Aviation and fossil fuels
replace fossil-fuels in the short term, SAF still lacks a lot of research and infrastructure to realize an actual change in emissions.
Hybrid power
Another potential short-term solution before more advanced technologies are developed is hybrid- electric power. The EU in particular has put a lot of support behind this technology, stating that it could be in the air within 15 years (Ceurstemont, 2020). The key idea is to use the advantages of electricity as much as possible, and then to use the minimum amount of fuel to make the flight feasible. While this would still mean burning hydrocarbons, it satisfies the role of a short-term improvement. A concept for a hybrid-electric plane developed by MIT in 2021 claims to be able to reduce direct aircraft emissions by as much as 95% (Chu, 2021). Similar to petrol vehicles, this can be achieved using an emissions-control system. By mounting the jet engines within the hold of a plane and using them to generate electricity to then power outboard propellors, the products of combustion can be kept onboard and filtered before being released into the atmosphere. MIT argues that, while this would not change the rate of fossil fuels being burnt, it would dramatically reduce the amount of pollutants entering the atmosphere (Chu, 2021). This also makes the adoption of such a technology much easier as the energy would still come from kerosene and would therefore allow a continued use of the existing infrastructure networks. Combining this with more sustainable fuels further down the line would further increase the effectiveness of such a technology. These two innovations together could mean a vast improvement for aviation, with more renewable fuels being burnt and less of the products entering the atmosphere. All while not impacting flight times.
Hydrogen and hydrogen fuel cells
In the search for alternative fuels, hydrogen has emerged as a major challenger to hydrocarbons. Combusting it produces only water vapour, making it one of the cleanest fuels available. In addition to this, it has a wider flammability range, m eaning that an aircraft’s engines could run on a leaner fuel mix in certain situations. It also can be used to power electrical systems when used in a hydrogen fuel cell. This fuel cell technology has already seen commercial use in automotive and transport industries, as it can constantly generate electricity from hydrogen and oxygen. This allows an electric vehicle using a fuel cell to run without heavy batteries and without the long wait for the vehicle to recharge, two traits that could succeed where the regular battery idea already failed. So important are these advantages, that hydrogen first powered a commercial airliner relatively long ago in 1988 with the Tupolev Tu-155. This ability to conserve fuel may seem inconsequential to the environment when the fuel in question produces no emissions. But this quickly changes when sourcing the hydrogen is considered. Whilst it is the most abundant element in the universe, it mostly exists in water and, ironically, hydrocarbons. Therefore, hydrogen must be refined. One of the most common methods of manufacturing hydrogen is a process known as steam-methane reforming. This is where high temperature steam and natural gassed are combined to produce hydrogen. This method however not only produces carbon monoxide as a by-product but is also very inefficient (Real Engineering, 2018). So, for hydrogen to graduate from more of a zero-emission marketing ploy to a genuine solution, we would need to improve the way in
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