Overview
ISO 13610:2025 - Sludge recovery, recycling, treatment and disposal - Determination of calorific value of sludge - specifies a laboratory method to determine the gross calorific value of sludge using a bomb calorimeter at constant volume and a reference temperature of 25 °C. The calorimeter is calibrated by combustion of certified benzoic acid. Results represent the gross calorific value with both the sludge moisture and the water from combustion considered as liquid water. The standard also explains how to derive net calorific value (operative heat typically used for thermal treatment at atmospheric pressure) and provides calculation options that reduce extra determinations.
Key technical topics and requirements
- Measurement principle: Combustion in a bomb calorimeter under oxygen at constant volume, with corrected temperature rise used to compute energy release.
- Reference conditions: 25 °C reference temperature; calibration by certified benzoic acid.
- Result definitions: Distinguishes gross calorific value (water as liquid) and net calorific value (water as vapour), and provides equations to convert between them.
- Apparatus and reagents: Includes requirements for calorimeter (isoperibol/adiabatic types), thermostat, crucibles (silica, nickel‑chromium, platinum or similar non‑reactive materials), ignition wire, pressure equipment, balances and pellet press.
- Procedure steps: Sample preparation, bomb preparation, assembling the calorimeter, combustion and temperature measurement, disassembly.
- Corrections & calibration: Corrections for heat exchange, ignition wire combustion, and reference temperature; calibration procedures and use of certified standards.
- Quality and reporting: Precision information (repeatability/reproducibility), calculation methods, and required test report content.
- Applicability: Method is explicitly applicable to all kinds of sludge.
Practical applications
- Assessing thermal energy potential of sewage sludge, industrial sludges and sludge-derived products.
- Supporting design and optimization of waste‑to‑energy, incineration, co‑combustion, pyrolysis and other thermal treatment processes.
- Characterizing fuel quality for sludge valorisation and recycling strategies.
- Providing laboratory data for lifecycle assessments, regulatory compliance, tender specifications, and feasibility studies.
- Assisting R&D and interlaboratory comparisons in sludge treatment technologies.
Who should use ISO 13610:2025
- Environmental and analytical laboratories performing calorimetry.
- Wastewater treatment plant operators and sludge managers evaluating energy recovery options.
- Engineers and consultants designing thermal sludge treatment facilities.
- Equipment manufacturers (calorimeters, combustion systems) and certification bodies.
- Researchers and policy makers involved in sludge valorisation and circular economy initiatives.
ISO 13610:2025 is a practical, standardized method for reliable calorific value measurement of sludge - essential information for energy recovery decisions and thermal process design.