There are two big problems associated with extracting liquid fuel from algae: getting the algae out of the water, and then getting the oil out of the algae. The pumps and centrifuges required to do this consume a lot of energy.
A California company, LiveFuels, is trying out a new, less energy-intensive approach: It is feeding the algae to small fish — and letting them do the job of harvesting.
After the fish fatten up, workers catch them in nets and process them for oil (as well as protein for animal feed). This is a bit like gathering whale oil, but the fish are closer in size to minnows. The resulting oil is a lot like the Omega 3 oil packaged into capsules and sold in supermarkets as a diet supplement. But it can be used to run cars and trucks, according to the company.
LiveFuels is trying out the concept at nine five-acre ponds in Texas, where it has been growing algae since 2006. It is testing different breeds of fish, and trying to determine at what stage of life it is most efficient to harvest them.
In addition to producing oil for fuel and protein for animal feed, the process would generate phosphates, from fish bones, for fertilizer. It would also be carbon-neutral (aside from transportation and manufacturing), since the algae absorb carbon from the water.