The same document projects that by 2050, passenger miles flown will be twice the 2017 figure and six times the 1990 figure, while aviation GHG emissions in the period from 2017 to 2050 will remain constant.
Even if the latter projection holds good (and we show below that it can’t), then, by the government’s own admission, aviation will comprise fully a quarter of Britain’s greenhouse gas emissions by 2050 and will be the industry with the greatest carbon emissions. The subtext is clear: aviation expansion is non-negotiable, environmental concerns are an add-on.
Obscuring the clouds
We are sceptical of Jet Zero’s calculations and give reasons below, but one general point should be made right away. Their focus is overwhelmingly on aviation CO2. The latest research, however, provides further evidence that two-thirds of aviation’s global-heating impact stems from non-CO2 emissions and cloud formation – such as contrail cirrus. For aviation’s actual impact, take the CO2 figure and multiply by three.
To put it in perspective, a return flight from London to New York, generating one tonne of CO2 per passenger on average, has an actual impact equivalent to three tonnes. According to the CCC, three tonnes is the total annual level of per capita emissions that Britain must be restricted to by the mid-2030s, if the 1.5C target is to remain even possible.
Or consider military aviation. Officially, it accounts for fully one third of all emissions on the British government’s tab, but when non-CO2 effects are factored in, that proportion rises sharply.
In the rest of this essay we introduce the government’s plans, identify their miscalculations, and demonstrate the limitations of relying on techno-fixes. We conclude by adding to the growing calls for demand management of aviation as well as a just and ecologically sustainable restructuring of our transportation infrastructure as a matter of urgency.
The Jet Zero projection for aviation CO2 emissions is an increase over the next decade from 37 million tonnes (Mt) in 2019 to 39 Mt in 2030, before a decline to 21 Mt in 2050. At that point, aviation will be ‘net zero’—assuming that those 21 Mt are captured and stored, or offset. That the chosen target dates, 2040 and 2050 for domestic and international aviation respectively, are far beyond the lifespan of the current government is significant.
The methods proposed to achieve decarbonisation are overwhelmingly technological. As spelled out by Grant Shapps, the transport secretary, the focus will be on “biofuels and electric aircraft.”
The model for aviation is the electric vehicles (EVs) strategy for road transport: a ‘business as usual’ approach that assumes ever-growing sales, little or no demand management, and a high-stakes gamble on technology.
In road transport, the plan is fraught with problems, not least the emissions from the extraction and the manufacturing processes, as well as the scarcity of wind and solar power. In this context, replacing all vehicles with EVs risks exceeding the global carbon budget. But while decarbonising road transport is deeply problematic, it is technically feasible. Adopting a similar strategy for aviation is not simply problematic, it is, at least for the foreseeable future, delusional.
Taxis in the air
Electric planes, according to Shapps, offer “boundless possibilities”. What Shapps and Jet Zero fail to mention is that due to the weight of batteries – which, unlike fuel, don’t burn off as you fly – electric flights will only be viable for short journeys with few passengers. The maximum range even of the tiny five and nine seater planes projected by two of the leading electric aircraft companies, Lillium and Eviation, is 800km – less than the 900km from London to Berlin – and neither of them is yet commercially operational.
Even in the aviation industry, the consensus is that we’re unlikely to see electric flights at 1,500km or longer, yet these journeys make up 80 percent of aviation emissions. In other words, electric planes are a substitute not for jet planes but for buses and trains. They’d be no more than an airborne taxi service: good news for the wealthy hoping to avoid congested roads and trains but with no positive effect on the lives of the majority, or on carbon emissions.
H is for hot air
Another technofix offered by the Jet Zero consultation is hydrogen flight. Hydrogen doesn’t suffer from the problematically low energy density by mass of lithium batteries, but because its energy density by volume is far lower than jet fuel it requires much bigger and heavier onboard storage tanks. Hydrogen planes would also require very extensive modifications to airport infrastructure.
The source of hydrogen is another concern. Only one percent is currently ‘green’ – i.e. produced with renewable energy. It is over thrice the price of ‘grey’ hydrogen, which itself is four times as expensive as kerosene.
Grey hydrogen is produced from fossil fuels, with CO2 released as a waste gas—around 830 million tonnes each year. If those emissions are captured, the hydrogen is known as ‘blue’. A recent study warns that blue hydrogen could be worse for the climate even than burning fossil gas, due to methane loss during its production plus the high energy inputs—still, typically, from fossil fuels.
