Algae can be grown for biofuel, in both photobioreactors and open ponds. Photobioreactors are completely controlled system, where all the growth factors such as light, CO2, temperature, Nutrients etc. are all artificially supplemented.
Algae are a very reliable renewable energy source. Naturally algae can grow in diverse but humid environmental conditions such as in open ponds with out any artificial care or treatment. But the bulk of algae biomass which is needed for biofuel production is very huge and growing of algae in open ponds can’t produce enough algae biofuel. Growing of algae in open ponds is more cost effective for food than for biofuel. The most preferable method of algae culture for biofuel is by using photobioreactors.
What are the requirements in photobioreactors for greater harvest? The requirements are-
- Water: could be either sea water or fresh water depending on the specific species of algae. For example micro algae requires fresh water and
- Carbon dioxide: Algae are consumes huge amount of CO2 so artificial injection of CO2 is must for higher yield of biofuel. Source of CO2 includes coal power plants or compressed CO2
- Optimum Temperature: also differ from species to species and the temperature range is 15 to 35 degree Celsius
- Nutrients: is applies in the form of fertilizers more or less similar with fertilizer applies to terrestrial crops. Nutrients including Nitrate, Phosphate, Iron etc
- Recycling of water: is useful to remove toxic or undesirable wastes which are produced by the algae
- Optimum level of stress: Under stress conditions algae produce higher amount of oils. Stress conditions can be created by reducing nutrient level, and moisture at the algaes' peak threshold.
- Light: light is artificially provided for optimum and fast rate of growth. In the photobioreactors the light sources could be florescent lamps. But some times in some photobioreactors natural sun light can be utilized, but most algae species are very sensitive to strong direct sunlight therefore the intensity of the sunlight should be reduced by using either tinted glasses or netting systems.
- pH: Algae loves alkaline waters so by all means the pH of the water should be kept at 8; the water in the pond or in the photobioreactors should be recycled regularly to keep the water at pH 8.
