Should Aviation Be Given Preferential Access to Scarce Land and Clean Energy Resources for SAF, Questions Paper

by Christopher Surgenor (CleanAir Online) An academic analysis of 12 roadmaps for decarbonising the global aviation industry finds they place a heavy reliance on biogenic fuels in the medium-term and synthetic e-kerosene in the longer term but largely omit a number of fundamental problems with sustainable aviation fuels, says a new science-led paper. Realising these roadmaps could require 9% of global renewable electricity and 30% of sustainably available biomass by 2050, with significant energy losses as SAF production is energy intensive and comes with a risk of clean energy displacement. Additional effects omitted in most roadmaps relate to the decadal time lags in re-sequestering biocarbon in the case of forest biomass and the impact of non-CO2 emissions. With competition over land and scarce clean energy, along with the high economic and political investments required, there is a question as to whether the use of SAF is a worthwhile climate action, say the authors.

Step-change technologies such as hydrogen-powered planes and battery-powered short-haul flights will lead to GHG reductions but at a small scale given the limited contribution of short flights to overall emissions. This reality means that fuel cells and battery technologies play no role in aviation decarbonisation roadmaps up to 2050 for long-haul flights, where 5% of flights over 4,000 km make up 40% of fuel use.

The long-haul network will only survive in its current form with liquid hydrocarbon fuels, says the paper, which focuses on the SAF pathways related to biomass, waste and power-to-liquid (PtL) e-kerosene, plus their resource requirements.

“Clearly, food, municipal and industrial waste volumes will only deliver a fraction (5 EJ in total) of energy, meaning that energy crops (5-10 EJ) and agricultural (10-12 EJ) and forest residues (10-20 EJ) become crucial. The land use implications are substantial.”

“Against this precarious backdrop and given the physical constraints on land and clean energy, the amount of SAF required to support aviation growth lacks critical and systemic assessment of feedstocks. Airlines have adopted a strategy that is dependent upon rapid and sustainable expansion of SAF because it is the only technical solution to maintaining long-haul flights,” say the authors.

“This paper provides insights into some of the trade-offs and risks, including competition over land and scarce clean energy, and the answer will differ for different countries.”

Susanne Becken, Professor of Sustainable Tourism, Griffith Institute for Tourism, Griffith University, Australia. She is a member of the Air New Zealand Sustainability Advisory Panel and member of the Independent Advisory Group of Travalyst.

David S. Lee, Professor of atmospheric science, Aviation and Climate Research Group Leader, Manchester Metropolitan University, UK. He is a member of the UK Jet Zero Council, a co-rapporteur of ICAO’s Impacts and Science Group, and a member of the UK CAA’s Environmental Sustainability Panel.