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It is estimated that over three billion people, which is almost half of the global population, will travel the world by air each year. As a result of these substantial transportation requirements, the aviation industry has evolved into the fastest, safest and most far-reaching form of transportation in around 70 years.
In addition to allowing family and friends to reconnect and introduce the world’s wonders to travelers, the world economy also benefits greatly from this industry by quickly transporting people and goods all over the world in a safe and rapid manner. In addition, the aviation industry also provides approximately 56 million jobs while only consuming approximately 2.2% of the world’s total energy. As the technology that powers this industry continues to advance to address its growing demands, federal regulatory agencies, such as the Federal Aviation Administration (FAA) of the United States, are devoting their resources to improving the environmental impacts of the aerospace industry.
Reducing Aviation Emissions
The exhaust produced by aircraft engines is comprised of approximately 70% carbon dioxide (CO2) and 30% water vapor concentrations. Less than 1% of aircraft exhaust contains pollutants such as nitric oxides (NOx), sulfur oxides (SOx), carbon monoxide (CO), unburnt or partially combusted hydrocarbons (HC), particulate matter (PM) and other potentially hazardous trace compounds. Since aircrafts typically flight at altitudes above 3000 feet, only about 10% of the total aircraft pollutant emissions are emitted below this level. Although these numbers may not seem impressive, the rising demand for travel services, which includes both passenger travel and freight transportation, is only expected to increase and subsequently pose a risk of increasing the concentrations of potentially hazardous emissions into the environment.
To address the concerns of rising aviation emissions, this industry is currently working towards improving the operation efficiency of their engines, incorporating the use of sustainable alternative fuels and developing low-emission technologies that can offset any harmful effects associated with the growth of this industry. For example, within the FAA, the Partnership for Air Transportation Noise and Emissions Reduction (PARTNER) program has recently completed Project 28, a mission that has been dedicated to improving the understanding of both the environmental and economic benefits of alternative jet fuels1.
Additionally, in the United Kingdom, the Potential for Renewable Energy Sources in Aviation (PRESAV) project successfully identified three renewable fuel alternatives that are warranted for future application in medium to long-term fuels for jet aircrafts. Although several fuels were investigated for their potential, of which included biodiesel, ethanol, methanol, Fischer-Tropsch synthetic (KT) kerosene, nuclear power, liquified hydrogen (H2) and liquified biomethane, only FT kerosene, biodiesel and hydrogen were fully investigated due to the various limitations associated with the other fuel options2. The conclusions of the PRESAV project included:
- Biodiesel: Before implementation of biodiesel into aircrafts, the PRESAV project determined that further research is still necessary to ensure that potential technical problems are addressed; however, the project anticipates that kerosene jet fuels blends containing 10-20% biodiesel may be achievable in the near future.
- FT Kerosene: Although the implementation of this fuel alternative is not expected to require many modifications to the current jet aircraft infrastructure, some fuel additives may be required as a result of the low sulfur and aromatic content of this fuel.
- Hydrogen: Unfortunately, the use of hydrogen in jet aircrafts would require significant changes to be made to the current infrastructure of aircraft jet engines, particularly to address the potential NOx production that can result of the use of this fuel option.
The global buzz surrounding the potential development of all-electric aircraft jets is expected to become a reality by the year 2022 at the earliest. For example, electric aircraft start-up company Zunum Aero, a company that has devoted their research endeavors to cutting air travel time in half. In addition, Zunum not only offers the most time-efficient mode of transportation, but also anticipates their aircrafts to have significantly lower noise and energy emissions as compared to traditional aircraft engines3. Zunum currently flies hybrid powertrain aircrafts, which are expected to transition to fully electric engines, and are equipped with batteries that are 12-20% of the total aircraft weight that match the specific distance requirements of the jet.
Similarly, Eviation, an Israeli start-up technology company, has also announced the development of both a nine-passenger aircraft, which can travel 650 miles per hour, and a commercial jet, that can travel 500 miles each hour, both of which are powered by purely electric energy sources4. The Alice commuter, which refers to the nine-passenger aircraft, is designed as a 2+9 configuration and distributed propulsion, all the while maintaining an exceptional lightweight structure that significantly reduces the noise and air emissions as compared to any other aircraft on the market today. Similarly, Orca, Eviation’s commercial model, is still in the early stages of development; however, is expected to have autonomous takeoff and landing features in addition to its highly energy and economical efficient functionality5.
Reference and Further Reading
- “Aviation Emissions, Impacts & Mitigation: A Primer” – Federal Aviation Administration
- “The Potential for Renewable Energy Source sin Aviation” – Imperial College of London
- “Technology” – Zunum Aero
- “Plane maker to test all-electric jet in 2019, sets sights on IPO” – CNBC
- “Orca” – Eviation