Like plants, algae use the sunlight for the process of photosynthesis. Photosynthesis is an important biochemical process in which plants, algae, and some bacteria convert the energy of sunlight to chemical energy. Algae capture light energy through photosynthesis and convert inorganic substances into simple sugars using the captured energy.

There are two main methods of cultivation

• Ponds
• Photobioreactors

Ponds

Since algae need sunlight, carbon-di-oxide and water for their growth, they can be cultivated in open ponds & lakes. More about open ponds are discussed here - Cultivation in open pond

Photobioreactors

A Photobioreactor is a controlled system that incorporates some type of light source. The term photobioreactor is more commonly used to define a closed system, as opposed to an open pond. A pond covered with a greenhouse could also be considered an unsophisticated form of photobioreactor. Because these systems are closed, everything that the algae  need to grow, (carbon dioxide, water and light) need to be introduced into the system. More about photobioreactors are discussed here - Cultivation in photobioreactors

There are several factors to determine the growth rate of algae. The following are the important factors that determine the growth rate of algae

• Light - Light is needed for the photosynthesis process
• Temperature: There is an ideal temperature range that is required for algae to grow
• Medium/Nutrients - Composition of the water is an important consideration (including salinity)
• pH - Algae typically need a pH between 7 and 9 to have an optimum growth rate
• Algae Type -  Different types of algae have different growth rates
• Aeration - The algae need to have contact with air, for its CO₂ requirements
• Mixing - Mixing prevents sedimentation of algae and makes sure all cells are equally exposed to light
• Photoperiod: Light & dark cycles

A Generalized Set of Conditions for Culturing Micro-Algae

Source: http://www.fao.org/docrep/003/w3732e/w3732e06.htm

Algae cultivation can be done in a variety of environments. Algae cultivation in various environments are discussed in the following pages.

• Cultivation in open pond
• Cultivation in closed ponds
• Cultivation in photobioreactors
• Desert-based algae cultivation
• Cultivation in waste water
• Marine algae cultivation
• Cultivation next to power plants

Algae cultivation is an environmentally friendly process for the production of organic material by photosynthesis from carbon dioxide, light energy  and water. The water used by algae can be of low quality, including industrial process water, effluent of biological water treatment or other waste water streams.

The open systems, in order to increase their efficiency, are generally designed as a continuous culture in which a fixed supply of culture medium or influent ensures constant dilution of the system. The organisms adapt their growth rate to this dilution regime, with the organism best adapted to the environment prevailing in the system winning the competition with the other organisms.

A drawback of the common open algae culture systems is the major risk of contamination by undesirable photosynthetic micro-organisms which can be introduced via air or rain.

An alternative to the drawback of the open system could be to carry out algae cultivation in closed photobioreactors. In these, the process conditions can be accurately controlled, and no infection carrying alga species will occur. A major drawback of the closed photobioreactors resides in the high investment costs which lead to high production costs.

Thus, cultivating algae for fuel is an area where more experimentation and research are still required.

Related Links

• Algae Hunter  - Finding stable algae ecosystems for commercial farming
• How to Grow Algae
• Grow Your Own Bioluminescent Algae
• Algal production
• The Start of the Food Chain - Micro Algae Culturing
• Algal Culturing Techniques – The text book is a comprehensive reference on all aspects of the isolation and cultivation of marine and freshwater algae, including seaweeds. It is divided into seven parts that cover history, media preparation, isolation and purification techniques, mass culturing techniques, cell counting and growth measurement techniques, and reviews on topics and applications of algal culture techniques for environmental investigations.
• Algae Culture