Algae are a diverse group of organisms that are mainly autotrophs. Autotrophs are organisms that mainly produce complex organic compounds by using simple inorganic molecules and light or in other instances by chemical reactions. Algae can be broadly classified into two main groups which are unicellular or multicellular. Seaweeds form the largest and most complex marine type of algae (Olanrewaju, Wan Nik, & Kader, 2013). It should, however, be noted that algae can further be classified in many different ways. Below is an illustration of some of these classification representations.
Green algae are classified into the Plantae kingdom and are, therefore, is in the same kingdom as plants. The blue-green algae also known as Cyanobacteria is classified as a prokaryote. Traditionally the cyanobacteria have been classified as algae. However from modern science, this has been disputed, and the term algae have been strictly assigned to eucaryotes (Olanrewaju, Wan Nik, & Kader, 2013). Algae is there characterized by a nucleus enclosed in a membrane with chloroplasts that are bound in one or more membranes. The modern way of classification also known as the phylogenetic classification is based on the close evolutionary relationships that exist between species is used instead of classical classification. The phylogenetic classification can be traced back to the 1950’s in Germany from a book that was published by Willi Hennig. Below is a figure showing a summary of the classification of algae.
Just as plants green algae are capable of performing photosynthesis thus producing oxygen and sugar from the reaction of water, carbon dioxide in the presence of sunlight. Due to the many commercial applications of algae, microalgae are usually algaculture to improve on the production this is mainly due to the difficulties experienced in their cultivation (Melis, 2011).
Use of algae as an energy source
Algae is viewed by many as the renewable source of energy that may be able to salvage people from the deteriorating effects of global warming while providing the energy security that is required. Studies have unraveled the potential that algae holds and if correctly developed could become the sustainable biomass source and thus energy and the required fuels (Olanrewaju, Wan Nik, & Kader, 2013). Currently our levels of development are still not tangible however caution should always be taken in the development of natural algae strains that may not cause adverse impacts on the ecosystem
Increasing oil prices have prompted improved interest in the use of algaculture as a source of biodiesel, bioethanol and a variety of other biofuels. The use of biodiesel is advantageous because it can be used as an alternative to existing diesel engines thus relieving engine designers and manufacturers of redesign and re-engineering of engine parts to fit the use of biodiesel. There has been extensive research in the past in the use of microalgae as a source of energy with inventions and production of biodiesel, bioethanol, and bioplastics.
The use of soybeans and sunflowers in the production of oil capable of producing biofuel has in the past received a lot of media attention and coverage; it is, however, important to note that the management and production of these plants are not sustainable in the long run because of increasing development and production costs. The use of microalgae has been shown to outperform the production from the traditional oil-producing crops and do not also require intensive management.
Biofuel can be produced from processing algae, the resultant algae fuels have been compared to the second generation biofuels and have shown a better yield. It has been shown that compared to terrestrial crops algae is capable of producing 30 to 100 times more energy this is being linked to the fact that algae as a whole take place in photosynthesis thus resulting in high amounts of oil production. For example, the production of oil from algae planted in an area equal to two car garages will be more than the oil produced from an entire football field of soybeans.
Currently, the biofuel from algae is relatively more expensive compared to the cost of the fossil fuels, it should, however, be noted that there is active research that is being undertaken to ensure that the production cost is minimized as possible to ensure that the algae fuel is affordable (Olanrewaju, Wan Nik, & Kader, 2013).
Production and use of algae fuel are environmentally friendly as algae grow in fresh, salty and even polluted waters. In fact, it should be noted that in waste water the growth of algae is undetectable as the waste acts as nutrients and thus accelerating its growth. Algal fuel being a biofuel is degradable in cases of spillage and therefore harmless to the environment as compared to the fossil fuels (Melis, 2011).
Algae oil extraction
A variety of methods can be employed in the extraction of algae oil. The simplest way of extraction of algae oil is through mechanical crushing used in conjunction with chemicals. Other methods that can be employed in algae oil extraction include; the use of chemical solvents for example benzene and hexane. In most food processes, hexane is employed because it is inexpensive (Zimba, 2012). The use of chemicals is, however, dangerous, and care should be taken when handling the chemicals so as not to be in contact with the skin or the vapors inhaled.
Algae oil can also be extracted through the use of enzymes; the enzymes are used in degradation of the cell walls with water being used as a solvent thus resulting in ease of oil fractionation. This method is however seldom used due to the high costs of extraction. A combination of this method with the ultrasonication method results in faster extractions and higher oil yields. The oil extraction process can be highly accelerated by the use of ultrasonic assisted extraction.
