How to Calculate Sustainable Aviation Fuel Blend Emissions
Airlines, corporate flight departments, and cargo operators are increasingly blending sustainable aviation fuel (SAF) with conventional Jet A to hit interim decarbonisation targets. Quantifying the avoided emissions is more nuanced than multiplying gallons by a single factor; it requires consistent lifecycle boundaries, careful handling of blend ratios, and transparent documentation of non-CO2 forcing multipliers. This walkthrough codifies a calculation framework aligned with CORSIA and corporate inventory standards.
SAF accounting should slot into a broader sustainability analytics stack. The Travel Carbon Footprint calculator contextualises passenger itineraries, while the Transport Sustainable Emissions tool helps reconcile modal shifts. Together with energy benchmarking guidance in our building energy intensity walkthrough, these resources support holistic carbon reporting.
Definition and reporting boundary
SAF blend emissions quantify the difference in lifecycle greenhouse gas output between a flight fuelled entirely with conventional Jet A and the same flight using a SAF blend. The output is expressed as CO2-equivalent (CO2e) avoided, typically in metric tons per uplift. Lifecycle boundaries must match your disclosure framework—CORSIA, ISO 14064, GHG Protocol Scope 3 Category 13, or a corporate science-based target. Include feedstock cultivation, fuel production, distribution, combustion, and non-CO2 effects if required.
Document whether book-and-claim certificates are bundled with the uplift. Book-and-claim enables emissions claims without physical delivery; if used, adjust documentation so auditors can reconcile virtual allocations with physical supply.
Variables, symbols, and units
Align all emission factors to kilograms of CO2e per gallon. Convert other units—litres, kilograms of fuel, or energy content—before plugging into the formula. Keep the blend percentage on an energy-equivalent basis, since many SAF pathways have slightly different densities.
- IJetA – Lifecycle intensity of conventional Jet A (kg CO2e per gallon).
- ISAF – Lifecycle intensity of the SAF pathway (kg CO2e per gallon).
- B – Blend percentage representing the share of energy provided by SAF (0–100%).
- V – Total fuel uplift for the flight (gallons).
- F – Optional non-CO2 forcing multiplier capturing contrail and NOx effects (dimensionless).
- Ebaseline – Emissions from 100% Jet A (kg CO2e).
- Eblend – Emissions from the SAF blend (kg CO2e).
- ΔE – Emissions avoided due to SAF (kg CO2e or metric tons CO2e).
Capture ancillary data such as flight number, aircraft type, engine model, and certificate identifiers. These attributes support audits and facilitate comparisons across fleets.
Core formula
The calculation combines baseline and blended intensities. Convert the blend percentage to a fraction, apply intensities, multiply by uplift volume, and apply the forcing multiplier if required. Convert kilograms to metric tons by dividing by 1,000 when reporting results.
Baseline emissions: Ebaseline = IJetA × V × F
Blend emissions: Eblend = [(1 − B/100) × IJetA + (B/100) × ISAF] × V × F
Avoided emissions: ΔE = Ebaseline − Eblend
Metric tons avoided: ΔEtons = ΔE ÷ 1,000
If ΔE is negative, the SAF pathway is performing worse than Jet A under your assumptions. That can happen when waste feedstock supply chains involve long transport distances or when indirect land-use change factors are high. Flag negative results for sustainability governance before publishing claims.
Step-by-step workflow
Step 1: Confirm lifecycle data
Obtain certified emission factors from your fuel supplier or lifecycle analysis provider. Ensure the SAF pathway is approved under ASTM D7566 and CORSIA, and record certificate numbers or Sustainability Declaration IDs.
Step 2: Normalise volumes
Convert uplifted fuel to gallons (or litres if required) and confirm whether volumes are already energy-equivalent. If not, apply lower heating value (LHV) ratios to translate the SAF portion into energy-equivalent gallons.
Step 3: Apply blend ratio
Express the SAF share as a fraction between 0 and 1. For book-and-claim transactions, align the claimed blend with delivered certificates rather than physical mixing ratios to avoid overstatement.
Step 4: Calculate emissions
Multiply intensities and volumes using the formulas above. Compute both ΔE and ΔEtons so sustainability teams can report in either unit. Round to two decimals for public disclosures and retain full precision internally.
Step 5: Record evidence
Archive supplier attestations, invoices, and measurement logs. Store them in a controlled repository linked to each uplift so auditors can trace the calculation end-to-end.
Validation and assurance
Reconcile aggregate ΔE totals against supplier sustainability reports and emissions registries. Differences should be explainable by rounding or timing. Conduct spot checks by re-running lifecycle models with alternative assumptions (for example, updated grid mix or feedstock transport distances) to evaluate sensitivity.
For corporate inventories, align SAF claims with Scope 1 or Scope 3 accounting policies. Ensure avoided emissions are not double-counted with voluntary carbon offsets or efficiency projects documented elsewhere.
Limits and interpretation
SAF availability is constrained, and most blends today fall below 50%. Treat ΔE as a snapshot for each uplift; long-term planning should model fleet-wide trajectories, supply contracts, and policy incentives. Remember that non-CO2 effects remain an active research area—the multiplier F is an approximation that should be updated as science evolves.
Communicate results with nuance. Highlight that SAF reduces lifecycle emissions but does not eliminate them, and pairing SAF with efficiency upgrades—winglets, weight reductions, or route optimisation—delivers more resilient progress toward net-zero aviation goals.
Embed: Sustainable aviation fuel blend calculator
Use the embedded calculator to combine emission factors, blend percentages, and optional forcing multipliers. It returns the avoided CO2e in metric tons with consistent rounding for audit-ready reporting.