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Government proposals for a Sustainable Aviation Fuels mandate: key questions still need to be answered

11th August, 2021

Ministers are planning “a new era of guilt-free flying” reported the Times in March, describing the launch of a competition for funding to make jet fuel from waste. As we have argued, some of the claims around the emissions reductions available from waste-based fuels appear wildly over-exaggerated – a point we return to later in this article. But the concept seems to have strong appeal for a Government keen to believe that ‘Sustainable Aviation Fuels’ or SAFs are just around the corner, waiting to save the day and to allow them to deliver their promise of net zero aviation without any interventions to limit aviation demand or airport capacity. Even better: “SAF production could generate a value added of up to £1,952 million per year for the UK in 2035, potentially supporting between 6,400 and 13,600 jobs” the Government claims, citing research by the aviation industry. 

SAF as the industry’s saviour?

Many in the industry now recognise that with carbon offsetting falling out of favour they have few options left in terms of near-term actions that might help tackle the aviation emissions problem, and there has been a focussed lobbying effort globally to seek governmental support for SAFs. In addition to existing incentives for the production of certain SAFs by way of the Renewable Transport Fuels Obligation, and competition funding for the production of new fuels, the Government is therefore now developing proposals to introduce a SAF mandate – a requirement for airlines to buy a certain amount of SAF. The first set of proposals were published for consultation in late July, with a closing date of 19th September. 

Rhetoric versus reality

In many ways the Government’s approach is in fact quite cautious. Rather than setting out specific mandate levels, the consultation provides a detailed review of the options. This is something we’d asked for. We sent a joint NGO letter to ministers specifically calling for a two-stage consultation to allow the scope and criteria of a mandate to be considered before any levels are set. 

There are some strong commitments in the proposals. They make specific reference to the need to reflect ‘the polluter pays principle’, and aim to focus on fuels that can deliver high carbon savings and that generally avoid direct or indirect land use or wider environmental impacts. Only a small range of fuels pass this test, they suggest: waste-derived biofuels, renewable fuels of non-biological origin (RFNBOs), SAF from nuclear energy and recycled carbon fuels (RCFs). 

There is a commitment not to allow SAFs from food or feed crops, and not to divert renewable energy from other applications into making e-fuels (those produced from captured CO2 combined with hydrogen obtained by electrolysing water). E-fuels are acknowledged as potentially delivering the highest carbon savings, but being the most expensive option, the consultation asks for suggestions about whether to give an additional incentive to e-fuels compared to waste fats (which are more readily available today but less likely to scale significantly in the long term).

The key issues still to be resolved

These criteria would seem to address most first-line criticisms of SAFs and it may turn out that once these caveats are applied, the volumes available to airlines are actually quite limited. In theory, they could act as an indirect brake on demand growth if an effective mandate was in place and costs were passed on to passengers. We have two big concerns, however, with the approach so far. 

The danger of relying on SAF

The first is that both the aviation industry and some politicians are keen to present SAFs as the big solution for aviation decarbonisation, creating the impression that airports can continue to expand, and people can continue to fly without worrying about the climate impacts, because in future we’ll be able to make fuels out of waste. In fact these fuels may be a rather small and/or expensive solution, and there’s a big danger in creating the illusion of climate action while in fact continuing very largely with business as usual.

Carbon accounting confusion

The other more fundamental and tricky problem is about the claimed carbon reduction figures associated with the fuels that the mandate would cover. The plan seems to be that figures would be drawn from databases that estimate the ‘net’ benefit of a given fuel compared with what’s currently happening, rather than with what needs to happen for the whole economy to achieve net zero emissions. 

Various figures are available that estimate CO2 reductions based on a ‘life cycle analysis’ of different fuels. This approach tries to account for impacts on other sectors and while it can sometimes highlight where things go wrong (such as crops being grown for biofuels on land that is in fact needed for agriculture or forestry) it can also throw up some very odd numbers, such as claims that using wastes in aviation fuel can cut emissions by over 100%, implying that flights using these fuels could lower overall emissions. 

The issue lies in the assumptions about what would have happened (to the waste in this case) if it hadn’t been turned into a fuel and burned in an aircraft. 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. 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. 

Can SAFs ever make sense in a net zero future? Maybe. Fuels that are generated from CO2 that has been captured from the atmosphere – a kind of advanced offset – could in theory provide a closed loop for carbon, although non-CO2 impacts would remain a challenge. Waste too, if it is from biological sources that contain CO2 that has been previously captured by plants (e.g. waste vegetable oils) could potentially work in the same way. The numbers, however, would need to be developed such as to avoid over-claiming as a result of false comparisons, and there are complications around the timeframes in terms of how long ago the CO2 was absorbed (because if you went back far enough you’d include coal and oil!).

The SAF consultation contains a section on how to avoid ‘double counting’ of emissions savings. If done right, this should address these issues. But the proposed scope appears to be limited to ensuring that the Department for Transport’s different SAF policies don’t reward the same tonne of CO2 reduction twice. The question of how to avoid double counting across the economy, on the assumption that the whole economy is decarbonising, is not addressed. 

Where does this leaves us? Next steps

While the Department for Transport has presented a careful consideration of the evidence currently available, some really critical details about the role of SAF in a net-zero compliant future aren’t made available. And without them it would be foolish to start creating incentives to ramp up SAF production by setting mandate levels. 

This is not to say that SAFs should all be dismissed. The risk of these fuels being used for greenwash purposes is ever-present. But simply pointing this out without then being able to say what alternative means of getting aviation to net zero would be better doesn’t achieve very much. In truth, all options are difficult – stopping flying or delivering permanent carbon removals are not easy alternatives. The possible role of SAF needs to stay on the table. But we’re not there yet in terms of a realistic picture of how much – or lower little – these fuels can really deliver in terms of decarbonisation.