Most companies that manufacture or process vegetable oils employ a combination of mechanical and chemical solvent extraction in extracting the oil. Other methods that may be employed in oil extraction include osmotic shock that is the sudden reduction in the osmotic pressure through which some cellular components may be released for example oil. The use of the supercritical fluid may also be employed in the extraction of oil; it involves liquefaction of carbon dioxide under pressure and heats so as the carbon dioxide to acquire both the properties of the liquid and gas (Zimba, 2012). The liquefied carbon dioxide is then used as a solvent in extracting oil from the algae. The cost of extraction of oil from microalgae is dependent on the method used and varies from method to method. Research is underway to develop even most efficient and effective ways of oil extraction from algae.
The oil extracted from the algae can be used in the production of a variety of biofuels; they include biodiesel production through transesterification of the algal oil. It involves reacting of algal oil and alcohol. Through fermentation and distillation of sugars, it is possible to produce bioethanol (C2H6O) and so many other products through a range of other methods.
As already discussed above, the potential of algae cannot be denied or in any case underrated by anyone. Compared to traditional oilseeds that produce about 10 to 50 gallons of oil per acre, algae is a mega oil producer and is capable of producing about 1000 to 5000 gallons of oil per acre (Melis, 2011).
The chemical composition of algae oil is normally similar to other crop oils; algal oil may be converted into renewable fuel by the use of existing technologies. Algae grows in almost every kind of environment and thus seldom competes for space with the crops. For example, algae do well in saline environments which are not suitable for growth of crops (Zimba, 2012). The growth of algae, therefore, can be used to give value to land considered non-productive. Algae plays a major role in the treatment of polluted water and also the recycling of carbon dioxide.
In spite of all these advantages enumerated above, there are a few challenges though that are faced when using algae in the production of energy. They range from strain selection, harvesting, and fuel conversion. Algae growth mainly occurs in shallow ponds and bioreactors, as stated from the introduction algae produce their food through photosynthesis and therefore light intensity is a key component for their production (Zimba, 2012). Advancements and research should be made to ensure effective light intensity for maximum production of oil from the algae. This is partly possible through optimization of the supply of carbon dioxide, nutrients and sunlight to the algae.
Harvesting of algae from the water is normally a challenge. After harvesting the algae is taken through an energy-intensive drying and oil extraction processes. Through drying and extraction methods used a lot of algal oil is lost (Olanrewaju, Wan Nik, & Kader, 2013). This calls for research on efficient ways of oil extraction and collection from the waterborne state of the algae.
The cost of production of algal oil is high thus resulting in increased algal fuels. Compared to the petroleum products the algal fuels are very expensive and therefore not competitive enough (Zimba, 2012). Research is underway to minimize as much as possible the production costs thus ensuring that the final’s product’s cost is affordable and within range and may, therefore, compete with other petroleum fuels.
Algae being an environmental friendly organism lead to treatment of polluted water and helps in balancing the carbon dioxide quantities in the atmosphere. Economically this is very viable, and thus, algal systems are viable too (Olanrewaju, Wan Nik, & Kader, 2013). Identification and extraction of valuable products in algae as a result of the advancing research for example nutrients and pharmaceuticals results in even better economic viability of algae.
Scientists are working round the clock to unlock the unknown potentials that algae may present. Many organizations and bodies have come up in a bid to convert algae into more forms of renewable fuels. The biofuels developed thus far have been compatible with the other fuels and petroleum products that have been in existence for long (Melis, 2011). This ensures compatibility and reduces the cost of redesigning and re-engineering of parts in order to be able to use these fuels.
Conclusion
With increased global warming due to the emissions resulting from the use of petroleum products, it is prudent to consider the development of other environmentally friendly products. This has motivated the production of algal oil that is being used in the manufacture of biofuels. Algae have replaced the traditional crops that were used in the production of oil due to its massive oil production per acre of the plantation. Several challenges, however, hinder the full implementation and production of biofuels key among them being the cost of production. The high cost of production of biofuels has led to high cost of the biofuels and therefore their on-competitiveness in the economic front. Research is however underway to ensure that the cost of production is reduced and thereby improve the competitiveness of the biofuels in the economic front.
References
Zimba, P. (2012). An improved phycobilin extraction method. Harmful Algae, 17, 35-39. http://dx.doi.org/10.1016/j.hal.2012.02.009
Melis, A. (2011). Hydrogen Production. Green Algae as a Source of Energy. PLANT PHYSIOLOGY, 127(3), 740-748. http://dx.doi.org/10.1104/pp.127.3.740
Olanrewaju, O., Wan Nik, W., & Kader, A. (2013). Potential of Macro Algae for Biomass Energy Source and Green House Gas Emission Carbon Capture. Biosci., Biotechnol. Res. Asia, 10(2), 653-658. http://dx.doi.org/10.13005/bbra/1177