Either a perennial with oily fruit (someone mentioned palm oil down below), or something where you can relatively easily use the entire plant. The idea I keep coming back to is algae bred or engineered for oil content, but I'm not actually sure how feasible that is.
> Mayali says that growing phytoplankton outdoors with natural light and finding a less energy-intensive method of powering production would help microalgae-based diesel compete.
I'm sorry, were they measuring the carbon footprint of growing algae by what it takes to grow it inside with artificial light?