Air travel and related carbon emissions are responsible for more than 2 % of global emissions. Although it might not sound much, if it were a country, it would rank as the 10th largest polluter. By 2020, the global aviation emissions are projected to be 70% higher than they were in 2005, and the International Civil Aviation Organization (ICAO) forecasts that they could grow 300-700% by 2050. When faced with these predictions, it is obvious something should be done to reverse the trend. As a mobility designer, I’d like to highlight some design ideas that could enhance current aircraft to make them more energy-efficient, or even replace them. I'll also touch on why we still haven't seen the level of investment into alternative designs required to cut air travel emissions.

Although planes are the dominant mode of long-distance transport today, several alternative concepts exist that could potentially replace them on many routes. The ripest alternatives are land-based ultra-fast trains, such as the magnetic “maglev”. These could be further turbocharged by near-vacuum tunnels, which could allow trains to compete with planes on speed and outperform them on capacity regionally: from city centre to city centre. Building and supporting high-speed train alternatives to air travel is the way forward, but while the infrastructure for high-speed trains is being built, there are a number of airborne alternatives.

Alternatives take off

Eighty years on from the Hindenburg disaster, modern technology allows us to build faster and safer airships for long-distance cargo transport. Airships have a massive advantage in not needing a lot of support infrastructure and are therefore a good option for direct point-to-point cargo transport. Within a very short time span, they can be rendered virtually emissions-free.

Another “forgotten” option is the ekranoplan. A Soviet-era part-plane part-hovercraft also known as a ground effect vehicle. This vehicle is designed to attain sustained flight slightly above a level surface – namely, water – by using the aerodynamic interaction between the wings and the surface. The energy consumption of the ekranoplan is roughly half that of propeller planes. The Soviet-built Lun-class ekranoplan had a range of 2,000km and a potential cruising speed at 550 km/h, making it a viable fuel-efficient alternative on many routes. Investors are already seeing the potential here. The Sea Wolf Express, a startup, plans to start a commercial ekranoplan route between Helsinki and Tallinn this year. The potential of using ekranoplans for future intercontinental travel shouldn’t be discounted.

Recently, we’ve also seen substantial developments with the designs of electrical vertical take-off and landing flights (eVTOLs). These have mostly been for single-person use, and if we’re to reduce our carbon emissions in the future, mass transit and not single-person transportation will be the solution. But what we’ve learned from single-person eVTOL design is how it allows us to distribute energy evenly between multiple electric engines. Compared to classic fossil-fueled propulsion, the potential for optimal and efficient use of energy with this technology is huge. As a consequence, we might see the return of multi-propeller aircraft, as electrical power is much easier divert to multiple engines as opposed to the concentrated power use of jet engines. This also opens up for revisiting other forgotten inventions such as the gyrocopter.

Furthermore, there’s the option of pursuing even more research into mimicking biology to reduce the aerodynamic forces that oppose an aircraft’s motion through the air. Arguably, no force is better at optimizing designs than evolution. Aircraft manufacturer Airbus has formed a design division to look even further into the potential of biomimicry. Experiments are being made using the large wingspan of the albatross as inspiration. With a special technique, the albatross can lock its wings in a position that allows it to glide without flapping its wings for many kilometers.

Combine this research with the potential for solar-powered planes. When a plane soars above the clouds during the daytime, there is an endless supply of solar power. The challenge today of electric planes is that of capacity, distance and battery size, and one area where research could be directed is in solar energy powering the long-sustained cruise above the clouds.

Speaking of electric and hybrid planes, solutions are being developed but not without bumps. The Israeli firm Eviation has launched a short-distance nine-seat all-electrical aircraft at the Paris Airshow, to be in operation by 2023. Rolls-Royce is working on a medium-range hybrid solution.

The emissions conundrum

The above examples highlight two problems concerning the advent of alternatives to present-day air transport. The first is that of capacity. Electrical long-haul large passenger aircraft still have long way to go in terms of range. Significant research and funding have to be allocated if the capacity of these flights is to come near present-day fossil-fueled flights.

Which brings us to the second and larger problem: investors are reluctant to commit fully to electrical and hybrid research and development. Mainly because there is no binding and comprehensive international agreement to reduce emissions from air travel.

