SAF blending: how sustainable aviation fuel is blended, certified and measured

Sustainable aviation fuel only reaches an aircraf reservoir after one critical step: blending. Neat SAF cannot be loaded into commercial aircraft on its own. It must be mixed with conventional Jet A1 at a controlled ratio, and released into the fuel supply chain as certified jet fuel. For fuel terminals, refineries, and distributors, SAF blending turns sustainability targets into a measurement, dosing, and documentation opportunity.

If you are planning a new SAF blending line or adapting an existing loading rack, the sections below will help you define the right questions before you talk to an equipment supplier.

On this page:

What is SAF blending?
The SAF blending process in 4 steps
ISOIL solutions for SAF blending
Accurate SAF blending starts with measurement

What is SAF blending?

SAF blending is the controlled mixing of neat sustainable aviation fuel, a synthesized blending component produced from biomass, waste or other non-petroleum feedstocks, with conventional petroleum-based jet fuel, so that the final blend meets ASTM D7566 and can be re-identified as standard Jet A under ASTM D1655.

SAF is a drop-in fuel. Once blended and certified, it behaves like conventional jet fuel: it uses the same pipelines, tanks, hydrant systems, refuelers and aircraft engines, with no modifications required. This is what makes it the most practical short-term lever for reducing aviation emissions, as explained in our guide to sustainable aviation fuel and aviation decarbonization. Why not simply use 100% SAF? Because most certified SAF components are chemically different from fossil jet fuel in ways that matter for aircraft systems.

The SAF blending process in 4 steps, from neat component to certified Jet A

Whatever the site layout, a SAF blending operation follows the same logical sequence: receive and protect the neat component, blend it at the right ratio, measure everything accurately, and certify the result before release.

Step 1: Receipt and segregation of neat SAF

Neat SAF arrives at the blending site with a certificate showing that it meets the requirements of its D7566 annex. It has to be stored and handled in dedicated, clearly identified tanks and lines, segregated from finished Jet A.

Step 2: Choice of blending method

The blending method depends on volumes, infrastructure and how the fuel leaves the site. The architectures are the same used across other types of fuel blending, from biodiesel to ethanol. The most common are:

In-line ratio blending: SAF and Jet A flow simultaneously through separate meters and are combined in the line at a controlled ratio. It suits continuous transfers and truck or rail loading.
Side stream blending: the SAF component is injected into the main Jet A stream through a smaller dedicated line, with the ratio controlled on the side stream.
Sequential blending: the two components are delivered one after the other into the same compartment or tank in the right proportions, and mixing happens in the receiving vessel.
In-tank (batch) blending: components are metered into a storage tank, circulated or mixed, then sampled and certified as a batch before release.

In-line methods reduce tank time and handling, while batch blending gives a single, homogeneous volume to certify. Many terminals combine both.

Step 3: Flow measurement and ratio control, the make-or-break step

This is where SAF blending succeeds or fails. The control system has to measure the volume of each component, compare the actual ratio with the setpoint in real time, and adjust control valves to stay within tolerance for the entire delivery, including start-up and end-of-batch transients.

Because SAF and Jet A have different densities and thermal expansion behavior, raw volumes are not enough. Accurate ratio control relies on temperature compensation to standard conditions (60 °F in US practice) and, where needed, density acquisition, so that the blend is calculated on comparable, corrected volumes rather than on what happens to flow through the pipe at a given temperature.

Step 4: Recertification, documentation and release

Certification follows a two-step logic. The neat component must meet its annex requirements, and after blending, the finished fuel is tested again against the main requirements of D7566, including the extended blend properties. Once it passes, the fuel can be re-identified as ASTM D1655 Jet A and handled like any other jet fuel downstream.

Every step must be traceable: component batches, blend ratio, corrected volumes, test results and release documents. This record supports both fuel quality assurance and the environmental attribute claims (such as RINs and tax credits) that make SAF economically viable.

ISOIL solutions for SAF blending

ISOIL has more than 60 years of experience in positive displacement metering and fuel handling systems, and its fuel blending equipment already serves biodiesel, bioethanol and FAME applications. The same architecture applies to SAF blending, where ratio accuracy, temperature compensation and legally relevant data are non-negotiable.

VEGA 3 multi-stream flow computer

VEGA 3 is the ISOIL modular flow computer designed to manage blending and loading operations, and it is suitable for SAF blending. It is approved under the MID European Directive (MI-005) by the Notified Body LNE, with Ex-d explosion-proof ATEX-IECEx hardware for installation in hazardous areas.

Blending architectures: sequential blending, ratio blending (up to 4 meters), side stream blending (up to 4 meters) and differential measurement.
Scalability: up to 6 measuring systems or loading arms, 12 meters and 16 products, with in-line blending of up to 4 meters at the same time and up to 8 additive injections per loading arm.
Corrected volumes: PT100 temperature input, density acquisition via 4–20 mA or ModBus RTU, and temperature compensation with API chapter 11.1 tables, with base temperature settable at 60 °F. Units include US gallons, barrels and °F.
Data integrity: dual pulse acquisition with continuous monitoring according to OIML R117, ISO 6551 level B and API chapter 5.5 level B; storage of 100,000 deliveries with MID criteria.
Integration: stand-alone operation or remote control from a Terminal Automation System via ModBus TCP or RTU, and data acquisition from positive displacement, turbine or Coriolis meters.

Custom blending skids

Every terminal has its own layout, flow rates and product mix. ISOIL designs custom, tailor-made blending skids for installation on transfer lines or at loading points, integrating meters, valves and the VEGA 3 flow computer into a single package matched to your SAF blending process.

Metering and data chain for aviation fuels

Blending accuracy depends on the meters as much as on the controller. ISOIL BM AVIO and SBM 75/150 positive displacement meters handle all aviation fuel types, including SAF, with ±0.1% measurement accuracy and ±0.01% repeatability across a flow range of 35 to 4,000 l/min (roughly 9 to 1,050 US gallons per minute). ISOIL pulse emitters with CAN bus communication transfer measured data securely to VEGA 3, and ISOIL calibration systems support periodic meter verification.

Tell us your blend ratio, flow rates, and loading configuration, and our engineers will outline the blending architecture that fits your terminal.

Accurate SAF blending starts with measurement

ISOIL helps fuel terminals and distributors build that system with the VEGA 3 flow computer, custom blending skids and aviation-grade metering. Explore the full range of ISOIL blending systems to compare architectures.

Contact our team to discuss your SAF blending project and request a proposal configured on your products, flow rates and certification requirements.