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Heading Towards Net-Zero Carbon Emission in Aviation.

Preparing greener initiatives for the next take-off.

Eagerly and hopefully waiting for the net-zero carbon emission missions to become a reality sooner. This refueling truck full of conventional kerosene might be replaced by a fully sustainable aviation fuel product in the near future. Image by Author.

When talking about carbon emission, the aviation industry committed to around 2%-2.5% of global carbon output. Let’s not get delusional about the low percentages. Instead, it should be looking at the weight figure that reaches a whopping 900+ million tonnes of CO2 in 2019 alone.

The industry is under intense pressure to reduce its carbon footprint. Heading for at least net-zero carbon emission is what is under the radar right now.

Sure, heading for electrification is without a doubt one way to commit to greener products, but that is for the long-term strategy when the technology is ready. For now, the medium-term prospect is heading for net-zero carbon emission. Start small they said. What is net-zero carbon emission by the way?

It is a process that still produces emissions, but it is offset by capturing the carbon back from the atmosphere to produce synthetic fuel, then use it to combust. It means that the fuel used to give engines the propelling characteristic is made from the carbon in the atmosphere.

While it is not in any means a clean process, it is also not the most carbon-spewing either, unless the power sources for the carbon-capturing facility or the hydrogen production is by burning fossil hydrocarbon.

Nevertheless, sustainable aviation fuel (SAF), hydrogen fuel cells and hybrid technology are currently on the commercial aviation agenda and making some hot news lately towards a greener environment.

Huge Mission Ahead

Sustainable aviation fuel or SAF is an artificial fuel made from a chemical conversion process. It will transform carbon through a synthesis process and over a catalyst to what we called the finished product as synthetic fuel. Since it is carbon-based, the carbon could be capture from the atmosphere in the form of gas which is the carbon dioxide itself. The combustion engine byproduct is recycled back to make the fuel.

Multiple processes are needed in producing synthetic fuel using Direct Air Capture (DAC) technology in one image. Image by Airbus.

These create a carbon cycle throughout the production-and-usage rotation. SAF not only exists as synthetic fuel but biofuel as well.

The good news is that multiple flights have flown using blended kerosene with synthetic fuel though the combined percentages of the mixture are low since it is in the early stage. In fact, some airlines already conducting commercial flights using this blended fuel, while many others have invested for future usage so far.

Eventually, these synthetic fuels will be replacing kerosene sooner rather than later.

Fulfilling the net-zero carbon emission mission must start from the production of the fuel itself or otherwise, it is just a pointless effort. The national carrier of the Netherlands, KLM said they are using blended kerosene and synthetic fuel coming from a production plant that uses renewable energy as a power source such as wind, hydroelectric or solar.

As the first airline to conduct the first commercial flight with paying passengers using blended conventional kerosene with sustainable synthetic aviation fuel, it was and is still a remarkable achievement so far.

…the first commercial passenger flight from Amsterdam Airport Schiphol to Madrid last month, was carried out on an admixture of 500 liters of sustainable synthetic kerosene. Shell produced the synthetic kerosene in its research center in Amsterdam based on CO2, water and renewable energy from sun and wind from Dutch soil.

Refueling the Boeing aircraft with kerosene and SAF mixture from the truck. Image by KLM.

That’s not all. Hydrogen also can act as fuel. Aircraft manufacturer, Airbus, has begun introducing a concept of using hydrogen to power the aircraft. The concept aircraft, ZEROe, will use hydrogen as a combustion medium and fuel cells to supply electricity for the aircraft. The byproduct of hydrogen combustion is just water, which is a lot cleaner compared to fossil fuel.

If you notice, when comparing both SAF and hydrogen as a fuel for the engines, hydrogen is much cleaner compared to SAF that still emits carbon (bonus point: they are sulfur-free, which means sulfur dioxide does not escape to the atmosphere) HOWEVER,

  • The emitted carbon can be captured back from the atmosphere through carbon dioxide extraction from direct air capture (DAC) technology.
  • Hundreds of times better compare to burning ‘liquid dinosaurs’.
  • Further researches and experiments could have a result in making SAF less carbon emitted, more cleaner and greener, lessen the production cost, etc
  • SAF can be brought forward much faster to use on the current combustion engine.

Hydrogen and SAF both have pros and cons. Yes, we cannot deny that hydrogen is cleaner in terms of emission but, we shouldn’t turn a blind eye towards SAF. SAF has a chance to be integrated into the current modern turbine engines and accelerated the usage in the future.

To kick start, blended kerosene with synthetic fuel coming from a renewable energy plant is already happening with multiple approved flights. Now that is something that worth mentioning. The prospect is much clearer compare to hydrogen.

By 2035, both Airbus and Boeing have a target to manufacture an aircraft that is fully capable of using sustainable energy as the propulsion power source.

The Challenges

It is not fair to view the responsibilities toward decarbonization from the aircraft manufacturers’ side only. Numerous sectors and industry players must hand-in-hand utilizing resources and knowledge to achieve this milestone; starting from production, storage, transportation, regulation, and so forth.

One of the challenges faced by the industry is bringing the SAF and hydrogen up to mass output scale once the demand is there. At the moment, only a handful of such production facilities are there that used renewable energy to produce either fuel or hydrogen. The reason for this is the lack of renewable energy infrastructures that could supply enough power to facilitate the increased production output.

Fortunately, more than 80% of all newly added infrastructures for electrical generations were using renewable energy last year, mostly using wind and solar energy as power sources.

Because commercial air transportation is flying from one continent to another, airport infrastructure worldwide needs to be ready for the arising changes. For instance, using hydrogen as fuel can change the current infrastructure 180 degrees.

Most countries need to step up their facilities to accommodate the storage requirement, transportation, maintaining the quality, and other regulatory procedures.

Nevertheless, I remember that I read somewhere that SAF can be used not only on the current turbine engine but also on existing fuel equipment and facility as well.

A bio-based solution often enables the reuse of existing infrastructure and equipment

These could ease up the burden imposed on the airport. It is a piece of great news for the whole industry. The usage of synthetic fuel could then be ramping up in a timely fashion, thus lowering the cost.

Speaking of, the price of synthetic fuel is much higher compared to conventional fuel at the moment. The production of SAF can overcome this challenge by commercializing it in mass-scale production. However, here comes the chicken and egg situation that pretty much sums up the reality right now. Without the fully utilized SAF aircraft, the fuel manufacturer does not simply pump out a large quantity of synthetic fuel and the cycle continues.

Our Best Bet

All the news about record high temperature in multiple places, massive flooding, rising ocean levels, and melting glaciers and icebergs are scary to think. Those greenhouse gases do mess up the climate that brought back many horrendous effects to us.

Now is the right time or, better yet, the best time for us to do the changes by accelerating the zero-emission initiatives. Having net-zero carbon emission is the least that we can do in this short to medium term.

Kudos to all the engineers and researchers, and not to forget for all the blood, sweat, and tears of the people, whether directly or indirectly in making this effort into reality. Soon, we will fly with aircraft having sustainable energy as their power source which is just amazing to even think about it.

In the meantime, this is our best bet to achieve at least net-zero carbon emission from air transportation as this industry is quite different compare to other modes. Before we see an electric commercial airliner flying from one continent to another carrying hundreds of people, this is the least we can do before any technology becomes mature enough to support fully electric aircraft system architecture.



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