Carbon-friendly jet fuel

Vapour trails.  Source: Transport & Environment

Electricity generation is transitioning to renewables.  Not fast enough, but it is happening.   There are no technological or economic barriers to achieving a 100% green grid--though there are, it's true, technical and organisational issues to be faced.  Similarly, over the next 15 or 20 years, it will be inevitable that our land transportation fleet will be electrified.  I'm not saying we should relax--fossil fuel interests will do their best to delay or prevent these transitions, but the economics has turned (or soon will) unambiguously in favour of the green alternatives.

That leaves air travel, sea transport, iron and steel, cement production, agriculture and land clearing.  Each of these is more complicated and difficult than transitioning generation to renewables and our ICE fleet to EVs.

Aviation is responsible for 5% of global warming and its rapid growth puts it on track to consume a quarter of the world’s carbon budget by 2050. There is a way to avoid this outcome but we need to act fast, a green transport NGO has said. By driving out the use of fossil kerosene fuel through carbon pricing and requiring aircraft to switch to synthetic fuels, the climate impact of flying can be reduced dramatically, according to a new report by Transport & Environment (T&E).

While high profile promises such as short-haul electric aircraft or more efficient aircraft designs every 20 years won’t be sufficient to solve aviation’s climate problem, new near-zero-carbon electrofuels can be produced today and deployed immediately using existing engines and infrastructure. Electrofuels are produced by combining hydrogen with carbon dioxide, but to do this sustainably the hydrogen must be produced using renewable electricity and the CO2 captured directly from the air.

Synthetic fuels have been used in the past to power aircraft but are significantly more expensive than aviation kerosene, which is tax free. Running aircraft entirely on synthetic fuels would increase the cost of a plane ticket by 58% assuming kerosene remains untaxed, or 23% if a proper carbon price would be levied on kerosene, the report finds. Biofuels produced from wastes and residues can make a limited contribution to replacing fossil kerosene. 

Andrew Murphy, aviation manager at T&E, said: “This report confirms that we need to decarbonise aviation if we want to avoid catastrophic global warming. The good news is that radically cleaner aviation is possible even with today’s technology. Getting to zero starts with properly pricing flying, and progressively increasing the use of sustainable synthetic fuels. There is a cost to this, but in light of how cheap subsidised air travel has become, and the incalculable cost of runaway climate change, it’s a price worth paying.”

To facilitate the progressive switch to electrofuels, demand for kerosene must start to be cut and carbon pricing must gradually be increased to the equivalent of €150 a tonne, the report finds. Taxing aircraft kerosene – currently exempt – and a strengthened EU ETS can help achieve this as can strict CO2 efficiency standards for planes and greater incentives for fleet renewal.

A leaked version of the European Commission’s strategy to decarbonise the EU’s economy by 2050 highlighted the potential role of synthetic fuels. Earlier this month the IPCC also emphasised the importance of synthetic jet fuel. Meanwhile, governments are pursuing a controversial UN offsetting scheme for aviation, known as Corsia. There are serious doubts over the environmental effectiveness of carbon offsets and the UN’s plan only caps airlines’ emissions at 2020 levels.

Andrew Murphy concluded: “Putting aviation on a pathway to zero won’t be easy but this report shows it can be done. If we want to succeed we need to stop pursuing false solutions. It’s crystal clear that the UN’s plan to let airlines offset their emissions is a distraction at best. We need governments to focus on the things that matter: proper pricing and cleaner fuels. The European Commission has a unique opportunity to commit to this in its 2050 decarbonisation strategy.”

[Read more here]

If we aimed to transition jetfuel for air travel to 100% synthetic kerosene over 20 years, the cost impact would be spread out and small.  For example, we could require that each year the percentage of synthetic kerosene in the fuel mix could be lifted by 5%.  That would mean that, ceteris paribus, jetfuel prices would rise by just 3% per annum.  And in 20 years, air travel would not be adding any new CO2 to the atmosphere.

There's another consideration.  The synthetic jetfuel would be produced by a variant of the Sabatier reaction.  This takes H2 from electrolysing water  and CO2 from the atmosphere and blends them at high temperatures and pressure in the presence of a catalyst to produce methane.  Once you have methane, other hydro-carbons can be made.  It seems inevitable that we will need to install more renewable capacity than we might on require on average to cater for consecutive days when the wind doesn't blow and the sun isn't shining strongly.  Ensuring grid stability with 100% renewables will likely require excess capacity as well as storage.  But that will mean that on days when the sun is shining and the wind is strong there will be excess electricity potentially available.  To stop the grid burning out, that surplus output will either have to be spilled, or output from wind and solar farms will have to be curtailed.  Which means, in effect, that that electricity will be free.  So the cost of producing synthetic jetfuel and synthetic natural gas could be much lower, given that their costs are high because the process is so energy intensive.  It's a win-win: surplus renewable power could be used to produce carbon-friendly jetfuel.