🔥 Total moisture of solid biofuels — simplified method, drying at 105 °C — PN-EN ISO 18134-2

Petrochemistry PN-EN ISO 18134-2

Overview

SCOPE (PKN card and clause 1 of ISO 18134-2:2024): a method for determining the moisture content of a test sample of solid biofuel by drying in an oven, used when the highest precision is not required — e.g. for routine control at the production site. It applies to all solid biofuels. The moisture content on the as-received basis is ALWAYS expressed relative to the total mass of the sample, i.e. in the wet state. Note of the standard: biomass may contain small amounts of volatile organic compounds that evaporate during drying; relative to the total moisture this is little, and the standard ignores it.

HOW IT DIFFERS FROM THE REFERENCE METHOD (clause 4). The sample is dried at 105 °C in an atmosphere of air to constant mass, and the moisture is calculated from the loss of mass. There are two differences from PN-EN ISO 18134-1 (the reference method, a separate entry in this database): the buoyancy effect IS IGNORED and ONE determination is enough. The standard explains buoyancy: a hot tray weighs less than a cold one, and the size of the effect depends on the size and mass of the tray. The reference method — with the highest precision — is Part 1.

REQUIREMENTS (clauses 5–7, text of the standard): • an oven adjustable in the range (105 ± 2) °C with ventilation that removes moisture; the tolerance applies to all places in the chamber; the air flow must not blow particles off the tray; • trays and vessels of non-corroding and heat-resistant material, with a smooth, clean surface, holding the whole sample in a thin, even layer; • a balance reading to 0.1 g; • samples are taken according to ISO 18135 or ISO 21945 and delivered to the laboratory in airtight containers or bags; the test sample is prepared according to ISO 14780 so that each particle has at least one dimension smaller than 31.5 mm; • sample mass at least 300 g; for fine fuels (sawdust, fuel dust) at least 100 g; • for fine particles (sawdust, pellets, olive stones, fine wood chips) the layer should not exceed 1 g of material per 1 cm² of tray area; • if condensation is visible on the inner walls of the packaging, the packaging is shaken so that the material reabsorbs the water, and only then is the sample transferred. WARNING ADDED IN THE 2024 EDITION (6.1): biofuels readily give off or take up moisture from the surroundings when they are not in equilibrium with them, and size reduction generates heat and air movement, which cause a loss of moisture. Sample preparation must be carried out so that the moisture is preserved to the greatest possible extent; very wet samples should be pre-dried according to ISO 14780 before size reduction — and then the moisture of the original sample is calculated using formula (2) in 8.3. WHERE AN ERROR HIDES BEHIND A SEEMINGLY CORRECT RESULT: size reduction of a wet sample before the determination. Part of the water evaporates in the mill, and the result from the oven looks correct, only it is too low.

EDITIONS (state of the PKN cards and the ISO website on 25.09.2026). PN-EN ISO 18134-2:2024-10 — English-language version, publication 02-10-2024, 16 pages, KT 144 Coke and Processed Solid Fuels; implements EN ISO 18134-2:2024 and ISO 18134-2:2024 [IDT]; replaces PN-EN ISO 18134-2:2017-03 in the Polish-language and English-language versions. The card has no "Wycofana" [Withdrawn] header. The 2017-03 edition (Polish-language version with the title "…Metoda suszarkowa — Część 2: Wilgoć całkowita — Metoda uproszczona" [… Oven dry method — Part 2: Total moisture — Simplified method]) was withdrawn on 02-10-2024. ISO website: ISO 18134-2:2024 — edition 3, published 2024-03, stage 60.60. Changes according to the foreword: a new title, a warning about moisture gains and losses in 6.1, updated references, more precise information on sample preparation, editorial corrections. Part 1 of this series, PN-EN ISO 18134-1:2023-02 (English-language version), is current according to its card.

HOW ACCREDITATION SCOPES CITE THE STANDARD. Measurement of 25.09.2026 on the database of PL accreditation scopes (1310 laboratories with entries): 23 entries at 18 laboratories — "PN-EN ISO 18134-2:2024-10" (19), "PN-EN ISO 18134-2:2017-03" (3, including one together with Part 1; a withdrawn edition), "PN-EN ISO 18134-2" without a year (1). Object: solid fuels — solid biomass, solid biofuels; one entry also covers solid recovered fuels (SRF), which do not belong to the solid biofuels within the scope of this standard. Methodology: "Zawartość wilgoci całkowitej" [total moisture content] (13 and variants), technique: gravimetric method. In 9 notations Part 1 (PN-EN ISO 18134-1) stands alongside — the laboratories are accredited for both routes. Declared ranges: from "(0,4 – 80,0) %" to "(1,0 – 85,0) %", most often from a few to 55–60 %.

THE KEY OF THE "LABORATORIES" TAB: "PN-EN ISO 18134-2" — 18 laboratories and 23 entries, without any foreign entries and without any omitted ones.

HOW FAR THE TEXT EXTENDS: the extract of ISO 18134-2:2024 made available by the publisher covers clauses 1–6 and 7.1. We do not have the course of drying and the constant-mass criterion (7.2 onwards), the formulas from clause 8 — including formula (2) for a pre-dried sample — or the precision data. We do not give these values.

Method principle

The biofuel sample in the as-delivered state is spread in a thin layer on a weighed tray and dried in an oven at 105 °C in air to constant mass. The moisture content is the loss of mass relative to the mass of the wet sample. Unlike the reference method (Part 1), no correction is made for the buoyancy of the hot tray and a single determination is carried out; for a pre-dried sample, the moisture of the original sample is calculated from a formula that takes the pre-drying into account.

Applications

• Routine moisture control of solid biofuels at the production site — wood chips, pellets, briquettes, sawdust, fruit stones
• Control of biomass deliveries to power plants and heating plants (moisture on the as-received basis)
• A determination accompanying the reference method PN-EN ISO 18134-1 in the same laboratory

Key parameters

Standard

Standard number

PN-EN ISO 18134-2:2024-10 (wersja angielska; wprowadza EN ISO 18134-2:2024 [IDT], ISO 18134-2:2024 [IDT])

Title (PL)

Biopaliwa stałe — Oznaczanie zawartości wilgoci — Część 2: Metoda uproszczona

Title (EN)

Solid biofuels — Determination of moisture content — Part 2: Simplified method

Step-by-step procedure

1. Sample

   Taken according to ISO 18135 or ISO 21945, delivered in airtight packaging; preparation according to ISO 14780 (particles < 31.5 mm in at least one dimension), without loss of moisture; a very wet sample — pre-dry it before size reduction.

2. Tray

   Weigh the empty, clean tray to the nearest 0.1 g.

3. Transfer of the sample

   If there is condensation in the packaging — shake it so that the material absorbs the water; spread the sample (≥ 300 g, fine fuels ≥ 100 g) in a thin layer, for fine particles ≤ 1 g/cm².

4. Drying

   At (105 ± 2) °C in air to constant mass. WE DO NOT GIVE the constant-mass criterion.

5. Calculation

   Moisture from the loss of mass, relative to the mass of the wet sample; for a pre-dried sample — formula (2) in 8.3.

6. Report

   State that the simplified method (Part 2) was used, and the edition of the standard.

Required equipment and apparatus

Health and safety (OHS)

• Hot trays and a 105 °C oven — heat-resistant gloves
• Drying of biomass — volatile organic compounds and the risk of ignition of fine dust; do not overload the oven
• Dust from size reduction of biomass — respiratory protection

Frequently asked questions