We could cut particulate pollution from air travel by 60% – but the journey has run into turbulence

Oh, lovely. Image: Getty.

When it comes to reducing carbon emissions, one of the biggest hurdles is the world’s addiction to flying. And this is only going to get more intense as developing countries grow bigger middle classes who want to explore the world for business and pleasure. The Conversation

In the UK, the climate change minister, Nick Hurd, has named transport as one of the two biggest environmental challenges facing the world. But while the government continues to invest in research and infrastructure for electric vehicles, clear action on addressing carbon dioxide for air transport has been lacking.

Our researchin collaboration with Manchester Metropolitan University and Missouri University of Science and Technology has shown that greener aviation fuels could cut not only carbon emissions but also reduce wider air pollution and improve air quality – a key issue in the ongoing debate around Heathrow’s proposed expansion.

The landmark 2015 Paris Agreement on addressing climate change did not include two sectors – aviation and maritime. This is despite aviation accounting for 2 per cent of global carbon dioxide emissions. This figure is growing by around 3 per cent a year. Attempts to decarbonise the aviation sector have so far proven complicated.

The process has been delayed by governments trying to agree on how to account for emissions: if a Dutch airline takes off in America and lands in Brazil, which country should take the responsibility for those emissions? The good news is that, in the autumn of 2016, the world’s governments came together under the UN’s specialist agency for aviation, the ICAO and finally reached an agreement. But this agreement is still voluntary and allows airlines to “offset” their carbon emissions.

Beyond this, the industry has set itself a targetto achieve carbon-neutral growth by 2020 and to halve emissions by 2050 compared to 2005 levels. This ambition can only be achieved by a combination of efforts including improvements in engine and airframes, such as new materials to make aircraft lighter, a more emissions-optimised approach to air traffic management and, crucially, by introducing greener alternatives to jet fuel.

These alternative aviation fuels could offer the UK airline industry between 15 per cent and 24 per cent reduction in CO2 emissions by 2050. The UK government is starting to take action, including issuing a consultation on whether to increase the obligation it puts on airlines to increase the level of so-called “renewable fuel” used currently. Running in parallel with this has been a consultation on the future growth of Heathrow airport – and, even in this, alternative fuels could play a part both in terms of lower CO2 emissions if alternative fuel use is increase, and because these fuels contain fewer particulates than conventional fuels.

Our research has shown that particulates from air travel could be reduced by up to 60 per cent by using synthetically produced fuels from feedstocks such as old cooking oil. In simple terms, the oil-baring feedstock can be heated with a catalyst to change its structure and extract the useful chemicals to form a type of fuel that can be used to power jet aircraft.

The Airbus 319 burns 640 gallons of fuel per hour. Image: Nordroden.

There are, of course, challenges which need to be overcome if the role of alternative aviation fuels in tackling climate change and air pollution is to be realised.

Aviation fuel has not changed substantially since the 1960s. The focus of improvements in the efficiency of engines and airframes has been on the continued improvements to technology to the point where we have a highly optimised system based on the use of traditional fuels. If the industry adopted fuels developed from non-conventional sources such as bio-crops this may, in turn, make it possible for the indsutry to make further improvements in engine and airframe technologies based on new fuels. There are three major challenges facing the industry.

Three challenges

Safety: This is the most obvious problem to overcome. The approval process for new fuels is extremely rigorous – airlines will not use fuels unless they know they are completely safe and will not affect the operation and reliability of the aircraft. This process can take several years to complete. To date, only a handful of alternative production routes have been approvedand the sector’s experience of dealing with new molecules in the jet fuel is increasing. Better modelling and earlier testing of fuels should help reduce the time, and cost, of this approvals process and efforts such as the US FAA and the ASCENT programme which aim to accelerate the approvals process in the future.

Economics: The technology for producing alternative aviation fuels is still relatively immature and at a small scale which means that the cost remains higher than for fuel from conventional sources. Further research and development – and increasing the scale of production – will address these issues, as will the introduction of regulations which reward and incentivise airlines to use these fuels.

Sustainability: We need to ensure that the production of alternative fuels works for the environment and people in the regions where these are produced. So, for example, in the case of biofuels, these shouldn’t compete for land with vital food crops. The use of municipal waste or offgases from industrial processes are two alternatives which do not compete with land use are gaining some traction as alternative fuels.

This is an issue that will only get more urgent as more people in developing economies choose to travel by air. We’ve already made a good start – since 2011, more than 2,200 commercial flights have used alternative fuels– but this has to be put in a context of more than 100,000 flights being made worldwide each day.

While the current agreement is voluntary, ICAO has managed to create one of the first global agreements to apply to a specific sector on carbon emissions. Industry and academia now need to deliver the advancements – supported, needless to say, by national governments. That will be crucial if we are to see greener skies overhead any time soon.

Simon Blakey is senior lecturer in mechanical engineering at the University of Sheffield.

