The Kleinman Center for Energy Policy at the University of Pennsylvania has published an analysis examining the use of renewable natural gas (RNG) as a feedstock for producing sustainable aviation fuel (SAF).

The piece, titled "From Waste to Wing: Using Renewable Natural Gas to Produce Sustainable Aviation Fuel," addresses a pathway in the SAF production stack that has received less attention than the fat- and oil-based routes dominating current output. RNG, also known as biomethane, is captured from decomposing organic waste at landfills, wastewater treatment plants and agricultural operations — methane streams that would otherwise vent or flare into the atmosphere.

The analysis sits at the intersection of two policy problems airlines cannot solve on their own. Aviation accounts for roughly two to three percent of global carbon dioxide emissions, and the sector has committed to net-zero by 2050 with SAF as its principal lever. Current SAF production, however, remains a fraction of jet fuel demand, and the feedstock base for approved pathways — chiefly used cooking oil, tallow and other lipids for HEFA-SAF — is constrained by supply that cannot scale to airline offtake agreements already signed.

That mismatch between airline demand and available feedstock is what makes alternative pathways like RNG-to-SAF relevant to fleet and network planning. Airlines in Europe face ReFuelEU Aviation mandates requiring SAF blending starting at two percent in 2025 and rising to 70 percent by 2050, while UK and Singapore schemes impose similar obligations. US carriers, without a federal mandate, have leaned on voluntary offtake deals and state incentives such as Illinois' SAF tax credit. Every new certified pathway expands the pool of fuel that can count toward those targets.

Methane captured from waste streams carries a dual climate argument: it displaces fossil jet fuel and it diverts a potent greenhouse gas. The Kleinman Center's analysis walks through how that captured methane can be converted into liquid hydrocarbons suitable for aviation use, positioning the pathway as a way to monetize waste-sector emissions reductions within transport fuel markets.

For airlines and lessors, feedstock economics determine SAF pricing, and pricing determines how quickly mandates translate into higher unit costs on routes where compliance is binding. Gas-based pathways compete for the same waste molecules that renewable diesel and renewable power producers want, and policy incentives — from the US renewable fuel standard framework to tax credits under the Inflation Reduction Act — shape which buyer wins the molecule.

The RNG route also faces certification questions. Under ASTM D7566, only a limited set of co-processing and synthetic routes accept non-lipid feedstocks, and any alcohol-to-jet or gas-to-liquid process must clear annex approval before fuel produced from it can enter commercial supply. Readers should treat capacity claims in this space as promises until certified production volumes actually flow.

The Kleinman Center analysis is policy-oriented rather than an engineering study, and its significance for the aviation audience lies in framing: waste-derived methane is one of several feedstock options the industry will need to aggregate if SAF targets are to be met with real gallons rather than announced agreements.

The full analysis is available on the Kleinman Center for Energy Policy website, and its publication signals growing academic attention to feedstock diversification as the binding constraint on aviation decarbonization.