As the Guardian reports, DARPA, the Defense Advanced Research Projects Agency

says it is just months away from producing a jet fuel from algae for the same cost as its fossil-fuel equivalent.

This is astounding news, and I’d like to know what assumptions are operating here.

As I’ve discussed previously here, there’s  evidence that the cost of supplying carbon dioxide for the algae is not always figured into balance sheets for oil-from-algae schemes. My understanding is that atmospheric carbon dioxide alone does not provide a sufficient growth rate of algae, so it must be provided.

And an approach such as using “free” carbon dioxide from power plants to grow algae is only an idea…it’s never been attempted, to my knowledge, even on a pilot scale. Nevertheless, such approaches are often assumed to be feasible in cost estimates of this type.