Biology

The modern economy is over dependent on fossil fuels which have numerous environmental implications. Fossil fuels are non renewable and due to massive exploitation, the supplies are diminishing at a very fast rate. Moreover, the world depends on the fossil fuels which come from politically unstable regions of the world making its supply unreliable. The United States government spends a lot of money in the importation of petroleum oil from the Middle East. The steady supply of oil to the United States is threatened by the increased competition from developing countries. This creates a need for the United States government to be independent in fuel production. This independence can be achieved by exploiting the renewable biodesel such as the promising microalgae (Pienkos  Darzins, 2009).

Microalgal Oil Production
The need to reduce the over dependence on fossil fuels by the world economy is inevitable. There is a need to focus on production of environmental friendly and renewable energy from the biomass. Current research has focused on production of biodiesel from oils from seeds or ethanol from cereals or sugarcane. The production of these oils creates competition for arable land with global food production. However, there are several research activities underway in the production of biodiesel from microalgae. There are several advantages of using aquatic biomass as opposed to terrestrial biomass in the production of biodiesel. Some of the advantages includes the efficient use of light, possibility of coupling energy production with water treatment and sequestration of carbon dioxide, unaffected by unfavorable weather conditions, ability to manipulate the chemical compositions and the large variety of species that can be used in energy production (Samori et al, 2009).

It is estimated that by mid 21st century, biofuels will account for between twenty and twenty five percent of fuels used in the road transport. This will be a big step towards the reduction of carbon dioxide emission to the atmosphere. However, this will create the need for large scales production of second generation fuels from terrestrial biomass and the third generation fuels from aquatic biomass. The challenges in the production of second generation biofuels and the advantages of the third generation fuels has resulted in massive engineering research and development in the promising microalgae fuel production. The production of biofuels from microalgae can be scaled up which will reduce the amount of arable land used in growing corn and sugarcane for biofuels production. However, it is limited by the survival of the microorganism, balancing the growth of the microalgae cultures and the lipid content, transgenic safety and seasonality of lipid harvesting among other technical limitations (Francisco et al, 2010).

Over the years, the United States government has made various attempts to promote production of biodiesels to introduce independence in fuel production. This led to the enactment of the Energy Independence and Security Act of 2007 which aimed at promoting production of renewable energy. The Aquatic Species Program which is an initiative of the Department of Energy has made several attempts since the late 1970s to produce renewable energy from microalgae. Their attempts have confirmed the potential of producing sustainable renewable energy from the aquatic biomass. Other countries in other parts of the world have also made similar attempts (Pienkos  Darzins, 2009).  

According to a research carried out by scientists from the National Renewable Energy Laboratory which aimed at investigating the promises and challenge that face the production of biodiesel from microalgae, there is no biofuels produced commercially in the United States from microalgae. However, a very small percentage of the microalgae biomass is used in the production of nutraceuticals and food supplement all over the world. The untapped energy source is as a result of the technical challenges that have not been triumphed over by technological and engineering development (Pienkos  Darzins, 2009).

The study indicated that up to thirty percent of the cost of production could be as a result of harvesting costs. The potential techniques that can be employed in harvesting include centrifugation which is very costly for economical application. Flocculation techniques have however been proposed as potential methods of reducing the costs. This indicates that there is much more to be done by the engineers in the development of cost effective harvesting techniques if third generation fuels production will be feasible. Despite these challenges, oils from microalgae are as promising as oils obtained from seeds. The oils can easily be converted into biodiesels (alcohol esters) through convectional transesterification reactions. This produces fuels with high oxygen content compared to the fossil fuels (Pienkos  Darzins, 2009).

In another experiment, the properties of fossil fuels produced from microalgae were compared with biofuels from convectional feed stocks. Investigations on whether these fuels meet the recommended standards were also investigated. Six strains of microalgae were studied. The stock cultures were maintained and propagated at standard conditions of temperature, medium and photon flux density for the same period of photoperiod. The study was carried out in a specially designed photo bioreactor. The biomass was harvested from the culture using centrifugation and decantation techniques and analyzed using gravimetric methods. Carbon dioxide sequestration was evaluated periodically using a polarographic probe. The lipids were extracted from the biomass using the Bling and Dyer method and later used to prepare the alcohol esters. The composition of fatty acids and the quality of the biodiesel was determined using various techniques (Francisco, 2010).

The results of the study indicated that among the six strains investigated, Chlorella vulgaris is the best feedstock for the production of biodiesel. This species had the highest carbon dioxide sequestration rate and lipid productivity. The species also had high biomass productivity and produced high lipid contents. Analysis of the esters prepared indicated that they had high concentration of saturated fatty acids and monosaturated fatty acids. The biodiesels had high ester content and met the convectional standards of biodiesels (Francisco, 2010).

In another experiment, varies methods of lipid extraction from Botryococcus braunii were investigated and a new method of extracting hydrocarbons forming the biomass was proposed. The culture was developed under standard conditions of medium temperature, pH and light intensity and harvested by centrifugation. The biomass was determined using gravimetric techniques. Lipids were then extracted from the freeze dried and liquid biomass using different solvents. The extracted hydrocarbons were analyzed using GS-MS techniques. The use of switchable polarity solvents in the extraction of hydrocarbons from the biomass produced the highest yield of hydrocarbons from the freeze dried and liquid biomass. The use of switchable polarity solvents which based on DBU and alcohol was proposed as the best method for extracting hydrocarbons from the biomass (Samor, 2010).

Conclusion
There is a need to reduce the overdependence of the world economy on fossils fuels. This is through the production of biodiesel from the biomass. The second generation fuels have been produced commercially in many countries of the world. Due to the challenges associated with production of seed based biofuels, numerous researches are being undertaken to increase the feasibility of microalgae biofuels production.