Under ICAO's CORSIA methodology, conventional Jet-A has a well-to-wake CI of approximately 88 to 89 gCO2e/MJ. Burning one megajoule releases approximately 73.7 gCO2 at the engine nozzle; extraction, transport, refining, and distribution account for the balance.
Green methanol-derived e-SAF delivers an 85 to 92 percent lifecycle CO2 reduction against that baseline under current green electricity grid assumptions. We examine the LCA behind the range, its drivers, and the records needed for regulatory compliance.
System Boundaries: What We Count
A well-to-wake LCA for aviation fuel has three main stages: well-to-gate, covering emissions to the fuel supply point; gate-to-wake, covering distribution and use; and, in some frameworks, end-of-life allocation for co-products. Engine-nozzle combustion is always included, so this is a full cradle-to-combustion analysis.
For fossil Jet-A, the boundary includes crude extraction, field processing, pipeline transport, refining, product distribution, and combustion. For green methanol e-SAF, it begins with renewable electricity generation or biomass input, then includes methanol synthesis, MtJ conversion, distribution, and combustion.
Matching boundaries is necessary for a fair comparison. If e-SAF upstream electricity emissions are omitted while fossil extraction emissions remain, the e-SAF result is artificially favorable. We include upstream emissions for both. We are not saying every LCA is comparable; we are saying studies using asymmetric boundaries require caution.
The Fossil Jet-A Baseline
The fossil Jet-A total of 88 to 89 gCO2e/MJ comprises approximately 73 to 74 gCO2e/MJ from combustion, 6 to 8 gCO2e/MJ from refining, 5 to 8 gCO2e/MJ from crude extraction and transport, and 1 to 2 gCO2e/MJ from distribution. CORSIA's LCAF methodology uses these values as the fossil comparator baseline.
The refinery energy mix also changes this baseline. Higher-carbon refinery energy raises upstream Jet-A CI, while cleaner energy lowers it. CORSIA uses a global average refinery energy mix, so a particular refinery's Jet-A may differ from the baseline. This distinction matters when e-SAF displaces specific fuel, not only the global average.
Green Methanol Production: The Critical Upstream Step
For e-methanol made by CO2 hydrogenation, captured CO2 combined with green hydrogen from electrolysis, methanol CI depends almost entirely on the electrolysis electricity's CI.
With the EU average grid emission factor for 2025, approximately 220 to 240 gCO2e/kWh depending on calculation method, and alkaline or PEM electrolyzer use of approximately 50 to 55 kWh per kg of hydrogen, EU-grid methanol has a significant upstream carbon burden. The resulting e-SAF may not meet ReFuelEU's 65 percent reduction threshold for eligible fuel status.
Contracted renewable electricity with documented additionality, at an effective factor of 10 to 30 gCO2e/kWh, substantially lowers methanol CI. Under these conditions, e-SAF reaches the stated 85 to 92 percent reduction. Variation in renewable electricity CI and electrolysis efficiency drives most of the range.
Biomethane-derived methanol uses different upstream CI accounting. Biomethane production receives a biogenic carbon sequestration credit for avoided methane emissions from organic feedstock. We must avoid double-counting this credit, and RED III, CORSIA, and GREET apply different rules, as discussed in our earlier regulatory comparison.
MtJ Conversion Process Emissions
MtJ conversion creates direct CO2 from the reaction chemistry. During MTO, some methanol carbon exits as CO2 instead of entering the olefinic product. Fractionation then removes lighter fractions outside the jet cut, which are recycled or burned on-site as process fuel.
At our pilot benchmark conditions, process-stage CO2 is approximately 8 to 12 gCO2e/MJ of e-SAF, depending on feedstock carbon balance and the share diverted to lighter products. This direct process emission is independent of upstream electricity CI. It is inherent to the reaction chemistry and cannot be removed by cleaner electricity sourcing.
Process energy, including electrical heating, compression, and hydrogen use in the hydrogenation stage, adds 5 to 10 gCO2e/MJ under renewable electricity conditions. Conversion therefore contributes approximately 13 to 22 gCO2e/MJ to e-SAF lifecycle CI, independently of upstream methanol CI.
