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CAN CSA ISO 18134-1-15: Determination of Total Moisture in Solid Biofuels – Technical Overview
A comprehensive analysis of the Canadian adoption of ISO 18134-1:2015 for moisture content measurement using the oven dry method
Introduction
The standard CAN/CSA-ISO 18134-1:15 (referred to here as ISO 18134‑1‑15) is the Canadian adoption of the international standard ISO 18134‑1:2015 – Solid biofuels – Determination of moisture content – Oven dry method – Part 1: Total moisture – Reference method. This document specifies the reference method for determining the total moisture content of solid biofuels by drying under controlled conditions. Accurate moisture determination is critical for trading, energy content calculations, and process optimization in the biofuel industry.
This article provides a technical breakdown of the standard’s scope, key requirements, implementation aspects, and compliance notes relevant to laboratories, manufacturers, and quality assurance professionals.
Scope and Application
ISO 18134‑1‑15 applies to all solid biofuels, including woody biomass, herbaceous biomass, fruit biomass, blends, and processed materials such as pellets, briquettes, chips, and sawdust. The method is suitable for total moisture contents ranging from 0.5 % to about 90 % (mass fraction).
It defines the reference oven dry method, which serves as the benchmark for calibrating or validating other indirect moisture measurement techniques. The standard explicitly excludes biofuels that decompose or undergo chemical changes at the specified drying temperature (e.g., some digested sludges or materials with volatile organic compounds that evaporate below 105 °C).
Tip: For materials prone to decomposition at 105 °C, refer to alternative methods such as the two‑stage drying procedure in ISO 18134‑2 (for high‑moisture samples) or ISO 18134‑3 (for low‑moisture samples).
Technical Requirements
Principle of the Method
A representative test portion is weighed, then dried in a ventilated oven at a specified temperature until constant mass is achieved. The loss in mass corresponds to the water evaporated. Total moisture content is expressed as a percentage of the initial mass.
Apparatus and Conditions
| Parameter | Requirement |
|---|---|
| Drying temperature | 105 ± 2 °C |
| Oven ventilation | Natural air circulation or forced; sufficient to remove moisture |
| Weighing balance | Readability 0.1 mg or 0.01 g depending on sample mass |
| Sample container | Corrosion‑resistant, with lid (e.g., glass, aluminum, stainless steel) |
| Drying duration | At least 24 h for most biofuels; until mass change ≤ 0.1 % |
Sample Mass and Particle Size
To ensure representativity and proper drying, the standard recommends maximum particle sizes and corresponding minimum sample masses:
| Maximum particle size (mm) | Minimum sample mass (g) |
|---|---|
| ≤ 4 | 10 |
| > 4 and ≤ 10 | 50 |
| > 10 and ≤ 20 | 200 |
| > 20 | 500 |
Warning: Using too large a particle size or too small a sample mass may lead to incomplete drying or poor repeatability. Always follow the table when preparing samples.
Calculation
Moisture content (M) is calculated as:
M (%) = [(m2 – m3) / (m2 – m1)] × 100
where:
- m1 = mass of empty container with lid
- m2 = mass of container with lid + test portion before drying
- m3 = mass of container with lid + test portion after drying
Implementation Highlights
Successful implementation of ISO 18134‑1‑15 requires careful attention to sample handling and laboratory practices:
- Sample collection and storage: Sealed, airtight containers to prevent moisture exchange. Analysis should be performed as soon as possible after sampling.
- Replicate determinations: At least two test portions; the mean is reported if the relative deviation of individual results is within ± 0.1 % after drying.
- Quality control: Regular use of certified reference materials or in‑house control samples to monitor accuracy.
- Safety: Drying at elevated temperatures can release dust or vapours; ensure adequate ventilation and use of personal protective equipment.
Success: Adherence to this reference method ensures that moisture data are comparable across laboratories and consistent with international trading specifications for solid biofuels.
Compliance and Notes for the Canadian Adoption
CAN/CSA-ISO 18134-1:15 is identical to ISO 18134‑1:2015. No technical deviations exist; only minor editorial and formatting changes may be present to meet CSA Group requirements. Laboratories seeking accreditation for moisture testing of solid biofuels in Canada typically adopt this standard.
Key compliance considerations:
- The method is considered the reference method; alternative methods (e.g., halogen dryers, NIR) must be calibrated against it.
- Measurement uncertainty must be evaluated according to ISO/IEC Guide 98‑3 (GUM) or similar.
- When testing materials with high volatile content, a check for decomposition (e.g., visual darkening or odour) should be reported.
Important: Do not use this method for biofuels that contain significant amounts of compounds that evaporate or decompose below 105 °C (e.g., certain treated woods, sludges, or manures). Such materials require a modified approach, such as vacuum drying or azeotropic distillation.
Frequently Asked Questions
Q: What is the difference between ISO 18134‑1 and ISO 18134‑2?
A: ISO 18134‑1 is the reference method using a single drying step at 105 °C, suitable for samples with moderate to low moisture. ISO 18134‑2 describes a two‑stage method for high‑moisture biofuels (above about 30 %), where the sample is pre‑dried at a lower temperature before final drying in the oven.
A: ISO 18134‑1 is the reference method using a single drying step at 105 °C, suitable for samples with moderate to low moisture. ISO 18134‑2 describes a two‑stage method for high‑moisture biofuels (above about 30 %), where the sample is pre‑dried at a lower temperature before final drying in the oven.
Q: Can I use a microwave oven or infrared dryer instead of the ventilated oven?
A: No, those are considered alternative methods. The standard requires a ventilated oven set at 105 ± 2 °C to maintain consistency with the reference method. Rapid heating methods can cause surface crusting or incomplete drying.
A: No, those are considered alternative methods. The standard requires a ventilated oven set at 105 ± 2 °C to maintain consistency with the reference method. Rapid heating methods can cause surface crusting or incomplete drying.
Q: How do I know when constant mass has been achieved?
A: Constant mass is assumed when the mass loss between two successive weightings (24 h apart) is ≤ 0.1 % of the initial sample mass. In practice, 24 h is sufficient for most solid biofuels; longer drying may be needed for large or dense particles.
A: Constant mass is assumed when the mass loss between two successive weightings (24 h apart) is ≤ 0.1 % of the initial sample mass. In practice, 24 h is sufficient for most solid biofuels; longer drying may be needed for large or dense particles.
Q: Is the Canadian standard identical to the international version?
A: Yes, CAN/CSA-ISO 18134-1:15 is an identical adoption of ISO 18134‑1:2015. No technical changes have been made; it is simply the Canadian implementation administered by CSA Group.
A: Yes, CAN/CSA-ISO 18134-1:15 is an identical adoption of ISO 18134‑1:2015. No technical changes have been made; it is simply the Canadian implementation administered by CSA Group.
This article is intended for informational and educational purposes. For official compliance, always consult the latest published version of the standard. Last reviewed: 2026.