Humans use algae as food, for production of useful compounds, as biofilters to remove nutrients and other pollutants from wastewaters, to assay water quality, as indicators of environmental change, in space technology, and as laboratory research systems. Algae is commercially cultivated for Pharmaceuticals, Nutraceuticals, Cosmetics and Aquaculture purpose.

Fuel source

• Algae can be used to make Biodiesel (see algaculture), Bioethanol and biobutanol and by some estimates can produce vastly superior amounts of vegetable oil, compared to terrestrial crops grown for the same purpose.
• Algae can be grown to produce hydrogen. In 1939 a German researcher named Hans Gaffron, while working at the University of Chicago, observed that the algae he was studying, Chlamydomonas reinhardtii (a green-algae), would sometimes switch from the production of oxygen to the production of hydrogen.
• Algae can be grown to produce biomass, which can be burned to produce heat and electricity. 

Food supplement:

1. It is a complete protein with essential amino acids (unlike most plant foods) that are involved in major metabolic processes such as energy and enzyme production.

2. It contains high amounts of simple and complex carbohydrates which provide the body with a source of additional fuel. In particular, the sulfated complex carbohydrates are thought to enhance the immune system’s regulatory response.

3. It contains an extensive fatty acid profile, including Omega 3 and Omega 6. These essential fatty acids also play a key role in the production of energy.

4. It has an abundance of vitamins, minerals, and trace elements in naturally-occurring synergistic design.

Chondrus crispus, (probably confused with Mastocarpus stellatus, common name: Irish moss), is also used as "carrageen". It is an excellent stabiliser in milk products - it reacts with the milk protein caesin, other products include: petfoods, toothpaste, ice-creams and lotions etc.,Alginates in creams and lotions are absorbable through the skin.

Fertilizer

Algae are used by humans in many ways. They are used as fertilizers, soil conditioners and are a source of livestock feed. Because many species are aquatic and microscopic, they are cultured in clear tanks or ponds and either harvested or used to treat effluents pumped through the ponds

Role Of Algae in Pollution control

• Algae are used in Wastewater Treatment facilities, reducing the need for greater amounts of toxic chemicals than are already used.
• Algae can be used to capture fertilizers in runoff from farms. When subsequently harvested, the enriched algae itself can be used as fertilizer.
• Algae Bioreactors are used by some powerplants to reduce CO₂ emissions. The CO₂ can be pumped into a pond, or some kind of tank, on which the algae feed. Alternatively, the Bioreactor can be installed directly on top of a smokestack.