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From Waste to Wing: Using Renewable Natural Gas to Produce Sustainable Aviation Fuel

Likhwa Ndlovu, Hélène Pilorgé, Shrey Patel, Haley McKey, Jennifer Wilcox | May 18, 2026
Fossil Fuels , Transportation

In Texas, renewable natural gas could support early markets for sustainable aviation fuel. But its potential depends on targeted policy support and rigorous carbon accounting.

Producing sustainable aviation fuel (SAF) at scale remains a challenge. This piece builds on previous work by exploring renewable natural gas (RNG) as a near-term pathway leveraging existing infrastructure.

What is Renewable Natural Gas (RNG)?

RNG is methane derived from organic waste streams such as manure, landfills, and wastewater. RNG’s climate benefits vary widely depending on the fate of the RNG, how upstream waste feedstocks are managed, and how associated emissions are controlled, mitigated, and evaluated.

Figure 1: Bar chart comparing greenhouse gas (GHG) intensity of renewable natural gas (RNG) from different livestock manure sources, measured in grams of CO2 equivalent per megajoule (gCO2e/MJ RNG). Six vertical stacked bars represent swine, dairy, dairy heifer, beef, layer hens, and broiler chickens. The y-axis ranges from about –300 to +100 gCO2e/MJ RNG, with a horizontal line at zero separating net-negative from net-emitting RNG. Each bar is divided into colored segments showing emissions components: anaerobic digestion, RNG production, avoided emissions, and biogenic CO2 capture and storage (CCS). Black dots indicate net emissions for each livestock type. Swine manure RNG has the lowest net emissions, around –210 gCO2e/MJ, making it strongly net-negative. Dairy RNG is also net-negative at about –80 gCO2e/MJ. Dairy heifer, beef, layer, and broiler RNG systems all show positive net emissions ranging from roughly +20 to +50 gCO2e/MJ. Two horizontal reference lines mark “Average RNG GHG intensity” near –10 gCO2e/MJ and “Average RNG GHG intensity + Biogenic CO2 CCS” near –80 gCO2e/MJ. Footnotes note that emissions estimates are based on U.S. manure management methods and GREET default assumptions for digester solid carbon sequestration.
Figure 1: Life cycle emissions from manure-derived RNG in Texas (Data source: R&D GREET 2025, DOE, 2025)

The Pathway

One proposed pathway converts RNG into hydrogen, combines it with carbon from direct air capture (DAC), and produces liquid fuels via Fischer–Tropsch synthesis. If the biogenic CO2 generated during hydrogen production is captured and stored, the process can create a hydrogen stream with a net-negative carbon intensity, meaning it removes more CO2 from the atmosphere than it emits. Pairing that hydrogen with atmospheric carbon from DAC creates fuels with the potential for net-negative lifecycle emissions—but at significantly higher cost than conventional fuel production.

A key design choice is whether to use the biogenic CO2 generated during hydrogen production directly as the carbon source for Fischer–Tropsch synthesis, or to store that CO2 and instead use carbon from direct air capture (DAC). The former may be simpler and lower cost. The latter enables a net-negative fuel when paired with geologic storage, but at a higher cost. This decoupling of fuel production and carbon removal may offer flexibility in how and where net-negative outcomes are achieved.

Figure 2: Flow diagram illustrating a carbon recycling pathway that converts livestock manure and captured carbon dioxide into sustainable aviation fuel (SAF) while storing carbon underground. On the left, a green pathway begins with atmospheric CO2 absorbed through photosynthesis, producing biomass that feeds cattle and generates manure. Manure enters a “biodigester + upgrader,” producing renewable natural gas (RNG). The biodigester also creates soil amendments and releases some CO2 to underground storage. In the center, RNG flows into a process labeled “SMR + WGS + CCS” (steam methane reforming, water-gas shift, and carbon capture and storage), which produces hydrogen (H2). Water enters this process, and captured CO2 is directed underground for storage. At the top center, direct air capture (DAC) removes CO2 from the atmosphere. The captured CO2 enters a reverse water-gas shift (RWGS) reactor, where it combines with hydrogen to produce carbon monoxide (CO) and water. Below, carbon monoxide and hydrogen feed a Fischer–Tropsch (FT) synthesis process that produces sustainable aviation fuel (SAF). SAF is then combusted, releasing CO2 and water back into the atmosphere, completing the carbon cycle. A legend at right defines abbreviations including DAC (direct air capture), RWGS (reverse water-gas shift), FT (Fischer–Tropsch), SAF (sustainable aviation fuel), SMR (steam methane reforming), WGS (water-gas shift), CCS (carbon capture and storage), and RNG (renewable natural gas). The diagram uses green arrows for biogenic carbon flows and blue arrows for atmospheric and fuel-processing carbon flows.
Figure 2: RNG-to-SAF pathway using Fischer-Tropsch synthesis

