SAF: why batteries do not work for planes 

Like flying? You're not alone, but it's a difficult industry to decarbonise. In most other areas, we're betting on electricity - but what do we do when planes can't handle batteries?

The aviation industry is a major contributor to global carbon emissions, making the transition to sustainable energy sources crucial.

While many forms of transportation, such as cars, buses, and even some ships, are increasingly shifting toward battery-electric propulsion powered by renewable energy, aviation presents unique challenges that make this transition far more difficult.

Instead, Sustainable Aviation Fuel (SAF) has emerged as a more viable pathway to decarbonizing air travel - but why?

Why batteries are not really viable for modern aviation

Batteries simply do not have the energy density required for commercial aviation. Jet fuel contains approximately 43 megajoules per kilogram, whereas the most advanced lithium-ion batteries struggle to exceed 1 megajoule per kilogram.

This means batteries are over 40 times heavier than jet fuel for the same amount of energy. Given that weight is a critical limitation in aviation, this discrepancy makes battery-electric commercial aircraft unfeasible, especially for long-haul flights.

Aircraft burn fuel as they fly, making them progressively lighter, which improves efficiency. Batteries, however, do not lose weight during discharge.

This means an aircraft powered by batteries must carry the same heavy load for the entire flight, increasing energy consumption and reducing efficiency.

Additionally, commercial aviation relies on quick turnaround times between flights.

Charging batteries for large aircraft would take significantly longer than refueling with liquid fuels, disrupting flight schedules and increasing operational costs. Rapid-charging solutions would also require enormous electrical infrastructure upgrades at airports.

Large-scale battery production requires lithium, cobalt, and other materials that are associated with significant environmental and geopolitical challenges. The mining and processing of these materials have negative ecological and social impacts, reducing the overall sustainability of battery-electric aviation.

Why SAF is a more viable solution for decarbonising aviation

SAF can be used in current aircraft engines with little to no modification, allowing airlines to reduce emissions without waiting for a complete technological overhaul of the industry. This enables a near-term reduction in aviation carbon footprints while maintaining operational feasibility.

Unlike fossil jet fuel, SAF is produced from renewable sources such as biomass, waste oils, and synthetic processes using green hydrogen and captured CO2. When produced sustainably, SAF can reduce lifecycle emissions by up to 80% compared to conventional jet fuel.

While current SAF production remains limited, scaling up production using renewable feedstocks, improved processing techniques, and power-to-liquid technologies can increase availability. This makes SAF a realistic and scalable solution in the near to medium term.

Air travel demand continues to grow, and simply reducing flights is not a practical solution for many industries, economies, and individuals who rely on aviation. SAF offers a way to significantly cut emissions while maintaining connectivity and economic viability.

While battery-electric propulsion may work for short-range urban air mobility and small aircraft, it is not a viable solution for long-haul commercial aviation due to energy density limitations, weight constraints, and infrastructure challenges. SAF, on the other hand, provides an immediate, scalable, and sustainable alternative that allows the aviation industry to cut emissions while maintaining existing operational frameworks.

In the push for greener skies, SAF represents the most promising pathway to a low-carbon aviation future.