Analysis of solid recovered fuels (SRF): methods, carbon 14 and regulation
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Solid recovered fuels (SRF) are composed of non-hazardous waste. They are used as fuel in certain industrial facilities. However, their composition can vary considerably depending on the materials they consist of and the preparation processes used.
To characterize these fuels, it is particularly necessary to determine their biomass content, i.e., the proportion of matter of biological origin they contain. This information makes it possible to distinguish the contribution of biogenic carbon from that of fossil carbon and helps to better characterize their energy use.
Several methods can be used to measure this fraction, including manual sorting, selective dissolution, and carbon 14 analysis. The NF EN ISO 21644 standard governs these methods for determining the biomass content of CSRs.
In summary:
- Recovered Solid Fuels (RSF) are fuels prepared from non-hazardous waste and intended for energy recovery.
- The analysis of CSRs makes it possible to characterize their composition and, in particular, their biogenic fraction.
- Three methods are provided by the standard NF EN ISO 21644: manual sorting, selective dissolution, and carbon-14 analysis.
- The NF EN ISO 21644 standard governs the determination of biomass content, but overall regulatory compliance also depends on the requirements applicable to the fuel and its use.
The analysis of CSR
What are CSRs?
Refuse-derived fuels are prepared from non-hazardous waste, from which certain fractions are selected and processed for use as fuel. They can contain various materials such as plastics, paper, cardboard, and textiles. Their composition depends on the waste collected, sorting operations, and upstream treatments.
Certain industrial facilities use SRF to produce heat or power energy-intensive processes. This use allows for the energy recovery of certain waste fractions that cannot be recycled under satisfactory conditions.
Why characterize them?
The composition of SRFs determines their energy properties and possible usage conditions. Their characterization can focus in particular on calorific value, moisture content, ash content, or the presence of certain undesirable elements.
Biomass content is another important parameter. Indeed, SRFs can contain both biogenic carbon, from recent biological materials, and fossil carbon, particularly present in certain petrochemical plastics.
Determining the proportion of biogenic carbon allows for better characterization of the fuel and assessment of the contribution of biomass-derived carbon. This information can also be useful for establishing certain greenhouse gas emission balances, according to the applicable calculation rules.
What methods are used to measure the biomass content of SRFs?
The NF EN ISO 21644 standard provides three methods for determining the biomass content of solid recovered fuels: manual sorting, selective dissolution, and carbon-14 analysis. The choice of method depends on the fuel's composition, the analysis objective, and applicable requirements. Here are the principles, advantages, and limitations of each.
| Method | Principle | Advantages | Limits |
| Manual sorting | Separate and weigh the different fractions according to their visual and physical characteristics | Concrete method, based on material identification | Difficult identification for mixed, composite, or poorly recognizable materials |
| Selective dissolution | To use chemical treatments to separate certain fuel fractions | Allows characterizing fractions according to their chemical behavior | The results can be influenced by the composition of the CSR and the behavior of the materials during processing. |
| Carbon-14 dating | Measure carbon 14 content to distinguish biogenic carbon from fossil carbon | Measurement based on the origin of carbon, without requiring visual identification of each material | Requires representative sampling and appropriate preparation. Conversion to mass or energy fraction may require additional data. |
Why use carbon 14 to analyze CSRs?
CSRs can contain materials of very different natures, sometimes difficult to identify or separate. In this context, a method based on the direct measurement of the carbon's origin provides complementary information to sorting or selective dissolution methods.
Carbon-14 analysis allows for the estimation of the biogenic carbon fraction in a sample, even when it contains mixed materials that are difficult to identify visually.
The reliability of the result nevertheless depends on several factors: the representativeness of the sample, the homogenization of the sample, its preparation, and the analytical method used.
It is also important to distinguish the biogenic carbon fraction from the total biomass content. The former corresponds to the proportion of carbon in the sample that is of biogenic origin. The latter can be expressed as a mass or energy fraction and requires additional data or calculations, in accordance with the chosen method.
Carbon-14 thus constitutes a relevant characterization tool for CSRs, but the results must always be interpreted in light of the analysis objective and the applicable framework.
NF EN ISO 21644: what framework for CSR analysis?
The NF EN ISO 21644 standard, titled "Solid recovered fuels — Method for the determination of biomass content", defines the methods used to determine this content in SRFs.
It provides for three approaches: carbon 14, selective dissolution, and manual sorting. It also frames the methods for determination and the expression of results, which can be presented on different bases, notably in carbon content, mass fraction, or energy fraction.
The standard is part of a set of references dedicated to solid recovered fuels, particularly for sampling and sample preparation. These steps are essential: an analytical result is only relevant if the sample studied correctly represents the batch concerned.
The choice of method must take into account the nature of the fuel, the intended use of the results, and the applicable regulatory or contractual requirements.
However, it is important to distinguish the determination of biomass content from overall regulatory compliance. Performing an analysis according to a standard is not sufficient, in itself, to demonstrate that a fuel or an installation complies with all applicable obligations.
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You might be asking yourself these questions about CSR?
The choice depends on the fuel composition, the analysis objective, and the applicable requirements.
Carbon-14 analysis allows for the estimation of the proportion of biogenic carbon present in a sample. The result therefore depends on the indicator being sought and the method applied.
CSRs bring together various materials whose proportion can change from one sample to another. The laboratory must therefore have a representative sample and apply appropriate preparation to obtain a relevant result. Homogenization and analytical preparation help to limit the effects of fuel heterogeneity.
No. The measurement distinguishes the contribution of biogenic carbon from that of fossil carbon, but it does not, on its own, provide a complete CO₂ emissions balance. To establish this balance, the quantity of fuel used, combustion conditions, and applicable calculation rules must also be taken into account.
The NF EN ISO 21644 standard provides three methods for determining the biomass content of SRF: manual sorting, selective dissolution, and carbon 14 analysis. The choice of method must take into account the nature of the fuel, the objective of the analysis, and the applicable requirements.
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