What influences the carbon emissions?

How much you fly?

The standard UK PPL mandates a minimum 45 hours of flight time. Many students will complete their PPL within this minimum number of hours, but others will take more time. Clearly, the more hours you spend in the air, the more carbon emissions will be generated.

What you fly

Most flight schools will use small, fairly fuel effecient aircraft. The Cessna 152 is a small 2 seater that is great to learn in. The Cessna 172 and the Piper PA28 are also common 4-seater options, for those who feel the 152 is too small. Check what options your school has and ask about fuel efficiency of their fleet.

You can also seek out a flight school that uses Pipistrel’s Electric Training Aircraft for PPLs. There are not too many of these schools yet, but it’s growing fast. The range of these aircraft are still quite low, but that is perfect for practising circuits whilst you learn. You’ll need to supplement this with lessons in a fossil fuel aircraft for longer navigational training, but the overall carbon emissions of this will typically be much lower than onlt using conventual powered aircraft.

Simulators can also be used to augment your flight training. This is very low carbon compared to real flight, but sadly the CAA will not count these hours towards your 45 hours required for the PPL. If you need extra practise to supplement the 45 hours, this can be the way to go.

What fuel?

AvGas (Aviation Gasoline) is used for the smaller aircraft that it’s typical to learn in. Kerosene is also used in aviation, but this is used for larger, jet engined aircraft.

AvGas varies from the gasoline used in vehicles in a few ways. Firstly, some AvGas still contains a small amount of Lead. Lead is added to Gasoline in the form of Tetraethyllead. It is used to increase performance, but is a neurotoxin and has been globally phased out in motor vehicles.

The second difference is that Motor Vehicle Gasoline is moving to include an increasing percentage of Ethanol BioFuel, a more sustainable fuel derived from plants rather than fossil fuels. In the UK, many parts of the US and many other countries, the most sold Gasoline (E10 Fuel) is 10% Ethanol, 90% Fossil Fuel.

Two common types of fuel used in light aircraft are shown here. The main difference is is the Lead addiative, the carbon emissions are approximatly the same.

Fuel	Lead	Ethanol Percentage	kg co2e/litre
91/96UL	None	None	2.51
100LL	0.56 g/l	None	2.51

¹ source

So, how can I calculate my emissions?

Fuel consumption of different aircraft will vary, but to estimate the emissions we will assume a normal training aircraft, doing normal training sorties will use 15l of AvGas per hour.

Therefore, the total litres used over the full PPL course will be:

15l of AvGas * 45 hours of training = 675 litres

To convert this to an amount of Co2e emitted, we again will make some assumption about the density of fuel, i.e. how to convert litres to kg. And, the Co2 emitted for each kg of fuel burned. This value will again vary per engine and how you are flying, but a 3.10 value is a good starting point.

So, with these numbers, we find the total emissions to be:

675 litres * 0.8 (kg/litre) * 3.10 (CO2/Fuel) = 1674 kg co2e

How does this compare to other activities

Mike Berner-Lee’s “How bad are Bananas” estimates the UK Average total emissions at 15 tonnes co2e (15,000 kg).

So, doing a PPL’s 45 hours would add 11% to the total yearly emissions for an average UK resident.

How to reduce it?

Luckily, there are a few simple approaches you can take to reduce the impact of learning to fly.

• Reduce the emissions directly as you fly, look for a school with electric aircraft, use BioFuels, find a school that makes use of simulators for training, or choose a smaller or more effecient aircraft to learn in
• Immediately remove an equivalent amount of carbon from the air. Direct Air Capture technologies exist, such as Climeworks. The cost of this is around £1,500.
• Invest in renewables technologies that will reduce fossil fuel emissions elsewhere. Examples are Abundance or ripple
• Offset with a project that has Additionality and Permanance. Carbon Offsetting Projects
• Offset with tree planting. Whilst this is a worthwhile project, it take a long time to soak up the carbon emissions and carbon stored in the biomass of trees can easily be realeased back to the enviroment due to wildfires or decomposition. However, the cost is very low and easy to add the total of of a PPL. The costs of offsetting a PPL with tree planting could be as low as £12.50, but do your due dilenge on the scheme you choose.

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Source: https://communicatescience.com/zoonomian/tag/cessna-172/