Do we have to resign from flying?

Nowadays many people are worrying more and more about the health of our planet. Slowly the big mass recognizes that we cannot deny, that we are moving towards serious problems. But still, this is rarely reflected in our decisions. As clear as it is that we must change our attitudes, as irrational it is how we actually behave. This is also reflected when it comes to aviation. Many people know that it has a heavy impact on the emission of greenhouse gases (GHG). However, the demand for air transportation was increasing and is increasing dramatically.
Let’s have a bit a closer look at the side effects of taking an airplane. Is it really that bad? What are our alternatives? Do we have to resign from flying to make it any better? Do we see solution in the long-run, are there any upcoming solutions to turn the bad fossil energy burning aviation into a greener aviation? I won’t be able to give a proper answer to all these questions, but hopefully I can show you some insights.


Is it really that bad?
This much is clear: Yes, it is bad. Flying accounts for approximately 2-2.5% of all global CO2 emissions (Grote et al. 2014). That doesn’t sound too bad, right? No, unfortunately the total CO2 produced by airplanes is rather secondary. There are at least five more reasons why flying is and becomes more and more a problem for the environment. Firstly, the total global warming impact by the greenhouse gases ejected by the air transportation must be around twice as high as the carbon dioxide alone. This because not only CO2 is produced, but also other GHG like nitrogen oxides (NOx) and methane (CH4). It is stated that a proportion of 3-4 % of all human made radiative forcing (this is a technical term which describes the process of warming up the globe) is caused by flying around (Staples et al., 2018). Secondly, most of the GHG are spread out when cruising on a critical altitude for our planet’s atmosphere (Niklas et al., 2017). Thirdly, not only the flight itself produces GHG in the airline industry. The transportation of air fuel, maintenance, processing and manufacturing airplanes leads to extra emissions which are not considered in the above numbers. Fourthly, the few percentage numbers you read before are misleading because you need to consider who is actually flying around. Obviously flying is expensive, thus mainly the people of the developed countries make up the passengers. Therefore, the proportion of aviation emissions on the total pollution is much higher for industrialized states. For instance, the UK had a proportion of 13-15% of all GHG in 2005, caused by the air transportation (The Gurdian, 2010). Today’s number will even be higher, if we consider the growth in the airline industry in the recent past. Fifthly, exactly this industry growth is an issue too. Many researchers and important industry stakeholders predict that air transportation will increase annually by 4-5% (Airbus, 2016; Boeing, 2016) compared to other industries emissions. Which will induce emissions to grow massively, assuming the fuel efficiency to stay constant.
To summarize, we can say that traveling by an airplane, is bad news for the environment. As it is also in many other sustainability subjects the case, the quantity of how much we fly, is a big part of the problem. Is therefore, reducing the demand for flying the only solution we have? In the short-run it seems so. But in the medium- and long-run we may have better options.

Forecast of growth of global air passengers in billions. Source:

What options do we have?
As we discussed before, flying has lot of negative impacts on our environment. In addition, these impacts will grow dramatically in the future, due to the strong industry growth. Compared to a car or train ride flying has the highest portion of emissions per traveled kilometer, indeed it has also big advantages. There is no other way to overcome long distances in a faster and cheaper way. That means we are very much dependent on an unsustainable technology. Then there is basically no alternative, to e.g. doing business overseas or visiting a friend who is living on another continent. To discuss new solutions which we may have available, I would like to introduce two different time horizons. It is important to understand that with time, the possible solutions are more diverse and valuable. It comes that far that, with upcoming technology, aviation could get rid off its bad carbon footprint, but of course such options need some decades to be developed and deployed.
In the short-term we know following options: First, simple resign from flying and forgo the possibility to travel around the globe. I agree, this in not an option for most of us. But when we cannot change the pollution of airplanes, we probably won’t have any other option in the long-run. That this in not happening, let us seek for better alternatives! Second, replacement of (shorter) flights by a train journey. It is commonly known that train rides are more sustainable than flights. If you were to take a domestic flight, instead of travelling by an electric high-speed train you may be responsible for 29 times more carbon dioxide (The guardian, 2009). But attention, the sustainability of a train journey depends heavily on the energy source of the train network. Electricity maybe produced with coal or other fossil energy which can reduce the greenness of your journey drastically. Thirdly, and now we come to the less known options, some industries are working on various alternative jet fuels. Most of these alternatives would work on a biological base and could be used with today’s airplane engines. Researchers are claiming that these technologies have the potential to reduce the GHG emissions of flying by 50% (Staples et al., 2018; M. Janić, 2018; M. Soria Baledon and N. Kosoy, 2018). Fourthly, an approach which could be implemented immediately. There is the idea to reduce local impact of air transportation by restricted airspaces. Apparently, there is a potential for climate optimized trajectories, also helps to reduce the holistic impact of aviation (Niklass et al, 2017).
In the long-term, there is basically (only) one possible solution which is really promising: hydrogen powered planes. The potential of aircraft turbines fired by liquid hydrogen (LH2) seem to be almost too good. Flights could become virtually emission free. The amount of HC (HC emission is an umbrella term for volatile organic substances) and CO2 produced by any flight would tend to zero. Additionally, due to the higher flammability of LH2, the NOx amount would also become much lower. Another big advantage of hydrogen fueled airplanes is mainly from political concern. LH2 can basically be produced everywhere (by electrolysis, but that’s a different topic). Therefore, the dependency on the oil producing states would be reduced. And of course, since the fuel would not have to be transported around the globe, this would also benefit the nature. (Yilmaz et al., 2012).

