How much fuel can we grow? How much land will it take?

wo very frequently asked questions.

Frequently given answers: "Not enough" and "Too much."

Are they the right answers?

Seeking to bridge the seemingly unbridgeable gap, there's widespread fascination with high-yielding oil crops, particularly oil-bearing algae (though it's still at the laboratory stage), with oil palms running second.

It seems obvious that the highest-yielding crops will produce the most energy from the least amount of land.

But high yield is not the only factor in farming, and it may not always be the most important factor. It can make more sense for a farmer to grow a lower-yielding crop if it has more useful by-products or requires fewer inputs or less labour or it fixes more soil nitrogen for fertiliser or it fits a crop rotation better. Or if it fits an integrated on-farm biofuels production system better. The how-much-land estimates don't seem to include such things as integrated on-farm biofuels production systems. There are quite a lot of things they don't include.