The Gulf Coast as a Testing Ground for RNG-SAF

Figure 3: Map of the southern United States showing locations and infrastructure related to renewable natural gas (RNG), sustainable aviation fuel (SAF), atmospheric CO2 capture, transportation pipelines, and underground carbon storage. The map covers Texas, Louisiana, Mississippi, Alabama, and neighboring Gulf Coast states. Colored symbols identify different facility types and infrastructure systems. Light blue circles represent renewable natural gas production facilities, including cattle and dairy farms, swine farms, landfills, and major wastewater treatment plants. Circle size indicates facility capacity in million standard cubic feet per day, ranging from less than 0.1 to more than 10. Numerous RNG facilities cluster along the Gulf Coast and throughout Texas. Magenta circles mark SAF production refineries and petrochemical industry sites, concentrated primarily along the Gulf Coast corridor between Houston and Louisiana. Gray circles indicate major airports associated with SAF use. Yellow outlined circles identify direct air capture (DAC) hubs for atmospheric CO2 capture, including commercial-scale facilities under construction or planned. Several DAC hubs appear in south and west Texas. Black and gray lines show transportation infrastructure, including CO2 pipelines, major jet fuel pipelines, and natural gas pipelines spanning the region. Blue shaded areas indicate Class VI wells and geologic formations suitable for underground carbon storage. Additional triangular symbols identify CarbonSAFE projects funded by the U.S. Department of Energy in different development phases, including feasibility, site characterization, and permitting. Legends at right and lower left explain symbols, facility categories, storage geology, and transportation infrastructure. A scale bar in the lower left shows distances of 100 miles and 100 kilometers, and a north arrow indicates map orientation.
Figure 3: Opportunities for RNG-to-SAF pathway in Texas and Louisiana using existing infrastructure and local resources (Data source: Airlines for America 2021, DOT-NPMS 2025, EIA 2023, EPA-agSTAR 2025, EPA-GHGR 2023, EPA-LMOP 2024, EPA-WTP 2026, ESRI 2025, NETL 2025, Roads to Removal 2024, USDA-NASS 2024, 1pointfive 2026, Heirloom Carbon 2026)

Texas offers a compelling landscape for RNG-to-SAF (Figure 2). The state has abundant waste feedstocks from cattle, landfills, and wastewater treatment plants, existing pipeline infrastructure, refining capacity, emerging DAC development, and CO2 storage resources already aligned along the Gulf Coast. At the same time, the scale of this opportunity is limited: Texas RNG potential could translate—after conversion losses—to roughly 6 million barrels of SAF annually. This is comparable to estimated private aviation fuel demand in the state, but far below total jet fuel use, suggesting RNG-to-SAF is best suited to niche, early markets rather than full aviation decarbonization.