What now?
We have seen, that flying is accountable for a big share of the our GHG emissions. This issue is from special concern because air transportation is supposed to grow drastically in the future. In the short-run there are multiply approaches to absorb the heavy impact flying has on our environment. The range is broad, from changing consumers habitants by taking increasingly the train or just simple resigning from air traffic to replacing todays kerosene with more sustainably biological based jet fuels. All these approaches could be part of a greener aviation in the short-term, but I believe that they won’t be able to solve the initial problem. The problem of burning fuel and polluting our air. Therefore, I would like to make following claim: in the short-run we need to reduce our attitude towards flying. We need to reduce our short distance flights consequently and replace them by a more adequate transportation like train or bus rides. We need to think about every long-distance flight more than once. Is it necessary to go that far for holidays? Can the business also be organized by consuming less air travels? In the long-run, I believe, people will be able to make aviation technology essentially greener. Hydrogen powered planes might be part of this solution. I believe that we will have the possibility to travel around our globe quite convenient and fast in a sustainable way. To make this happen, the politics, the researchers, the visionary a lot of good engineering is needed. It seems to me, that we as consumers can less contribute to this visionary solution. But I think an alert mindset, and the willingness to support disruptive innovation, even with our taxes can be helpful to the mission of making aviation greener.

Yilmaz I., Ilbas M., Tastan M., Tarhan C., 2012. Investigation of hydrogen usage in aviation industry. Energy Conversion and Management. Vol. 63 pp. 63-69.

Baledon M. S., Kosoy N., 2018. “Problematizing” carbon emissions from international aviation and the role of alternative jet fuels in meeting ICAO’s mid-century aspirational goals. Journal of Air Transport Management. Vol. 71 pp. 130-137

Janic M., 2018. An assessment of the potential of alternative fuels for “greening” commercial air transportation. Journal of Air Transport Management. Vol. 69 pp. 235-247.

Staples M. D., Malina R., Suresh P., Hileman J. I., Barrett R. H., 2018. Aviation CO2 emissions reductions from the use of alternative jet fuels. Energy Policy. Vol. 114 pp. 342-354.

Grote M., Williams I., Preston J., 2014. Direct carbon dioxide emissions from civil aircraft. Atmospheric Environment.  Vol. 95 pp. 214-224.

Niklass M., Lührs B., Grewe V., Dahlmann K., Luchkova T., Linke F., Gollnick V., 2017. Potential to reduce the climate impact of aviation by climate restricted airspaces. Transport Policy. Vol. and pp. not available. (accessed 23.12.2018)

The Guardian, 2009. Emissions by transport type. The Guardian Online. 02.09.2018. (accessed 23.12.2018)

The Guardian, 2010. Aviation Q&A: the impact of flying on the environment. The Guardian Online. 06.04.2010. (accessed: 23.12.2018)

Airbus, 2018. Global Market Forecast 2018-2037. (accessed 23.12.2018)