SIST EN ISO 21656:2021 PDF

Overview

EN ISO 21656:2021 / ISO 21656:2021 - "Solid recovered fuels - Determination of ash content" specifies laboratory methods for measuring the ash content of all solid recovered fuels (SRF). Adopted by CEN in 2021 and superseding EN 15403:2011, the standard is intended for laboratories, producers, suppliers, purchasers and regulatory or inspection bodies involved in SRF quality control and trade.

Key topics and technical requirements

• Scope: Methods for determination of ash content of SRFs, including treatment of coarse inert materials (removed ash contributors - rac) in total ash calculations.
• Principle: Heating a prepared sample in air to controlled temperatures and times and calculating ash from the mass of inorganic residue.
• Two temperature methods:
  • Method A: Ash content determined at (550 ± 10) °C (commonly used for biomass-rich SRFs and for many elemental determinations).
  • Method B: Ash content determined at (815 ± 10) °C (captures effects from carbonate decomposition and volatile inorganic losses).
• Apparatus & limits: Examples given in the standard include inert ash dishes (depth 10–20 mm, sample load ≤ 0.1 g/cm²), furnaces with uniform temperature and 5–10 air changes/min ventilation, and balances with 0.1 mg readability.
• Sample handling: Requirements for sampling, pre-drying, removed ash contributors (rac), and sample preparation are referenced (ISO 21645, ISO 21646 and ISO 21660-3).
• Calculation, precision & reporting: Procedures for calculating ash on as-received and dry bases, inclusion of rac in total ash, precision data (repeatability/reproducibility limits), and mandatory test report contents.
• Validation: Use of automatic thermogravimetric equipment is permitted if validated against the reference method.
• Environmental considerations: Annex B addresses environmental aspects related to ash determination.

Applications and users

• Who uses it: Analytical laboratories, SRF producers/suppliers, fuel purchasers, waste-to-energy plants, environmental regulators, and certification/inspection bodies.
• Practical uses:
  • Quality control and specification compliance for SRF batches.
  • Determining inorganic fraction for combustion performance, emissions forecasting and ash handling logistics.
  • Basis for further elemental/trace analysis (references to EN 15410 / EN 15411 for elemental determinations).
  • Contractual testing and regulatory reporting.

Related standards

• ISO 21637 - SRF vocabulary
• ISO 21645 - SRF sampling methods
• ISO 21646 - SRF sample preparation
• ISO 21660-3 - Moisture determination (oven dry method)
• EN 15403:2011 - superseded by EN ISO 21656:2021
• EN 15410 / EN 15411 - referenced for major and trace elemental determinations

This standard is essential for consistent, repeatable ash-content measurement of solid recovered fuels and supports reliable fuel specification, combustion planning and regulatory compliance.