SAFs are being held up as the aviation industry’s carbon-free saviour – but in reality they’re a deeply problematic ‘solution’. Helen Coffey finds out more
The impressive-sounding “inaugural meeting of the International Aviation Climate Ambition Coalition”, held at this year’s Cop26, attracted some of the world’s wealthiest and most influential countries, 英国を含む, US and France. The never-before-seen meeting between 23 nations took place at the climate conference in Glasgow earlier this month – but what was actually achieved when it came to air travel?
A declaration was made by the signatories, one that included a number of pledges to “acknowledge”, “recognise” and “recall” that aviation emissions have quite a big impact on global warming.
実際には, the language seemed largely to suggest a lot more “recognising” of the problematic nature of growing CO2 output from air travel than, いう, actually doing anything to reduce it. But among the very tepid promises were a few more practical suggestions. The coalition agreed to “promote the development and deployment, through international and national measures, of sustainable aviation fuels that reduce life-cycle emissions and contribute to the achievement of the UN Sustainable Development Goals (SDGs), in particular avoiding competition with food production for land use and water supply.”
This may not be your first time hearing the phrase “sustainable aviation fuels”, or SAFs – because 2021 was the year that the 航空業界 and governments alike seemed to collectively decide that these would be the saving grace of a practice that is increasingly under the microscope for its damaging climate impact.
In September this year, British Airways operated its first flight using sustainable aviation fuel (SAF). The airline said the flight from London Heathrow to Glasgow demonstrated how “aviation is decarbonising”.
以前に 2021, its parent company, International Airlines Group (IAG), became the first European airline group to commit to powering 10 のパーセント フライト with sustainable aviation fuel by 2030.
The group said it would purchase a million tonnes of sustainable jet fuel per year, “enabling it to cut its annual emissions by 2 million tonnes by 2030. This equates to removing 1 million cars from Europe’s roads each year.”
At the Dubai Expo 2020, held this month, the UK’s transport secretary Grant Shapps named SAFs as the main near-term solution for decarbonising air travel. “Long-term targets need to be balanced with short-term goals like expanding the rollout of sustainable aviation fuels," 彼は言った.
And across the pond, Airlines for America (A4A), the industry trade organisation representing the leading US airlines, announced in March that its member carriers had pledged to work with government leaders and other stakeholders to “make 3 billion gallons of cost-competitive sustainable aviation fuel available to US aircraft operators in 2030”.
So what’s the problem? Sustainable equals good, もちろん? ああ, that it were so simple. Let’s have a look at the problems plaguing this contentious branch of the emissions reductions plan…
SAFs have to be blended with kerosene
When you see an airline claiming a flight is powered by SAF, there is an immediate caveat – it is not running on ただ SAF. 実際には, SAF will only make up a minority of the fuel used. It is always blended with regular old fossil fuels – in fact, it has to be. The highest amount that can currently be mixed is 50 per cent SAF, and it’s usually less than that. The historic BA flight I mentioned earlier? It was powered by SAF blended at 35 per cent with traditional jet fuel, 意味 65 per cent was still kerosene.
SAFs cause at least as many in-flight emissions
The branding of this type of fuel has been, I’ll admit, extremely clever. The seductive words “sustainable aviation fuels” suggest they produce fewer emissions than regular jet fuel when the plane is airborne; this simply isn’t the case. Airlines claim that SAFs can reduce CO2 emissions by up to 80 per cent versus fossil fuels, but they emit at least as much CO2 as kerosene in-flight, as well as the same harmful non-CO2 emissions, which also have a significant warming effect.
実際には, most SAF is jet fuel that’s produced from “sustainable” feedstocks, such as waste cooking oil and other non-palm waste oils from animals or plants; solid waste from homes and businesses, such as packaging, 論文, textiles and food scraps that would otherwise go to landfill or incineration; forestry waste, such as waste wood; and energy crops, including fast-growing plants and algae. So any claimed greenhouse-gas savings are built into the “life cycle” of the fuel – the way it’s produced – rather than during the flight; 例えば, by growing a crop that absorbs carbon from the atmosphere, which is then converted into fuel. With the right balance – if the same amount of carbon was being removed from the atmosphere in the creation of the fuel as was then emitted when it was burnt at altitude – this could arguably lead to carbon-neutral flights.
But often this “life cycle” approach to fuel emissions is not based on carbon removals, but rather makes assumptions about what would have happened to, 例えば, the waste used to make the SAF if it hadn’t been turned into a fuel. “As waste with a high proportion of ‘biogenic’ material in it can generate methane – a powerful greenhouse gas – if left to rot, a large benefit is assumed to arise if the waste is instead turned into aviation fuel, even though this still generates at least as much CO2 as fossil kerosene once burned,” according to the Aviation Environment Federation (AEF). “The claimed ‘net’ reduction therefore relates to avoided emissions rather than to any actual reduction. But to achieve net zero by 2050 across the economy, these methane emissions will need to be avoided as well as aviation emissions reaching net zero, not instead.”
SAFs can’t be scaled up to the required levels at present
This is one of the biggest obstacles that airlines and governments are currently failing to address. With the best will in the world, scalability is a massive issue – because SAFs currently take far more money and resources to create than fossil fuels. And the ways in which you could swiftly increase the scale – for instance, by annexing great swathes of land to grow single, fast-growing crops – are a nightmare for biodiversity, and raise big red flags at a point when we need to be using land to feed a growing population.
による analysis by consultancy McKinsey, to ensure no more than 1.5C warming above pre-industrial levels (as defined by the Paris Agreement), SAFs would have to account for 20 per cent of all jet fuel by 2030 – or, at a minimum, 10 パーセント, “in a scenario in which transportation lags in decarbonisation compared with other sectors”.
And yet a 2021 論文 from the International Council on Clean Transportation (ICCT), which estimated SAF feedstock availability to meet growing European Union demand, concluded that “without taking into account the political or economic barriers to SAF production, we estimate that there is a sufficient resource base to support approximately 3.4 million tonnes of advanced SAF production annually, または 5.5 per cent of projected EU jet fuel demand in 2030. The estimated production potential takes into account feedstock availability, sustainable harvesting limits, existing other uses of those materials, and SAF conversion yields.”
It’s unclear, その後, how myriad airlines expect to be able to be meet even their underwhelming 10 per cent SAF targets by that same year.
The end result? SAFs have a part to play when it comes to lowering aviation emissions – but a relatively small part, rather than the starring role they are currently being cast in by the industry and politicians alike.