Flying on bio-jet fuel: Is it ready for take-off?

Come fly with me, we’ll fly, we’ll fly away
If you can use some exotic booze
There’s a bar in far Bombay
Come on fly with me, we’ll fly, we’ll fly away

Frank Sinatra

Flying has served as an inspiration for many great songs-writers, either by symbolizing freedom (“vogelvrij”) or, like in the above example of Frank Sinatra, as something romantic and spontaneous. Who did not dream as a child of sitting on Aladdin’s magic flying carpet? One could argue that current commercial airline flights might not be as romantic and adventurous as a flying carpet, nonetheless, it did not constrain us from flying increasingly more in the last decade. Just like the love-story in Aladdin had the villain Jafar, our love for flying has a grim side too. As we flew more, greenhouse-gas emissions increased as well: the aviation sector increased its emissions by 76.1% between 1990 and 2012. In 2012, the aviation sector was responsible for around 2% of the global CO2 emissions and is predicted to grow between 200%-360% by 2050, as developing countries are expected to fly more in the future (figure 1). The best way to reduce our personal carbon footprint is to take less flights. Yet, would it also be possible to make flying itself more environmentally-friendly with the use of biofuels?

Figure 1. Source: Carbonbrief

            Multiple airline companies have been asking this very same question. In 2007 the first bio-jet fuel powered non-commercial flight flew on waste vegetable oil. The years after this event, various companies experimented with a wide range of biofuels (coconut, algae, agricultural residues). Currently, a regular commercial flight between Amsterdam and Los Angeles is powered by used cooking oil. This almost sounds too good to be true: Is it merely a stunt by the aviation industry to appear greener or are they actually planning to use bio-jet fuels in the near future?
              It appears that airlines are taking bio-jet fuels seriously. Members of the  International Air Transport Association (IATA), which is around 85% of all commercial flight operators, have agreed to aim for a carbon-neutral growth by 2020 and a 50% reduction of green-house gas emissions relative to 2005 by 2050 (figure 2). To reach this goal, the first step is to improve efficiency. This can be done by improving the industry’s technology, operations and infrastructure, for example with aircraft modifications or optimized navigational systems. However, to reach the 50% emission reduction by 2050, greater efficiency is not enough and renewable technologies need to implemented. Although electric- or solar-powered planes are being developed, replacing whole aircrafts is often not an option for airlines, as planes are expensive and thus airlines want to use their current planes as long as possible. This leaves one option: biofuels. As the engines of the planes do not need to be replaced or modified, the use of biofuels is easily integrated.

Figure 2: Emissions from aviation industry with and without action. Source: IRENA

So, if we are already able to safely fly regular commercial flights on bio-jet fuels, why are we not implementing it on a larger scale? To answer this question, we have to take a closer look at the bio-jet fuel itself (as described in a technology brief by the International Renewable Energy Agency (IRENA)). These commercially available bio-jet fuels often are oleochemical-derived, so called HEFA-jet. To produce HEFA-jet, oil and fat feedstocks like cooking oil or tallow are used, which must go through various deoxygenation processes that require significant inputs of hydrogen (figure 3).  Unfortunately, HEFA-jet without subsidies is still more expensive than fossil fuel. Next to this, as the same process also produces renewable diesel, HEFA-jet competes with HEFA-diesel, which has a larger market with higher sales prizes. Consequently, most companies that produce HEFA-fuels mainly focus on HEFA-diesel. Another concern for the currently available HEFA-jet is regarding its sustainability. Upscaling the production would require a significant amount of land to provide the feedstock necessary.  More sustainable options, for example waste cooking oil, are often only available in smaller quantities, making it impossible for larger production.

Figure 3. Source: IRENA

Therefore, the solution for making flying more renewable does not lie with the currently used HEFA-biofuels. Luckily there are other technologies for producing bio-jet fuels that might be able meet the future demand, however, it might take five to ten years before they are commercially available. Other options make use of different chemical processes (thermochemical instead of biochemical/oleochemical) as well as different feedstocks (agricultural matter, lignocellulosic biomass, algae,  municipal or industrial waste). A more detailed description of these alternatives can be found within the IRENA-report.
              Thus, there is still a lot of uncertainty regarding bio-jet fuels. Oddly enough, the IRENA-report mentions that the IATA predicts bio-jet fuels can reduce emissions in comparison to fossil jet fuel between 50-95%. Upon closer inspection these numbers were based upon data provided by E4tech that did not include direct and indirect land use change. Depending on the carbon-storage of the land being cleared for the production of bio-fuels, it could take decades or centuries before the biofuel contributes relatively less emissions than fossil fuels, ultimately compromising the actual sustainability of using bio-jet fuels.

In conclusion, due to economical constraints and uncertainty surrounding the sustainability of bio-fuels, most commercial flights will not be using bio-jet fuel soon. Nonetheless, the fact that there is uncertainty does not mean it is impossible. With hopefully the right research and policies, a safe, economically viable and, most importantly, sustainable bio-jet fuel can be developed for commercial use. For now it might not be the most environmentally-conscious choice to spontaneously take a  flight to Bombay for some exotic booze like Frank Sinatra. But a beer whilst camping in Texel would just be as romantic, right?

