Algae for Biofuel Production

Investing in Algae Biofuel says

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

While Solazyme's exact species and strains of algae are a closely guarded secret, Dillon assures that the company uses several obscure strains as their workhorses. "You're lucky if you can get 10 papers to come up on PubMed that name them," he smiles. "We look at algae that have been isolated from all over the world," from Irish peat bogs to equatorial swamps. For feedstock, Solazyme's algae eat anything from waste glycerol and sugar cane to sugar beet pulp and molasses. "You can use just about anything," Dillon says, as long as the feedstock is high-volume and low-cost.

Dillon says that Solazyme's algae produce some hydrocarbons, but mostly triacylglycerides. To make their biodiesel, the company takes the glyceride backbones from these fats and adds methanol. To get renewable diesel, they take that fatty acid methyl ester and "hydrotreat" it, stripping off oxygens and saturating the molecule with hydrogens. That gives them a straight-chain alkane, not much different from the diesel that flows from gas pumps into millions of diesel engines everyday across America. In nature, algal cells are rarely above 30% oil. Yields of 50-60% oil per gram of dry weight of algal cells are considered excellent. Solazyme's algae, however, stores 75% oil per gram of dry weight. "We have incredibly good scientists here," Dillon says.

Dillon says that he expects Solazyme to be producing algal biofuel at "demonstration levels of tens to thousands of gallons" per day by 2009, and aims to be producing its fuel products at commercial levels by 2011. "The scalability is not something that frightens me too much," he says.