Oleaginous algae for Triacylglycerol feed stock for conversion to biofuel

Oleaginous algae are economically important algae, that have a potential to produce more than 20% of oils (mainly Triacylglycerol) per dry cell weight. Many oleaginous strains of algae for bio diesel production are now known by scientists. These strains can produce large quantities of oils. Algae has a potential to produce the highest yield of biofuel than all the other major feed stocks. Yearly yield potential of algae range from 5,000 gallons per acre to 20,000 gallons per acre, which is the greatest yield potential than even the best yielding vegetable oil producer plants, such as soy beans and palm oils. All algae species produce eleven types of oils, from this oils the one which is used as a feed stock for biofuel is Triacylglycerol. This type of oil is produced by algae mainly as a response to stress situations, for its use as storage of starch or energy. In alga farms stress situations are created by nutrients starvation, high temperature and high light intensity as the algae are aging normally. Naturally most oleaginous strains produce more Triacylglycerol while aging.

Nutrient starvation: is done by depleting the nitrogen, silicon and phosphate supply of the algae. This will cause the algae to produce more Triacylglycerol.

Temperature increase: As the temperature increase the production of Triacylglycerol also increases.

Light intensity increase: Higher light intensity increases Triacylglycerol. Light intensity is increased by exposing the algae to direct scorching sunlight.

Algae species that produces more amount of Triacylglycerol in response to stress situations are:

• All of: Green algae species
• Many of: Diatom Species
• Some of: Haptophytes, Eustigmatophytes, Chrysophytes and Xanthophytes species
• None of: Cyanobacteria or Blue Green algae species

Naturally under no stress environmental conditions Green algae, Diatoms, Haptophytes, Eustigmatophytes and Chrysophytes have an average of 26% of oil, but under stress conditions their average oil content increases significantly to 45% per dry cell weight.

The yield from oleaginous algae is much more in hundreds of fold as compaired to the yield produced from the best oil producer crops. The reason for this is due to the ability of each and every algae cells to perform a range of various physiological functions starting from CO2 fixation to Triacylglycerol production and accumulations by it self. But in crops such as soy beans this physiological functions took place in separate and specific parts of the plant such as in seeds.

These days production of biofuel is gaining increasing popularity because of different reasons.

1. Algae are easy to grow. Algae needs little attention to grow, it can grow easily in sewages, farm outlets, barren and unproductive lands, salt water and in hot dry desert climate.
2. Algae reproduce very rapidly, this will make algae production for biofuel a lot sustainable, continual and unseasonal.
3. Algae produces 7 to 30 times more yield of oils than all of the oil crops combined. In other words it has high potential of yield per hectare.
4. Ease of the use of coal power plants as CO2 source for alga culture.
5. Its use to purify seawages and drainage canals from toxic chemicals and excess fertilizers.
6. Its huge ability to reduce green house gases such as carbon dioxide.
7. For its other economically important byproduct such as pigments, cosmetic products, animal feed, food products such as proteins, carbohydrates, vitamins and omega-3.
8. Increasing new discoveries and techniques to grow algae in open ponds and phobiotoreactors. 

But there are also some serious impediments for the applicability of producing biofuel from algae. The estimated production cost is very high and most of this cost involves in setting up the centrifugal system to extract the oils and in running the system, the estimated cost could reach hundreds of millions of USD. Other minor problems include unavailability of reliable carbondioxide source, high evaporation losses,  contamination and enough water source.

Taking all the high production costs in to consideration now days, it is much more advisable to grow algae for food companies than for biofuel purpose, but biofuel production from algae have a very huge potential for the future and a lot of research are underway to slash the paralyzing cost of production. As for me the future looks greener.  

Growing Algae for Biofuel

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.