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A start to addressing aviation emissions
Can offsets and biofuels make future international aviation growth ‘carbon-neutral'?
An SEI analysis finds significant potential for offsets and, to a lesser extent, alternative jet fuels to reduce emissions, but stresses the importance of high standards and certification to ensure benefits and avoid negative impacts.
Air travel and freight play a growing role around the world. Passenger bookings nearly doubled from 2004 to 2015, to 3.5 billion, and are expected to rise to 6.63 billion by 2032, while cargo flights nearly triple, to 4.4 million in 2040. And with this growth, greenhouse gas emissions are rising as well.
International aviation emitted about 490.4 million tonnes (Mt) of carbon dioxide in 2013, 1.5% of global CO2 emissions from fossil fuel combustion that year. The UN agency that oversees the industry, the International Civil Aviation Organization (ICAO), expects CO2 emissions to rise to 682–755 Mt by 2020 and to 1223–1376 Mt by 2035, even with projected efficiency improvements in aircraft and operations.
Amid growing pressure to curb aviation emissions, ICAO set a global aspirational goal that growth from 2020 onward be "carbon neutral" in terms of net CO2 emissions. Improvements to aircraft technology and operations would narrow the gap. The rest would be closed by using alternative fuels and a Market-Based Measure (MBM) for carbon offsets.
In a study commissioned by WWF-UK, SEI examined the potential supply of offsets and of biofuels, considering both climate benefits and potential sustainable development impacts. SEI found offsets from project types for which there is high confidence in environmental integrity, and which also advance sustainable development goals, could accommodate 70–90% of ICAO's projected demand for emission reductions from 2020-2035.
"Our study shows that over the next 15–20 years, airlines can achieve ICAO's carbon neutral-growth goal even if they set a high bar for the types of carbon offsets they use," says Derik Broekhoff, a senior scientist at SEI-US in Seattle and author of the offset analysis.
"By focusing on high-confidence mitigation actions with strong sustainable development potential, ICAO can ensure that airlines make a lasting contribution towards avoiding serious climate change," Broekhoff adds. "Realizing this potential will require strong standards and third-party certification, but there is no need to shy away from these due to supply concerns – robust offsetting can be a viable short-term solution to global aviation emissions growth."
SEI estimates biofuel production could reach 1.8 Mt by 2020 and 14 Mt per year by 2035 if capacity grows by 14%, the average annual growth rate that U.S. bioethanol achieved between 2000 and 2015.
The emission reductions that could be achieved by using that growing supply of alternative fuels depend on the production method ("pathway") and feedstock used. Rob Bailis, a senior scientist at SEI-US in Boston, estimated the savings if the fuels reduced emissions by 25% or 75% relative to conventional jet fuel – in both cases, assuming they were produced with little or no impact on land use. From 2020 to 2035, the savings would range from 0.1 to 0.3 Gt CO2e.
Safeguards will be needed to ensure that the production of alternative fuels does not have land use change impacts, or harm social welfare or the environment, Bailis says. "Recent experience with biofuels for ground transport shows us that, while the industry is capable of rapid growth in response to strong demand, it can come at an environmental and social cost.
Carrie M. Lee, an SEI-US scientist in Seattle and coordinator of the project, adds that putting aviation on a path consistent with keeping global warming below 2°C will require actually reducing emissions."It is encouraging to see ICAO and airlines taking action, but the current proposals are just a start," Lee says. "While the global MBM can help reduce emissions over the short term, the real question is: how do we get where we need to be in 2050 and beyond? Offsets can't be a long-term solution to decarbonizing the international aviation sector."