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ICCT: alternative jet fuels unlikely to deliver the bulk of GHG emission reductions needed by aviation

A new study by a team at the International Council on Clean Transportation (ICCT) has concluded that the large-scale deployment of alternative jet fuels (AJFs) and the ability of the aviation sector to mitigate greenhouse gas (GHG) emissions through their use will be capped by a number of factors: the sustainability and availability of feedstock; the production cost; and the extent to which those fuels will be commercialized.

Based on the study, the ICCT team suggests that while the use of AJFs can deliver some GHG savings, it is unlikely that AJF alone can meet the bulk of the GHG reductions projected to be needed. The authors recommended that ICAO stipulate a GHG reduction threshold in order for a given AJF to qualify under CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation), and to include indirect emissions in its life-cycle accounting.

The International Council on Clean Transportation (ICCT) 2
Selected pathways for alternative jet fuel production. Adapted from Brooks et al. (2016); Chuck (2016b); FAPESP, Boeing, Embraer, & UNICAMP (2013); Lorne (2016); Mawhood, Cobas, & Slade (2014); and Sizmann, Roth, & Jeßberger (2016). Source: The ICCT. Click to enlarge.

The study evaluates the potential opportunities and risks for AJFs by assessing their sustainability, cost, and constraints to deployment. Among the findings of the literature review of various life-cycle assessments of the carbon intensity of AJF fuels:

  • AJF produced from vegetable oil-based feedstocks tend to have a higher carbon intensity than conventional jet fuel when land-use change effects are taken into consideration.

  • AJF produced from sugar and starch feedstocks deliver only a small GHG benefit.

  • Only AJF from lignocellulosic energy crops, agricultural residues and waste feedstocks are shown to provide substantial emission reductions compared to conventional jet fuel.

  • The feedstocks that provide the largest carbon reductions in AJFs are constrained in their supply and will likely also be in demand from competing sectors such as road transport.

ICCT1
Potential contribution of alternative jet fuels to GHG emission reductions in international aviation. Estimates of AJF emissions include technology and operations improvements. Source: The ICCT. Click to enlarge.

Although estimated demand for jet fuel amounts to 24–37 EJ in 2050, the absolute maximum amount of lignocellulosic biofuel that could be available for the aviation sector is around 4 EJ in 2050, resulting in emission reductions up to around 360 million tonnes CO2. The actual amount of low carbon AJF that will be available is likely much lower, the authors posited. In the worst-case scenario, the use of high-GHG feedstocks, such as palm oil, could actually increase emissions by as much as 10%.

Estimated production costs (Nth-of-a-kind plants) for AJF from lignocellulosic feedstocks range from US$1,000–8,000/tonne; conventional jet fuel costs on the order of US$470–860/tonne. AJF from sugar and starch is estimated at US$800–4,800$/tonne. AJF from vegetable oil is more technologically mature, and costs are estimated at US$1,000–2,000/tonne. Reported costs from actual purchased fuels are considerably higher—as is expected from first-of-a-kind biojet facilities.

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Comments

SJC

They make progress all the time, hybrid jets can help.

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