The hydrogen hype is pushed by fossil-fuel companies, fearful that their assets will become stranded. The dubious actors behind this technofix have been cooking the books on which the government’s aviation calculations rely, and appear determined to exaggerate any positive potential of hydrogen.
In short, hydrogen offers no realistic alternative to kerosene in the near to medium future, and aviation insiders know this. Willie Walsh, until recently CEO of International Airlines Group, admits that, even in the 2030s, no long-haul hydrogen flights will be possible. Their more substantial hopes, which have been carried over into the Jet Zero agenda, are tied to sustainable aviation fuel (SAF).
Fields of fuel
SAF can be grouped into two types, biofuel and synthetic electrofuel. Both carry significant problems.
Commercially available SAFs are mostly ‘hydroprocessed esters and fatty acids’ (HEFA) derived from agricultural crops such as palm oil or from waste products such as used cooking oil.
The best-known HEFA-using aviation entrepreneur was Richard Branson, in the mid-2000s. To burnish his image as an eco-conscious businessman – and therefore one who could supposedly be entrusted to run airlines in the age of climate crisis – he arranged for coconut oil to part-fuel a flight from London Heathrow to Amsterdam.
Technically, the mission was accomplished. But the sustainability implications were troubling. To have fuelled that short hop with 100 percent coconut oil would have required three million coconuts. The entire global crop would supply Heathrow for only a few weeks—and it’s one of 18,000 commercial airports worldwide. Following this stunt, coconut oil was never used in a Virgin flight again.
SAFs continue to be held up by industry and governments alike, including in the Jet Zero plan, as central to aviation decarbonisation.
But, energy crops such as palm oil (or coconuts) are not sustainable in any reasonable definition of the term. For energy production they’re a sub-par use of land: solar panels convert solar energy for human-use much more efficiently.
In competing with agricultural crops, their downsides are legion. They contribute to GHG emissions from land-use change, and to land-ownership concentration; they cause food price rises, food insecurity, deforestation, peat burning, water shortages, and biodiversity loss. One such example – in 2019 alone the palm oil suppliers to Neste, the world’s largest biofuel producer, were accused of deforesting at least 10,000 hectares and setting 13,000 forest fires.
Biofuel crops produce GHG emissions in other ways too. Their inputs include large quantities of energy and fertilisers, a major source of nitrous oxide, as well as hydrogen – largely from fossil gas – for the hydrotreatment of oils. Biomass from plantation-grown trees is seen by many in the aviation industry as the new cornucopia, but it suffers from all the same drawbacks.
Pollution into fuel: is there a catch?
For sustainable fuel, attention has therefore shifted to other sources. One is CO2 extracted from the air by Direct Air Capture technologies and converted into SAF. This may offer potential in the distant future but currently is far too expensive at £900 per tonne of CO2 and produces fuel at around four times the price of conventional fuels. The process is also energy intensive. If all current (pre-Covid) flights were powered by synthetic fuels, they “would consume more energy than the world’s total electricity generation from renewable sources today”.
Other sources include forestry residues – such as bark, branches, and sapling thinnings, municipal and business waste, and industrial offgases.
Forestry residues are not a serious alternative. They compete with more pressing uses: decarbonising electric power, fuelling ground transport, and Bioenergy with Carbon Capture and Storage (BECCS). Waste and offgases, however, look potentially promising. We contacted two leading firms in these sectors, Velocys and LanzaTech, to ask for detail.
Of the 27 million tonnes of waste collected annually by Britain’s councils and businesses, Velocys’ representative told us, much consists of water, and recyclable substances such as metals and “inerts.” These are removed. The remainder is heated using the Fischer-Tropsch process. Contaminant gases are washed out and what remains, chiefly hydrogen and carbon monoxide, is converted to SAF.
The Fischer-Tropsch technology is thoroughly proven—it’s of 1920s vintage. But can Velocys use it to produce sustainable fuel, in sufficient quantities, and in time to achieve the government’s Net Zero target? We doubt it.
First, the product, jet fuel, is very expensive to produce, and competes with other more pressing needs such as diesel for buses or trucks.
