U.S. researchers have developed a highly efficient way of creating biofuel out of crop waste.

The researchers at the University of Wisconsin-Madison developed a chemical process that converts gamma-valerolactone, a derivative of the woody and grassy parts of plants, into fuel.

The chemists say the resulting biofuel, called alkenes, is powerful enough to be used as jet fuel, unlike ethanol which lacks the energy density needed for such an application.

Converting crop waste, the non-edible parts of food crops, into biofuel is especially attractive because it doesn't require converting food crop land into crops specifically for biofuel.

The process starts with gamma-valerolactone (GVL), a colourless liquid with an herbal smell that is used as an additive in perfumes.

The researchers developed a process using metal catalysts that converts GVL into jet fuel. Their research appears this week in the journal Science.

The process does give off carbon dioxide, a greenhouse gas, but the researchers point out that all biofuel production processes do and their process produces a pure stream of carbon dioxide that's suited for underground sequestering.

"With very minimal processing, we can produce a pure stream of jet-fuel-range alkenes and a fairly pure stream of carbon dioxide," said Jesse Bond, a post-doctoral researcher at UW-Madison, in a statement.

The process has only been tried on the laboratory scale, but it could be adapted to an industrial setting, if the cost of making GVL could be brought down.

"The bottleneck in having the fuel ready for prime time is the availability of cost-effective GVL," said David Martin Alonso, also of UW-Madison.

"Once the GVL is made effectively, I think this is an excellent way to convert it to jet fuel," he said.