Kansas State University researchers claim that optimistic projections of algae biodiesel production are not realistic.
“We found that phycologists — algae scientists — maintain that some popular estimates of producing 200 to 500 grams of algae per square meter of open pond per day weren’t feasible because there’s simply not enough sunlight coming through the atmosphere to do so,” Pfromm said. “Unless we can change the sun, such production is physically impossible — and the hard numbers prove that. Most economists wouldn’t necessarily recognize this as an issue in a business plan because it’s dictated by physics, not finances.”
The team used a more realistic, yet still optimistic, production number — 50 grams per square meter per day. They determined it would take 11 square miles of open ponds making 14,000 tons of algae a day to replace 50 million gallons of petroleum diesel per year — about 0.1 percent of the U.S. annual diesel consumption — with an eco-friendly algae alternative.
The cheaper open pond approaches face problems with water evaporation rates (big underground water reservoirs are already getting depleted), invasion by organisms that eat algae, and invasion by algae species that can out-compete any species ideal for oil production, whether natural or genetically engineered.
Natural algae produce oil best when they are nitrogen-starved.
“Algae don’t make oil out of the kindness of their hearts. They store energy as oil when they are starved for nitrogen so they can make more algae in the future,” Pfromm said. “The end result is the yield isn’t that high because we can either stress the algae to produce more oil or let them reproduce very efficiently — not both.”
Lots of selection for higher production crops amounts to selecting away overhead aimed at protection against predators and competitors. The same will apply to genetically engineering algae for higher oil production. So methods to keep out other species will need to be developed for that are open. I think this is a very hard set of problems to solve.