♻️ Gross calorific value and net calorific value of solid recovered fuels (SRF) — PN-EN ISO 21654

Petrochemistry PN-EN ISO 21654

Overview

SCOPE FROM THE PKN CATALOGUE CARD, IN FULL (our translation): "This document specifies a method for the determination of the gross calorific value of a solid biofuel at constant volume and at a temperature of 25 °C in a combustion vessel calorimeter calibrated by combustion of certified benzoic acid."

AN ERROR IN THE SCOPE ON THE PKN CARD. On the same card the title reads "Solid recovered fuels -- Determination of calorific value", and the scope — "…gross calorific value of a solid biofuel…". The text of the adopted document settles it: clause 1 of ISO 21654:2021 (first edition, 2021-06; publisher's preview, read on 23.09.2026) reads "This document specifies a method for the determination of gross calorific value of solid recovered fuels at constant volume and at the reference temperature 25 °C in a combustion vessel calorimeter calibrated by combustion of certified benzoic acid." PN-EN ISO 21654:2021-12 adopts ISO 21654:2021 [IDT], so the standard concerns solid recovered fuels — it is the word "biofuel" in the scope on the card that is wrong, not the title. Accreditation scopes cite this standard for solid recovered fuels and wastes, not for biofuels (below). For solid biofuels this database has a separate entry — on PN-EN ISO 18125.

WHAT THE SCOPES SAY. The subjects are solid recovered fuels (SRF), combustible wastes ("alternative fuel") and wastes with codes including 19 08 01, 19 08 05 and 19 12 12, among them sewage sludge. The test is called "Gross calorific value" (Ciepło spalania) (in some records with a range, e.g. "(6000 – 45000) kJ/kg") and "Net calorific value (calculated)" (Wartość opałowa (z obliczeń)) (13 entries at 9 laboratories; in 4 of them added in the same description as "Gross calorific value"); one laboratory is accredited for "Gross calorific value of the non-biodegradable fraction" (Ciepło spalania frakcji niebiodegradowalnej). Technique — "Calorimetric method" (Metoda kalorymetryczna) (32 of 42 entries, in the technique field or in the description of the test); one record says "High-temperature combustion method with IR detection" (Metoda wysokotemperaturowego spalania z detekcją IR).

EDITION AND PREDECESSOR. PN-EN ISO 21654:2021-12 in the English version (74 pages, KT 144 Coke and Processed Solid Fuels; the card has no "Withdrawn" heading — status of the card as of 23.09.2026) adopts EN ISO 21654:2021 and ISO 21654:2021 [IDT]; according to the card it replaces PN-EN 15400:2011 — English version (58 pages), whose card has the heading "Withdrawn and replaced by PN-EN ISO 21654:2021-12" and the withdrawal date 27-12-2021. "PN-EN 15400:2011" still stands in 2 records at one laboratory (measurement of 23.09.2026).

RELATED ENTRIES IN THIS DATABASE. Gross and net calorific value are also described here by the entries on PN-ISO 1928 (solid mineral fuels), PN-EN ISO 18125 (solid biofuels) and PN-G-04513 (a national standard, withdrawn but listed in a regulation). For solid recovered fuels: PN-EN ISO 21663 (carbon, hydrogen, nitrogen, sulphur) and PN-EN ISO 21656 (ash).

WHAT WE DO NOT GIVE. We do not have the text of the standard — PKN sells it. That is why WE DO NOT GIVE the sample mass, the method of its preparation, the corrections, the formulae for converting the gross calorific value into the net calorific value or the requirements for the calorimeter.

SCALE OF CITATIONS (measurement of 23.09.2026). The key "PN-EN ISO 21654" — 20 laboratories / 42 entries, the same as across all forms of notation. The key also covers the record with a hyphen instead of a colon before the year ("PN-EN ISO 21654-2021-12", AB 081).

Method principle

The gross calorific value is determined at constant volume and at a temperature of 25 °C in a combustion vessel calorimeter calibrated by combustion of certified benzoic acid — that is what the scope from the PKN card says (which, incidentally, mistakenly calls the tested material "solid biofuel"; clause 1 of ISO 21654:2021 speaks of solid recovered fuels). In accreditation scopes the net calorific value is a "calculated" quantity; WE DO NOT GIVE the formulae.

Applications

• Gross and net calorific value of solid recovered fuels (SRF) and combustible wastes (subjects from accreditation scopes)
• Gross calorific value of the non-biodegradable fraction — in the scope of one laboratory

Key parameters

Standard

Standard number

PN-EN ISO 21654:2021-12 (wersja angielska; wprowadza EN ISO 21654:2021 [IDT] i ISO 21654:2021 [IDT])

Title (PL)

Stałe paliwa wtórne — Oznaczanie wartości opałowej

Title (EN)

Solid recovered fuels — Determination of calorific value

Step-by-step procedure

1. Calibration

   The calorimeter is calibrated by combustion of certified benzoic acid (card).

2. Determination of the gross calorific value

   At constant volume, at a temperature of 25 °C (card). WE DO NOT GIVE the mass and the preparation of the sample.

3. Net calorific value

   In accreditation scopes given as a "calculated" quantity. WE DO NOT GIVE the formulae.

4. Entry in the report

   State the full designation PN-EN ISO 21654:2021-12 — the predecessor PN-EN 15400:2011 still stands in one scope.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The calorimetric bomb is a pressure vessel — operation only according to the instructions of the instrument manufacturer
• Solid recovered fuels are produced from waste — when preparing samples, protection of the respiratory tract and hands

Frequently asked questions