Overview
ISO 18122:2022 - Solid biofuels - Determination of ash content specifies a laboratory method to determine the ash content of all solid biofuels. The standard defines required apparatus, sample preparation and conditioning, a controlled ashing procedure (standard final temperature 550 ± 10 °C), calculation rules and reporting. Ash is measured as the residue after controlled combustion; results are reported on a dry basis and used for quality control, fuel contracts and combustion management.
Key topics and technical requirements
- Scope and purpose: Method for reporting ash content of solid biofuels (e.g., wood pellets, agricultural residues, shells, straws).
- Apparatus: inert ashing dish (porcelain, silica, platinum) with maximum test-portion loading of 0.1 g/cm², uniform-temperature furnace, balance with 0.1 mg resolution, desiccator with controlled desiccant.
- Sample preparation: Laboratory and general analysis samples prepared per ISO 18135 and ISO 14780; nominal particle top size ≤ 1 mm (smaller for some fuels).
- Conditioning: Two accepted approaches - ash directly from a general analysis sample with concurrent moisture determination (ISO 18134‑3), or use a dried test portion kept absolutely dry before weighing.
- Controlled ashing program:
- Heat from cold to 250 °C over 30–50 min (4.5–7.5 °C/min); hold 60 min to drive off volatiles.
- Increase to 550 ± 10 °C over ~30 min (≈10 °C/min); hold at least 120 min.
- Minimum of two determinations per sample.
- Completion criteria: If incineration doubtful, reload at 550 °C for additional 30 min cycles until mass change
