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Take One Cup of Algae ...

June 17, 2012 - References to algae as a source of biofuel have been on the upswing, so I thought it might be time to find out if there's anything to it.  Climate skeptics have done the requisite piling on, accentuating their disbelief with snide comments alluding to "pond scum."  Funny thing is, that's exactly the kind of algae that renders the best fuel!  With over 100,000 species to choose from - kelp is one of them - it's fortunate indeed that the one that seems to work best can literally be found in just about everyone's backyard.  When we lived in North Carolina, we had a portion of a former farm pond on our property, which extended into our neighbor's yard.  Because we left the trees and grasses surrounding the pond in place, we had no problem with algae.  Our neighbors, on the other hand, had cleared away trees and undergrowth, allowing the sun to shine directly on their pond for hours.  Algae loves sunshine, and they had a pondful to prove it.

Right now you're thinking, if we're surrounded by plants that nobody wants that can be turned into fuel, what are we waiting for?  You'll be surprised to learn, as I was, that algae-based biofuels research began all the way back during Jimmy Carter's administration.  That's when scientists figured out that the kind we see everywhere is the best kind for making fuel.  Since then, it's also been determined that placing algae biodiesel plants near oil refineries makes a lot of sense, because carbon dioxide is the other element (along with water) that fosters the growth of algae.  That means the CO2 given off by oil refineries is recycled when used by industrial algae farms, thereby reducing pollution.

Here's where it all becomes somewhat amazing: a 100 acre algae biodiesel plant could potentially produce 100 million gallons of biofuel a year.  Of course, it should be pointed out that a plant such as this does not consist of a 100 acre pond, with one guy skimming algae off the top with a large sieve.  Why doesn't it consist of this?  Because bad weather can stunt algae growth, and contamination can find its way into the algae.  In addition, the water in which algae grows must be kept at a certain temperature for optimum growth, something difficult to achieve in outdoor conditions.

A biodisel plant is more likely to utilize vertical growth/closed loop production, in which algae is contained in clear plastic bags, so that the sun can penetrate both sides.  The bags are "stacked" on hangers, as part of a bioreactor system.  Yes, the system is outdoors, but it's protected from rain by a cover, and from contamination by the bags.  Closed-tank bioreactors are another form of biodiesel plant.  This entirely indoor operation allows for the growing of algae under ideal conditions.  This encourages high yields from daily harvests.  A third type of plant, a variation on the closed-container plant, utilizes fermentation in order to hasten growth.  Algae is fed sugar under carefully controlled conditions.  This plant design, amenable to use anywhere in the world, would be highly dependent upon sugar availability.

In whatever way the algae is grown, once it is harvested, the oil contained in the plant must then be expelled by means of an oil press.  You see, half of algae's composition, by weight, is lipid oil - the reason it has been the subject of decades-worth of research!  Expelling the oil found in algae with a press allows for a 75 percent extraction rate.  The hexane solvent method, when combined with pressing, brings that rate up to 95 percent.  Since I don't know anything about hexane, including whether or not it causes cancer, I don't know how sustainable this method is.  A third method, which is both labor intensive and costly, is known as the supercritical fluids method.  While its extraction rate is 100 percent, the added work and expense make it the least popular.

When can we expect to buy algae-based biofuel?  The day may not be far off.  As an alternative to food-based biofuel, it's time may well have arrived.


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