ASTM D7579-25 PDF

Full title and description

ASTM D7579-25 — Standard Test Method for Pyrolysis Solids Content in Pyrolysis Liquids by Filtration of Solids in Methanol. This test method specifies a filtration-based laboratory procedure using methanol as the dispersant/solvent to recover and quantify particulate (pyrolysis solids/char) present in pyrolysis liquids (pyrolysis oil/bio-oil).

Abstract

This standard describes a simple, reproducible filtration procedure for determining the solids (char) content of pyrolysis liquids. The method covers sample handling, dilution with methanol, filtration, drying and gravimetric determination of recovered solids and is suitable across a wide range of solids concentrations. The 2025 revision incorporates inter-laboratory study (ILS) data contributed by CEN and clarifies safety and handling considerations for reagents and sample matrices.

General information

• Status: Active
• Publication date: April 1, 2025 (published); ASTM webstore record last updated April 24, 2025.
• Publisher: ASTM International
• ICS / categories: 71.040.40 (Chemical analysis)
• Edition / version: D7579-25 (revises D7579-09(2019))
• Number of pages: 4

Scope

This test method describes a filtration procedure to determine pyrolysis solids (char) content in pyrolysis liquids using methanol to suspend/dilute the sample and to aid filtration. It is intended for pyrolysis liquids with any range of solids concentrations and includes material from an inter-laboratory study executed by CEN/TC 19/WG 41.2. The method defines sample preparation, filtration media and apparatus, drying and gravimetric calculation of solids content; it does not replace required site- or project‑specific safety practices.

Key topics and requirements

• Scope and applicability — designed for pyrolysis liquids/bio-oils with a wide range of solids content.
• Sample preparation — dilution and dispersion of pyrolysis liquid in methanol to enable representative filtration.
• Filtration procedure — selection of filter media, filtration technique and control of filtration variables to retain particulate.
• Drying and gravimetric determination — conditioning and weighing filters before and after filtration to calculate mass of recovered solids.
• Calculation and reporting — procedures for expressing solids content (mass percentage or mg/g) and reporting relevant test conditions.
• Safety and reagents — handling of methanol and pyrolysis liquids, reference to Material Safety Data Sheets (MSDS) and laboratory safety practices.
• Inter-laboratory validation — incorporation of results and recommendations from a CEN-conducted ILS to improve reproducibility.

Typical use and users

Used by analytical and quality laboratories in biofuel and pyrolysis research, producers of pyrolysis oil, fuel testing laboratories, research institutions studying thermochemical conversion, and regulatory or standards bodies assessing fuel handling and storage risks related to particulate content. Typical applications include product quality control, process optimization, storage stability assessment and comparative laboratory studies.

Related standards

Revises and replaces earlier published versions of ASTM D7579 (for example D7579-09 and its subsequent reaffirmations). It is associated with other ASTM and CEN methods for characterization of pyrolysis oils and liquid fuels (test methods for stability, viscosity, water content and related fuel properties) and with CEN work on pyrolysis oil solids determination referenced in the inter-laboratory study incorporated into this revision.

Keywords

pyrolysis solids, char content, pyrolysis oil, bio-oil, filtration, methanol, gravimetric determination, solids content, biofuel analysis

FAQ

Q: What is this standard?

A: ASTM D7579-25 is a standardized laboratory test method that defines a filtration and gravimetric procedure to measure the solids (char) content in pyrolysis liquids using methanol as the dispersant/filtrate medium.

Q: What does it cover?

A: It covers sample preparation, filtration media and technique, drying/conditioning of filters, gravimetric calculation of recovered solids and reporting of results. The method is applicable across a broad range of solids concentrations and includes ILS data contributed by CEN.

Q: Who typically uses it?

A: Analytical and quality-control laboratories for bio-oil and pyrolysis product manufacturers, researchers in thermochemical conversion, fuel testing labs and regulators concerned with fuel handling and storage performance.

Q: Is it current or superseded?

A: As published in 2025 (designation D7579-25), this is the current active revision and it supersedes prior editions such as D7579-09(2019).

Q: Is it part of a series?

A: It is part of ASTM’s D02 committee family of standards covering petroleum products and liquid fuels and sits alongside other test methods for characterization of pyrolysis oils and related fuel properties; the 2025 revision also incorporates CEN ILS material, reflecting cross‑committee collaboration.

Q: What are the key keywords?

A: Pyrolysis solids, char, pyrolysis oil, bio-oil, filtration, methanol, gravimetric, solids content, biofuel analysis.