The Truth about Carbon-Neutral Flights

Given the climate-change activism that’s intensifying around air travel’s dependence on fuel, you’ve probably seen a lot about “carbon neutral” flights lately, along with reports of planes that can be powered entirely by something called “biofuel.” The idea behind both is obvious: People want to add as little carbon as possible to the atmosphere. And the idea that we can take carbon neutral flights is true—but it’s more nuanced than you might think.

What Are Carbon-Neutral Flights?

Here’s a bit of clarification on the issue, and what travelers should know about carbon neutral flights.

Biofuels (which are fuels made from plants, and therefore not fossil fuels) do not contribute less carbon than regular petroleum-based fuels when they burn. They do, however, absorb carbon when they’re growing—offsetting the new carbon that’s created when they burn. So: Flying a jetliner on biofuel doesn’t reduce the amount of carbon injected into the atmosphere in itself; rather, it’s an accounting process.

It might surprise some people that making a flight carbon neutral is a mathematical rather than an engineering process. Simply put: The reason biofuels can be called carbon neutral at all is that while they were growing the plants used to make the biofuels generated enough oxygen and took in enough carbon dioxide to offset the carbon later dumped into the atmosphere. In photosynthesis, plants, algae, and some microbes absorb carbon dioxide, water, and solar energy, and convert them into oxygen and sugars. The plants, algae, and microbes use the sugars to build their structures and do whatever else they do. So when you convert those plants, algae, and microbes to a useful fuel and burn them in a jet engine, you’re just returning the amount of carbon that the sources originally took out. But unlike fossil fuels, biofuels are renewable: After you harvest a batch, you grow another.

How likely is it that this changes? Present technologies offer no practical way to power transport aircraft other than by burning fuel containing carbon in the atmosphere, regardless of how that fuel is produced. Battery/electric and solar/electric flights may be practical for short-haul or specialized applications, but if you want to fly from New York to California, the only way to get you there right now is by burning something. If you could burn pure hydrogen rather than hydrocarbons you could (in theory) fly carbon neutral, but hydrogen requires very large and very heavy tanks. For now, it’s fly by adding carbon to the atmosphere, or don’t fly.

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But any time you can substitute a ton of biofuel for petroleum, you’re coming out ahead. And the atmosphere doesn’t care whether you burn that ton in an airplane or in a truck or in power plant.

Carbon Taxes on Passengers?

How likely are airlines to switch to biofuels? Considering that petroleum generally works better than biofuel for aviation, airlines are likely to treat the problem not by flying on biofuel but instead by paying some sort of carbon tax that offsets emissions and incentivizes other industries to switch to biofuel. That keeps everybody happy: The airlines enjoy top efficiency, and the planet gets a break.

Biofuel almost defies precise economic analysis. It may look good in isloation, but not so much if it requires lots of water or if it displaces food crops. It may take a lot of energy to harvest and process. Biofuel economics could provide lifetime job security for lots of economists and accountants.

If the system works reasonably well, the net result will be that people who fly will pay higher fares in order to pay those taxes that offset the carbon. Governments can also nudge travelers along by taxing short-haul flights in areas with good alternative high-speed rail service, but that’s not likely to happen in the U.S. or Canada any time soon. What’s most likely to happen first is that airlines see a carbon tax—which could certainly affect your wallet, but also the planet.

More from SmarterTravel:

• 12 Ways to Travel Sustainably and Still Have a Great Vacation
• 11 Endangered Bucket List Destinations (and How to Visit Them Responsibly)
• Climate Change Travel: The World’s Most Endangered Places

Consumer advocate Ed Perkins has been writing about travel for more than three decades. The founding editor of the Consumer Reports Travel Letter, he continues to inform travelers and fight consumer abuses every day at SmarterTravel.