Clean air transport: batteries or biojet or both - but let’s get on with it
by Mike Scott, March 14, 2019
In his last article for Energy Post, Mike Scott looked at how airlines are under increasing pressure to reduce their greenhouse gas emissions rather than offsetting them as they do now. How can it be done? There is no one-size-fits-all solution for the varied size of aircraft and flight distances but that should be no excuse. Battery innovation offers solutions for some cases whilst biojet (aviation biofuel) can fill many of the remaining gaps. Dithering over which is the right path is delaying the deployment of green technologies the sector needs if it is to achieve significant, sustainable GHG emissions reductions and allow us to use aircraft with a clear conscience.
Aviation transport is finally coming under scrutiny because its current share of global emissions – about 2% (3% in EU) – is set to rise sharply in line with business growth while other sectors are actually reducing their emissions. In simple terms, it will start to stick out like a sore thumb. Moves to tackle the issue, including an industry commitment to carbon-neutral growth from 2020, are controversial because the proposed scheme allows airlines to buy carbon offsets from low-carbon projects in other sectors. How to cut emissions at point-of-use is rising rapidly up the agenda.
Direct, point-of-use options to cut emissions are limited first of all by the fact that it is much more difficult to use low-carbon technologies such as batteries in aviation than other areas because the more powerful a battery is, the heavier it must be, making them impractical.
Consequently, airlines are facing questions from investors who are concerned that they are not tackling the problem with sufficient urgency. A new study of 20 airlines from the Transition Pathway Initiative shows that none of them has a clear plan for cutting their own emissions after 2025.
Yet, while there is little prospect of electric long-haul aircraft in the foreseeable future, there is plenty that the industry can already do to minimise its impact. Indeed, electric planes are seen as part of the solution – for smaller aircraft and shorter journeys.
A number of companies are working on electric aircraft, from Lilium’s five-person vertical take-off flying taxi to Ampaire’s 19-seater vehicle up to Wright Electric’s plans for a 150-seat aircraft that would be able to make trips of 300 miles or less. Easyjet is planning to fly Wright Electric planes on its short haul European routes from 2027.
It is not just start-ups looking at this space, though. Siemens is working on a number of projects, including the Magnus eFusion electric test plane, the Pipistrel Alpha Trainer and a nine-seat commuter plane being developed by Israeli start-up Eviation. It has also formed a partnership with Airbus and Rolls-Royce to create hybrid-electric propulsion systems for commercial aircraft.
Some people think that hybrid aircraft, with both a battery and a jet fuel engine, will be the first step towards cleaner flying – including Boeing, which has invested in Zunum Aero, which is building a plane that can fly 12 people up to 700 miles, with the aim of becoming fully electric when technology allows.
But despite all these initiatives, no-one thinks battery-powered aircraft will be ruling the skies in the next decade or so. A more immediate option is to replace fossil fuel-based jet fuel with biofuel alternatives – also known as biojet. The first flight using biojet fuel was made more than a decade ago. Feedstocks have included jatropha, camelina, algae, brassica carinata, waste vegetable oil and saltwater-loving halophytes. These relatively obscure feedstocks are favoured to ensure that biofuels production does not displace crops from agricultural land or encourage deforestation.
A company called LanzaTech is producing what it calls “next generation ‘advanced’ fuels” by recycling waste industrial gases like those produced from steel making and other heavy industrial processes and turning them into ethanol, which can be turned into jet fuel. Supported by Virgin Airlines, it says that with government support, it could build three plants in the UK by 2025, producing up to 125 million gallons of sustainable fuel per year – enough to provide half the fuel for all Virgin Atlantic’s UK outbound flights and save almost 1 million tonnes of life-cycle carbon.
It adds that “if the technology were rolled out worldwide to the world’s eligible steel mills (65% of all), this alone could produce enough fuel to meet around 20% of the current commercial global aviation fuel demand”. And the technology can be used on oil refineries and agricultural waste as well.
But there is little sign that biofuels or carbon capture fuels are set to displace petroleum-based fuels any time soon, in part because the aviation sector requires exhaustive testing to ensure fuels are safe – it took Lanzatech two years to receive certification for its fuel. However, it’s hard to avoid the suspicion that the lack of progress is also the product of a lack of urgency within the industry. United is leading the pack, having committed to buy 1 million gallons of biofuel a year, which sounds impressive until you discover that its fleet uses 4 billion gallons of fuel annually.
It may be that, now the first fuels are starting to be certified for use in aircraft, the process for other feedstocks will speed up, which will help the investment case for building production plants, and that the sector will suddenly scale up rapidly.
In the meantime, work continues on improvements at the margins, from techniques such as more efficient route management and glide landing, and continued lightweighting of aircraft and their components, thanks to composite materials and technologies such as 3D printing, which can produce parts with the same strength while using less material than previously. Other options include increased use of batteries or fuel cells for auxiliary power, more efficient conventional jet engines and measures to reduce drag, such as non-stick coatings that prevent insects from sticking to the fuselage.
All of these things should be seen as a way for the industry to pursue business growth with impunity whereas under the current habit of offsetting carbon – which evidently doesn’t reduce air traffic – emissions will keep rising and the reputation of the air transport industry will suffer as a result. The question as to which technology will mature first seems a dangerous, delaying distraction and while the industry is holding back on both because it’s not sure which will be the winner, we will continue to feel pressured to fly less.