Three other microalgae are sold as natural food supplements: chlorella (green algae), aphanizomenon flos-aquae (blue-green algae), dunaliella (red algae), and haematococcus (green algae).

Chlorella - green microalgae
In the 1960s, early research focused on chlorella. This green microalgae is a small spherical cell with a cell nucleus, and appeared a billion years after blue-green algae. This was the first commercial success for microalgae, cultivated by specially designed high tech commercial farms. Thousands of tons have been sold each year for the past 20 years. Farms in Taiwan, Southern Japan and Indonesia produce almost the entire world supply.

Three drawbacks limit its potential as a new food resource for the developing world. First, chlorella culture is easily contaminated by undesirable weed algae. Unlike spirulina which flourishes in highly alkaline water unfriendly to other algae, chlorella grows in normal water conditions where many algae grow. Chlorella is grown in individual batches, started in a sterile test tube, moved to indoor tanks and then outside to larger ponds. When it achieves maximum density, the entire batch is harvested. Controls required for batch cultivation are more difficult for less sophisticated developing world farms.

Second, unlike spirulina, tiny chlorella cells cannot be harvested by a screen. Expensive centrifuges are required to separate the cells from pond water. Spirulina can be harvested with a simple cloth or a fine screen.

6.16. Chlorella cells in the microscope.

Third, chlorella's hard cellulose cell wall protects its nucleus but resists digestion by the human body, and nutrients cannot be fully absorbed. Commercial farms crack open this hard cell wall in the drying process, or mechanically crush it. Cell breaking procedures would be costly for low technology farms.

When researchers rediscovered spirulina in the 1960s, they praised its nutritional value and ease of cultivation. Even though chlorella was cultivated first, many algae scientists soon afterwards forecast spirulina would become a food of the future.

Aphanizomenon - blue-green algae
Many people have asked about the differences between spirulina and wild blue-green algae harvested from lakes. Spirulina is one kind of blue-green algae with a centuries long history of safe human consumption,known to be safe and nutritious. Hundreds of published scientific studies over the past thirty years have documented no toxicity.

Blue-green algae is also called cyanobacteria. Wild species grow in lakes and waterways, consuming whatever nutrients are in the water. Some species of cyanobacteria are toxic just like mushrooms and some land plants. Most kinds of microcystis, anabaena and aphanizomenon are toxic. Wild blue-green algae has not been subject to spirulina’s long safety testing.

6.17. Aphanizomenon flos-aquae cells in the microscope.

Companies that harvest wild blue-green algae from natural lakes cannot have the same control as growing spirulina at Earthrise Farms. Harvesting wild algae presents a far greater risk of contamination by cyanobacterial toxins. Spirulina can be cultivated in a pure culture, uncontaminated by other cyanobacteria. Farms can be specially designed and operated to produce spirulina under controlled conditions that do not allow the growth of other contaminant cyanobacteria as in lakes and waterways. Quality control tests assure spirulina meets all international food safety and quality standards.

Dunaliella for beta carotene
Dunaliella likes hot climates and needs water even saltier than the ocean, making places like the Dead Sea in Israel a good location. Farms are located in Israel, California, Hawaii and Australia. This microalgae is too salty to be eaten directly as a whole food, but its beta carotene, over 10 times more concentrated than spirulina, is extracted as an oil or powder and sold as a natural food supplement and antioxidant and a color for aquaculture feeds.

Haematococcus for astaxanthin
Recent production in Hawaii and other locations has been launched. Astaxanthin, a carotenoid pigment, is extracted to color salmon flesh, and will also be sold as an antioxidant food supplement.