Will it take flight? This question is increasingly raised by those mindful of the environment. Boarding a plane might seem like the only realistic choice, especially during hard times or when loved ones live far away.
We can certainly engage in some air travel as part of a sustainable future, but we must first dispel certain misconceptions and clearly outline feasible ways to lessen our global warming footprint.
The most common myth is that sustainable aviation fuels (SAFs) can resolve our issues. This label is misleading, as SAFs often don’t live up to their name.
Here’s why: there are three primary categories of SAF. The first type is derived from waste, particularly used cooking oil. However, this only accounts for about 2-3% of global flights. The second type consists of synthetic SAFs produced from raw materials like captured carbon dioxide, using renewable energy. The efficiency of these processes is quite low (at least 2 kilowatt-hours of energy are needed to generate 1 kWh of fuel), which is a misguided use of limited renewable resources. The third type is made from crops, which puts immense pressure on farmland and the food system, posing major challenges. In reality, sustainable aviation fuel is not the revolutionary solution many hope for.
Another hopeful concept I often encounter is the idea that electrification or hydrogen fuel could decarbonize aviation. However, electrification is practical only for short-haul flights; battery weight makes it unfeasible for long distances. Hydrogen poses its own challenges due to its bulky storage requirements, even when compressed to 700 times atmospheric pressure.
On a brighter note, there are significant opportunities that haven’t garnered enough attention.
Potential solutions for greener aviation have been overlooked until recently. The high, wispy trails produced by aircraft exhaust – which account for over 60% of the climate impact of flights – carry even more weight when considering their short-term influence over the next two decades.
These contrails reflect Earth’s heat back into the atmosphere and function somewhat like a blanket. However, their overall impact is complex. They can not only trap heat but also reflect sunlight on clear days, creating a cooling effect that mainly occurs during the day, particularly over dark surfaces like oceans. Unfortunately, the warming effect tends to dominate during warm nights over dark surfaces.
By making small adjustments to flight paths, we can manage contrail formation. Changing an aircraft’s altitude or trajectory in specific weather conditions can be beneficial. Deliberate modifications while flying over sunny waters could yield positive results. A slight alteration in flight routes—just 1.7%—could potentially reduce contrail warming impacts by almost 60%. Real-time modeling is essential for integrating this into flight planning, similar to current practices for avoiding storms and managing air traffic.
This presents a relatively cost-effective solution that requires industry leadership. Once contrail management becomes established, the role of SAF might shift significantly, allowing it to contribute to cleaner burning and mitigate the worst impacts of contrails on more challenging flights.
Does this imply we can ignore the climate ramifications of flying? Unfortunately, no. Yet, understanding these factors provides a legitimate reason for optimism.
Mike Berners-Lee is the author of True Climate: Why We Need It and How to Get It
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Source: www.newscientist.com
