Sustainable Aviation Fuel (SAF) Blend Emissions & Cost Calculator

Introduction

Sustainable aviation fuel, usually shortened to SAF, is a drop-in alternative to conventional jet fuel that can be made from waste oils, residues, biomass, or synthetic pathways that use renewable electricity and captured carbon. Airlines rarely operate on neat SAF alone. Instead, SAF is typically blended with conventional Jet-A or Jet-A1 because supply, certification rules, and airport logistics still limit how much can be used on any given flight.

This calculator focuses on the question planners usually face first: if I change the blend percentage, how do emissions and direct fuel cost move? To answer that, the page combines your total fuel burn with emission factors and prices for both fuel types. The result is a fast browser-based estimate of the blended lifecycle emission factor, total CO₂ emissions, percent reduction relative to a 0% SAF baseline, and the extra fuel cost or savings. It is designed for quick comparisons between routes, suppliers, procurement offers, and SAF pathways rather than for regulatory reporting.

How to use the calculator

1. Enter total fuel burn in kilograms (kg) for a flight, route, or fleet planning period.
2. Enter the SAF blend fraction as a percentage from 0 to 100. Example: 20 means 20% SAF and 80% conventional fuel.
3. Provide emission factors in kg CO₂ per kg fuel for both conventional fuel and SAF. If possible, use values built on the same lifecycle boundary.
4. Provide unit costs in $/kg for both fuels so the model can estimate the direct purchase impact of the blend.
5. Select Calculate Emissions to see the weighted emission factor, total emissions, reduction versus baseline, and cost difference.

A good way to use the page is to hold fuel burn and blend percentage constant while changing only the SAF emission factor and SAF cost. That lets you compare pathways such as HEFA, Fischer–Tropsch, alcohol-to-jet, or power-to-liquid on the same operational demand. If you are preparing a budget note, run a low, central, and high case for the SAF factor and price so decision-makers can see how sensitive the outcome is.

Formulas used (weighted-average model)

The calculator uses a straightforward weighted-average approach. Let F be total fuel burn in kg, b the SAF blend fraction as a decimal, e_j the conventional fuel emission factor, e_s the SAF emission factor, c_j the conventional fuel cost, and c_s the SAF cost. Because the model treats the blend as a simple mass mix, the same fraction is used in both the emissions and cost equations.

• Weighted emission factor: EF = b·e_s + (1 − b)·e_j
• Total emissions: E = F·EF
• Baseline emissions (0% SAF): E₀ = F·e_j
• Emission reduction (%): R = (E₀ − E) / E₀ × 100
• Blended fuel cost: C = F·(b·c_s + (1 − b)·c_j)
• Cost difference vs. baseline: ΔC = C − (F·c_j)

Two practical details are worth noticing. First, the percent reduction comes from the gap between the SAF and jet-fuel emission factors and the share of SAF in the blend. Second, the dollar premium depends on both blend fraction and fuel burn. That means the same 20% blend can look manageable on a short sector but much more expensive on a long-haul route. Those paired effects are why emissions and cost need to be viewed together rather than in isolation.

Worked example (using the default inputs)

Suppose a flight or planning period burns 10,000 kg of fuel and uses a 20% SAF blend. If conventional fuel has an emission factor of 3.16 kg CO₂/kg and SAF is 0.50 kg CO₂/kg, then the blend lowers the weighted factor because one-fifth of the fuel now carries the lower lifecycle value.

• EF = 0.20×0.50 + 0.80×3.16 = 2.628 kg CO₂/kg
• Total emissions E = 10,000×2.628 = 26,280 kg CO₂
• Baseline E₀ = 10,000×3.16 = 31,600 kg CO₂
• Reduction R = (31,600 − 26,280) / 31,600 × 100 ≈ 16.8%

For costs, if conventional fuel is $0.80/kg and SAF is $1.50/kg, the same blend increases direct fuel purchase cost because the SAF portion is more expensive per kilogram.

• Blended cost C = 10,000×(0.20×1.50 + 0.80×0.80) = $9,400
• Baseline cost = 10,000×0.80 = $8,000
• Cost difference ΔC = $9,400 − $8,000 = $1,400

This example is useful because it shows the core planning trade-off in one place: the blend produces a meaningful emissions reduction, but it also creates a premium that procurement or policy support may need to absorb. If a tax credit or supplier discount narrows the SAF price gap, the same emissions benefit may come at a much smaller extra cost.

