The key ingredient to initiate photosynthesis is light as it is involved in the conver­sion of carbon dioxide to carbohydrates. As compared to higher plants, algae require relatively low intensity of light for proper development. Solar waves are

the primary source of light. Only 43-45 % of the total solar radiations are involved in commencement of photosynthesis. These radiations are termed as PAR or Photosynthetically Active Radiation. About 27 % of PAR is converted to carbohy­drates. The rate of biomass growth can be established by considering the following relation:

P = aE. l

where P is the rate of production of dry algae and is measured in g/m2/day, E is the efficiency of photosynthesis, I denotes light energy in kcal/m2/day, and the symbol a represents the conversion coefficient (g/kcal).

The light source in the cultivation system can be either natural, artificial, or com­bination of different light sources. The cheapest source is the solar energy, which is utilized in open pond systems, which require a large area for construction and have a higher contamination risk. In closed systems, fiber optics and solar concentrators can be used to maximize the effect of sunlight. As compared to fluorescent lamps, LED lights are shown to be more economically stable.

13.2.1.4 Nitrogen

Being the main constructing element of proteins and nucleic acids, nitrogen plays a significant role in algal metabolism.

13.2.1.5 Phosphorous

This element is used in the form of phosphates because if it is present in any other state, it may become unavailable to the algae due to its ability to combine with other metallic ions, which results in precipitation.

13.2.1.6 Additional Nutrients

Apart from the above-mentioned nutrients, trace amount of vitamins and metals like sodium, calcium, magnesium, manganese, zinc, copper, iron, and molybdenum are also required for efficient growth of algal culture.

13.2.1.7 Space

Unlike other organisms, algae are very versatile and do not require arable land for productive growth. They can be cultivated in ponds, water bodies, and even reactors. Issue of appropriate space is not a concern and does not put a strain on the budget or available resources.