Decarbonizing long-haul aviation requires permanent solutions with real climate benefits

Blog Post AviationCarbon Dioxide Removal
Published December 18, 2020

Frances Wang

Associate Director, Carbon Dioxide Removal

Amy Malaki

Associate Director, Transportation

Ambitious airline commitments in direct air capture are needed but they must lead to clear reductions in the use of fossil fuels.

Aviation industry emissions are projected to triple by 2050, so returning to business as usual after Covid-19 recedes is simply not a viable option if the world is going to meet the goals of the Paris Climate Agreement. Aviation has lagged in making ambitious emissions reduction commitments. To be successful, the sector will need to rely on a variety of emission reduction approaches — curbing demand for flying, more efficient and novel new zero-carbon aircraft designs, a robust market for truly sustainable aviation fuels, and investments in carbon removal to address the remaining emissions.

Promising actions are happening. Recently, United Airlines announced an ambitious greenhouse gas reduction goal of 100% by 2050, and committed to doing so without voluntary offsets, or purchasing “credits” from projects that prevent or remove the equivalent amount of greenhouse gas emissions elsewhere. It also plans to invest in direct air capture (DAC) as part of this commitment.

Direct air capture removes historic carbon dioxide (CO2) pollution from the air. It is then stored permanently underground or used to create CO2-based products. In the case of United’s investment, the removed carbon dioxide will be used for enhanced oil recovery (EOR) by injecting it into depleted oil wells to encourage oil production. The injected CO2 remains in the well and is stored permanently underground.

While United Airlines’ investment in permanent and verifiable emissions removal via direct air capture is a definite step in the right direction, it is important to differentiate this investment in DAC from the emissions reductions that might result from this investment. Instead of using removed CO2 for enhance oil recovery, better options to advance DAC and achieve higher climate benefits are available, such as reusing CO2 to create sustainable aviation fuel or storing carbon permanently without EOR. Scaling up these solutions requires further investments and support from the public and private sectors.

Unlike conventional offsets, direct air capture to storage offers permanent CO2 removal

Long-haul aviation creates residual emissions that are hard to mitigate because, unlike road transport, the sector lacks currently scalable clean technology alternatives. To date, the sector has relied mainly on offsetting, a problematic and limited solution to address its emissions. Combating these emissions requires meaningful actions to reduce fossil fuel use as well as permanently remove and store excess CO2.

Direct air capture removes historic emissions from the atmosphere and stores it underground, with an estimated 78% to 98% of injected CO2 remaining safely stored for the next 10,000 years. As a result, DAC offers a more impactful, long-term alternative to conventional offsets that face a variety of measurement, verification, and permanence issues.

Investment in or the procurement of direct air capture offer three major advantages for companies looking to address emissions from long-haul aviation:

  1. Compliance. By removing and permanently storing CO2 emissions, credits are generated for purchase by air airlines and other eligible procurers for emission compliance purposes.
  2. Decarbonization. Combining CO2 removed from the atmosphere with clean hydrogen creates carbon-neutral fuels usable by today’s aircraft and offers a viable pathway to decarbonize, rather than offset, carbon emissions from flights.
  3. Risk management. CO2 removed by direct air capture does not face the same reputational and climate risks associated with conventional offsets. Our recent blog discusses the distinction between carbon dioxide removal and conventional offsets in more detail.

Pairing direct air capture with synthetic fuel production can help decarbonize aviation

The climate benefit from United’s investment in direct air capture for enhanced oil recovery is unclear and depends on whether the oil produced will displace or add to existing production. The story is further complicated because, on one hand, revenue from selling CO2 for EOR increases demand for DAC, driving down costs and encouraging new project developments. On the other hand, the U.N. Intergovernmental Panel on Climate Change clearly states that in order to reach climate goals, we need to deploy carbon dioxide removal as well as reduce fossil fuel use. In addition to diminishing the overall climate benefit of DAC, EOR has received an ambiguous reception and even skepticism from local communities and environmental justice groups. Bundling an otherwise climate-beneficial technology such as direct air capture with EOR risks its social license.

Alternative pathways exist for businesses interested in investing in or procuring direct air capture. While direct air capture to storage without EOR would benefit the climate with less trade-offs, its high cost is unattractive to investors today. Absent strong policy signals, producing DAC-based fuels in lieu of fossil kerosene for fuel long-haul flights would both provide a revenue stream to scale direct air capture while at the same time eliminating the use of questionable conventional offsets.

After the purification process, captured CO2 is combined with green hydrogen through a chemical process powered by renewable energy to create synthetic kerosene. This fuel is compatible with today’s engines and because it’s simply a combination of carbon, oxygen, and hydrogen, early research reveals it has lower non-CO2 emissions than conventional fossil fuels as well. The production of this fuel takes up less land than crop-based fuels, and as a result, is less likely to compete with food production. With further research and development, including recent support from the U.S. federal government, this fuel can be carbon-neutral when produced using renewable energy, thus eliminating the need for offsets altogether and helping to create demand to scale direct air capture and green hydrogen industries globally.

Investment in direct air capture is a great start and should be emulated by other looking for near-term solutions to permanently address emissions from long-haul aviation. However, United needs to be crystal clear about the details — in particular how the investment will be directed, and how this investment fits into the airline’s overall plan to reduce its carbon footprint, since the airline has not committed to buying carbon removal. These details will be crucial to fully understanding the impact of this announcement and full transparency is critical to building trust and support with the public and policymakers.