Monday, December 18

Using Algae as a Fuel Source

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Algae as the ideal bio-fuel source

My thoughts sometimes lead me to want to be a farmer. What would I raise? Pond scum.

There are many varieties of algae. The best one to raise for conversion to diesel is Spirulina, in my opinion. It is durable, requires little assistance to grow, and is not as susceptible to contamination as other varieties.

On a side note, many people refer to the product made from algae, as well as from several other sources, as “biodiesel”. This is a misnomer. The diesel that is refined from crude oil has a biological origin. To be accurate, virtually all diesel is biodiesel.

There are two common approaches to growing algae to be turned into diesel. The most common method is to dig shallow ponds, stock with a “starter” supply of algae, and let it grow. Once it has covered the pond (this happens rapidly) it can be harvested by skimming the algae off the surface. It only grows on the surface, to a depth of ½ inch or so, which means there is no need to construct a pond deeper than a few inches. It grows so fast that as much as 30% of the crop can be harvested every day. In a cold climate, the operation can only run during the warm months. In the south, though, the algae can be grown and harvested outdoors for eight or nine months a year.

The other method is to grow the algae indoors. In a heated building, this type of operation can run year-round. It is more expensive to design and build, and operation is more material and labor intensive, but it can operate 365 days a year.

Whichever method is chosen to grow the algae, processing is a fairly simple matter. The algae is skimmed from the surface and squeezed to extract as much water as possible. Then the fat (which is what you want) is separated from the wet mass. There are a variety of methods available for doing this. There are chemical processes that will yield the highest return, but the machinery is expensive and complex to operate. The simplest process is to compress the algae as much as you can, then separate the fatty part, which will float on water. Some varieties of algae will yield fat content between 50% and 70% by weight. The fat is then shipped to a refinery and sold.

This is not pie-in-the-sky, futuristic, dreamworld technology. It is being done today in several places. PetroSun has several big projects underway, and there are others. There are a number of designs out there for projects of this sort, some involving large outlays of capital to get stated. Right now I am looking at creating a system that uses troughs inside a building with slow-moving shallow water. Underneath the water will be perforated PVC pipes carrying carbon dioxide, which is what the algae need to grow, along with sunlight.

Raising algae to produce diesel is practical, feasible with existing technology, profitable (if the business planning is done correctly), and it is definitely green and renewable. If you are really concerned with environmental issues and want to end up with little or no waste, the remaining product after the oil-producing content has been removed can be crushed and dried and used for animal feed.

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