Plants captured about eight times the energy used by humans worldwide each year, a speaker told last week's NNFCC conference.

So there is ample stored solar energy in biomass to meet global needs in the drive to move away from dependence on fossil fuels, particularly oil, says Bruce Dale of Michigan State University.

He believes cars and lorries could eventually run on "grassoline" derived from crop material.

Rebutting some of what he terms the myths surrounding biofuel production in the "fuel versus food" debate, Prof Dale estimates that the USA's human demand for protein and calories could be met by growing corn on just 5% of the country's arable land.

"We don't grow food," he says. "We grow feed."

Most US farm output goes to feed livestock, whose calorie and protein demands are, respectively, six and 10 times those of humans.

Advances in technology, such as AFEX (ammonia fibre expansion) treatment of cellulose to "unlock" fermentable sugars, can allow that feed to be produced more efficiently in biorefineries making biofuel, he says.

Studies at MSU's Biomass Conversion Research Laboratory show that the area needed to generate large amounts of fuel from biomass - and the overall cost - can be significantly reduced by recovering protein.

The process allows much more to be extracted from a given amount of biomass, so people will not starve because of large-scale biofuel production, stresses Prof Dale. "It's much more likely that food supplies will increase."

Nor will the environment be devastated, he adds. "Actually, environmental improvements are both possible and likely."

But growers merely supplying biomass will see little benefit, he warns. "More than a century of bitter experience has taught farmers that when they simply sell a raw crop, they fall ever further behind."

But biorefineries cost at least $250m, so it is hard for farmers to take part.

Transporting the raw material is another potential barrier. Supply chains are set up for grains, not bulky biomass, and the chemical/fuel industries have no experience of them.

A way forward could be to set up regional biomass processing centres, suggests Prof Dale. These would pre-treat biomass from a range of sources to produce a uniform raw material for fermentation.

Among several advantages, the move could ease transport, simplify contracts and stimulate local development, he says.