Public awareness around the negative environmental impacts of flying has risen considerably over the last few years. However, the aviation industry continues to grow, and more people are flying now than ever before.
There’s hope that new advancements in aviation technology will allow us to continue our flying habits while bringing carbon emissions down, making the business of air travel more environmentally friendly. But is the prospect of sustainable flights something we can count on, or just a lot of hot air?
Electric engines are scheduled to start replacing gas engines on some short-haul commercial flights in 2022. Rather than burning jet fuel, these engines rely on a rechargeable battery to operate. Like electric car engines, they do not generate CO2 emissions and can be powered with renewable energy.
However, the battery needed to fly an electric plane is much heavier than fuel and takes up much more space, significantly limiting the load that can be carried and the distance that can be travelled. This technology could only be used for flights of up to 1000 kilometres, as the battery would need to be re-charged after that.
"The battery needed to fly an electric plane is heavier than fuel and takes up more space, limiting the load that can be carried and the distance travelled."
For mid-range flights, hybrid engines are a less carbon-intensive possibility – but they would still have to use polluting jet fuel to operate.
Unless there is a breakthrough in designing rechargeable batteries that are lighter and more durable, long-haul flights won’t benefit from this technology at all. According to the Air Transport Action Group, 80% of the aviation industry's emissions come from passenger flights longer than 1,500km.
So if planes have to burn fuel to complete longer journeys, are there any ways to make it more sustainable?
Biofuels are currently the most promising alternative to fossil fuels, but biofuels made from plants are typically monoculture crops, which are a disaster for biodiversity, and are a key driver of deforestation. Several airlines are now pursuing biofuel made from waste products, such as ethanol captured from the waste gases of steel mills.
"Biofuels are a promising alternative to fossil fuels, but biofuels made from plants are typically monoculture crops, which are a disaster for biodiversity."
While recycling all of our waste materials into energy sounds ideal, it isn’t without its drawbacks. Fossil fuels are still needed to create waste materials to begin with, and the process of making biofuel produces its own emissions. Additionally, synthetic fuels don’t behave in exactly the same way that fossil fuels do, so can’t be more than 50% of fuel used on a flight. As these biofuels are up to four times the price of fossil fuels, they are also fairly unpopular with airlines. Alternative fuels currently make up less than 1% of fuel used in the industry, so scaling up would be a massive challenge.
If decarbonising jet fuel isn’t the answer, should we be looking at ways to reclaim the carbon after it has been pumped into the atmosphere?
Carbon capture devices are already used on submarines and spacecraft. They rely on ‘scrubbers’ which absorb CO2 a similar way to plants. Direct Air Capture (DAC) is a process that would use scrubbing technology at a much larger scale, taking CO2 out of the air and storing or burying it in the ground.
DAC is still in its early stages of development, and scaling up to make a global impact on flying emissions would require a huge amount of investment. Plus, the energy required to run such operations would be massive.
One of the biggest problems with relying on carbon capture to offset the effects of flying is that CO2 isn’t the only harmful emission planes release into the air. Nitrogen oxide (NOx) is another greenhouse gas, as are the vapour contrails left behind by planes. These emissions are more harmful at high-altitude than if they were released at ground level, with roughly double the warming effect.
"A big problem with relying on carbon capture to offset the effects of flying is that CO2 isn’t the only harmful emission planes release into the air."
Time is Running Out
We’re just scratching the surface here of a whole industry devoted to decreasing the negative effects of flying. There are many more experimental technologies that have been proposed to help curb the crisis, including innovative new wing designs, solar planes and the introduction of hydrogen fuel cells.
The problem shared by all of these technologies is that they are in the early stages of development and are relatively small-scale. At the current rate of air travel expansion and with the lack of any cheap, quick fixes on the horizon, it seems as though an increase in aviation emissions is inevitable. As we have been given 10 years to make significant reductions to our carbon emissions before the effects of climate change become irreversible, we really can’t afford to let this happen.
Currently, there is no silver bullet technology that will reduce air travel carbon emissions to zero by 2050. The only way to significantly and realistically reduce emissions is if we all make the decision to fly less.