growth. With vertical growing, algae are placed in clear plastic bags, so they can be exposed to sunlight on two sides. The bags are stacked high and protected from the rain by a cover. The extra sun exposure increases the productivity rate of the algae, which in turn increases oil production. The algae are also protected from contamination.

Other companies working to produce algae for biodiesel are constructing closed-tank bioreactor plants to help increase oil rates even further. Instead of growing algae outside, indoor plants are built with large, round drums that grow algae under ideal conditions. The algae are manipulated into growing at maximum levels and can be harvested every day. This yields a very high output of algae, which in turn yields large amounts of oil for biodiesel. Closed bioreactor plants can also be strategically placed near energy plants to capture excess carbon dioxide that would otherwise pollute the air.

Researchers are testing another variation of the closed-container or closed-pond process -- fermentation. Algae are cultivated in closed containers and fed sugar to promote growth. This method eliminates all margin of error since it allows growers to control all environmental factors. The benefit of this process is that it allows the algae biodiesel to be produced anywhere in the world. But, researchers are trying to figure out where to get enough sugar without creating problems.

Let's learn more about the pros and cons of algae biodiesel.

DO-IT-YOURSELF ALGAE BIODIESEL?

A number of books and services claim you can produce your own biodiesel -- even with algae. Making biodiesel in your garage requires a lot of time, money and effort on your part. It can be dangerous. Be cautious, or leave it up to the experts!

CAN YOU SAY TRANSESTERIFICATION?

Algae biodiesel researchers and engineers are using a process studied in organic chemistry called transestrerification to come up with efficient ways to make algae biodiesel fuel. In this process, an alcohol and an ester compound are mixed, and through the resulting reaction produce a different type of alcohol and a different type of ester. The same process is used to make polyester fabrics. An ester -- a special type of chemical compound in which an acid has had one of its hydroxy groups -- or a molecule of hydrogen and oxygen bonded together -- replaced by a molecule of oxygen. This process allows the oil that comes from the algae to be altered into biodiesel through a specific chemical reaction.