ISO 21911-1:2022

Overview

ISO 21911-1:2022 specifies an analytical method for quantifying spontaneous heat generation (self-heating) in solid recovered fuels (SRF) using isothermal calorimetry. The standard defines the principle, required apparatus, sampling and sample‑handling procedures, test procedure and reporting requirements to measure thermal power (heat flow) produced by SRF samples. It quantifies heat output but does not identify the chemical, biological or physical source of that self-heating.

Key topics and technical requirements

• Method: Direct measurement of heat flow using isothermal calorimetry; continuous, real‑time logging of thermal power normalized to sample mass (mW/g).
• Analysis temperatures: Screening procedure includes 50 °C and 70 °C (typical calorimeter operating range 5 °C–90 °C).
• Apparatus:
  • Isothermal calorimeter with sample and inert reference channels; calibrated for analysis temperature (Annex A).
  • Sample vials: glass, airtight lids with inert seals, minimum 20 ml volume (larger vials allowed with scaling).
  • Balance with at least 10 mg resolution.
• Performance:
  • Minimum sensitivity: 100 µW.
  • Data acquisition: continuous logging at intervals ≤ 10 s.
  • Baseline stability and low noise per Annex A.
• Sampling and sample handling:
  • Sampling in accordance with ISO 21645.
  • Minimum laboratory sample volume 500 ml.
  • Transport/storage in airtight, completely filled containers to limit reactions with oxygen; document sample history.
• Test reporting: Recorded test data, measurement files, and specified reported data elements as outlined in the standard.

Practical applications

• Hazard and risk assessments: Quantify self-heating potential for stored SRF to evaluate fire risk and spontaneous ignition potential.
• Quality control: Routine screening of SRF batches to detect fractions with high thermal activity.
• Storage and transport safety: Inform handling, stacking, and ventilation strategies to prevent heat build-up in warehouses, silos or transport containers.
• Incident prevention and insurance: Provide objective data for safety procedures, regulatory compliance and insurance underwriting.

Who should use this standard

• SRF producers, recyclers and fuel processors
• Laboratories performing thermal analysis and quality control
• Logistics and storage operators handling SRF
• Energy plants and combustion facilities that use SRF
• Equipment manufacturers, consultants, regulators and insurers assessing SRF safety

Related standards

• ISO 21645 - Solid recovered fuels - Methods for sampling (referenced)
• ISO 21637 - Solid recovered fuels - Vocabulary (referenced)
• Other parts of the ISO 21911 series (see ISO website for full list)

Keywords: ISO 21911-1:2022, solid recovered fuels, self-heating, isothermal calorimetry, heat flow, thermal power, sampling, risk assessment, storage safety.