Activating the Market

Figure 4: Line graph showing how blending sustainable aviation fuel (SAF) made from renewable natural gas (RNG) with conventional Jet A fuel affects carbon intensity and fuel cost. The chart is titled “Blending RNG – SAF with commercial Jet A.” Subtitles indicate the CO2 source is direct air capture and the hydrogen source is RNG from manure plus biogenic carbon capture and storage (CCS). The horizontal axis shows SAF share in the fuel blend from 0% to 100% by volume. The left vertical axis shows carbon intensity in kilograms of CO2 equivalent per gallon, ranging from about –25 to +15 kgCO2e/gal. The right vertical axis shows fuel cost in dollars per gallon, ranging from about $2.5 to $17.5 per gallon. A solid purple line shows the carbon intensity of the blended fuel decreasing steadily as SAF content increases. At 0% SAF, the blend matches conventional Jet A fuel at about +9 kgCO2e/gal. As SAF content rises, carbon intensity falls below zero around one-third SAF blend, reaches approximately –6 kgCO2e/gal at a 50% blend, and approaches about –20 kgCO2e/gal at 100% SAF, indicating net-negative emissions. Shaded purple bands represent uncertainty ranges for carbon intensity. Three dashed cost lines show increasing fuel costs with higher SAF content under different policy incentive scenarios. The red dashed line represents SAF cost without incentives and rises steeply to the highest cost at 100% SAF. The blue dashed line represents cost with the U.S. 45V hydrogen tax credit and rises more moderately. The green dashed line represents cost with both 45V and 45Q carbon capture incentives and remains the lowest-cost SAF pathway. Shaded colored bands around each dashed line indicate uncertainty ranges. Vertical dashed markers identify approximate SAF blend levels where the fuel becomes net-zero or net-negative in emissions. Another marker highlights the 50% blend level. A horizontal gray line near the bottom marks the approximate cost of conventional Jet A fuel.
Figure 4: Carbon intensity and cost comparison of two RNG-SAF pathways. The 45Q and 45V tax credits are not stacked; 45Q applies to the captured CO2, 45V applies to the RNG-SMR (excluding all CCS credits). Average manure and swine manure both max out 45V and benefit similarly from 45Q. FT-SAF must currently be blended with at least 50 % conventional jet fuel (excluding greyed-out areas).

Conventional jet fuel typically averages around $2.50 per gallon; however, prices surged above $4.00 in early May 2026.  SAF pathways are estimated at $3–10. RNG-to-SAF will require policy support (e.g., tax credits for carbon storage and low-carbon fuel production like  45V, 45Q, 45Z) to compete.

It’s also important to ensure enabling policy doesn’t have unintended consequences. Incentives tied to avoided methane emissions can inadvertently encourage the expansion of concentrated animal feeding operations. Alternative manure management strategies may offer lower-cost emissions reductions, reinforcing the need to evaluate RNG alongside competing options.

The Cowpath Forward

Texas has the resources to support RNG-to-SAF, but three actions could build momentum:

  1. Create pathway-agnostic RNG incentives. Expand Texas RNG incentives beyond onsite energy use so RNG can qualify as an intermediary fuel for SAF production.
  2. Accelerate certification of higher SAF blends. Current ASTM standards limit FT-SAF blending to 50%. Increasing allowable blends would enable deeper emissions reductions.
  3. Develop rigorous monitoring and verification. Credible lifecycle accounting, including methane leakage, feedstock sourcing, and CO2 capture, is essential to ensure RNG-based SAF delivers genuine climate benefits.

While RNG alone cannot fully decarbonize aviation, it may play a targeted early role in the effort. Integrating waste-derived methane, DAC, and existing Gulf Coast infrastructure offers a pragmatic pathway to scale SAF—provided that policies prioritize environmental integrity and rigorous carbon accounting.

Likhwa Ndlovu

Ph.D. Student, Chemical and Biomolecular Engineering

Likhwa Ndlovu is a Ph.D. student in the Department of Chemical and Biomolecular Engineering at the University of Pennsylvania. His research focuses on leveraging geoscience principles for the responsible deployment of carbon management solutions.

Hélène Pilorgé

Research Associate, Clean Energy Conversions Lab

Hélène Pilorgé is a research associate with the University of Pennsylvania’s Clean Energy Conversions Laboratory. Her research focuses on carbon accounting of various carbon management solutions and on Geographic Information Systems (GIS) mapping for responsible deployment of carbon management.

Shrey Patel

PhD Candidate, Chemical and Biomolecular Engineering

Shrey Patel is a PhD candidate in the Department of Chemical and Biomolecular Engineering at the University of Pennsylvania. His research focuses on the integration of carbon dioxide removal with low carbon energy sources.

Haley McKey

Former Senior Fellow

Haley McKey is a former senior fellow at the Kleinman Center. She is a carbon dioxide removal communications strategist with a passion for community engagement and responsible CDR deployment.

Jennifer Wilcox

Presidential Distinguished Professor

Jen Wilcox is Presidential Distinguished Professor of Chemical Engineering and Energy Policy. She previously served as Principal Deputy Assistant Secretary for the Office of Fossil Energy and Carbon Management at the Department of Energy.

 

 

 

 

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