Although aviation is not the largest contributor to Greenhouse gas emissions (currently less than 10% of global emissions) it is not only one of the most intensive emitters for the product (Revenue Passenger-km) that it produces, it is also the fastest growing polluter in the world. European aircraft manufacturer Airbus’ 20 year Global Market Forecast for 2009 expects that almost 25 000 new aircraft will be delivered and demand for air travel to triple by 2028, meaning that there would be almost 32 000 planes flying worldwide by then rather than just under 16 000 last year.
This inherent increase in aircraft size, should it happen, is already an improvement because a larger aircraft has a better per passenger fuel consumption than the smaller aircraft even if its overall fuel consumption is higher. As an example the Boeing 737-800 burns about 11% more fuel than the smaller Boeing 737-600 but can carry up to 27% more passengers, overall this economy of scale reduces per passenger fuel burn by almost 20% without actually improving the operational methods or technology involved in air travel. This does however only affect the per passenger emissions and not the total emissions, meaning that despite larger aircraft overall emissions may still rise.
Aircraft emissions have been falling steadily as a result of technology improvements since the first jet aircraft flew in the 1950’s; fuel consumption for early jets regularly exceeded 8 kg of fuel per km for an aircraft which typically had no more than 130 seats (the Comet 1 of 1952 had no more than 44), an aircraft like the A380 uses around 11 or 12 kg/km but can carry over 500 people, a per passenger fuel consumption better than some small cars.
Many other improvements should also occur over the next 5-10 years, such as more lightweight materials (Carbon-fibre, plastics and Glass re-enforced aluminium) used in construction of aircraft such as the new Boeing 787, to reduce weight and therefore fuel burn.
Improvements to air traffic control procedures such as the introduction of continuous descent approaches (currently being trialled at Zurich Airport) or GBAS and ADS-B (currently being developed) can reduce the amount of time that aircraft spend circling, allow more direct routes and therefore reduce fuel burn and emissions. Another improvement could be to remove the rule that keeps aircraft at a set altitude to ensure air traffic controllers aren’t overworked, the most fuel efficient height for an aircraft is to perform a gentle but continuous climb as the aircraft loses weight from burning fuel.
Changing cruising altitudes has also been proposed as a way of reducing contrails from aircraft by flying lower but this would mean flying through thicker air using more thrust , burning more fuel and increasing CO2 and NOX emissions, so a balance needs to be struck and it may even be the case that it is better for jet aircraft to fly even higher (45-50 000ft). The issue is not as clear cut for propeller-driven aircraft which are require a certain air density to be able to move forward at all, but propellers are actually more fuel efficient than pure jets at slower speeds and lower weights, which is why turboprops are the propulsion method of choice for smaller, slower moving aircraft used between smaller airports separated by short distances.
Increasing the pressures and temperatures inside an aircraft’s engines improves it’s efficiency so it burns less fuel which is beneficial with regards to peak oil as well as producing less CO2, but running at higher temperatures and pressures means that more oxygen and nitrogen molecules fuse together creating more NOX emissions. Increasing an engine’s bypass ratio also improves its efficiency (and reduces noise emissions for those living near airports) but requires a larger engine diameter which requires more weight, engine improvements using current technology are therefore
very much a balancing act in deciding whether less CO2 is worth producing more NOX or whether less noise and better fuel efficiency is worth the extra weight.
Reducing the number of intersecting runways at airports and replacing them with parallel runways can also reduce emissions as aircraft spend less time waiting to land while also reducing the risk of accidents and the workload of air traffic controllers.
Overall, progress in environmental terms in the airline industry is still painfully slow. It was not until the late 1980s that winglets (vertical fins at the wing tips to reduce drag) first appeared on commercial aircraft, and not until the 2000s that most new aircraft had them, despite the fact that the potential fuel saving from winglets (about 8% as compared to the same aircraft without them) was first considered and proved successfully in 1977. Some aircraft can safely fly for over 30 years, meaning that many aircraft still in operation were designed in the 1980s and are based on 1970’s technology and have 1970s environmental capabilities to match, meaning that some of these aircraft burn twice as much fuel as modern aircraft that carry the same number of passengers. Even upgrades of older aircraft can reduce fuel consumptions by up to 15%.
Considering that aviation involves such modern technology that is increasingly at the limit of what science can actually achieve, innovation and environmental progress remain painfully slow, possibly as a result of the incredibly tight economic margins in which airlines operate. This lack of initiative and cautious approach to new ideas means that many potential major breakthroughs such as Blended Wing Bodies go almost completely unresearched. The most likely catalyst for drastic improvements in emissions and fuel consumption are likely to be high fuel prices and taxation of Greenhouse gas emissions rather than a decision by the airlines on the grounds of social responsibility or conscience.
Per passenger emissions are around 60% less than they were 40 years ago but the total amount of travel by air is roughly 4 times greater than 30-35 years ago meaning that total aviation emissions have risen by over a third in the last 40 years. In future this growth rate is predicted to continue meaning that it will be increasingly difficulty to offset more flying by making flying more efficient.
Overall, it is impossible for aviation to achieve any of the growth predicted by Airbus’ Global Market Forecast without accounting for all of the greenhouse gases that can be sustainably emitted, unless a ground breaking change, of the magnitude of the jet engine, occurs within the next few years. If such a change does not come about, the predicted growth will mean that the emissions targets required to limit the global temperature rise cannot be met.
The District Fellows Movement is the 16-20 year old members of the co-operative educational youth charity, the woodcraft folk, whose ideology is based on the principles of equality, peace, social justice and co-operation, with an emphasis on the empowerment of young people.
DF meetings usually consist of a group of like minded individuals meeting up at a regular time and place (someone's house, or a pub for instance, or even a community hall if the group is large enough) and taking part in usual woodcraft activities. These activities range from co-operative games, orgainising events, workshops and discussions, and general socialising!
The DF movement also meets up on a national basis frequently, to hold both social, educational events and business events allowing everyone to be involved in the running of DF's...
Althing: 3rd to 5th September
Old/New: 8th to 10th October
Blank Canvas: 29th to 31st October
Midlands Thing: 3rd to 5th November
