Mankind dreamed of flying for centuries. Now almost 3 billion of us take it for granted. That’s how many will have boarded an aircraft somewhere on this planet last year. How many of those felt guilty because they knew that flying is probably the single most polluting action you can do which contributes to global warming? Probably not many.

For people aren’t going to want to stop flying any time soon. For many, it’s the only way to get to their loved one or to that important business meeting in the time available. Very often it’s also the cheapest travel mode.

The aviation industry has for many years refused to bow to pressure to reduce its impact on climate change. Airline fuel is not taxed – unlike virtually every other kind of fuel. With no incentive to change, why should it?

Besides, we all like cheap flights, don’t we? But something has to give. The industry knows that the writing is on the wall.

It does not want mandatory restrictions. Besides, how do you legislate against a global industry? The European Union has bravely tried and incurred the ire of American and Asian airlines.

The industry is putting its faith in market-based measures. It is researching lighter aircraft and more sustainable fuels. The big question is, can there ever be sustainable alternatives to fossil-fuel kerosene deliverable in sufficient quantities to meet the ever-growing demand for flights, which is forecast to grow by around 5% per year in the medium term?

Members of the International Air Transport Association (IATA) are responsible for around 85% of all commercial flight operations. They have voluntarily committed to carbon neutral growth in 2020 onwards and a halving of greenhouse gas emissions from the sector by 2050.

One way of achieving this challenging objective will be an agreed standard on what constitutes a ‘sustainable’ fuel (if that is not an oxymoron). The standard must be objective and applicable throughout the world.

At the moment there is legislation in several countries about biofuels used in road transport. Any biojet fuel reported within those territories has to comply with the criteria. The main examples are the EU Renewable Energy Directive (RED) and the Renewable Fuel Standard (RFS2) in the US.

There are also some voluntary schemes for the certification of biomass sustainability, but they all differ in detail and scope.

Right now, airlines operating international flights must juggle the requirements of different jurisdictions. Ideally, in the future, airlines should be able to buy fuel anywhere, and use it on any flight knowing that it is compliant with legislation anywhere.

The IATA has commissioned research into how this might come about. It’s worked with the consultancy Ecofys to assess RED and RFS2 for suitability, and looked at other options.

It then conducted a stakeholder workshop with representatives of the airlines and the bio jet fuel industry. The options that received the most support where the mutual recognition of RED and RFS2, and the development of a new meta-standard for aviation biofuels. The results have just been published in a report: Assessment of sustainability standards for biojet fuel.

Mutual recognition between the two big standards would mean that biojet fuel could be freely traded between the European Union and the USA. The two standards could provide the basis for an internationally accepted approach to biofuels sustainability. The two standards share a common basis in that they both include requirements for greenhouse gas saving and restrictions on land conversion for growing biofuels.

The IATA says that ideally the International Civil Aviation Organization (ICAO), the UN’s civil aviation organisation, would take up the role of negotiating a legislative route for the two standards to harmonise. The ICAO is due to debate these and other environmental aspects of flying at its March 2015 gathering in Poland.

But judging by the fact that the ICAO took around 10 years to even begin considering the possibility that it should respond to climate change, don’t hold your breath for any sudden developments. This is an industry which, despite the breathtaking speed of its aircraft, moves at a glacial pace when instituting technological change and responding to environmental concerns.

Besides, there is the question of whether it is possible to provide enough biofuel and feed the world and have a sufficiently biodiversity planet. That depends on technological breakthroughs yet to be achieved.

Frederic Eychenne, Airbus’ head of new energies, believes that to achieve true sustainability, biofuel, like food, will have to be locally-sourced. “Different countries grow different crops. They have different refineries in place. Sustainability isn’t just about reducing emissions in the air. We have to consider the whole life-cycle in terms of production,” he says.

Many biofuels will come from algae. Others will come from fermenting cellulose. All of them are expensive, at least three times more than current biofuels.

A research unit in Leuna, Germany, to produce isobutene from renewable raw materials.A research unit in Leuna, Germany, to produce isobutene from renewable raw materials. Source: Fraunhofer Center for Chemical-Biotechnological Processes.

One technical obstacle is that isobutylene is used to make fuel additives and kerosene – jet fuel – but nowhere in nature is isobutylene made using bacteria. One company, LanzaTech, is working with Global Bioenergies, to prove it’s possible to develop an artificial pathway allowing the direct fermentative production of isobutylene from waste carbon monoxide, but the development of the technology is taking a long time. The same is true for other potential routes.

However Global Bioenergies did report a breakthrough in November when, for the first time, it managed to produce fermentative isobutene in an industrial environment, after six years of trying, as this video shows:

In the long term, perhaps the limit on flying will be this: through legislation and the high cost of new fuels, flying will become more expensive. Demand will come down. Legislation will control fuel standards with respect to greenhouse gas emissions.

But it will take decades. Meanwhile the planet is warming, and the most climate-friendly thing you can probably continue to do is not to fly. Remember, one short flight will wipe out all the benefits of the other green things, like recycling, that you do.

This article is published in collaboration with Sustainable Cities Collective. Publication does not imply endorsement of views by the World Economic Forum.

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Author: David Thorpe is Special Consultant of Sustainable Cities Collective.

Image: An EasyJet aircraft comes into landing during sunset at East Midlands airport, central England October 5, 2008. REUTERS/Darren Staples.