Here is the problem with this statement. The article states this technology was abandoned in the 60's because it was too expensive compared to traditional drilling. The only reason why algae is "profitable" is because congress and the environmental lobby has artificially increased the price of oil production and gas refining. If we would drill more of a relatively free natural resource, oil would be a commodity it should be and Hawaii beaches won't be turned green with algae.
Your analysis is very simplistic. The current cost of fuel is driven more by increased demand, than by congress. You also neglect technological progress, which has most likely lowered the cost of biodiesel-farming relative to drilling.