[Ref Flight International Magazine 28Jan-3Feb 2020]
The target set by IATA a decade ago calls for a 50% reduction in net aviation CO2 emissions by 2050, relative to 2005 levels, and carbon-neutral growth from 2020.
Lord Adair Turner, who now chairs the Energy Transitions Commission (ETC) – a group specialising in the decarbonisation of hard-to-abate sectors, suggested that “The target for 2050 should be a 100% reduction… and this should be “possible” to achieve without relying on carbon offsetting. The route should instead involve electrification of short-haul flights and a shift to 100% drop-in low-carbon fuels for long-haul flights.
As things stand (在目前情況下/照目前情況) , aircraft electrification efforts are still in their infancy and the use of sustainable aviation fuel (SAF) is restricted both by a 50% blend limit with conventional jet fuel and negligible supplies. Biofuels currently represent less than 1% of the world’s total jet fuel supply.
Switching over to alternative fuels will be expensive, however, with biofuels costing up to three times more than conventional kerosene.
Such a significant shift to alternative fuels is unlikely to materialise without help from governments. Air BP, which supplies sustainable aviation fuel to commercial and business aircraft operators, is keen to see regulators create a more favourable environment to enable the fledgling market to get off the ground..
Mandating the use of biofuels by airlines is another way in which governments can increase take-up, and this is already starting to happen.
There is also the potential for governments to incentivise airlines to use sustainable fuels through adjustments to eco-taxes by charging those flying on conventional fuels more.
Companies can also play a direct role. For example, airline can make a SAF-fuelled delivery flight.
But with limited supplies of low-carbon fuels and competition from other transport modes, airlines are restricted in how much they can buy.
Hydro-processed esters and fatty acids fuels, such as those derived from used cooking oil, are the most commercially developed of the five certificated pathways. But while these fuels can help satisfy short-term demand over the next five to 10 years, their production will be limited by “the availability of sustainable feedstocks” in the longer term, a senior consultant at sustainable energy consultancy E4Tech suggested.
Adam Morton, head of environmental technology at Rolls-Royce, believes that “There is no silver bullet. We will have to pull all the levers extremely hard.”
But the engine manufacturer changed its view after the UN Intergovernmental Panel on Climate Change published its landmark report in 2018, which warned of dire consequences if global warming were to exceed 1.5°C (2.7°F).