The Green Report: The Newest Innovations in Sustainable Travel

In our green issue, we take an in-depth look at the aviation industry’s efforts to reduce its environmental impact. Learn about the latest innovations in sustainability, both in the air and on the ground. Plus, easy tips for sustainable travel practices during every part of your journey.

Aviation Is Reducing Its Environmental Impact

Airlines worldwide are committing to reducing their environmental impact, with many setting targets of net-zero carbon emissions by 2050. This requires new technologies, changing how aviation does business—and dramatically reducing their use of conventional jet fuel.

By an enormous margin, the environmental impact of aviation comes from direct jet-fuel burn. Everything else is almost a rounding error.

As one example: United Airlines’ 2021 direct emissions were some 21.37 million metric tons, of which 21.25 million were the gross emissions from mainline aircraft. Of the remaining approximately 117,000 tons, roughly two-thirds came from facilities including maintenance, engine testing and so on, while a third came from mainline ground vehicles.

Other initiatives, such as removing single-use plastics onboard or reducing food waste, will make a small and sometimes locally significant difference. But if any changes add weight to the cabin, that’s unlikely to be an environmental win.

One critical task is to reduce this fuel burn. Part of that is lighter planes, using more carbon fiber and advanced metals.

That’s why, for most passengers, this sustain-ability revolution will be almost invisible: You’ll be flying in lighter and more efficient planes with more sustainable service, but seats and cabins will mainly evolve from what we see today rather than being revolutionary changes. The big question is how to power the airplanes of the future—and an even bigger one is how to reduce the impacts of the airplanes of today, which will be flying for decades to come. New, lower-emission power sources such as battery-electric, hybrid and hydrogen aircraft are on the horizon for the 2030s or 2040s. Early indications and aviation research trajectories suggest that these will, at least initially, be most applicable to shorter routes of an hour or a few hours, leaving long-haul flights primarily powered in the way they are now: by jet fuel. But it may not be the same kind of jet fuel.

Jet Fuel of Some Form Will Still Be Needed for Decades

Whether a 600-passenger Airbus A380 jet or a 42-seater ATR turboprop, modern commercial airplanes are powered by burning jet kerosene. This is often referred to as Jet A-1, the specification for the exact mix used in most of the world. In many ways, this fossil fuel is similar to the diesel fuel used in many trucks and automobiles, and it is refined and processed from crude oil.

Like burning fossil fuels, jet engines contribute to global warming by emitting greenhouse gases. Jet-engine exhaust comprises roughly 70 percent carbon dioxide, just under 30 percent water vapor, and less than one percent each of carbon monoxide, nitrogen oxides, sulfur oxides, volatile organic compounds, atmospheric particulates and other trace components. The water vapor in the exhaust, together with some of the other components, also creates contrails and contributes to cloud formation, which has additional warming effects.

To calculate the climate-change impact of all these emissions in terms of global warming, they are usually converted to carbon-dioxide equivalents. But it’s not just the emissions that are a problem: It’s where they are emitted and how they interact with the atmosphere. While the science behind calculations is complex, recent studies suggest that the impact of the non-CO2 emissions—essentially, particulates, contrails and cloud formation—could be around half to two-thirds of the total warming impact of aviation. To reduce this impact, aviation uses three key technologies: more sustainable fuels like biofuels, hydrogen via combustion or fuel cells, and battery-electric or hybrid aircraft.

Sustainable Aviation Fuels

The solution with the most significant impact over the next 30 years will be using more sustainable aviation fuels (SAFs). These are, in essence, kerosene created from non-fossil-fuel feedstocks. These include processing biomass, plants, sugar fermentation, alcohol and waste products into a biofuel.

Their sustainability stems either from reduced emissions or a sequestration process during production. For example, municipal solid waste converted to SAF would otherwise have generated methane in a landfill. At the same time, plant-based SAF absorbs carbon dioxide during growth, which is emitted when burned. However, none of these are zero-emission fuels, with even the greenest fuels estimated to leave around 20 percent of the current emissions footprint compared with fossil kerosene. On the plus side, some of the non-CO2 effects are reduced: The chemical structure of SAFs differs from fossil kerosene, with fewer “aromatic” impurities such as sulfur, meaning that its overall climate impact is lower. The big barrier to SAFs is production. Researching, developing, certifying and industrializing takes years and significant investment. Airlines are doing an increasingly good job in signaling demand to the market. However, governments will still likely need to step in to speed up development and encourage greater investment.

Hydrogen and Hydrogen Fuel Cells

The new aircraft of the 2040s and beyond will most likely be powered by hydrogen, either by direct combustion (burning hydrogen in jet engines) or through electric engines powered by hydrogen fuel cells. Airbus is betting on hydrogen technology: It’s using the original A380 test-bed aircraft to trial hydrogen engines fixed to the back of the fuselage.

Hydrogen is a lot less energy-dense than kerosene, so more fuel storage will be needed onboard. That will require a change in how aircraft are shaped and technological advancements to supercool the hydrogen into liquid. Early suggestions include large fuel tanks along the fuselage or within the cabin, or a different shape like blended-wing-body aircraft.

Since most hydrogen today is produced using coal or gas, an industrial system is required to produce it in a low-carbon way. There’s also the Hindenburg factor: People hear “hydrogen” and think “boom,” and that’s something aviation needs to figure out. And if it is looking at hydrogen combustion rather than fuel cells, it will still need to account for the contributions to global warming from contrails and cloud formation.

Battery-Electric and Hybrid Aircraft

Today’s batteries aren’t powerful enough for large-scale use in anything larger than a commuter plane, and aren’t likely to be for some decades to come. Small aircraft carrying perhaps 10 to 50 passengers might be powered by battery-electric or hybrid options between now and 2050, but this end of the market is unlikely to tip the scale.

