Overview
ISO 16948:2015 - Solid biofuels - Determination of total content of carbon, hydrogen and nitrogen specifies an instrumental method for measuring the total carbon (C), hydrogen (H) and nitrogen (N) contents of solid biofuels. The method is based on complete combustion of a prepared test sample and quantitative gas analysis of the combustion products (CO2, H2O, N2/NOx), with provisions for removing interferences and converting nitrogen oxides to molecular nitrogen prior to detection.
Keywords: ISO 16948:2015, solid biofuels, carbon hydrogen nitrogen, CHN analysis, elemental analysis, combustion analysis, biofuel quality control.
Key topics and technical requirements
- Scope & principle
- Describes instrumental CHN determination by combustion and gas analysis.
- Products of combustion are treated to ensure all H, C and N are converted to measurable gaseous forms.
- Reagents and calibration
- Use analytical-grade carrier gas (e.g., helium) and oxygen per instrument manufacturer instructions.
- Calibration substances and Certified Reference Materials (CRM/SRM) are recommended to verify accuracy.
- Apparatus requirements
- Functional requirements include complete conversion of C/H/N, removal of interfering species, reduction of NOx to N2, and detector responses that correlate with gas concentrations (linear or appropriately characterized).
- Sample preparation
- Test sample is prepared to a nominal top size of 1 mm (ISO 14780); moisture content to be determined concurrently (ISO 18134-3).
- Test portions weighed with high relative accuracy and introduced per instrument type.
- Procedure, calibration and QA
- Establish and maintain calibration functions, routinely verify with calibration substances, CRMs/SRMs and control samples, and record performance characteristics.
- Results & reporting
- Results expressed as mass fractions; test report and performance characteristics are defined in the standard.
Applications and who uses it
ISO 16948:2015 is used to support:
- Quality control in biofuel production and trading (pellets, wood chips, agricultural residues).
- Energy calculations - hydrogen content for net calorific value; carbon content for CO2 emission estimations; nitrogen content to assess potential NOx emissions.
- Laboratories and accreditation - analytical and testing labs performing elemental analysis and issuing certified results.
- Regulators and researchers monitoring fuel properties, emissions or validating combustion models.
- Instrument manufacturers designing CHN analyzers and establishing calibration/validation protocols.
Related standards
- ISO 16559 - Terminology for solid biofuels
- ISO 14780 - Sample preparation for solid biofuels
- ISO 16993 - Conversion of analytical results between bases
- ISO 18134-3 - Moisture determination (referenced for concurrent moisture analysis)
ISO 16948:2015 ensures traceable, repeatable CHN measurements for reliable fuel characterization, emissions assessment and combustion performance evaluation.
