Oil ExtractionAlgae oils have a variety of commercial and industrial uses, and are extracted through a wide variety of methods. The simplest method is mechanical crushing. Since different strains of algae vary widely in their physical attributes, various press configurations (screw, expeller, piston, etc) work better for specific algae types. Often, mechanical crushing is used in conjunction with chemicals (see below).

Chemical solvents: Algal oil can be extracted using chemicals. Benzene and ether have been used, oil can also be separated by hexane extraction, which is widely used in the food industry and is relatively inexpensive. The downside to using solvents for oil extraction are the dangers involved in working with the chemicals. Care must be taken to avoid exposure to vapors and direct contact with the skin, either of which can cause serious damage. Benzene is classified as a carcinogen. Chemical solvents also present the problem of being an explosion hazard.[9]Soxhlet extraction is an extraction method that uses chemical solvents. Oils from the algae are extracted through repeated washing, or percolation, with an organic solvent such as hexane or petroleum ether, under reflux in a special glassware.[10] Enzymatic extraction: Enzymatic extraction uses enzymes to degrade the cell walls with water acting as the solvent, this makes fractionation of the oil much easier. The costs of this extraction process are estimated to be much greater than hexane extraction.[11] The enzymatic extraction can be supported by ultrasonication. The combination "sonoenzymatic treatment" causes faster extraction and higher oil yields. [12] Expression/Expeller press: When algae is dried it retains its oil content, which then can be "pressed" out with an oil press. Many commercial manufacturers of vegetable oil use a combination of mechanical pressing and chemical solvents in extracting oil.

Osmotic shock: Osmotic shock is a sudden reduction in osmotic pressure, this can cause cells in a solution to rupture. Osmotic shock is sometimes used to release cellular components, such as oil.

Supercritical fluid: In supercritical fluid/CO2 extraction, CO2 is liquefied under pressure and heated to the point that it has the properties of both a liquid and a gas, this liquified fluid then acts as the solvent in extracting the oil.[13]

HYPERLINK "http://en.wikipedia.org/wiki/Algaculture" \l "cite_note-supercriticalfluids2-13" \o "" [14] Ultrasonic-assisted extraction: Ultrasonic extraction, a branch of sonochemistry, can greatly accelerate extraction processes. Using an ultrasonic reactor, ultrasonic waves are used to create cavitation bubbles in a solvent material, when these bubbles collapse near the cell walls, it creates shock waves and liquid jets that causes those cells walls to break and release their contents into the solvent.[15]Other methods are still being developed, including ones to extract specific types of oils, such as those with a high production of long-chain highly unsaturated fatty acids.[7]

HYPERLINK "http://en.wikipedia.org/wiki/Algaculture" \l "cite_note-AlgaeHarvestNewMethods-7" \o "" [8][edit] Algae as an energy source[edit] Biofuels productionMain article: Biofuel from algaeCurrently 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, bioethanol and biobutanol may be the only viable method by which to produce enough automotive fuel to displace current world gasoline usage.[16]Microalgae have much faster growth-rates than terrestrial crops. The oil yield per unit area of algae is estimated to be 5,000 to 20,000 gallons per acre, per year (4.6 to 18.4 l/m2 per year); this is 7 to 30 times greater than the next best crop, Chinese tallow (699 gallons).[17]The difficulties in efficient biodiesel production from algae lie 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 methods have largely been abandoned 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 exclusively on open-ponds. Algae in an open-pond environment are subject to wide swings in temperature and pH, and competition from invasive algae and bacteria. Open systems using a monoculture are also vulnerable to viral infection. The open-pond method makes the entire effort dependent upon the hardiness of the strain chosen, requiring it to be unnecessarily resilient (compared to a closed system) in order to withstand the environmental conditions. For a given amount of photosynthetic energy, an algae strain producing relatively high levels of oil will produce relatively less protein and/or carbohydrate, 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.

Some open sewage ponds trial production has been done in Marlborough, New Zealand.[18]A feasibility study using marine microalgae in a photobioreactor is being done by The International Research Consortium on Continental Margins at the International University Bremen.[19]Research into algae for the mass-production of oil is mainly focused on microalgae; organisms capable of photosynthesis that are less than 2 mm in diameter, including the diatoms and cyanobacteria; as opposed to macroalgae, e.g. 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 the raw materials for the system, such as CO2 and nutrients; but it changes those wastes into resources.

The corporations Chevron, Honeywell, and Boeing are starting algae businesses. According to Boeing's technology leader for energy and emissions, Dave Daggett, 'In the past two years, we have changed from algae skeptics to proponents'. [20] The development challenge is to reduce the cost of producing algae oil in commercial volumes, i.e. billions of gallons.

"'In Europe, refiners are producing 1.4 billion gallons a year from rapeseed, soy, and other plants. In all, the world consumed $1.7 billion worth of biodiesel last year. That should grow to $26 billion by 2020, says market researcher Global Insight.'" [20] These figures project an average growth of over 20% per year.

[edit] Hydrogen productionMain article: Biological hydrogen production (Algae)Algae can be used as a biological source for the production of 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 alga), would sometimes switch from the production of oxygen to the production of hydrogen.[21] Gaffron never discovered the cause for this change and for many years other scientists failed in their attempts at its discovery. In the late 1990s 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.

[edit] BiomassAlgae can be grown to produce biomass, which can then be harvested and burned in the same manner as wood, to produce heat and electricity.[22][edit] MethaneThrough the use of algaculture grown organisms and cultures, various polymeric materials can be broken down into methane.[23][edit] SVOThe 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 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 of America that went into effect in the fall of 2006.

[edit] Refining to traditional transport fuelsThere are processes for vegetable oil refining that can produce gasoline, diesel, propane, or kerosene from the oil extracted from algae.