Reducing emissions: Does the growth of aviation simply outpace innovation?

While there is a lot of talk about “net zero” carbon emissions and reducing the greenhouse gas emissions of aircraft, one common concern raised is that while many approaches are being taken to try and reduce overall greenhouse gas emissions, the savings are simply not significant enough. With the anticipated continued growth of aviation, could we see a continued increase in greenhouse gas emissions due the growth of the industry simply outpacing innovation aimed at reducing emissions?

The biggest emitters offer the hardest problem to solve

While there are a lot of examples on this site of aircraft that potentially offer net-zero or near-zero greenhouse gas emissions in the next few years, they’re all small and short-range. As discussed in the “What will power aircraft in the future?” article, fully electric aircraft are simply too heavy for bigger and / or longer-range applications, and hydrogen technology isn’t very mature yet at this point. Hydrogen fuel-cell applications also aren’t realistic for longer range aircraft at this point.

TUI Fly Boeing 737 promoting the Deutsche Bahn ICE trains to get to the airport (source: Wikimedia Commons)

So, while this means within the coming years, we’ll start seeing more and more all-electric aircraft and perhaps some hydrogen fuel-cell aircraft, they will mostly replace small regional and general aviation aircraft, which represent only a small portion of the overall greenhouse gas emissions of aviation. Further, many of these aircraft fit in the urban air mobility (air taxi) segment which doesn’t really exist today, so at best they replace what used to be a taxi ride. And even tens and tens of thousands of air taxis were to be sold over the coming decades, they’d mostly just replace taxis, which in many countries are quickly moving to adopt electric cars as it is. Perhaps some helicopters will be replaced with zero-emission aircraft, but this isn’t likely to be common and thus not a significant impact. Rail travel can certainly replace aircraft on certain shorter routes, especially domestic or relatively short distance international travel, but can only offer somewhat equivalent service on a relatively small portion of flights.

This means that the biggest emitters of greenhouse gas emissions in aviation, medium-to-long range airliners, are not really being seriously tackled. Synthethic Aviation Fuels may offer some reduction in carbon emissions, but availability is low, and they do not eliminate greenhouse gas emissions, they merely reduce them. eFuels offer a larger reduction, being net-zero in carbon emissions, but production would need to come from fully “green” power sources to make the biggest difference and as of May 2022, too few initiatives are underway to produce eFuel at anywhere near the scale required to see significant use of it in aviation. Liquid hydrogen burning aircraft have a lot of potential to replace carbon-based fuels entirely and would offer a truly zero carbon-emission aircraft (assuming the production of hydrogen itself does not cause emissions), however, this technology still seems to be decades away from being ready to be used at scale and in all design studies done today liquid hydrogen aircraft don’t perform nearly as well as their jet fuel counterparts.

In a a January 2022 study done by Jayant Mukhopadhaya and Dan Rutherford for the International Council on Clean Transportation, even in the most optimistic scenario sketched where all flights that can reasonably be replaced by liquid hydrogen burning aircraft adopt it from 2035 onwards, carbon emissions (not overall greenhouse gas emissions) are basically capped, but not significantly reduced. This does assume that for many routes liquid hydrogen simply cannot be adopted as no suitable liquid hydrogen aircraft can be built and airlines would not be willing to compromise (eg. more connections to create shorter legs).

The economics of change

The clear picture that has emerged is that climate-friendly aviation is both more expensive and less practical. Airlines will most likely have to compromise both on range and payload. And if they insisted on operating certain routes but lacked the range to do so, more connections would be required. In short, the change would be costly for airlines and inconvenient for passengers. So while airlines may be interested in adopting climate friendly aircraft, doing so would be an immediate competitive disadvantage on many routes, and the orders seen from the airline industry today are primarily for small and short range regional airliners where there’s less complication.

Passengers may indicate that they’d rather fly a climate friendly aircraft and thus be willing to pay more and / or deal with the inconvenience caused by having more connections. But for many people flying is already expensive and inconvenient as-is, and those traveling on business may be forced to pick the cheapest airline offering by their company. So, it’s unlikely that idealism alone would be enough to make this work. Leaving it up to the individual will only get you so far.

So, is it all futile?

Woman holding up cover from a flyer called “The illusion of Green Flying” at a 2017 protest in Berlin (source: Wikimedia Commons)

Even if current studies aren’t optimistic about current innovations being able to reduce overall greenhouse gas emissions of aviation, that doesn’t mean we should not bother trying to innovate at all. The development of low-to-zero greenhouse gas emission aircraft should be encouraged as that is still better than not making any effort at all. And yes, even though this is an aviation website, some flights really should be replaced with alternative modes of transport like trains. Some countries in particular, such as the United States, lag behind considerably when it comes to rail transport and there’s no reason to believe people wouldn’t take trains on shorter routes if the infrastructure existed.

But for true change to happen in aviation, the only thing that can truly drive radical change is pressure from governments and other regulatory agencies. Some small steps are being taken, such as France voting in April 2021 to ban regional flights that could’ve been done with a train in under 2.5 hours instead and have no connections. This may seem like a radical step but in practice only affected a whole five flights. CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation) is a more substantial initiative developed by the International Civil Aviation Organization (ICAO). It aimed to cap net carbon-emissions to 2020 levels by forcing carbon offsetting for any emissions beyond those levels on international flights. However, this just caps things at the 2020 level, it doesn’t result in an actual reduction. Further, it caps it by forcing airlines to offset part of their emissions elsewhere, it doesn’t stop the emissions from happening and places a lot of faith in the carbon offsetting schemes. Plus, carbon emissions aren’t the only greenhouse gas produced. And since only the growth of international flights is in scope, large domestic aviation markets such as the United States and China aren’t affected.

Such changes then aren’t anywhere near as radical what is needed to truly reduce emissions in a meaningful way. What governments and regulatory bodies could do that would make a change:

  • Create incentives to operate climate-friendly aircraft
  • Create stricter disincentives to operate aircraft with higher greenhouse gas emissions
  • Ban particularly inefficient practices
  • Be advocates not just at a national scale, but at an international scale
  • Invest in innovation

The goal should be to affect all competing airlines equally so that decisions to adopt new technologies that may be climate friendly but less competitive aren’t ignored due to economics. Further, fighting climate change shouldn’t be presented as merely a burden. It is an opportunity to innovate and an opportunity to create new jobs in a very high industry. Pressure should primarily be exerted on governments and other regulatory agencies that have the ability to affect such change.

This will not come easy, as despite there being a lot of political grandstanding about climate, many such agencies very actively oppose even relatively minor measures. For example, the European Union wanting to impose tax on jet fuel for flights within the Europe was met with instant criticism by the International Air Transport Association (IATA), with their SVP of Environment and Sustainability claiming that the added cost would reduce the ability of airlines to invest in green technologies. But clearly, a lack of tax on fuel provides a clear cost advantage for using conventional aircraft over alternatives. Clearly, there is still a lot of opposition left to overcome.