Overview
ISO 9831:1998 specifies the bomb calorimeter method for determining the gross calorific value (higher heating value) of animal feeding stuffs, animal products, faeces and urine. The method measures heat released at constant volume by combusting a weighed test portion in an adiabatic, isothermal or static bomb calorimeter and calculating calorific value from the observed temperature rise and the calorimeter’s effective heat capacity.
Key topics and technical requirements
- Scope and principle: Combustion in oxygen inside a sealed bomb calorimeter; water of combustion condensed at calorimeter temperature; reference temperature 25 °C for thermochemistry.
- Reagents and materials: High-purity water (ISO 3696 grade), oxygen free from combustibles, certified benzoic acid as a thermochemical standard, silica gel, NaOH titrant and indicators.
- Apparatus:
- Bomb rated for oxygen pressure (charge to 3 MPa; do not exceed 3.3 MPa).
- Metal calorimeter vessel with stirring and compatible water jacket (adiabatic, isothermal or static).
- Thermometer with corrected accuracy ~0.002 °C; reading accuracy for typical 2–3 °C rises ≈0.004 °C.
- Crucibles (silica, nickel/chromium or platinum), ignition circuit, analytical balance (0.1 mg), briquette press.
- Sample preparation:
- Follow ISO 6498 for test-sample preparation and ISO 6496 for moisture determination.
- Typical test portion: pellets of 0.5 g to 5 g (mass chosen to give ~2–3 °C temperature rise).
- Special procedures for liquids, high-fat, or fresh samples are provided in annexes.
- Calibration and corrections:
- Determine the calorimeter’s effective heat capacity (annex A) - mandatory if unknown and recommended at intervals (e.g., ≤6 months).
- Correct for ignition fuse heat, thermochemical corrections, and heat losses to the jacket.
- Safety and quality:
- Precautions for high-pressure oxygen systems (no oil/grease).
- Equipment inspection for corrosion and pressure relief devices.
Applications and users
ISO 9831:1998 is used by:
- Analytical laboratories performing calorific-value testing for feed and animal-product characterization.
- Animal feed manufacturers and quality-control teams verifying energy content of feeds.
- Research institutions studying animal nutrition, waste energy content (faeces/urine), and thermochemical properties.
- Regulatory and standards organizations requiring traceable, repeatable calorimetry results.
Practical benefits include reproducible gross energy measurements for feed formulation, nutritional studies, energy-balance assessments and interlaboratory comparability.
Related standards
- ISO 1928 (solid mineral fuels calorimetry)
- ISO 3696 (water for laboratory use)
- ISO 6496 (moisture in animal feeding stuffs)
- ISO 6498 (sample preparation)
- ISO 651 / 652 / 1770 / 1771 (thermometers)
Keywords: ISO 9831:1998, bomb calorimeter, gross calorific value, animal feeding stuffs, calorimetry, effective heat capacity, benzoic acid, adiabatic calorimeter, isothermal calorimeter, sample preparation.
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