Biodiesel is the most common fuel that algae can make. It is very similar to the diesel fuel used in cars and trucks, but has a few important differences. Biodiesel is made of oils that are slightly thicker than regular diesel. It is also better for the atmosphere than conventional fuel because it burns cleaner.
All cells basically consist of carbohydrates, proteins, and lipids (a form of fat). In algae, and other plants such as corn and soybeans, the lipids are used to make biodiesel. To harvest these lipids, algal cells must first be separated from the water in which they have been growing. This is typically accomplished with a machine called a centrifuge that spins the algae and water very rapidly, forcing the algae to the bottom of a container. The water is just poured off the top.
Once the algae are removed from water, the lipids are extracted from cells by chemically breaking open the cells and using a liquid called a solvent to dissolve the lipids. This liquid is then purified and the result is a substance that is kind of like vegetable oil. That oil is then turned into biodiesel by adding chemicals and heat.
There are ways to use raw algae as a form of fuel, but they are not traditional types of fuel. For example, you can burn algae like a piece of paper, creating heat that can be turned into electricity. Also, some microbes use algae as a food source and expel natural gas such as methane when they digest it. Raw algae can also be added to animal feed as a source of protein, in effect fueling the growth of farmed animals.
- Cameron Coates, graduate student, Center for Marine Biotechnology and Biomedicine
To read more about how algae can make fuel, read our story “Green Bullet” at http://explorations.ucsd.edu/Features/2008/Green_Bullet/.