Air New Zealand has come clean on the sustainable biofuel it plans to flight test with Boeing and Roll-Royce later this year - and it will be produced from jatropha, an inedible plant that can grow on arid land. Air NZ says jatropha meets its three "non-negotiable" criteria for a bio-fuel: it must be environmentally sustainable without competing with food sources; it must be at least as good as today's jet fuel; and it should be significantly cheaper.

Photo: Maxo India

A single RB211 engine on an Air NZ 747-400 will run on jatropha-based bio-jet fuel in a flight test planned for the fourth quarter of this year. The airline is sourcing the jatropha oil for the test flight from "environmentally sustainable" plantations in South Eastern Africa and India. The land used to grow the jatropha "was neither forest land not virgin grassland within the previous two decades", and the soil and climate is not suitable for food crops, says Air NZ.

The Auckland-based airline expects to use at least 1 million barrels of sustainable fuel a year by 2013 - 10% of its annual needs - and says it has offers from organisations in Asia and African willing to guarantee enough jatropha oil supply to meet that target. And it is expecting bio-jet fuel from jatropha to be 20-30% cheaper than kerosene. The airline is also investigating algae-based biofuel.

There is a lot of excitement, and hype, around jatropha, a fast-growing shrub with inedible seeds and a high oil yield - 200gal per acre compared with 55gal for soy and 110gal for canola. It can grow in infertile or exhausted soil and needs little water. There are cautions being sounded: the plant is midly toxic, requiring careful handling; the yields are still unreliable; and harvesting is labour-intensive. But a lot of work is underway to overcome these drawbacks.