International aviation produced an estimated 490.4 million metric tons of carbon dioxide emissions in 2013, about 1.5% of global CO2 emissions from fossil fuel combustion that year, and as the role of aviation in the global economy expands, those emissions are expected to rise, to 682–755 tons by 2020 and 1223–1376 tons by 2035.

The International Civil Aviation Organization (ICAO) has set a global aspirational goal that the industry’s growth from 2020 onward be “carbon-neutral” in terms of net CO2 emissions. This paper focuses on two means to achieving this goal: the use of alternative fuels and a global market-based measure that would allow airlines to offset some of their emissions. It examines the potential supply of carbon offsets and of jet fuel alternatives from different biofuel pathways, and considers both climate benefits, and potential sustainable development impacts.

The authors find that in 2020–2035, carbon offsets from project types for which there is high confidence in environmental integrity, and which also advance sustainable development goals, could yield emission reductions of around 3.0 gigatons (Gt) CO2e, or 70–90% of ICAO’s projected demand for emission reductions of 3.3–4.5 Gt CO2e. Including project types with medium confidence in environmental integrity would expand the potential supply to 4.6 Gt CO2e. Further expanding eligibility to project types with neutral development impacts would increase supply to 5.1 Gt CO2e. Jurisdiction-scale reducing emissions from deforestation and forest degradation (REDD+) programmes could add another 2.4 Gt CO2e of offsets.

The potential supply of alternative jet fuels is subject to greater uncertainties, but the authors estimate that 0.1–0.3 Gt CO2e of emissions could be avoided by using biofuels produced with little or no land use change impacts and backed by strong sustainability certification schemes.

The analysis shows that ICAO can apply high environmental and sustainable-development standards to both carbon offsets and alternative fuels without compromising its 2020 “carbon-neutral” goal.

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Note: This document was updated on 7 June 2016 to correct an editing error on page 45 (cumulative alternative jet fuel use).