Algae are green plants, primarily they requires sunlight, carbon dioxide and mineral nutrients. On the other hand they also requires optimum environmental conditions such as the right pH and temperature. Algae grow and thrive mostly in water and moist environmental conditions. Depending on the algae species, algae can grow either in fresh water or sea water. The majority of microalgae thrive in fresh water, though many micro algae can grow also in sea waters too. Most of the macroalgae are the dominant types of green plants in the seas and oceans.
Sunlight requirements
Algae which lives in deep waters require very low intensity of sunlight, but algae species which lives on the surface of the water or in a very shallow waters require direct sunlight. In most modern photobioreactors light is provided artificially from fluorescent lamps. This kind of lamps are good option to control the intensity of light based on the particular species of algae.
Carbon dioxide and other gases
Algae consumes very huge amount of carbon dioxide, than terrestrial green plants. For algae cultured under photo bioreactors and open ponds, carbon dioxide is supplied artificially in the form of bubbles. The optimum concentration of carbon dioxide to grow algae for biodiesel purpose is up to 3%.
Oxygen is the byproduct of photosynthesis as a result very high concentration of oxygen in the water can be toxic to the algae for it reduces photosynthesis efficiency. To avoid oxygen toxicity the water should be constantly stirred and recycled to remove the excess oxygen.
Some photobioreactiors get their carbon dioxide from flue gas. This type of gas contain up to 15% of carbon dioxide. In addition to this it is also a mixture of many other gases such as nitrogen dioxide, sulphur dioxide, etc. Most algae can make use of this extra mixture of gases as a nutrient sources.
Mineral nutrients, Vitamins, and hormonal requirements
Because of the diverse nature of algae species in their nutrient requirements, it is very difficult to generalize the amount and rate of each nutrient required by algae. But most scientists agree that all algae needs a set of 14 elements, these are Nitrogen, Phosphorus, Magnesium, Potassium, Sulphur, Calcium, Molibdium, Zinc, Iron, Copper, Manganese, Oxygen, Hydrogen and Carbon. In addition, some elements are required by some or more algae, these are Cobalt, Iodine, Sodium, Boron, Chlorine, Silicon and Bromine. For example diatoms need an additional silicon for optimum growth. All algae uptake dissolved inorganic nutrients such as nitrates, nitrites, ammonium and phosphates.
Vitamins such as vitamin B12 and thiamine and growth regulators could give better yield of algae. The concentration of the vitamins and growth regulators and the method of applications will depend on the particular species of algae.
pH requirements
The ideal pH for most algae species is between 7 to 9 pH levels. The culture medium should be kept alkaline with an average pH of 8. Most algae are very sensitive to acidic culture medium and they perform very badly under acidic conditions.