Politically, the main problem is that of assigning responsibility. As per both the Kyoto Protocol and the Paris Agreement, air transport and connected emissions are not attributed to a single country’s carbon footprint, and therefore are not counted when that country calculates how to comply with international agreements to reduce emissions. The emissions from a plane travelling between Stockholm and Copenhagen, for instance, do not figure in either the Swedish or Danish carbon footprint. The consequence is that neither the Swedes nor Danes need to reduce their international air transport emissions if they want to comply with the Paris Agreement.

A modern airship, the Zeppelin NT D-LZZF, in 2010.
A modern airship, the Zeppelin NT D-LZZF, in 2010.
Image: AngMoKio/Wikipedia

Not including air travel in a country’s calculation towards reducing emissions is foolish, and this is one reason emissions are rising. Solutions tend to be local, uncoordinated and with little impact. Take the two aforementioned countries: Sweden puts an environment tax on air travel, whereas they don’t in Denmark, for no obvious reason other than politics. That is why we need international agreements to ensure that everyone complies.

In the European Union, there is a system – the EU Emissions Trading Scheme – through which the union levies airlines requiring them to buy carbon indulgences through a quota system. But the system suffers from two drawbacks. First, it only applies within the European Economic Area, due to opposition from the United States and China. Second, trading is based on market mechanisms. It is designed with the expectation of the market fixing a problem rather than using the most common and tested government tool: tax.

Championing a global tax

Many economists argue the way forward is a global carbon tax. A tax that rises depending on the amount of pollution generated, and thereby by the damage done. The more a product or action pollutes, the more expensive it should be. This nudges the consumer into choosing more environmentally friendly options – such as trains, when applicable – as they would be cheaper. And it also forces the emitter to seek greener alternatives and for investors to look in that direction as well.

A global carbon tax on air travel would also promote entrepreneurial solutions in less congested markets. Take the story of Kenyans leapfrogging the rest of the world with mobile money solutions. Interregional air traffic on the African continent is relatively small at the moment. Combined with the Open Skies initiative in the African Union and a carbon tax, we might see the continent spearhead a transportation revolution.

Income generated through the carbon tax could be split between research into green technologies and as compensation to the developing world, as they’ll feel the brunt consequences of climate change, and historically have emitted far less.

However, having a working carbon tax requires global agreement, commitment and potential for sanctions. The obvious international authority to use for this task is ICAO, the specialised aviation agency of the United Nations. Steps have already been taken to create agreements through ICAO, but the project suffers due to a lack of ambition and commitment. Targets are designed to keep emissions from rising rather than reduce them. But, as an active part of global air traffic management and technical standard definitions for aircraft, ICAO is an obvious choice to also include the monitoring of range and emission data for aircraft. So, sooner rather than later, an international agreement needs to be reached to put a carbon tax on all air travel, domestic and international, and ICAO should be given the resources to monitor and levy the tax. A carbon tax would have a clear effect on the choice of more efficient fossil fuels in the short term.

Emissions per passenger km on various modes of transport
Emissions per passenger km on various modes of transport
Image: BBC

Fuelling the debate

In terms of energy reduction, there is the future option of electrofuels – a synthetic alternative to current fossil fuels. These fuels can be produced by combining hydrogen with carbon from CO2. With the hydrogen produced using additional renewable electricity and with the correct source of CO2 (ideally air capture), such fuels can be close to near-zero emissions and carbon circular. However, we’re still a long way from this, and funds generated by the carbon tax could be allocated for research into the development of these.

Biofuels are another option, but we have to be especially mindful of the production process of these. Many biofuel types today are considered “green” alternatives, but this is usually only if the indirect land-use change isn’t considered. Farmland used for biofuels could be replaced by eco-friendly agriculture or carbon-storing forests. An example could be Brazilian ethanol produced on sugar canes. Although it is a highly efficient alternative to fossil fuels, it comes at the expense of the Amazon rainforest. This is why strong regulation and proper definition of biofuels are a minimum requirement should we consider them as fuel alternatives. Any use or support of biofuels should only be considered if certification of proper land usage is present.

The future of international air travel is dependent on the community of international decision-makers picking the right options. These options include a carbon tax and assurances that the political framework is set in place to support a reduction of aviation emissions. With these assurances, we'll see long-forgotten aircraft designs revisited, present-day designs enhanced and new solutions surfacing.