Algae ... could supply all U.S. diesel power using a mere 0.2% of the nation's land. In fact, enough algae can be grown to replace all transportation fuels in the U.S. on only 15,000 square miles or 9.6 million acres of land. That's about the size of Maryland.
Biofuels are really a form of solar energy. Because crops convert solar energy into chemical energy in a process called - anyone, anyone - photosynthesis. It's this chemical energy, in the form of oils, that we need to produce biofuels.
According to the UNH report , the more efficient a particular plant is at converting solar energy into chemical energy, the better it is from a biofuels perspective. So in this area algae's the clear winner. In fact, algae does this so well that up to 50% of its body weight can be fat, or the oil needed to make biodiesel. That makes algae the highest yielding feedstock for biodiesel, producing 24 times more oil per acre, on average, than the next leading feedstock - palm oil at 635 gallons/acre/year.
In fact, one company can produce 180,000 gallons of biodiesel every year from just one acre of algae. That comes to about 4,000 barrels, at a cost of $25 per barrel or $.59 per gallon. To put that in perspective, it takes 3,750 acres of soy to make the same amount of biodiesel at a cost of about $2.50 per gallon for 4,000 barrels.The Wikipedia entry on algae biofuel says
Algae grow rapidly and can have a high percentage of lipids, or oils. They can double their mass several times a day and produce at least 15 times more oil per acre than alternatives such as rapeseed, palms, soybeans, or jatropha. Moreover, algae-growing facilities can be built on coastal land unsuitable for conventional agriculture.
The hard part about algae production is growing the algae in a controlled way and harvesting it efficiently. ... Most companies pursuing algae as a source of biofuels are pumping nutrient-laden water through plastic tubes (called "bioreactors" ) that are exposed to sunlight (and so called photobioreactors or PBR). Running a PBR is more difficult than a open pond, and more costly.
Algae can also grow on marginal lands, such as in desert areas where the groundwater is saline, rather than utilise fresh water.
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 (i.e., type of photobioreactor) that is best suited to that strain. There is also a need to provide concentrated CO2 to turbocharge the production.Waste water can be used as a nutrient for biofuel production:
A possible nutrient source is waste water from the treatment of sewage, agricultural, or flood plain run-off, all currently major pollutants and health risks. However, this waste water cannot feed algae directly and must first be processed by bacteria, through anaerobic digestion. If waste water is not processed before it reaches the algae, it will contaminate the algae in the reactor, and at the very least, kill much of the desired algae strain. In biogas facilities, organic waste is often converted to a mixture of carbon dioxide, methane, and organic fertilizer. Organic fertilizer that comes out of digester is liquid, and nearly suitable for algae growth, but it must first be cleaned and sterilized.Future Oil