We've often wondered what happened to the GreenFuel/APS algae pilot: now we know.
Getting the whole thing to run smoothly [...] was tougher than expected. GreenFuel could grow algae. The problem was controlling it. In 2007, a project to grow algae in an Arizona greenhouse went awry when the algae grew faster than they could be harvested and died off. The company also found its system would cost more than twice its target.
The closed photobioreactor model used by GreenFuel (and others) appears especially challenging in terms of up-front expense.
I recently posted a link to a paper by Jeff Hassania which discusses the sobering economics of algae.
A GreenFuel Technologies timeline is available at BiofuelsDigest.