Overview
ISO 21640:2021 - Solid recovered fuels - Specifications and classes defines a common classification and specification system for solid recovered fuels (SRF) produced from non‑hazardous waste. Its purpose is to enable transparent trade, safe use in energy conversion, and improved environmental protection by providing a standard template for specifying SRF properties and a class system based on key fuel characteristics.
Key points:
- Applies to SRF produced from non‑hazardous wastes (municipal, industrial, C&D, sewage sludge, etc.).
- Provides a specification template (Annex A) and compliance rules for classification and declaration of conformity.
- Clarifies that SRF classification is not an end‑of‑waste criterion; legal end‑of‑waste decisions lie with authorities.
Key topics and technical requirements
- Three main classification characteristics:
- Net calorific value (NCV) - economic/energy characteristic (reported as arithmetic mean, as‑received).
- Chlorine (Cl) - technical characteristic affecting combustion and corrosion (arithmetic mean, dry basis).
- Mercury (Hg) - environmental characteristic (median and 80th percentile on as‑received; the higher value determines class).
- Class system (1–5): each characteristic is assigned a class number based on limit values. Examples from the standard:
- NCV (MJ/kg ar): Class 1 ≥ 25; 2 ≥ 20; 3 ≥ 15; 4 ≥ 10; 5 ≥ 3.
- Cl (%, dry): Class 1 ≤ 0.2; 2 ≤ 0.6; 3 ≤ 1.0; 4 ≤ 1.5; 5 ≤ 3.0.
- Hg (mg/MJ ar): median limits ≤ 0.02, 0.03, 0.05, 0.10, 0.15; 80th percentile limits ≤ 0.04, 0.06, 0.10, 0.20, 0.30.
- Specification template (Annex A): obligatory and optional fuel properties to record, using ISO SRF test methods where available.
- Compliance and conformity: statistical rules for sampling and measurement, rules for start‑up, changes and exemptions are covered (Clauses 8–9). Declarations templates and calculation guidance are provided in annexes.
Applications and practical value
- Enables sellers and buyers to agree on fuel quality using a standard SRF specification and class code, facilitating trade and cross‑border movement.
- Helps energy producers, cement and power plants, and waste‑to‑energy operators select appropriate SRF grades for their combustion technology.
- Supports regulators and permit authorities by standardizing reporting and environmental evaluation of SRF use.
- Useful for producers and quality managers to document conformity, perform quality control, and communicate with equipment manufacturers.
Who should use ISO 21640:2021
- SRF producers and processors
- Fuel traders and logistics operators
- Waste‑to‑energy, cement and industrial boiler operators
- Regulators, environmental authorities and auditors
- Test laboratories and equipment manufacturers
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