Planes across Europe will soon run on renewable fuel made from vegetable oil and animal fat in a bid to tackle climate change and toxic air.

The new fuel will pour into planes mixed with traditional kerosene at Geneva Airport from next year but the millions of passengers travelling through the busy hub each year won’t notice the difference. The planes will run just as smoothly and engine performance is even slightly improved, says Matti Lievonen, the boss of Neste, the Finnish company that’s supplying the fuel.

He hopes that the deal will act as a blueprint that can be rolled out all over the world and says Neste has spoken with ten hub airports about implementing similar arrangements, including two of Europe’s busiest - Schiphol and Heathrow.

Geneva is initially aiming for 1 per cent renewable fuel starting from the end of next year and Lievonen says he hopes to increase that in future. There’s certainly room for expansion - Lufthansa tested the fuel on more than 1,000 flights in 2011 with a 50-50 blend of renewables to kerosene. “It worked amazingly well,” Lievonen says. “Engine performance improved. We have a very good track record in aviation and it’s an exciting growth area for us.” Carbon emissions were reduced by 47 per cent.

“We need airlines and hub airports that really want to use the technology,” Lievonen says.

Sustainable fuels have so far made a small dent in the vast and consumption of the airline industry, but their impact is growing. Boeing successfully tested out the renewable fuel on its new 787 Dreamliner jet in 2014 and several airlines have recently begun to use jet fuels made from waste. Last year, United Airlines agreed to purchase 15 million gallons of biofuel from US firm AltAir, while British Airways signed a deal last month with Velocys to supply jet fuel made from some of the 15 million tonnes of waste UK households send to landfill each year.

Despite the competition, Lievonen is confident that his firm will remain the world’s leading producer of renewable diesel. “We have the advanced technology to make renewable fuel and we are the only company that can make it at the real industrial scale required,” he says.

Neste’s renewable diesel comes in a number of forms, which can be used in any traditional diesel engine, meaning it can also make a contribution to cutting the air pollution choking many cities around the world and killing millions of people.

Diesel cars have taken much of the flak for the toxic air blighting many cities after revelations that car makers spent years duping the public into thinking they were pumping out far lower levels of pollutants than they actually were.

London Mayor, Sadiq Khan, earlier this month introduced a charge for older, more polluting, diesel cars and several countries have announced eye-catching deadlines for the eradication of the internal combustion engine altogether.

But the delivery dates for most of these promises lie decades in the future, meaning that those who promised them are unlikely to be held to account. While Khan’s policy is effective immediately, experts estimate it will affect just 6,500 vehicles and is therefore likely to have little impact on air quality or greenhouse gas emissions.

Lievonen says 100 per cent renewable diesel waste can play a significant part in reducing lowering CO2 emissions and air pollution right now.

A plane fills up with a blend of renewable diesel and traditional jet fuel at Geneva Airport (Neste)

The Finnish company’s fuel pumps out much less of the harmful pollutants associated with fossil diesel - up to 40 per cent less particulate matter and 10 per cent less NOx. When used in its purest form it also produces up to 90 per cent less carbon emissions.

Renewable diesel is fundamentally different from most other fuel produced with waste fat or vegetable oils, known as biodiesel. The latter has been around in one form or another since Rudolf Diesel used fuel made from peanuts to test the engine he invented at the 1900 World’s Fair in Paris. While biodiesel can only be mixed with normal fuel up to a certain percentage before engines and infrastructure have to be modified, renewable diesel can simply be “dropped in”, meaning it can potentially play a greater role in making existing fleets of vehicles more friendly to the planet.

Thanks to heavy investment in research and development, Lievonen says Neste can now make viable fuel from waste fat that would have been unusable a few years ago, allowing it to ramp up production massively. The company has a sprawling network that reaches all over the world, collecting millions of tonnes of assorted waste from ten different types of sources.

Some of the key inputs are pig, beef and poultry fat which is collected from slaughterhouses and then rendered down. Fish fat from farms in Southeast Asia makes its way to the company’s processing plant in Singapore. Vegetable oil byproducts from industrial food production as well as used cooking oil from restaurants are collected, with the whole mix then refined into a clear, clean-burning liquid.

