Greening Air Travel

by Alex Steffen
Air travel seems to be one of the few unsustainable practices for which there is no good fix or substitute. Because of their inefficiency and the high altitudes at which they fly, jet engines are particularly potent greenhouse gas emitters. What’s more, there don’t really seem to be any super-cool engine technologies waiting [...]

by Alex Steffen
Air travel seems to be one of the few unsustainable practices for which there is no good fix or substitute. Because of their inefficiency and the high altitudes at which they fly, jet engines are particularly potent greenhouse gas emitters. What’s more, there don’t really seem to be any super-cool engine technologies waiting in the wings: there’s no hybrid-electric car waiting to replace this SUV.

That doesn’t mean that a whole bunch of people aren’t out there looking for some interim solutions. A whole host of small steps have been proposed: using electric vehicles to taxi; flying directly; using shorter and steeper approaches; shutting down engines during delays; reducing the number of first- and business-class seats;

They probably all have some merit, but they are comparatively minor fixes. Big fixes still await discovery, and finding them has been made more urgent by both the increasingly bad news about climate change, and the large and growing protest movement best symbolized by the Heathrow Climate Camp earlier this month:

For the hundreds of climate-change activists who’ve camped out by Heathrow Airport…there is just one way to reduce aircrafts’ carbon footprint: stop flying. “Aviation is a luxury we can live without,” says a protester named Merrick. Air travel, he says, is booming, multiplying greenhouse gases just as the climate-change imperative starts to bite. “It has to be scaled right back.”

For obvious reasons, the aviation industry would like to find another solution. For perhaps less obvious reasons, I’d like them to succeed: Cheap travel is an essential aspect of growing a global culture of planetary responsibility. Sending large numbers of young people to far-off places (without rifles in their hands) is one of the best hopes we have for developing a truly global culture. At very least, let me say that my own such travels were absolutely fundamental in making me a person who cares about humanity and the planet as whole.

So, what do we do?

Boeing has launched the 787, which conserves significant fuel (using around one-fifth less) compared to its predecessors. Some sources say that other airplane improvements already on the drawing boards might combine with operational efficiencies to slash another half of the greenhouse gas emissions of the most up-to-date planes within the next three decades.

Unfortunately, the old, jet-fuel-guzzling planes may remain in use for decades — and the number of people flying is expected to grow to at least four times (some estimate six times) in the same time period. Boeing itself estimates the size of the global airplane fleet will double by 2026.

Some positive impact could be made immediately by including airplane emissions in carbon pricing and regulation schemes (international agreements currently exclude them). That would create financial incentives for change. A modest interdisciplinary effort has been launched to encourage research into greener flying. The chief executive of the International Air Transport Association, Giovanni Bisignani, has called for zero emissions flights…by 2050.

Boeing has partnered with the Brazilian biofuels firm Tecbio and is hot after an algal-based jet biofuel:

“You would have to plant an area the size of Florida with soy beans to provide a 15 percent blend of jet fuel” for the whole U.S. aircraft fleet, said Dave Daggett, who heads energy and emissions research at Boeing Commercial Airplanes’ product development unit. “Clearly that’s not going to be appropriate.”

…It would take a lot of land to produce enough crops like soybeans to propel fuel-hungry jets. The increasing use of crops like corn and soybean to produce ethanol and biodiesel is already stirring a controversy of its own. Some argue these biofuels are creating a negative impact on the environment and on food prices.

The solution could lie in the algae, experts say. These slimy aquatic creatures not only absorb great quantities of carbon dioxide during their lifetime, but they are also the source of energy-rich oil that can be turned into fuel. Lurking in the depths of their ponds, they take a lot less space than horizontal conventional above-ground crops — and they can live in brackish water. A huge algae bio-reactor — a series of chambers or ponds outfitted to boost growth — could supply more fuel in less space than other plants. “Instead of needing all of Florida, you could provide the whole world’s fleet with biojet fuel if you had a bio-reactor the size of Maryland,” Daggett said.

The obvious problem is that while slime-fuels are still a long way off, the problems of global warming are already here. (And even if a Maryland-sized collection of biotech ponds was certain to be a good idea — and there are real reasons for skepticism — there are even more reasons for skepticism about crop-based biofuels, which substitute an unsustainable supply of biofuels created through factory farming and soil mining for an unsustainable supply of fossil fuels… but that’s another thread).

Nonetheless, it’s encouraging to see at least some efforts at thinking outside the cockpit.