This article was originally published on The Conversation. Read the original article.


Everything you ever wanted to know about the Seoul Metro System but were too afraid to ask

Gwanghwamoon subway station on line 5 in Seoul, 2010. Image: Getty.

Seoul’s metro system carries 7m passengers a day across 1,000 miles of track. The system is as much a regional commuter railway as an urban subway system. Without technically leaving the network, one can travel from Asan over 50 miles to the south of central Seoul, all the way up to the North Korean border 20 miles north of the city.

Fares are incredibly low for a developed country. A basic fare of 1,250 won (about £1) will allow you to travel 10km; it’s only an extra 100 won (about 7p) to travel every additional 5km on most lines.

The trains are reasonably quick: maximum speeds of 62mph and average operating speeds of around 20mph make them comparable to London Underground. But the trains are much more spacious, air conditioned and have wi-fi access. Every station also has protective fences, between platform and track, to prevent suicides and accidents.

The network

The  service has a complex system of ownership and operation. The Seoul Metro Company (owned by Seoul City council) operates lines 5-8 on its own, but lines 1-4 are operated jointly with Korail, the state-owned national rail company. Meanwhile, Line 9 is operated jointly between Trans-Dev (a French company which operates many buses in northern England) and RATP (The Parisian version of TfL).

Then there’s Neotrans, owned by the Korean conglomerate Doosan, which owns and operates the driverless Sinbundang line. The Incheon city government, which borders Seoul to the west, owns and operates Incheon Line 1 and Line 2.

The Airport Express was originally built and owned by a corporation jointly owned by 11 large Korean firms, but is now mostly owned by Korail. The Uijeongbu light railway is currently being taken over by the Uijeongbu city council (that one’s north of Seoul) after the operating company went bankrupt. And the Everline people mover is operated by a joint venture owned by Bombardier and a variety of Korean companies.

Seoul’s subway map. Click to expand. Image: Wikimedia Commons.

The rest of the lines are operated by the national rail operator Korail. The fare structure is either identical or very similar for all of these lines. All buses and trains in the region are accessible with a T-money card, similar to London’s Oyster card. Fares are collected centrally and then distributed back to operators based on levels of usage.


The Korean government spends around £27bn on transport every year: that works out at 10 per cent more per person than the British government spends.  The Seoul subway’s annual loss of around £200m is covered by this budget.

The main reason the loss is much lower than TfL’s £458m is that, despite Seoul’s lower fares, it also has much lower maintenance costs. The oldest line, Line 1 is only 44 years old.

Higher levels of automation and lower crime rates also mean there are fewer staff. Workers pay is also lower: a newly qualified driver will be paid around £27,000 a year compared to £49,000 in London.

New infrastructure is paid for by central government. However, investment in the capital does not cause the same regional rivalries as it does in the UK for a variety of reasons. Firstly, investment is not so heavily concentrated in the capital. Five other cities have subways; the second city of Busan has an extensive five-line network.

What’s more, while investment is still skewed towards Seoul, it’s a much bigger city than London, and South Korea is physically a much smaller country than the UK (about the size of Scotland and Wales combined). Some 40 per cent of the national population lives on the Seoul network – and everyone else who lives on the mainland can be in Seoul within 3 hours.

Finally, politically the biggest divide in South Korea is between the south-west and the south-east (the recently ousted President Park Geun-Hye won just 11 per cent of the vote in the south west, while winning 69 per cent in the south-east). Seoul is seen as neutral territory.  


A driverless train on the Shinbundang Line. Image: Wikicommons.

The system is far from perfect. Seoul’s network is highly radial. It’s incredibly cheap and easy to travel from outer lying areas to the centre, and around the centre itself. But travelling from one of Seoul’s satellite cities to another by public transport is often difficult. A journey from central Goyang (population: 1m) to central Incheon (population: 3m) is around 30 minutes by car. By public transport, it takes around 2 hours. There is no real equivalent of the London Overground.

There is also a lack of fast commuter services. The four-track Seoul Line 1 offers express services to Incheon and Cheonan, and some commuter towns south of the city are covered by intercity services. But most large cities of hundreds of thousands of people within commuting distance (places comparable to Reading or Milton Keynes) are reliant on the subway network, and do not have a fast rail link that takes commuters directly to the city centre.

This is changing however with the construction of a system modelled on the Paris RER and London’s Crossrail. The GTX will operate at maximum speed of 110Mph. The first line (of three planned) is scheduled to open in 2023, and will extend from the new town of Ilsan on the North Korean border to the new town of Dongtan about 25km south of the city centre.

The system will stop much less regularly than Crossrail or the RER resulting in drastic cuts in journey times. For example, the time from llsan to Gangnam (of Gangnam Style fame) will be cut from around 1hr30 to just 17 minutes. When the three-line network is complete most of the major cities in the region will have a direct fast link to Seoul Station, the focal point of the GTX as well as the national rail network. A very good public transport network is going to get even better.