ISO/TC 238 - Solid biofuels

This document establishes a vocabulary for solid biofuels. This document only includes raw and processed material originating from — forestry and arboriculture, — agriculture and horticulture, and — aquaculture. NOTE 1 Chemically treated material cannot include halogenated organic compounds or heavy metals at levels higher than those in typical virgin material values (see also ISO 17225-1:2021, Annex B) or higher than typical values of the country of origin. NOTE 2 Raw and processed material includes woody, herbaceous, fruit and aquatic biomass and biodegradable waste originating from above sectors. Materials originating from different recycling processes of end-of-life-products are outside the scope of this document but relevant terms are included for information. Liquid biofuels (ISO/TC 28/SC 7), natural gas (ISO/TC 193) and solid recovered fuels (ISO/TC 300) are outside the scope of this document.

This document describes a method for determination of grindability of graded thermally treated and densified biomass fuels such as classified in ISO/TS 17225-8, for the purpose of preparing fuels with a defined particle size distribution for effective combustion in pulverized fuel boilers. The grindability characteristics determined by the test method provide guidance as to the pulverizing mill performance when utilizing such fuels. Apart from pelletized materials as described in ISO/TS 17225-8, the method can also be applied to non-compressed or non-densified thermally treated biomass as specified in ISO 17225-1:2021, Table 14 and Table 15. The results created with this method are not relevant for large wood chips, since limitations apply for large pulverizing coal mills, which are typically not used for grinding materials such as chips.

This document determines the fuel quality classes and specifications of graded hog fuel and wood chips for industrial use. It covers only hog fuel and wood chips produced from the following raw materials (see ISO 17225-1, Table 1): — 1.1 Forest, plantation and other virgin wood; — 1.2 By-products and residues from wood processing industry; — 1.3 Used wood; — 1.4 Blends and mixtures. This document covers hog fuel that has pieces of varying size and shape, produced by crushing with blunt tools such as rollers, hammers, or flails, and wood chips which are defined as chipped woody biomass with a sub-rectangular shape and a typical length of 5 mm to 50 mm typically in the form of pieces with a defined particle size produced by mechanical treatment with sharp tools such as knives. See 1.1.2 in ISO 17225-1, Table 1 for by-products and residues from wood processing industry, which can include chemically treated material (e.g. glued, painted, laminated), are not allowed to contain halogenated organic compounds or heavy metals at levels higher than those in typical virgin material values or higher than typical values of the country of origin (see Annex B in ISO 17225-1). NOTE If 1.4 Blends and mixtures includes 1.3.2 Chemically treated used wood, it can be only used in the installations permitted to use 1.3.2.

This document determines the fuel quality classes and specifications of graded non-woody briquettes. This document covers only non-woody briquettes produced from the following raw materials (see ISO 17225‑1:2021, Table 1): — 2 Herbaceous biomass — 3 Fruit biomass — 4 Aquatic biomass — 5 Biomass blends and mixtures NOTE 1 Herbaceous biomass originates from plants that have a non-woody stem and which die back at the end of the growing season. It includes grains or seeds crops from food production or processing industry and their by-products such as cereals. NOTE 2 Blends and mixtures include blends and mixtures from the main origin-based solid biofuel groups woody biomass, herbaceous biomass, fruit biomass and aquatic biomass. Blends are intentionally mixed biofuels, whereas mixtures are unintentionally mixed biofuels. The origin of the blend and mixture is to be described using ISO 17225‑1:2021, Table 1. If solid biofuel blend or mixture contains chemically treated material it shall be stated. NOTE 3 Thermally treated biomass briquettes (e.g. torrefied briquettes) are not included in the scope of this document

This document determines the fuel quality classes and specifications of graded firewood. This document covers only firewood produced from the following raw materials (see ISO 17725‑1:2021, Table 1): — 1.1.1 Whole trees without roots; — 1.1.3 Stem wood; — 1.1.4 Logging residues (thick branches, tops etc.); — 1.2.1 Chemically untreated by-products and residues from wood processing industry.

This document determines the fuel quality classes and specifications of graded non-woody pellets. This document covers only non-woody pellets produced from the following raw material (see ISO 17225‑1:2021, Table 1): — 2 Herbaceous biomass — 3 Fruit biomass — 4 Aquatic biomass — 5 Biomass blends and mixtures NOTE 1 Herbaceous biomass originates from plants that have a non-woody stem and which die back at the end of the growing season. It includes grains or seeds crops from food production or processing industry and their by-products such as cereals. NOTE 2 Blends and mixtures include blends and mixtures from the main origin-based solid biofuel groups woody biomass, herbaceous biomass, fruit biomass and aquatic biomass. Blends are intentionally mixed biofuels, whereas mixtures are unintentionally mixed biofuels. The origin of the blend and mixture is to be described using ISO 17225‑1:2021, Table 1. If solid biofuel blend or mixture contains chemically treated material it shall be stated. NOTE 3 Thermally treated biomass pellets (e.g. torrefied pellets) are not included in the scope of this document.

