The Virgin Group chairman proposed "starting grids" be set up at major airports which would allow a plane to be towed from its stand by a small tug closer to the runway before takeoff, reducing the time engines are running.

This would reduce fuel consumption and on-the-ground carbon emissions for Virgin Atlantic aircraft by more than 50 per cent ahead of take-off at London's Heathrow Airport and almost 90 per cent at New York's John F Kennedy airport, Mr Branson said in a statement.

So now we know: Richard Branson doesn't read the Guardian. On Thursday, it published an extract from my book showing that there are no foreseeable substitutes for aviation fuel (kerosene) that don't currently cause more harm than good. A few hours later, Branson announced that he would be investing £1.6bn in technologies intended to reduce climate change. First among them would be alternative fuels for aircraft.

And that, I'm afraid, is that. As the Intergovernmental Panel on Climate Change discovered, "There would not appear to be any practical alternatives to kerosene-based fuels for commercial jet aircraft for the next several decades." There is, in other words, no technofix. The growth in aviation and the need to address climate change cannot be reconciled. In common with all other sectors, aviation's contribution to global warming must be reduced in the UK by some 87% if we are to avoid a 2C rise in global temperatures. Given that the likely possible efficiencies are small and tend to counteract each other, an 87% cut in emissions requires not only that growth stops, but that most of the aeroplanes flying today be grounded. I realise that this is not a popular message, but it is hard to see how a different conclusion could be extracted from the available evidence.

Helen mentioned something about Kerosene from light, sweet crude actually running out in a few years' time, especially on the current consumption trends. So, if Kerosene does run out, Monbiot will get what he wants and planes will be grounded.

Those whom the Gods wish to destroy They first make mad. -- Euripides

Ethanol, being an alcohol with similar properties to methanol, is also unsuitable as a jet fuel for similar reasons. Ethanol's energy density and specific energy are too low, and would thus limit aircraft range and maximum payload.

At low power settings ethanol jet engines would emit acetaldehyde (C2H4O) again bringing localised health problems around airports, especially for ground support staff.

Ethanol's flash point of 12°C is even lower than methanol's, so it would not meet jet fuel specification requirements, and would present major safety dangers.

So Monbiot was right for the worng reasons.

The study evaluates other possibilities, too. I summarise:

• Biodiesel: as additive, it raises the cloud point (Monbiot directly lifted a sentence from the study here) as well as the freezing point, but there is research into refined biodiesel blends for which the effects are less. Fatty acids in biodiesel can be oxydised, but the resulting storage problem is minimal when it is a 10% additive. Production cost is significantly above that for oil-derived jet fuel even at the lower limit, potentially multiple times of it. There is also the issue of conflict with the needs of road traffic (which as afew et al calculated already can't be supplied from domestic biodiesel production).

• Methanol: problems as for ethanol.

• Synthetic kerosene: poor lubricity due to lack of sulphur and low aromatic content, but this can be mitigated with additives. Effect of lack of aromatic stuff on turbines must be investigated with tests. Somewhat lower energy density, impacts long-range flights. Too small domestic capacity for biofuel production (they calculate 10% of present demand). This is a very expensive option.

• Liquefied methane: needs special engines, expensive, methane leeaks during the production chain or in the air have greenhouse effect [and for lack of a 'methane cycle', like the carbon cycle for CO2, this can't be ignored for biogas-methane].

• They speak of liquefied H2 too. Significant aircraft modification needed. No solution yet for reducing nitrogen oxide emissions (solutions for kerosene-burning engines not applicable). Very expensive.