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Ways to Harvest Algae

Algae are a large and diverse group of organisms that have plant-like characteristics. The smallest algae are unicellular and the largest algae, giant kelp, can grow as much as 195 feet long. Algae have an immense amount of uses in fields as diverse as scientific research and pollution control. One of the most promising aspects of algae is that it may become the major fuel source of the world if it can be properly harvested. The biggest issue with this development is that harvesting algae can be inefficient and expensive, but there are some effective methods of harvesting algae.

Froth Flotation
- Once algae have grown in sufficient quantities as to require harvesting, it is difficult to remove them from the water. Froth flotation is one method developed to combat this problem. The basic principle of floth flotation revolves around using air to separate the algae from the water, at which point the algae can be captured. The design uses a tube that the growth solution is pumped through along with a vertical tube that has air being pumped into it. As the algae pass the vertical tube, they are carried along with the froth created by the pumped air. At the top of the vertical tube, various devices capture the algae from the froth so that you can store and harvest it.
Centrifuge
- A centrifuge is a machine that places the algae into a rotational movement with the force being applied perpendicular to the direction of movement. This causes a centripetal acceleration which, due to the sedimentation principle, causes the algae to settle at the bottom of the container it is in. The downside to this method is that the algae may be damaged and that it is expensive and time consuming.
Chemical Flocculation
- Flocculation is different from precipitation because in flocculation the particles are in suspension rather than dissolved in the solution. Flocculants are chemical compounds that cause algae to flocculate out of solution. Alum and ferric chloride are commonly used flocculants. Chitosan is a good flocculant, but it is expensive. The disadvantage of flocculation is that you may have a hard time separating the chemicals from the algae once it has been flocculated.
Auto Flocculation
- You also may be able to get the algae to flocculate out of solution without chemicals. If you are able to interrupt the carbon dioxide supply of the algae, they will flocculate. This discovery is an important development because it makes harvesting easier.

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