Overview
EN ISO 18708:2025 - Solid recovered fuels - Determination of bulk density - defines a standardized laboratory method to determine the bulk density of solid recovered fuels (SRF) using a standard measuring container. The method applies to SRFs whose nominal top particle size is less than 1/3 of the container diameter specified in the standard. Results are reported together with moisture content and can be expressed both “as received” and on a dry-matter basis.
Key topics and technical requirements
- Measurement principle: fill a standard container with a representative test portion, apply specified densification (shock exposure), weigh the filled container and calculate bulk density from net mass per standard volume.
- Apparatus: defined measurement containers (large, medium, small), scales/balances with specified performance, scantling and a wooden board for sample handling. Annex A gives an example apparatus for controlled shock exposure.
- Sampling & sample preparation: references to ISO sampling and preparation methods to ensure representative test portions (see ISO 21645, ISO 21646).
- Procedure details: instructions for container volume determination, combination of container size with dropping/densification height, and the measurement procedure itself (including provisions for “fluff” and pelletized SRF).
- Calculations: methods to compute bulk density both as received and adjusted for dry matter using moisture determination (ISO 21660-3).
- Performance characteristics: the standard defines requirements for repeatability and reproducibility limits and requires reporting of test conditions and results.
- Supporting information: interlaboratory test results, experimental studies and environmental aspects are included in informative annexes (B–D).
Practical applications and users
- Why it matters: bulk density is a key quality parameter for SRF affecting sampling plan design, transport capacity, storage space calculations and energy density estimates (e.g., MWh/m³).
- Who uses it:
- SRF producers and processors (compaction, drying, pelletizing)
- Accredited testing laboratories performing SRF quality control
- Waste-to-energy operators and fuel buyers assessing specifications
- Logistics and storage planners calculating payload and silo capacity
- Regulators and conformity assessors validating SRF declarations
- Benefits: standardized, repeatable measurements enable reliable comparison of SRF lots, optimized transport/storage planning and consistent input data for energy and environmental assessments.
Related standards
- ISO 21637 - SRF vocabulary
- ISO 21645 - SRF methods for sampling
- ISO 21646 - SRF sample preparation
- ISO 21660-3 - Moisture determination (oven dry method)
- EN 15415-1 - SRF particle size distribution (screen method)
Keywords: EN ISO 18708:2025, bulk density, solid recovered fuels, SRF, measuring container, sampling, moisture content, energy density, standard method.