Algae harvesting advances in New Mexico

By Jerry W. Kram | June 17, 2008
Web exclusive posted July 15, 2008 at 12:48 p.m. CST

The Center of Excellence for Hazardous Material Management in Carlsbad, N.M., successfully performed what it called a "commercial-sized" harvesting experiment at its pilot-scale algae pond. The algae was extracted from 12,000 gallons of water, approximately half the contents of the pond, and its oil content was used to produce biodiesel.

According to Doug Lynn, the center's executive director, several different membrane and chemical methods have been used to extract the algae. Previous work at the center using filters to concentrate the organisms proved unsuccessful. Lynn was especially pleased with a method call flocculation which uses chemicals to make the algae clump and settle out of the water. "It results in a thick paste a lot like peanut butter," he said.

The pond produced two grams of algae for each liter (0.26 gallons) of water. Lynn said two grams per liter is considered to be quite a dense algae culture. "The water looked like pea soup," he said. While two grams, which is about the weight of a dime, may not seem like a lot, Lynn said the algae will replace itself in about one day, allowing for continuous harvesting. "The seemingly small quantity extrapolates out into a huge amount of biomass in what you would consider a normal growing season for a land based crop," he added.

The oil content of algae is about 30 percent on a dry weight basis. The algae paste that was collected was still about 90 percent water. "We are encouraged because the algae maintained a fairly high oil content," Lynn said. "When we extracted the oil it yielded a very high quality lipid. We transesterfied those lipids and those methyl esters are now being examined by an ASTM certified lab."

The Center of Excellence for Hazardous Material Management raises a marine species of algae in brine from underground aquifers to prevent contamination from local freshwater algae. Early in the tests an algae predator became established in the pond but was easily controlled. Analysis of the algae paste showed a small number of diatoms had grown in the pond and the some foreign organic matter had blown into the pond from the surrounding area, but overall the algae culture was remarkably pure.

Harvesting algae and extracting the oil are significant challenges to economic oil production from algae, Lynn said. "We have to come up with a cost effective means where we can get the algae out of solution," he said. "The extraction, though, is still the biggest challenge for this industry right now. Regardless of what you read, there are some extraction methods out there that work quite well but are simply not economically viable." The center is testing both chemical and mechanical methods for extracting algae oil. Lynn said he is cautiously optimistic that the right combination of harvesting and extraction techniques can be found that will produce algae oil for about $80 a barrel.
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