Algae As A Biodiesel Feedstock

Chlorella SP are single-cell green algae that reproduces quickly with only carbon dioxide, water, sunlight, and a few minerals.

Chlorella is a genus of single-celled green algae, belonging to the phylum Chlorophyta. It is spherical in shape, about 2 to 10 μm in diameter, and is without flagella. Chlorella contains the green photosynthetic pigments chlorophyll-a and -b in its chloroplast.

Through photosynthesis it multiplies rapidly requiring only carbon dioxide, water, sunlight, and a small amount of minerals to reproduce.

The name Chlorella is taken from the Greek word chloros meaning green and the Latin diminutive suffix ella meaning “small.

The following is an excerpt from “Algae as a Biodiesel Feedstock: A Feasibility Assessment”, by Ron Putt.

Fuels from algae oil could either be biodiesel, which is a methyl ester produced via a straightforward reaction between most any vegetable oil and methanol, or straight (so called “green”) diesel, which is essentially the same as petro-diesel. Microalgae, as plants, store energy as carbohydrates and lipids, and these lipids are similar to those produced by row crops such as soy. Algae lipids can be extracted via processes similar to those used for soy, and sold to biodiesel producers, who are currently lipid­ feedstock-limited. The meal remaining after extraction is rich (about 50%) in protein, and can therefore be used as a high-value ingredient in animal feeds.

Algae-To-Biodiesel

The seminal work on algae-to-biodiesel was performed in the wake of our nation’s first energy crisis (mid 70’s to mid 90’s) by the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) in Golden, Colorado, whose original mission for the algae project was carbon dioxide mitigation (Sheehan 1998).

During the early years of their program they discovered that some of the algae species were capable of producing 50% or more of their weight in lipids, under the proper growth conditions, and the program therefore transitioned to algae-to-biodiesel.

The program included laboratory and field work to identify the most promising species and to optimize growth conditions for maximizing lipid yield per acre. Their key findings were that (1) high-rate open ponds, capable of producing 30 grams of algae per square meter per day, at 30% lipids content (yielding 4,000 gallons of biodiesel fuel per acre annually), would be the only capital-cost effective approach (as compared with a variety of enclosed photobioreactors) for producing lipids for transportation fuels, (2) native species of algae should be used, since they would take over the ponds anyway, and (3) the price of biodiesel produced from algal lipids would be in the $2-4 per gallon range. The program was shut down in the mid-90’s when gasoline returned to a dollar per gallon.

Read the complete feasibility assessment here.