Aviation and Climate: Green Fuels and Offsets

Why flying is one of the hardest sectors to decarbonise, how sustainable aviation fuel and international carbon schemes work, and what India plans.

Aviation produces a few percent of global carbon dioxide emissions, and the share could grow as air travel increases. It is among the hardest sectors to decarbonise.

Why it’s hard

Energy density: jet fuel packs a lot of energy into little weight. Batteries are far too heavy for long flights.
Long aircraft lives: planes built today will fly for decades.
Global industry: emissions over international waters are hard to assign to countries.

Sustainable aviation fuel

Sustainable aviation fuel, or SAF, is jet fuel made from sources such as used cooking oil, agricultural waste or, in future, green hydrogen and captured carbon. It can be mixed with ordinary jet fuel and used in existing planes.

SAF can cut lifecycle emissions substantially compared with fossil fuel.
But it currently costs two to three times more than regular jet fuel, and supply is very limited.

India has set indicative targets for blending SAF into jet fuel for international flights, starting at 1 percent in 2027 and rising to 2 percent in 2028. Indian Oil and others are building SAF capacity, and India’s large supply of agricultural waste could be a feedstock.

CORSIA

The International Civil Aviation Organization created CORSIA, a scheme requiring airlines to offset growth in international aviation emissions by buying carbon credits. Participation was voluntary in early phases; India planned to join the mandatory phase later in the decade.

Other approaches

Fuel-efficient aircraft: new planes use significantly less fuel.
Operational improvements: better air traffic management and routes.
Future technologies: hydrogen and electric aircraft for short routes are being researched but are years away.

The economics

SAF and offsets raise costs, which may increase fares.
Policies such as blending mandates and subsidies are needed because SAF isn’t yet competitive.
The EU has introduced SAF blending mandates for flights from its airports.

The cooking oil flight

A demonstration flight uses a blend of regular jet fuel and SAF made from used cooking oil and waste. The plane flies normally, but the blended fuel costs much more, showing the challenge of scaling up.

Thinking electric planes will soon replace jet fuel

Batteries are too heavy for most commercial flights. SAF and efficiency improvements are the main near-term tools.

Key takeaways

Aviation is hard to decarbonise because of fuel energy density and long aircraft lives.
Sustainable aviation fuel can cut emissions but costs two to three times more.
India set indicative SAF blending targets starting at 1 percent in 2027.
CORSIA requires offsets for international aviation emissions growth.