Second, there isn’t remotely enough of it. Even if Velocys were to collect all of Britain’s municipal and business waste, the annual yield would be only two million to three million tonnes of SAF. UK-departing flights already require 15 million tonnes each year.
Third, as with synthetic e-fuels, the energy requirements are prohibitive. Renewable energy supply is far lower than is widely supposed. Together, wind and solar provide only three percent of the world’s energy supply, and the overall renewable energy investment total has been flat since 2015.
Finally, Velocys, like most alternative SAF projects, has not demonstrated commercial-scale viability and there are strong grounds for scepticism. American bioenergy company Solena went bust in 2017 having failed in a near identical project. According to recent research by Andrew Rollinson, most large-scale commercial gasification plants fail. The technology, he notes, “has high risks associated with multiple pathways for fire, explosion, and the release of environmental toxins”.
Regarding Velocys’ proposed first commercial plant in Britain, at Immingham, its representative admits: “We have yet to raise the construction capital. It takes many years to develop these sorts of projects. The engineering required is considerable, plus there are all sorts of commercial constraints.” If everything goes quickly and smoothly it could be functional “in the mid-2020s.” Don’t hold your breath.
LanzaTech’s core technology is ingenious: Clostridium bacteria combines carbon monoxide and hydrogen to form ethanol, for conversion into jet fuel.
Its ideal locations are blast furnaces, the offgases of which include carbon monoxide and hydrogen. LanzaTech expects its facility adjoining the Port Talbot steelworks to yield 80,000 tonnes of fuel annually.
So far, so impressive. But let’s maintain perspective. Those 80,000 tonnes, LanzaTech UK’s managing director Jim Woodger tells us, represent “0.6 percent of UK jet fuel usage.” As steel production itself shifts from fossil fuels in pursuit of its net zero goals, the supply of those offgases will dwindle. And when LanzaTech looks beyond steel, they find feedstocks containing less or no hydrogen, which must then be manufactured. They are looking at DAC to SAF projects but here again the energy needs, says Woodger, are “very large” and the bottleneck is “the availability of renewable electricity.”
Other possible feedstocks include forestry waste, as discussed above. They also include sources of ‘second-generation bioethanol,’ such as straw. But these too face many competing uses, the available quantities are low (Woodger estimates enough to supply at most “two or three” facilities of similar size to the Port Talbot plant in the UK) and the jet fuel would be expensive—perhaps two to four times dearer than kerosene.
As with Velocys, production can’t be scaled up at will. “It takes three years, realistically, to do an overall project,” says Woodger, and only then can you transfer efficiency improvements to future projects. LanzaTech’s CEO, Jennifer Holmgren, has noted that using recycled CO2 or CO costs far more than refining oil, and bringing the cost curve down could take “30 or 40 years.”
The wider aviation industry knows that synthetic fuels cannot be ramped up quickly. The Sustainable Aviation group admits that in Britain a production level of 600 kt of SAF won’t be achieved until the mid-2030s at the earliest.
Even the lowest usage scenario it envisages “would exceed globally available waste oils and fats” and would require “substantial new volumes of oil crops.” These would likely include palm oil—or, in order to evade regulation, its derivative known as Palm Fatty Acid Distillate. In both cases, it’s utterly unsustainable, and a green light for the chainsaws and bulldozers.
An interim conclusion
As a means for Britain to achieve its climate targets, electric and hydrogen aircraft, we have shown, are white elephants. As to biofuels, they are burned, producing CO2 and other GHGs as well as creating a host of other problems. Alternative SAFs are speculative and prohibitively expensive. To put it generously, they’re over-hyped. What of the three remaining cards in the Jet Zero pack: efficiency, carbon capture and storage (CCS), and offsets? And if Jet Zero is scrapped, what are the alternatives?
We turn to these topics in Part 2, which is available online now.
Gareth Dale, the lead author of this report, will be a keynote speaker at the SMALL IS THE FUTURE event held by The Ecologist and the Schumacher Institute in Bristol on Saturday, 17 June 2023. Tickets are selling fast, so book now to avoid disappointment.
Gareth Dale teaches politics at Brunel University. His articles appear here and here. He tweets at @Gareth_Dale.
Josh Moos teaches heterodox economics at Leeds Beckett University. He is also working on a PhD on aviation, climate change and alternatives to growth.