Evolving with climate change: decarbonizing Commercial Aircraft
Decarbonization is becoming one of those buzzwords in the same way “organic,” “non-GMO” and “sustainability” have worked their way into everyday conversation. Regardless of how you feel about the science, we are running out of time to reverse the human impact on climate change. Something drastic needs to happen and it begins with rethinking the youngest of our major transportation technologies.
The interplay of aviation and climate change
Consider two of some of the most popular airline models in service today: Boeing’s 737-800 and the Airbus A320. On a hypothetical flight from New York to Los Angeles, the Boeing burns through nearly 12,523 kg per hour (3308 gallons/hr) and the Airbus is a slightly more efficient 12,028 kg per hour (3177 gallons/hr).
That’s one flight among the many hundreds that occur in a day across one country. Keep that in the back of your mind for later.
These numbers are a ballpark estimate since so many factors can alter how much fuel an individual aircraft including weather, takeoff weight, and other performance characteristics. It all contributes to heating the atmosphere. In fact, according to the BBC, as of 2019, aviation is responsible for 2.5 percent of the world’s carbon emissions. This is expected to grow in the coming years, but the pandemic resulted in a sharp decrease in the demand and use of fossil fuels. Experts at the International Energy Agency found that the “…decline in CO2 emissions from oil use in the transport sector accounted for well over 50% of the total global drop in CO2 emissions in 2020.” In particular, the IEA observed international aviation took a huge hit in 2020, with global flight activity reaching a low in April 2020 of 70% below the level in 2019.
In short—the air was “cleaner” during the height of the pandemic.
What makes air travel such a big contributor to climate change involves what is spewed out in those contrails crisscrossing the skies. In addition to the ever-famous carbon dioxide, jet engines also produce nitrogen oxide (NO), water vapor, soot, and sulfate aerosols as by-products. Together they work to trap heat and increase the net warming of the atmosphere.
Commercial aviation should have evolved a decade ago—period
This may come as a shock to many people, but the airline industry is chock full of old airplanes that have been in service for more than 20 years. It is becoming more obvious that across the multitude of industries, we should have transitioned and evolved away from fossil fuels more than a decade ago. We have known for years aggressive action needs to take place to offset some of the damage to the environment. However, for the aviation industry, it isn’t as simple as slapping new energy-efficient engines onto old airplanes.
You can get away with doing that to cars by making them hybrid, but that option does not exist so easily the larger the aircraft. Remember the two plane crashes involving the Boeing 737 MAX? In a nutshell, Boeing wanted to catch up to their rival Airbus by replacing the MAX’s older engines with a more fuel-efficient design.
This required an immense amount of engineering and new software to compensate for the engine’s effect on the airplane’s flight characteristics. Twin demons of wanting to beat the competition and airlines wanting to save money resulted in serious design flaws, poor pilot training, and two preventable tragedies.
You would think with companies having a strong desire to save money they would have invested in technology that does so. Unfortunately, time is proving some people misappropriated the “if it ain’t broke don’t fix it,” adage.
Decarbonizing small aircraft can be achieved by going electric or even hybrid. Right now, there are numerous companies experimenting and refining smaller electric airplanes. The newest type is called “eVOLT,” which stands for “electric vertical take-off and landing.” These peculiar aircraft look like a cross between a regular airplane with several propellers that enable them to take off like a helicopter. Boeing, Airbus, and most recently Tesla all have been creating these new vehicles for flight in the hopes of ushering in a new era of air taxi service.
Of course, lithium batteries have their limitations. The aircraft mentioned above would only satisfy short-haul flights with extremely limited passengers. To date the largest airplane created that doesn’t run on fossil fuels is the eCaravan crafted from a Cessna Caravan and can carry nine passengers.
Batteries: the most unrealistic solution for commercial aviation
Putting aside the environmental issues obtaining lithium causes, battery-powered aircraft are impractical. Take the eCarvan, it can only travel within a 100-mile radius of its home base—that is approximately 1,400 miles less than its turboprop gas-guzzling sister. It all comes down to weight, something that in aviation can quite literally make or break an aircraft.
How heavy your aircraft is can determine a myriad of things. Weight determines everything from how much runway you need to take off and land to how stable the aircraft is in flight (i.e. where the center of gravity is located). The primary problem with batteries is they are heavy!
For context on how this affects large aircraft, Oscar Serpell from the Kleinman Center for Energy Policy writes,
“…the cutting-edge battery pack of the Tesla Model 3 electric car has a gravimetric density of 168 Wh/kg. If we apply this energy density to the requirement for a passenger aircraft such as a Boeing 747 flying from JFK to Heathrow, a single flight would need approximately 3881 metric tons of battery packs. A 747’s maximum take-off weight is 333 metric tons, one-tenth the weight of the batteries needed to power it.”
It is more pragmatic to look beyond batteries and consider synthetic fuel. Currently, the European Union is funding SOLAR-JET, a program that is producing renewable kerosene that comes directly from sunlight, water, and carbon dioxide. Concentrated sunlight converts carbon dioxide and water to a synthesis gas (syngas) for use in jet engines.
This is not the only option for decarbonization. There is of course an aircraft already in existence that we all straight up forgot about.
A zeppelin by any other name is still an airship
It is amazing how often looking to the past can help you blaze a new trail to the future. Usually when one hears the term “airship,” they often immediately think of the Hindenburg disaster, but airships have come a long way since that mishap. These giant football-like lighter-than-air aircraft are seeing a new resurgence as a potential alternative to the jets dominating the skies.
An Austrian study from scientists at the International Institute of Applied Systems Analysis (IIASA) say, “hydrogen-filled airships or balloons could carry hydrogen with a lower fuel requirement and shorter travel time compared to conventional shipping” (Popular Mechanics). They propose using jet streams (high-velocity wind current covering the Earth’s upper atmosphere) for scheduled routes.
Lockheed Martin is redeveloping old airship technology for future use in hauling cargo internationally. Engineers on the project are implementing what they call their “air cushion landing system” or ACLS to improve the maneuverability of their airships. The ACLS uses hovercraft technology to allow the aircraft to taxi on unpaved surfaces such as water or gravel.
Clearly, there is more than one solid answer to reducing our carbon footprint over the next decade. The wise choice would be to dive in full steam ahead and start using a combination of all the technologies mentioned here. The author personally is looking forward to a future where blimps and eVOLTs dot the skies like so many science fiction movies once promised.
For more information about the topics presented visit:
How airships work
eVOLT Companies emerging in 2021