References:

Aviation biofuel. (2019, May 01). Retrieved from https://en.wikipedia.org/wiki/Aviation_biofuel#cite_note-one-10

CarbonBrief. (2016, August 10). Retrieved from https://www.carbonbrief.org/explainer-aviations-battle-to-limit-rising-emissions

E4tech (2009). Review of the potential for biofuels in aviation. Retrieved from: https://www.theccc.org.uk/archive/aws2/Aviation%20Report%2009/E4tech%20%282009%29,%20Review%20of%20the%20potential%20for%20biofuels%20in%20aviation.pdf

Fargione, J., Hill, J., Tilman, D., Polasky, S., & Hawthorne, P. (2008). Land Clearing and the Biofuel Carbon Debt. Science,319(5867), 1235-1238. doi:10.1126/science.1152747

Goodall, C. (2017, January 19). How to reduce your carbon footprint #GlobalWarning. Retrieved from https://www.theguardian.com/environment/2017/jan/19/how-to-reduce-carbon-footprint

KLM. (2016, September 08). Retrieved from https://news.klm.com/klm-to-operate-biofuel-flights-out-of-los-angeles/

IATA (2015). IATA Sustainable Aviation Fuel Roadmap, International Aviation Fuel Roadmap, Montreal-Geneva. Retrieved from: https://www.iata.org/whatwedo/environment/Documents/safr-1-2015.pdf

IRENA (2017), Biofuels for aviation: Technology brief, International Renewable Energy Agency, Abu Dhabi. Retrieved from: https://www.irena.org/documentdownloads/publications/irena_biofuels_for_aviation_2017.pdf

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7 thoughts on “Flying on bio-jet fuel: Is it ready for take-off?

  1. Hi, thank you for your interesting blog post. I was not aware that there is already a viable biofuel alternative to the regular fuel used in airplanes. I was wondering though, given that you mention that sustainable bio-fuel option such as waste cooking oil is not available in large quantities, isn’t it possible to mix different sustainable biofuels? To mix second (e.g. agricultural waste, woody crops) and third generation biofuels (e.g. algae), which would be a sustainable mix that does not bring about the high CO2 emissions from land-use changes?

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  2. Thank you for your response, Julia! I am not sure if it is possible to mix different sustainable bio-jet fuels, as they need to meet certain safety requirements. They are able to mix regular fuels with bio-jet fuels, however, that might not be a guarantee that you can mix different bio-jet fuels. I do agree that the fuel should come more from third generation biofuels like algae, however, the technology appears to not be there yet for such biofuels. Especially biofuel from algae is seen as the perfect solution, however, many complications (both economically and environmentally) still need to be resolved (https://pubs.acs.org/doi/pdf/10.1021/es300917r).

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  3. Thank you for the post, great to see that there is at least some action from side of the aviation industry! The problems you describe with HEFA-jet fuel often seem to be economical. The alternative product of the process, HEFA-diesel, is more profitable and the fossil fuel variant is cheaper than its biofuel counterpart. Wouldn’t increased taxation on fossil jet fuel, instead of subsidies, solve both problems? As the fossil jet fuel becomes more expensive, the demand for HEFA-jet fuel increases and chemical plants will shift their production from HEFA-diesel to HEFA-jet fuel. Of course the problem of land usage remains, and that is not so easily solved.

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  4. Heya! Thanks for the post!
    Flying’s been bugging me for ages as well. It is so convenient but comes at a huge cost. Eating veg, recycling waste and only using a bicycle makes one feel good about oneself, but if at the same time one keeps flying 4 and more times a year all that effort is basically wasted.
    I still can’t wrap my head around the fact that airlines live in this tax-free status, whilst trains and other way more sustainable ways of transport are taxed.
    Anyways, got a couple of questions. Have you looked into how the aviation industry is following its pledges through the 2015 IATA Fuel Roadmap report? It’s almost 2020, would be interesting to see how the growth is going.
    What are your thoughts on carbon offsetting that’s available when you are buying the plane ticket?
    Have you heard about hydrogen aircraft? There is some research going on and I’ve heard people saying that it might be THE thing for short-haul flights.
    I personally don’t think phasing in biofuels will happen too smoothly. I think they should finally tax air traffic heavily and use that money for R&D in carbon capture and storage. At the current price air travel cannot be sustainable.

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  5. Hi, thank you for the post. I think besides economical constraints, there are also the environmental issues with biofuels that make the term ‘sustainable’ questionable. While there is of course the potential of a cut in greenhouse gas emissions, it still takes a massive toll in terms of biodiversity by means of land use change. I have more hope for electric flying as a sustainable alternative. You mention that you don’t think this is an option for current airlines but do you not think that subsidies and fuel tax could change this? Until then, I think we just have to put up with less flying.

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  6. Hey, great post! I had a question about the economic viability of biofuels. From what I know, Jetfuel is often exempt from tax (or subsidized) would you know what the impact would be if we take away this preferential treatment for fossil jet-fuel? would this tip the balance in favour of Bio-based fuels?

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  7. I am just echoing the same idea that has been brought up by a couple of other people here already: taxes. It may very well be that if jet fuel is no longer tax-exempt then a greener alternative might take precedent. But I honestly wonder how well that would sit with most of us, the consumers. Flying is something that I personally struggle with. I live on the other side of the world from any of my family members: the ones closest to me live a 10-hour flight away. I fly for around 40 hours a year, on a year where I only see my family for the holidays. If the decreasing trend of airplane tickets were to be reversed and prices were to start increasing, this would come at a serious emotional and mental cost to me as I would probably no longer be able to afford to see my family twice a year or even once a year. Which brings me back to my original question: would we as consumers, overall, seriously support tax exemptions being reversed and airplane ticket costs increasing? I personally doubt it.

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