Sustainable aviation is one of the workhorses of the new economy. Both the commitment to innovative designs such as the v-shaped plane that we covered in a previous article and the use of alternative fuels seek to reduce the carbon footprint of this transportation system. However, electric or hydrogen fuel cell systems are still under development and will not be taking to the skies anytime soon. For the time being, the industry is turning to fuels based on industrial oils, but the cost is still high, and they are usually used to produce diesel rather than kerosene. On the other hand, organic waste is used to obtain methane, a gas with no application in aviation today. Fortunately, it seems that researchers at the US National Renewable Energy Laboratory have found a solution.
The journey from a landfill to fuel tanks
Currently, much of the organic waste with a high percentage of moisture ends up in landfills or, at best, is used to produce methane. However, the new technique presented in the scientific publication PNAS makes it possible to convert this type of waste into sustainable kerosene, whether of animal or vegetable origin. The secret lies in interrupting the methanation process and obtaining volatile fatty acids (known as VFA). Two catalytic processes are then applied to generate a fuel suitable for aviation. The final step involves adding 30 % conventional kerosene to the mixture.
According to the researchers, the new strategy offers several advantages. On the one hand, there is a net reduction of 165% in greenhouse gas emissions. This figure is the result of combining the reduction in aircraft emissions and landfill emissions. In addition, combustion produces 34% less soot, a residue that multiplies the heat buildup due to CO2.
After demonstrating the feasibility of the process in the lab and passing industry certification processes, the team is set to conduct the first tests on real aircraft in 2023 with Southwest Airlines, a U.S. carrier.
Green hydrogen: the future of aviation
Derek Vardy, the engineer who led the study, points out that this strategy is an essential milestone for sustainable aviation. However, it will only be a transitional phase. True sustainability will come from the use of fully renewable energy sources. In that sense, green hydrogen, generated through an electrolysis process powered by renewable energy, could be one of the great assets of aviation of the future. That is the vision of Airbus, which has presented the ZeroE project with three prototypes powered by liquid hydrogen. The largest model will reach a range of 2,000+ nautical miles. In addition to operating with modified gas turbines, the hydrogen will generate electricity, enabling a hybrid propulsion system.
According to Glenn Llewellyn, Airbus VP of Zero-Emission Aircraft, the high energy requirements per unit mass of large passenger aircraft make it impossible to use 100% electric propulsion. In other words, the weight and volume of the critical battery system would prevent the plane from flying efficiently. That is why, today, green hydrogen seems the most realistic path to sustainable aviation.