The process is not entirely uncontroversial. Some of the vegetable oil residue is from palm oil processing. Lievonen says Neste is merely using waste from an industry that would be there anyway. Environmental groups contend that buying the leftovers directly supports palm oil cultivation, which has been linked to large-scale deforestation.

Peter Behrle, a biofuels expert, and founder of US waste treatment firm, Lantern Environmental, says different people have different ideas about what is defined as waste. Animal fats can also be used in many other purposes such as making soap he says.

Planes, trains or automobiles?

While renewable diesel can help clean up our air, filling up the tanks of passenger cars isn’t the most useful application for the product. Whatever may or may not be achieved by policies such as Khan’s T-charge, Lievonen, predicts that all cars in inner-city areas are likely to be electric in the foreseeable future.

Public backlash against the dieselgate scandal has already begun. UK sales of diesel models in September slumped more than a fifth on the same month last year. Electric car sales, while still tiny by comparison, are gathering pace.

But heavy-duty vehicles, such as lorries and buses, as well as shipping and aviation, are responsible for greater proportions of both diesel consumption and CO2 emissions around the world than passenger cars.

In London, for example, the Mayor’s figures show that cars account for 11 per cent of NOx emissions, while rail transport and lorries belched out almost a quarter. In certain busy areas, buses contribute far more to poor air quality than cars do.

Neste has already partnered with a number of cities, including San Francisco, San Diego and Helsinki, to run their entire bus fleets on 100 per cent renewable diesel. By comparison Transport for London uses a 20 per cent biodiesel blend from a UK company, Argent Energy, to fuel around a third of the capital’s buses.

London is one of many cities battling poor air quality, partly due to diesel engines (Getty Images)

HGVs, which travel punishing schedules over long-distances, often across multiple borders, are likely to take far longer than passenger vehicles to make the switch to electric, Lievonen says, though he won’t put a precise timeline on it. These vehicles have diesel, rather than petrol engines, because the former are seen as more durable and can travel up to 1,000 miles on a single tank.

Batteries that can reliably shift heavy loads over such distances at an economical cost, do not yet exist, and – even at the current rapid pace of technological advancement – appear unlikely to replace diesel any time soon.

Tesla boss Elon Musk said last month that his company would unveil an “unreal” new electric-powered truck before the end of October but it remains to be seen if it will be a viable alternative to diesel equivalents, at least in the short term. Reuters reported that Tesla’s new car will have a maximum range of 200 to 300 miles.

Electric air travel is also a long way off. easyJet recently said it hopes to fly small electric passenger planes up to 335 miles within a decade, but the concept, developed by Wright Electric, relies on batteries continuing to develop at their current rate for the next ten years. And that’s just to fly the distance between London and Edinburgh.

The plane of the future? Wright Electric is partnering with easyJet on an electric-powered plane (Wright Electrics)

While Musk is partial to a “moonshot” idea, and easyJet’s announcement is based on speculative assumptions, Lievonen has a solution that is already proven to work.

Demand for clean alternatives to fossil diesel is unlikely to be a problem. On the other hand, supply might be. Even if you account for the ever more sophisticated production methods pioneered by firms like Neste and Argent, there are limits to the sources of renewable fuel, says Behrle.

“Clearly nobody is going to start killing more pigs and chickens to make more diesel, so if one company increases its usage it takes away from others,” he says. “Biodiesel may or may not be the best use for that animal fat but if I’m a soap manufacturer, I’m not going to stop buying it.”

But Neste plans to continue it expansion. In 2015 it became the world's largest producer of renewable fuel from waste and it currently has capacity to make 2.6 million tonnes (3.2 billion litres) a year. It says that it aims to ramp up production to 3 million tonnes by 2020 and 4 million tonnes by 2022 - enough to power several million cars for a year.

Behrle says the real growth area left, particularly in the UK, is in the dirty oil collected in grease traps at restaurants and hotels. Argent now successfully makes fuel out of the vast “fatbergs” that clog up Britain’s sewer system when cooking oil and other solids are thrown down sinks or flushed into loos.

Lievonen admits that there is a finite amount of waste that Neste can refine and says even current production levels are “just a drop” when compared to the world’s current thirst for oil.

The company is focused on continually improving its technology and partnering with the most environmentally minded companies and cities. Neste runs buses for Google in and around the tech firm’s mammoth Santa Clara headquarters, and also powers UPS delivery vans across the US.