Of all the charges leveled against environmentalists, perhaps the most unfair is the accusation that we are opposed to technological change. Most of the greens I know are fascinated by gadgets (sometimes to the exclusion of better solutions), while some of the people we confront seem terrified by new technologies, and react to them — witness the campaigns against windfarms — with irrational hostility.
But because environmentalists tend to have a feeling for material constraints, we recognize that solutions cannot be conjured out of thin air. In some cases they just don’t appear to exist.
There are two reasons why we make such a fuss about flying. The first is that, even as governments promise to cut emissions, everywhere airports are expanding. In the UK, the government expects the number of airline passengers to rise from 228 million in 2005 to 480 million in 2030. Before long, there will scarcely be a patch of sky without a jet in it. The other is that there are no alternative means of propelling people through the air that are not more destructive than burning ordinary aviation fuel. Or so we think.
The airline companies prescribe two cures that are even worse than the disease. Even before they are deployed commercially in jets, biofuels are spreading hunger and deforestation. At first sight, hydrogen seems more promising. If it is produced by electrolysis using renewable electricity, it’s almost carbon free. The prohibitive issue is storage. Hydrogen contains just a quarter of the energy as the same volume of jet fuel (kerosene), which means that planes could fly long distances only if they were filled with gas, rather than passengers or cargo.
This means that if hydrogen planes are to fly commercially, they need much wider bodies than ordinary jetliners. The Royal Commission on Environmental Pollution says that “the combination of larger drag and lower weight would require flight at higher altitudes” than planes fueled by kerosene.
A technology that is green at ground level becomes an environmental disaster in the stratosphere. Hydrogen’s great advantage — that it produces only water when it burns — turns into a major liability: in the stratosphere, water vapor is a powerful greenhouse gas. The commission estimates that hydrogen planes would exert a climate-changing effect “some 13 times larger than for a standard kerosene-fuelled subsonic aircraft.”
But there is another use for this gas, though I am aware that it will go down like a lead balloon with most of my readers. The word airship elicits a fixed reaction in almost everyone who hears it: “What about the Hindenburg?”
It’s as if, every time someone proposed traveling on a cruise ship, you were to ask: “But what about the Titanic?”
Yes, there was a spectacular disaster — 71 years ago. It has lodged in our minds because, like the Titanic, the Hindenburg was bigger and plusher than any craft built before it, and it was carrying rich and prominent people. The conflagration was witnessed by journalists and broadcast all over the world. It also became the technology’s funeral pyre: the Hindenburg was doomed long before it burnt, as airships were already being displaced by airplanes.
Though the designs have changed, their disadvantages have not disappeared. While a large commercial airliner cruises at about 900kph, the maximum speed of an airship is roughly 150kph. At an average speed of 130kph, the journey from London to New York would take 43 hours. Airships are more sensitive to wind than airplanes, which means that flights are more likely to be delayed. But they have one major advantage: The environmental cost could be reduced to almost zero.