Assumptions and interpretation notes

Emission factors vary by methodology and system boundary. A commonly cited combustion-related factor for conventional jet fuel is around 3.16 kg CO₂ per kg fuel, but lifecycle values can be higher once extraction, refining, and transport are included. SAF lifecycle factors can range widely depending on feedstock choice, process energy, land-use effects, transport distance, and how co-products are treated in the accounting method.

The calculator treats the blend as a simple mass-based mixture and assumes the same operational fuel burn regardless of blend. In practice, certified SAF is intended to be operationally compatible with existing aircraft, yet small differences in density or energy content can still exist. For high-level scenario analysis those differences are often secondary, but for engineering-grade fuel planning you would want a more detailed performance model.

How to interpret the results in practice

The weighted emission factor is the quickest way to compare one blend scenario with another because it compresses the mix into a single number. Lower is better. The total emissions figure then scales that factor by your fuel burn, which means it reflects both operational size and fuel quality. If two flights use the same blend but different amounts of fuel, the percent reduction may be similar while the absolute tonnes of CO₂ avoided are very different.

The emission reduction percentage is best used when speaking to climate targets, while the fuel cost difference is more useful for budgeting and contracting. Decision-makers often need both at once. A blend that looks attractive in percentage terms may still require a large budget on high-burn operations, whereas a modest blend on a large fleet can still avoid substantial absolute emissions. That is why this calculator keeps the arithmetic transparent instead of hiding it behind a single sustainability score.

Limitations

• CO₂ only: Non-CO₂ effects such as contrails, NO_x, and soot are not included.
• Single emission factor per fuel: Real supply chains can have multiple stages, seasonal changes, and regional variation.
• No uncertainty ranges: Results are point estimates; sensitivity analysis is strongly recommended.
• Cost scope: Only direct fuel purchase cost is modeled; infrastructure, contracting, certificates, and policy incentives are excluded unless you adjust the input prices yourself.
• Blend constraints: Regulatory and certification limits may restrict maximum blend levels for certain SAF pathways or aircraft programs.

After you run a calculation, the key outputs are also shown in the table below for quick scanning and easy copying into notes, presentations, or internal reports.

Background: SAF pathways, policy, and practical context

SAF can be produced through several pathways. The Hydroprocessed Esters and Fatty Acids (HEFA) pathway is currently the most mature, converting waste lipids into jet-range hydrocarbons via hydrotreating and isomerization. Alcohol-to-jet routes ferment sugars into alcohols which are then upgraded into hydrocarbons. Fischer–Tropsch synthesis can transform municipal solid waste or biomass into syngas and then into liquid fuels. Power-to-liquid concepts combine captured carbon dioxide with green hydrogen to produce synthetic hydrocarbons. Each pathway comes with its own energy requirements, feedstock constraints, and land-use questions, so the same SAF label can hide very different lifecycle outcomes.

Policy instruments strongly influence SAF adoption. Blending mandates, tax credits, low-carbon fuel standards, and carbon pricing can narrow the cost differential between SAF and conventional fuel. Programs such as ReFuelEU and various national incentives are meant to accelerate supply, but the quality of emissions claims still depends on transparent lifecycle data and credible certification. If the electricity mix is carbon intensive or feedstocks create indirect land-use change, the real climate benefit can shrink.

When interpreting results, remember that lifecycle assessments depend on assumptions about feedstock sourcing, transportation distances, process efficiency, and co-product allocation. A simple sensitivity check is to run the calculator several times with a low, central, and high SAF emission factor, such as 0.2, 0.5, and 1.0 kg CO₂/kg. If the business case changes dramatically across that range, the decision deserves more detailed sourcing analysis before commitments are made.

Finally, SAF is only one lever in aviation decarbonization. Fleet renewal, operational efficiency, air traffic improvements, demand management, and future aircraft technologies also matter. This page deliberately focuses on blend arithmetic so you can quantify the immediate emissions and cost implications of a SAF procurement choice before layering on other strategies.