Nick Hollinghurst - promoting social democracy as a Liberal Democrat and working for a greener world!

The Climate Emergency has finally landed - and there will be worse and more frequent visits in the future. However the UK government's "net-zero" aviation strategy - first called in 2021 - has yet to take off. Widely described as a "pie in the sky", it depends on almost unavailable and grossly unsustainable alternative fuels in the immediate future and vast supplies of hydrogen to fuel yet-to-be-developed propulsions systems later on.

The last time a technically ignorant and cloth-eared UK government tried to foist hydrogen technology onto aviation it led to the tragic of the loss of the airship R101 on its maiden flight to India in 1930. It got no further than Northern France and burst into flames and crashed with only 6 survivors out of the 54 on board. The Air Minister at the time, a number of senior government officials and most of the design team were among the fatalities. The German Nazi government followed up in 1937 with its own disaster, with 36 people killed. Although their airship, the Hindenburg, successfully crossed the Atlantic it caught fire on arriving in New Jersey.

A common factor was that both governments were trying to rush the completion of prestige projects without sufficient technological understanding by the decision makers.

The UK government re-announced its "Jet Zero Strategy" on 19th July 2022, with a target of cutting carbon dioxide emissions from civil aircraft to net zero by 2050. This depends on the usual mix of mitigation, "green fuel" and magic technology. The mitigation includes the planting of trees somewhere - but will they now survive in the higher temperatures? - the extraction of CO₂ from the atmoshpere - but money, energy and repositories are needed to do that - and of course the famous hydrogen and its associated technology.

Hydrogen is currently produced from natural gas just as it has been for a century or so in the water-gas process - but this produces a great deal of CO₂. It can also be produced by electroysis of water using surplus electricity from solar panels or from wind turbines, but this is not a very efficient process and the hydrogen is difficult and expensive to compress and store. It can even slowly diffuse through stainless steel. A hydrogen fuel, precisely because it does not produce carbon dioxide, would not perform well in either a jet engine, a turbine or an internal compustion engine. It could, if highly purified, be used to produce more electricity via a fuel cell but this would then need an electric motor to power a propellor.

Although the production of hydrogen from surplus wind or solar energy, despite the inefficiency of the process, is sensible, the most economic subsequent use of the hydrogen would be as an additive into the natural gas network (up to 20%) over the next 10 years or so.

It is difficult, despite slick words and pictures, to envisage any practical or effective way that hydrogen could usefully be an aviation fuel. Besides, even if you could miraculously make aviation "carbon-neutral", there would still remain the condensation trail air heating problem, since this is due to the emission of water vapour and its condensation at high altitudes, quite unconnected with any carbon dioxide. If a plane were to use hydrogen fuel in place of hydrocarbons then water vapour would be produced in greater quantities.

Not only is the condensation trail heating effect of aviation nine times greater than the greenhouse gas heating effect of its CO₂ emissions, but also it is often neglected in calculation the atmospheric damage of aviation - which, when correctly calculated, is truly enormous.

There is also the additional disturbance to atmospheric gas chemistry caused by NO_x emissions.

Altogether, aviation now has to be viewed as a highly damaging and polluting form of travel. Aviation will have to be significantly reduced - and quickly. It is hopeless trying to pretend, as the UK government is doing, that we can carry on not only with the present number of flights, but with the current increasing trend being maintained. It is unviable under any circumstances.

It was good to have air travel accessible to the many - unlike 40 years ago when it was only for the wealthy few - and it enabled people to enjoy long distance travel to exotic locations for holidays. But now we are more aware of the dangers of uncontrolled climate change and know we have to make drastic changes to our lifestyles and behaviour.

An update of Hertfordshire County Council's Sustainable Herts Strategy presented to this week's Environment Cabinet Panel reveals that this crucial strategy almost completely ignores the negative effect that the council's growth proposals will have on carbon emissions and biodiversity across Hertfordshire.

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