This document determines the fuel quality classes and specifications for solid biofuels of raw and processed materials originating from a) forestry and arboriculture; b) agriculture and horticulture; c) aquaculture. Chemically treated material may not include halogenated organic compounds or heavy metals at levels higher than those in typical virgin material values (see Annex B) or higher than typical values of the country of origin. NOTE Raw and processed material includes woody, herbaceous, fruit, aquatic biomass and biodegradable waste originating from above sectors.

This document determines the fuel quality classes and specifications of graded wood pellets for non-industrial and industrial use. This document covers only wood pellets produced from the following raw materials (see ISO 17225‑1:2021, Table 1): — 1.1 Forest, plantation and other virgin wood; — 1.2 By-products and residues from wood processing industry; — 1.3.1 Chemically untreated used wood. Thermally treated biomass pellets (e.g. torrefied pellets) are not included in the scope of this document.

This document specifies a method for the determination of water sorption in a laboratory setting and provides a measure for how the durability is impacted as a result of immersion in water. Post-immersion durability reduction is calculated as the difference between the durability of the as-received sample and the durability of the wetted product.

This document determines the fuel quality classes and specifications of graded wood briquettes. This document covers only wood briquettes produced from the following raw materials (see ISO 17225‑1: 2021, Table 1): 1.1 Forest, plantation and other virgin wood 1.2 By-products and residues from wood processing industry 1.3.1 Chemically untreated used wood NOTE Thermally treated biomass briquettes (e.g. torrefied briquettes) are not included in the scope of this document.

This document determines the fuel quality classes and specifications of graded wood chips. This document covers only wood chips produced from the following raw materials (see ISO 17225-1:2021, Table 1): 1.1 Forest, plantation and other virgin wood; 1.2 By-products and residues from wood processing industry; 1.3.1 Chemically untreated used wood. This document covers only wood chips, which are produced with sharp tools, and does not cover hog fuel, which is produced with blunt tools.

This document specifies basket heating tests for the characterization of self-heating properties of solid biofuel pellets. This document includes: a) a compilation of basket heating test methods; b) guidance on the applicability and use of basket heating tests for solid biofuel pellets; c) information on the application of basket heating test data for calculations of critical conditions in storages. Data on spontaneous heat generation determined using this document is only associated with the specific quality and age of the sample material. The information derived using this document is for use in quality control and in hazard and risk assessments related to the procedures given in ISO 20024. The described methods can be used for other substances than solid biofuel pellets (e.g. wood chips).

This document summarizes current knowledge concerning a test method and its technical implementation, and existing knowledge about the bridging performance of biofuels. The document consists of three parts, as follows: — Part I: Method for direct determination of bridging behaviour, to make it available for research and development purposes (see Clause 4). — Part II: Implementing the measurement principle, to assist in the construction of test apparatus and to illustrate the performance of a bridging test (see Clause 5). — Part III: Experience and results from bridging tests, to provide typical results on bridging for a wide range of biofuels already tested (see Clause 6).

This document: a) specifies a general test procedure for quantification of the spontaneous heat generation from solid biofuel pellets using isothermal calorimetry; b) specifies a screening test procedure for wood pellets using an instrument temperature of 60 °C; c) establishes procedures for sampling and sample handling of solid biofuel pellets prior to the analysis of spontaneous heat generation; and d) gives guidance on the applicability and use of isothermal calorimetry for calculation of the net reaction rate of the heat producing reactions of solid biofuel pellets. The test procedure given in this document quantifies the thermal power (heat flow) of the sample during the test, it does not identify the source of self-heating in the test portion analysed. Data on spontaneous heat generation determined using this document is only associated with the specific quality and age of the sample material. The results are product specific. This document is applicable to solid biofuel pellets only. The information derived using this document is for use in quality control and in hazard and risk assessments related to the procedures given in ISO 20024:2020.

This document defines a method for determination of off-gassing (permanent gases) and oxygen depletion from woody as well as non-woody biomass, including densified materials such as pellets and briquettes, as well as non-densified materials such as chips. The method is also applicable for thermally treated materials, including torrefied and carbonized materials. The emission and depletion factor and emission and depletion rate for various gas species emitted from sample within a closed test container is determined by means of gas chromatography. The emission and depletion factor and emission and depletion rate provide guidance for ventilation requirements to keep gas concentrations below Permissible Exposure Levels (PEL) in spaces where workers can be exposed to the enclosed atmosphere.

