ISCC and C14 Testing: Ensuring Compliance in Co-Processed Fuels

Discover how ISCC certification and C¹⁴ testing work together to verify bio-based content in co-processed fuels. Our host Florencia Bahamonde and our expert Liam Mills explain what co-processing is, why radiocarbon testing is the gold standard, and how Intertek helps organizations meet EU sustainability requirements with confidence. 

Follow us on- Intertek's Assurance In Action || Twitter || LinkedIn.

Transcript

Florencia: Hello, and welcome to Intertek’s ISCC Awareness Series, where we delve into the latest in sustainable practices, the ISCC certifications, and their impact on the world of business and beyond. I'm your host today, Florencia Bahamonde, ISCC  Sr. Global Program Manager joined by Liam Mills, our Sustainable Hydrocarbon Specialist.

Liam: Hi, Florencia! Glad to be here.

Florencia: In this episode, we unpack how co-processing is helping refineries transition toward renewable fuels—without rebuilding infrastructure.
We’ll explore how ISCC certification and ¹⁴C testing work together to verify what’s truly bio-based.
From regulatory requirements to scientific proof, here’s what you need to know to certify co-processed fuels with confidence.

Florencia: Let's start from the basics. What exactly is co-processing, and why is it so relevant in today’s biofuels landscape?

Liam: Co-processing refers to the simultaneous refining of fossil and biomass-based feedstocks in the same production unit—like hydrotreating vegetable oil together with straight run kerosine to produce drop-in fuels such as jet fuel. It’s a widely adopted strategy because it leverages existing refinery infrastructure while helping producers meet renewable energy targets. In the EU, co-processed biofuels can contribute to RED III targets, provided their bio-share is verified and certified. The outputs are chemically identical to fossil fuels, which makes them compatible with current engines and fuel systems—without blend limits.

After certification, organizations may begin to trade, process, or label certified material in line with ISCC requirements.

Florencia: So co-processing is both efficient and strategic—no wonder it’s gaining ground in the biofuels sector. Let’s now look at what certification requires.

Liam:  I will leave this one to you, Florencia, so What are the core requirements under ISCC EU for certifying co-processed fuels?

Florencia: The ISCC EU framework, aligned with EU Regulation 2023/1640, outlines specific requirements for co-processed fuels. 

First, companies must implement a robust mass balance system covering the co-processing unit. 

Every biomass input must be ISCC-certified, and all inputs and outputs must be fully traceable. 

The critical requirement is verifying the bio-based content, and this is where ¹⁴C testing becomes essential. ISCC allows either direct ¹⁴C testing using methods like AMS or LSC, or model-based methods like mass or energy balance—but these must be regularly calibrated against ¹⁴C results to remain valid. Fuel samples also need to be archived for at least 2 years to support traceability and retrospective checks.

Liam:  So, while documentation and traceability are fundamental, it’s the ¹⁴C testing that gives credibility to the entire process. Without scientifically-backed verification of the bio-content, the sustainability claims would be unverifiable—and that’s exactly what ISCC is designed to prevent.

Florencia: Liam, now is your turn - why is ¹⁴C testing the gold standard for bio-content verification?

Liam: Only recently living biomass contains detectable amounts of radiocarbon (¹⁴C), while fossil carbon contains negilble levels of C-14. That’s why ¹⁴C testing is the only molecular-level method to distinguish bio-carbon from fossil carbon when they are chemically identical. It can be used to prevent fraud and greenwashing by validating actual bio-content. This is especially important in co-processing, where physical appearance and composition of fuels can’t reveal their origin. Regulation (EU) 2023/1640 mandates ¹⁴C testing for outputs claiming renewable energy contributions in the EU.

Florencia: That distinction is essential. In a context where bio-based and fossil fuels are chemically indistinguishable, radiocarbon analysis offers the only scientifically accepted means to verify sustainability claims. It’s not just a regulatory requirement—it’s a foundation for trust, traceability, and credible certification under ISCC.

Florencia: So we’ve established why ¹⁴C testing is essential for verifying bio-content—but how does this testing actually work in practice? What are the methods available to companies, and how are they applied in the certification process?

Liam: In practice, there are two primary methods for ¹⁴C testing: Accelerator Mass Spectrometry (AMS) and Liquid Scintillation Counting (LSC). AMS is highly sensitive and suitable for virtually any sample type—solid, liquid, or gas. LSC, while more cost-effective, works well for liquid samples, particularly when the expected bio-content is above 1%.

Operators may also use indirect methods, like yield or energy balance models, to estimate bio-share—but these models must be calibrated and periodically validated using ¹⁴C testing. 

In either case, testing must be performed by accredited laboratories, and operators are required to apply the same method consistently across all installations within the co-processing system boundary. All outputs with renewable claims must be traceable to validated bio-content results.

Florencia: Exactly—and from the certification side, ISCC requires that system users clearly define their testing methodology, whether direct or indirect, in the technical basis document submitted for approval. For indirect methods, regular ¹⁴C calibration testing is mandatory to maintain validity, and any deviation above the threshold—3% in the first year, 1% from the second year onward—must be addressed.

We also emphasize that testing must occur within the defined system boundary, and the method applied must be consistent across all relevant installations. It’s this structured, science-based approach that allows ISCC to ensure robust traceability and verifiable sustainability claims in co-processed fuels.

Florencia:  To wrap up—why is it so important to align ISCC certification with robust ¹⁴C testing?

Liam:  Because without accurate bio-content verification, sustainability claims can't be trusted. ¹⁴C testing ensures compliance with EU rules and provides the scientific proof behind those claims.

Florencia: Exactly—and that’s why Intertek is such a valuable partner. We combine ISCC certification expertise with accredited ¹⁴C testing services—offering clients a streamlined, end-to-end solution. Together, we help companies meet regulatory requirements with confidence and integrity.

Liam: For companies seeking further clarification or support, we encourage you to connect with an Intertek technical expert. You can reach out to us directly via email or submit an inquiry through our website—we’re here to help guide you from regulatory guidance to lab-tested proof of compliance. 

Florencia: That’s all for today’s episode of Intertek’s ISCC Awareness Series. Thank you for tuning in, and special thanks to Liam for sharing his insights. Stay tuned! We will continue diving into the ISCC certification in our next episodes.