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Algae as an energy source
( Dikutip dari artikel Wikipedia di http://en.wikipedia.org/wiki/Algaculture )
Currently most research into efficient algal-oil production is being done in the private sector, but if predictions from small scale production experiments bear out then using algae to produce biodiesel may be the only viable method by which to produce enough automotive fuel to replace current world gasoline usage.
Microalgae have much faster growth-rates than terrestrial crops. The per unit area yield of oil from algae,(estimated to be from between 5,000 to 20,000 gallons per acre, per year), is 7 to 31 times greater than the next best crop, palm oil(635gal).
Algal-oil processes into biodiesel as easily as oil derived from land-based crops. The difficulties in efficient biodiesel production from algae lie not in the extraction of the oil, which can be done using methods common to the food-industry such as hexane extraction, but in finding an algal strain with a high lipid content and fast growth rate that isn't too difficult to harvest, and a cost-effective cultivation system (ie, type of photobioreactor) that is best suited to that strain.
Open-pond systems for the most part have been given up for the cultivation of algae with high-oil content. Many believe that a major flaw of the Aquatic Species Program was the decision to focus their efforts exclusivly on open-ponds, this makes the entire effort dependent upon the hardiness of the strain chosen, requiring it to be unnecessarily resiliant in order to withstand wide swings in temperature and pH, and competition from invasive algae and bacteria.
The energy that a high-oil strain invests into the production of oil is energy that is not invested into the production of proteins or carbohydrates, usually resulting in the species being less hardy, or having a slower growth rate. Algal species with a lower oil content, not having to divert their energies away from growth, have an easier time in the harsher conditions of an open system.
Research into algae for the mass-production of oil is mainly focused on microalgae, (which is a term generally referred to as organisms capable of photosynthesis that are less than 2 mm in diameter, including the diatoms and cyanobacteria), as opposed to macroalgae, (ie. seaweed). This preference towards microalgae is due largely to its less complex structure, fast growth rate, and high oil content- (for some species).
Some commercial interests into large scale algal-cultivation systems are looking to tie-in to existing infrastructures, such as coal power plants or sewage treatment facilities. This approach not only provides for the needs of the system, such as CO2 and nutrients, which, if the facility were built independently, would have to be otherwise acquired, but in addition it remediates waste. In July 2006, Petro Sun Drilling Inc, a oilfield service company, announced the creation of Algae BioFuels, a wholly owned subsidary dedicaced to this area.
The algal-oil feedstock that is used to produce biodiesel can also be used for fuel directly as "Straight Vegetable Oil",(SVO). While using the oil in this manner does not require the additional energy needed for transesterification,(processing the oil with an alcohol and a catalyst to produce biodiesel), it does require a special engine designed for its use, or modifications to a normal diesel engine, whereas biodiesel can be run in any modern diesel engine, unmodified, that is designed to use ultra-low sulfur diesel, the new diesel fuel standard for the United States that goes into effect in the fall of 2006.
Algae can be grown to produce hydrogen. In 1939 a German researcher named Hans Gaffron, while working at the University of Chicago, observed that the algae he was studying, Chlamydomonas reinhardtii (a green-algae), would sometimes switch from the production of oxygen to the production of hydrogen. Gaffron never discovered the cause for this change and for many years other scientists failed in their attempts at its discovery.
In the late 1990's professor Anastasios Melis a researcher at the University of California at Berkeley discovered that by depriving the algae of sulfur it will switch from the production of oxygen (normal photosynthesis), to the production of hydrogen. He found that the enzyme responsible for this reaction is hydrogenase, but that the hydrogenase will not cause this switch in the presence of oxygen. Melis found that depleting the amount of sulfur available to the algae interrupted its internal oxygen flow, allowing the hydrogenase an environment in which it can react, causing the algae to produce hydrogen. Chlamydomonas moewusii is also a good strain for the production of hydrogen.
Algae can be grown to produce biomass, which can then be harvested and burned in the same manner as wood, to produce heat and electricity.
Sumber : Algaculture