Offsets

For any kind of onboard combustion, it seems likely that there will be residual climate emissions equivalents. Aviation’s answer: offsetting, in essence a system of carbon credits that reduce others’ emissions to compensate for those from aviation. The idea of offsetting is not universally approved, but for industries such as aviation whose activities (and thus emissions) are classified as “hard to abate,” believable, certified offsetting—rather than thinly veiled greenwashing—must be a crucial part of their sustainable future.

Illustration: Yo Hosoyamada

Travel Sustainably From Your Front Door to Your Hotel Room

If you’ve had the environment on your mind while traveling lately, you’re not alone. Eighty-one percent of global travelers reported that sustainable travel is important to them, according to recent research from Booking. com, with half saying that news about climate change has encouraged them to make more sustainable travel decisions.

Air travel is responsible for nearly three percent of global climate emissions, says The International Council on Clean Transportation. A single flight can produce three tons of carbon dioxide per passenger. And for every metric ton of carbon dioxide produced, the ice cover in the Arctic is reduced by 32 square feet, according to research in Science magazine. The numbers are enough to give you “flygskam,” the newly coined Swedish term for “air travel guilt.” The good news is you don’t have to give up travel or luxury to make an impact when you’re on the road. Making minor adjustments can create significant changes in your carbon footprint and even make your trip more comfortable.

Going Digital

Remember when all plane tickets were paper? It’s easy to skip this step now. Download your airline’s app for a digital ticket and to keep track of travel documents for your flights, all conveniently in one spot.

In Transit

Fly on newer aircraft. More than two percent of global carbon emissions originate with the aviation industry, but airlines are stepping up with more fuel-efficient engines and streamlined designs that reduce emissions. Newer aircraft, such as Boeing 787s and Airbus A350s, are made with lighter-weight composite materials that reduce fuel burn and CO2 emissions. These planes are more eco-friendly and provide a smoother ride with less drag, a lower cabin altitude and a higher humidity level, reducing jet lag for a true win-win for travelers.

Other initiatives by airlines to combat climate change include the reduction of plastics and a shift to more biofuels. For example, Alaska Airlines is the first U.S. carrier to phase out plastic cups in flight—replacing the 55 million previously used with paper—moving towards eliminating single-use plastics by 2025.

Choose nonstop flights. Planes use the most fuel on takeoff and landing, so avoiding extra trip legs reduces this excess usage. Bonus: You’ll also have less chance for additional flight delays this way.

Consider a train instead of a plane for short trips. According to the EPA, rail travel produces up to 73 percent fewer emissions than flying. Plus, trains emit almost six times fewer greenhouse gases than a plane, per data from the science experts at The Company of Biologists. And trains efficiently bring travelers to the heart of cities, eliminating the need for additional airport transportation. Train travel has become such a popular green alternative to flying that French lawmakers voted to ban short domestic flights last year as part of a broader climate bill intended to slash carbon emissions by 40 percent by 2030.

In the U.S., Amtrak estimates that 32 million customers avoided up to 660 million kg of carbon dioxide equivalent (CO2e) by riding Amtrak instead of flying in 2019. And when Amtrak’s new Acela cars launch later this year, they will use 40 percent less energy per passenger utilizing all-electric power on the Northeast Corridor, truly making train travel the eco-friendly option to help shrink your travel carbon footprint.

Also, add a reusable bottle to your bag. More than one million plastic bottles are used every minute around the world. Cut down on your plastic bottle usage by adding a refillable option to your carry-on.

At Your Destination

Rent an electric or hybrid vehicle. EVs produce zero tailpipe emissions and just a third of the carbon dioxide of a standard car. Hybrid engines produce half the CO2 of a regular engine. With EV and hybrid rentals more widely available, and an increasing number of hotels offering charging stations, this is an easier switch than ever before.

Dine out. Here’s a tasty option for your next trip: Choose restaurants that use real glassware, cutlery, dishware and napkins, all of which translate into a reduction of single-use plastics and paper and ultimately less waste. Visiting regional restaurants that source their ingredients locally instead of national chain options adds another layer of sustainability.

Stay at a sustainable hotel. There’s good news for travelers regarding eco-conscious practices at lodging options. Most major hotel players have programs to cut back on waste and lessen their impact on natural resources. Hilton, for example, implemented a soap recycling program and offers digital keys through its app, eliminating the ubiquitous plastic cards. Four Seasons is committed to eliminating single-use plastics and non-com-postable materials across its portfolio. Marriott has committed to reducing water intensity by 15 percent, carbon intensity by 30 percent, and food waste by 50 percent by 2025. Hyatt, Fairmont and IHG all have myriad “green” initiatives in place. Follow good hotel protocol. To support your hotel’s sustainability initiatives, use towels more than once, turn off lights when not in use, and close the window curtains when you’re out to keep the room cool.

Back Home

Offset your carbon footprint. Once you’ve returned home, neutralize the effect of your travels with carbon offsets, a practice where you measure your travel footprint and then donate a coordinating sum of money to projects working to clean up the atmosphere—for example, reforestation. “Carbon offsetting allows us to become more sensitive to our impact on the planet and gives us the opportunity to contribute to global projects trying to remove or avoid putting more carbon dioxide into the atmosphere,” explains Nelly Gedeon, founder of Wayaj Earth Friendly Travel. You can calculate and purchase carbon offsets from your airline, hotel or organizations certified by the United Nations.

To quickly calculate your impact, figure that 1,000 miles of air travel generates approximately 500 pounds of carbon emissions per passenger. This is according to the carbon offset website Terrapass, which equates this amount to planting four trees at the cost of $8. It’s an easy way to keep traveling while helping the planet.