The UN’s aviation body has estimated that replacing conventional jet fuels with sustainable alternatives would cost up to US$60bn/year from 2020 to 2050, Climate Home reported on 2 August.

This would require around 170 new bioenergy refineries to be built every year through to mid-century, catering for annual growth of 4% through 2030 and beyond, the report said.

“Even under this scenario, achieving carbon neutral growth exclusively from the use of sustainable alternative fuels is unlikely to happen in 2021 or shortly thereafter as an initial ramp-up phase is required before production of alternative fuels can reach the levels mentioned above,” the International Civil Aviation Organisation (ICAO) report said.

The international aviation industry has committed to carbon neutral growth by 2020 and the ICAO said aviation now accounted for 2% of global CO2 emissions but was expected to rise as the industry expanded through Asia, Africa and South America, the report said. Ethiopia, Malawi, Serbia, Sierra Leone, Uganda and Vietnam and were among countries projected to see 7-8% growth in flights each year.

CO2 emissions from flying were likely to hit 682-755 megatonnes by the end of the decade and 2,500MT by 2050, the ICAO said.

Better engines, paints, flying techniques and improvements to infrastructure could knock off just under 1,000MT/year, leaving a gap of 1,039MT.

“Sustainable alternative drop-in fuels are the only practical renewable energy option available for aircraft today,” said Boubacar Djibo, head of ICAO’s airport transport bureau in the report.

“While the technical feasibility, environmental impacts and safety of biofuels have been well-demonstrated, integrated thinking is now required to accompany their large-scale deployment.”

The ICAO said the aviation industry could rely heavily on offsetting its greenhouse gas emissions from 2020.

But the costs of offsetting emissions were likely to be steep, ranging from US$1.5-6.2bn in 2025 to US$5.3-23.9bn in 2035, depending on carbon prices.

“The analysis also shows that the cost of carbon offsetting for operators would range from 0.2-0.6% of total revenues from international aviation in 2025; and 0.5-1.4% of total revenues from international aviation in 2035,” the report said.