Roadmap to decarbonising aviation
Introduction
Aviation is one of the fastest growing sources of greenhouse gas (GHG) emissions and the most climate-intensive mode of transport. Globally, aviation emissions have more than doubled in the last 20 years (EEA, 2017) and, when including the significant non-CO, climate effects of aircraft flying at altitude, the sector is responsible for an estimated 4.9% of total anthropogenic forcing (Lee et al., 2009) (Figure 9.1).
Aviation emissions in Europe have doubled since 1990, while globally they could, without action, double or treble by 2050. Such emissions growth needs to be reversed and brought to zero by 2050 if we are to meet the goals of the Paris Agreement. Otherwise, growth in aviation emissions could rapidly consume the limited carbon budget to remain within the 1.5 and 2 °C targets of that agreement (Lee et al., 2009).
The Intergovernmental Panel on Climate Change (IPCC) special report on limiting global warming to 1.5°C (IPCC, 2018) made it clear: rapid and far-reaching transitions are needed in all sectors, including transport, in order to reach net zero emissions by 2050. This includes full decarbonisation of all sectors of the economy where this is technically possible. Europe, due to its historical contribution to climate change, should lead the way.
So far few effective policies are in place to address this emissions growth. The aviation emission trading scheme (ETS) in Europe is restricted to flights within Europe which cover about one third of total EU outbound emissions, yet emissions within Europe continue to grow each year and now represent 3.6% of total EU CO, emissions - up from 1.5% in 1990 (EEA, 2017). At the global level, ICAO’s CO, standard for new aircraft has proven to be technology' following while the global offsetting scheme CORSIA, due to start on a voluntary basis in 2021, addresses out-of-sector emissions and will have no impact on aviation CO, itself.There are no regulations in place addressing the sectors significant non-CO, climate impacts at altitude.
In November 2018, and following a request by European governments, the European Commission said it would present a strategy' to decarbonise the economy in line with the Paris Climate Agreement. In this study, we examine
Aviation’s runaway emissions growth
2% global CO2
5%
global warming
4-+6°/o
f EU emissions in 2017
since 1990
- *7= TRANSPORT * Ost'»«"
- 1= BMRONMBTT
Figure 9.1 Global and European aviation growth.
whether a credible pathway to zero or near zero emissions exists for European aviation within the same timeframe. The scope of the study covers flights within and departing from Europe which matches the scope of including aviation emissions in the EUs 2030 reduction target. It takes broadly accepted passenger and emissions growth forecasts out to 2050, considers the role that various policies can play in reducing fuel demand from the sector, either by improving efficiency or reducing demand, and then proposes how the remaining fuel demand can be decarbonised.
The study first looks at likely emission scenarios out to 2050 and examines various design, technical and operational measures that, either within today’s knowledge or being more ambitious, could impact that growth trend. We then consider various taxation options for pricing aviation carbon which, combined, would represent an effective carbon price of €150/tonne. An assessment is then made of the likely availability' and price of sustainable alternative fuels (biofuels) against the background of the considerable and largely unsuccessful experience with such fuels in EU road transport. The remaining fuel demand is that which will need to be replaced with electrofuels, and we examine supply' and price issues.
Background
While uncertainties exist, we do know that the sector will have a substantial fuel demand well into the 2030s, 2040s and beyond; the period when the European economy needs to increasingly decarbonise. This study finds that expected technology and operations efficiency improvements in the sector will not mitigate the expected fuel demand and emissions growth from aviation. Generating incremental efficiency improvements from current aircraft designs is becoming ever more costly and difficult. Further operational improvements remain possible but do not achieve decarbonisation and will require that the right policies be in place.
Aside from policies which will incentivise improvements in efficiency, measures which suppress the growing demand for air travel will be needed. Carbon pricing can and needs to play a central role in bringing forward further efficiency improvements and reductions in fuel demand. Exempt from kerosene taxation and with most European aviation emissions excluded from the EU ETS* intra EU scope, there is much to be done. We show that introducing fiscal measures that, combined, represent a carbon price equivalent to €150 a tonne can moderate fuel demand growth from the sector through reductions in traffic, incentivising a combination of design and operational efficiency improvements and modal shift. Other measures highlighted include stricter fuel efficiency standards and incentives to speed up fleet renewal. Combined, these measures could cut fuel demand by some 12 Mtoe, or 16.9% in 2050 compared to a business-as-usual scenario.
That still leaves substantial and increased fuel demand in 2050 which, based on todays technology; can be reduced only through the use of sustainable alternative fuels. Advanced biofuels could play a role; however, strict sustainability safeguards are needed to ensure advanced biofuels offer genuine emission savings. These are not yet in place. If fuels with poor environmental and climate credentials are excluded, we estimate that advanced sustainable alternative fuels could play a role — meeting up to 11.4% of the remaining 2050 fuel demand in our scenario. To close the gap, the study focuses on synthetic fuels, namely electrofuels, produced through combining green hydrogen with carbon from CO,. With the hydrogen produced using additional renewable electricity, and with the correct source of CO, (direct air capture), such fuels can be close to near zero emissions and carbon circular. However, if electrofuels are the only way to decarbonise and fuel demand remains high, then there will be an enormous demand for renewable electricity, possibly equivalent in 2050 to some 28% of Europe’s total electricity generation in 2015 — or 95% of the electricity using renewables currently generated in Europe.
We do not rule out the role that radical new aircraft designs, for example hydrogen or electric aircraft, could play in significantly reducing aviation emissions. However, such aircraft are not expected to be in operation in significant numbers until the 2040s, and it will be especially challenging to replace conventional aircraft for long-haul flights. Should hydrogen aircraft technology develop more rapidly, this would not be at odds with significant investment in synthetic fuels, as hydrogen is a key input for electrofuels.
Aside from decarbonising aviation fuels, the warming from aviations non-CO, effects at altitude is considerable, and there remains a lack of policy focus and investment in scientific research on this topic.This failure to act means we are unable either to propose a suite of mitigation measures or to estimate their effects.
The case for acting on aviation emissions is clear — a failure to do so will fatally undermine efforts to achieve the goals of the Paris Agreement. We do not recommend offsetting, as this solution is incompatible with the decarbonisation logic of the Paris Agreement because the agreement requires emissions from all sectors to be reduced. The ICAO scheme CORSIA, due to start on a voluntary basis in 2021, addresses out-of-sector emissions and will have no impact on aviation CO, or non-CO, itself.
