Determination of Bio-Based Hydrocarbon Content in Diesel Fuels and Intermediate Distillates Using DIN 51637 Liquid Scintillation Method

The German Standards Institute (DIN) standard, “DIN 51637 Liquid petroleum products - Determination of bio-based hydrocarbon content in diesel fuels and medium distillates by liquid scintillation method,” describes a method for directly determining the bio-based hydrocarbon content of hydrogenated vegetable oil (HVO) in commonly used diesel fuels using liquid scintillation. Since the total content can originate from both bio-based hydrogenated vegetable oil (HVO) and biodiesel (fatty acid methyl ester, FAME) present in the diesel fuel, the FAME content is determined separately using infrared spectrometry according to DIN EN 14078 so that the bio-based HVO content can then be determined by subtraction/calculation.

The DIN 51637 standard includes a precise test method for measuring the bio-based hydrocarbon content in diesel fuels and related products. This standard addresses the growing need to verify the renewable content in fuels amid biofuel blending requirements.

The main purpose of the DIN 51637 standard is to enable the direct measurement of bio-based components, particularly hydrogenated vegetable oil (renewable diesel), in conventional petroleum-derived diesel fuels and their intermediate distillates.

Hydrogenated vegetable oil is a readily usable biofuel produced by hydrogenating vegetable or animal fats, possessing a hydrocarbon structure almost identical to fossil diesel. Unlike conventional biodiesel (fatty acid methyl esters or FAME), hydrogenated vegetable oil does not contain oxygen and mixes seamlessly without restriction. However, this similarity makes it difficult to distinguish from fossil fuels using conventional chemical analysis.

The DIN 51637 standard applies to marketed diesel fuels containing bio-components such as HVO, and ensures proper traceability and compliance with sustainability regulations.

The DIN 51637 standard uses liquid scintillation counting, a radiometric technique that measures the carbon-14 isotope content, as its test method.

Since fossil fuels are millions of years old, the carbon-14 isotopes they contain have completely decayed. Biologically derived materials (those obtained from current plants or animals) contain carbon-14 isotopes at modern levels resulting from atmospheric absorption. Higher carbon-14 isotope levels indicate a directly biologically derived fraction.

Liquid scintillation counting methods include the following:

• The fuel sample is directly mixed with a scintillation cocktail (no complex preparation is required for many samples).
• Detection of beta emissions from carbon-14 isotope decay using a liquid scintillation counter.
• Calculation of biologically derived hydrocarbon content based on carbon-14 isotope measurements.

This direct approach is more efficient compared to alternatives that require burning or graphitization.

Diesel fuels can contain both hydrogenated vegetable oil (HVO) and biodiesel (FAME). Both contribute to the carbon-14 isotope.

• This standard requires the separate determination of FAME content using infrared spectrometry (according to DIN EN 14078 standard).
• The bio-based hydrogenated vegetable oil content is then calculated by subtracting the FAME additive.

Advanced liquid scintillation counting devices can account for quenching effects (e.g., color or chemical interference) for more accurate results.

Liquid scintillation counting is a highly sensitive analytical technique used to measure the radioactive activity of samples emitting low-energy beta particles (e.g., from carbon-14 isotopes) or alpha particles. It is widely accepted as the standard method for the quantitative determination of low-energy radioisotopes in fields such as environmental monitoring, biochemistry, radiocarbon dating, and biofuel analysis (DIN 51637 standard). Unlike other detectors that directly measure ionization, liquid scintillation counting converts energy from radioactive decay into flashes of light (scintillations), which are then counted.

The DIN 51637 standard plays a critical role in verifying the biofuel content:

• Compliance with legal regulations (e.g., renewable fuel requirements in Europe).
• Traceability in sustainable aviation fuel and hydrogenated vegetable oil (HVO).
• Quality control of the fuel mixture.

Tests offered by advanced laboratories are generally performed using similar methods, such as the EN 16640 standard (for broader biofuels) or the ASTM D6866 standard (using accelerator mass spectrometry).

As the energy sector transitions to low-carbon alternatives, standards like DIN 51637 ensure transparency and prevent greenwashing in fuel claims.

Here are a few standards related to the DIN 51637 standard:

• The standard “EN 16640 Bio-based products - Bio-based carbon content - Determination of bio-based carbon content by radiocarbon dating” is applicable to the bio-derived carbon content in various products.
• The standard “ASTM D6866 Standard test methods for determining the bio-based content of solid, liquid and gaseous samples using radiocarbon analysis” is an equivalent standard that uses the carbon-14 isotope for bio-derived content.
• The standard “DIN EN 14078 Liquid petroleum products - Determination of fatty acid methyl ester (FAME) content in intermediate distillates - Infrared spectrometry method” is intended for determining the amount of FAME.

In conclusion, the DIN 51637 standard supports the global transition to sustainable transportation fuels by providing a robust, science-based tool for determining the amount of renewable hydrocarbons in diesel fuel.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services to businesses in accordance with the "DIN 51637 Liquid petroleum products - Determination of bio-based hydrocarbon content in diesel fuels and medium distillates by liquid scintillation method" standard.