Combustion at the Engine Nozzle
At the nozzle, e-SAF combustion releases approximately 73.7 gCO2/MJ, about the same per unit energy as fossil Jet-A. Fossil fuel adds ancient geological carbon to the atmosphere for the first time; in CO2 hydrogenation e-SAF, the methanol synthesis step captured this CO2 from the atmosphere or industrial point sources.
When the boundary includes the CO2 capture credit in upstream methanol synthesis, net combustion CO2 for the CO2 hydrogenation pathway is approximately carbon-neutral. The LCA credits the CO2 consumed in methanol synthesis, offsetting combustion emissions on a molecular mass balance basis.
This captured-carbon mechanism produces the 85 to 92 percent CO2 reduction: most carbon burned at the nozzle was captured upstream. Remaining lifecycle emissions arise from conversion energy and upstream methanol production energy, not combustion CO2 itself.
Electricity Grid Sensitivity
Electricity input CI is the largest source of variation in final e-SAF CI. Across the relevant range, the relationship is approximately linear: changing the electricity factor by 100 gCO2e/kWh changes final e-SAF CI by roughly 15 to 20 gCO2e/MJ, depending on process electricity use per unit of output.
The compliance implication is direct. CORSIA eligibility and ReFuelEU thresholds require documented renewable electricity, not grid-average power paired with carbon offsets. LCA results follow the electricity that powers electrolysis, not what the producer buys in the offset market.
- Under certified renewable electricity (approximately 10 to 30 gCO2e/kWh): e-SAF CI of approximately 7 to 15 gCO2e/MJ, representing 83 to 92 percent reduction against the CORSIA fossil comparator
- Under EU average grid electricity (approximately 220 to 240 gCO2e/kWh): e-SAF CI of approximately 38 to 55 gCO2e/MJ, representing 37 to 57 percent reduction
- Under coal-heavy grid electricity: e-SAF CI likely approaches or exceeds the fossil comparator baseline, negating the environmental value of the pathway
LCA Documentation for Regulatory Compliance
For CORSIA and ReFuelEU, a compliant LCA must document the methanol pathway and inputs, electricity source and additionality, MtJ yields and energy inputs with byproduct allocation, and carbon accounting at every process stage with stated assumptions.
CORSIA permits an approved LCA using its LCAF methodology or, where applicable, a default from the CORSIA Default Carbon Intensities tables. A novel producer absent from those tables needs an independent CORSIA-methodology LCA, with third-party verification mandatory for Phase 2 eligibility documentation.
ReFuelEU requires RED III delegated-act-aligned records, including renewable hydrogen content and temporal correlation for electricity supply. In practice, renewable generation and hydrogen production must match monthly, or under strict interpretation hourly. Hourly matching is not universally enforced today, but regulation is moving that way.
Producers pursuing multiple frameworks need documentation designed for each framework, rather than one LCA claimed to cover all three. Their data requirements and allocation methods differ enough that one study rarely transfers without reparameterization.
What This Comparison Shows and Does Not Show
The 85 to 92 percent lifecycle CO2 reduction is real and achievable with suitable electricity. We are not saying it covers aviation's full climate impact; it describes fuel CI within this LCA scope.
Standard fuel CI accounting excludes aviation's non-CO2 warming effects at altitude, including contrails, nitrogen oxide chemistry, and water vapor deposition. These effects are real and significant. Research estimates may double or triple aviation's effective climate forcing versus CO2 alone, although their magnitude and permanence remain under study. CORSIA and ReFuelEU CI accounting does not include them.
CI accounting is the regulatory framework and the language of SAF mandate compliance. Within it, renewable-electricity green methanol e-SAF performs well against fossil fuel. We are not saying the CI reduction covers aviation's full climate story; we are saying it is a large, genuinely beneficial CO2 reduction. Compliance decisions still require the relevant framework's documented inputs, boundaries, and allocation method.
AI process control software for methanol-to-jet e-SAF production. Zurich, Switzerland.