This document provides principles and requirements for safe handling and storage of solid biofuels pellets in commercial and industrial applications. This document is using a risk-based approach to determine what safety measures should be considered. Facilities with a storage capacity This document covers the handling and storage process of pellets in the following applications: — at a pellet production plant from the outlet of the cooler unit until loaded for transportation; — at a commercial distributor from the receiving station until loaded for transportation; and — at an industrial end-user from the receiving station until fed into the fuel preparation or combustion process. Although unloading and loading of e.g. vessels, trains or trucks are included in the operational envelops defined above, the safety aspect of the transportation itself is beyond the scope of this document. This document also gives specific guidance on detection and suppression systems and preparatory measures to enable safe and efficient firefighting operations. Guidance on the management of fire and explosion incidents is also specified.

This document describes simplified methods for taking samples of solid biofuels in small scale applications and storages including preparation of sampling plans and reports. The main focus is on storages with a size of ≤100 t. This document is applicable to the following solid biofuels: 1) fine (up to about 10 mm nominal top size) and regularly-shaped particulate materials that can be sampled using a scoop or pipe, e.g. sawdust, olive stones and wood pellets; 2) coarse or irregularly-shaped particulate materials (up to 200 mm nominal top size) that can be sampled using a fork or shovel, e.g. wood chips, hog fuel and nut shells; 3) large pieces (above 200 mm nominal top size) which are picked manually (e.g. firewood and briquettes). This document can also be used for other solid biofuels not listed above if the procedures described in this document are applicable. This document specifies methods to be used, for example, when a sample is to be tested for moisture content, ash content, calorific value, bulk density, mechanical durability, particle size distribution, ash melting behaviour and chemical composition. Additionally, it describes a method for the reduction of sample size and defines requirements on handling and storage of samples. NOTE 1 If higher precision of analytical results is needed or when in doubt if this document is applicable ISO 18135 can be used. Using the number of increments given in this document the resulting precision for analytical results can be estimated with the formulas given in ISO 18135. NOTE 2 Pellets can generate CO and CO2 off gasses by nature. If pellets are sampled, check for CO and CO2 and O2 levels prior and during the sample taking process in a confined space like a container, silo or shed and have another person standby at the entrance.

This document specifies a method for the determination of the characteristic temperatures for the ash melting behaviour of solid biofuels.

This document provides principles and requirements for the safe handling and storage of wood pellets in residential and other small-scale applications. It covers the supply chain from loading of the delivery truck, requirements of delivery trucks, connections to the end-user's store and the delivery process. It also covers the design and construction of pellet storage systems. This document addresses risks of fires, dust explosions, off-gassing, oxygen depletion, damage to appliances and buildings through swelling of pellets and other health risks. It is applicable to wood pellets according to ISO 17225-2.

ISO 14780:2017 defines methods for reducing combined samples (or increments) to laboratory samples and laboratory samples to sub-samples and general analysis samples and is applicable to solid biofuels. The methods defined in this document can be used for sample preparation, for example, when the samples are to be tested for calorific value, moisture content, ash content, bulk density, durability, particle size distribution, ash melting behaviour, chemical composition, and impurities.

ISO 18125:2017 specifies a method for the determination of the gross calorific value of a solid biofuel at constant volume and at the reference temperature 25 °C in a bomb calorimeter calibrated by combustion of certified benzoic acid. The result obtained is the gross calorific value of the analysis sample at constant volume with all the water of the combustion products as liquid water. In practice, biofuels are burned at constant (atmospheric) pressure and the water is either not condensed (removed as vapour with the flue gases) or condensed. Under both conditions, the operative heat of combustion to be used is the net calorific value of the fuel at constant pressure. The net calorific value at constant volume may also be used; formulae are given for calculating both values. General principles and procedures for the calibrations and the biofuel experiments are presented in the main text, whereas those pertaining to the use of a particular type of calorimetric instrument are described in Annexes A to C. Annex D contains checklists for performing calibration and fuel experiments using specified types of calorimeters. Annex E gives examples to illustrate some of the calculations.

ISO 19743:2017 specifies a method for the determination of content of heavy extraneous materials larger than 3,15 mm by the use of sink-and-float separation combined with elutriation. This document is applicable to woody biomass in accordance with ISO 17225‑1:2014, Table 1.

ISO 18135:2017 describes methods for preparing sampling plans and certificates, as well as taking samples of solid biofuels, for example, from the place where the raw materials grow, from production plant, from deliveries, e.g. lorry loads, or from stock. It includes both manual and mechanical methods, and is applicable to solid biofuels that are either: - fine (particle sizes up to about 10 mm) and regularly shaped particulate materials that can be sampled using a scoop or pipe, for example, sawdust, olive stones and wood pellets; - coarse or irregularly shaped particulate materials (particle sizes up to about 200 mm) that can be sampled using a fork or shovel, for example, wood chips and nut shells, forest residue chips, and straw; - baled materials, for example, baled straw or grass; - large pieces (particle sizes above 200 mm) that are either picked manually or automatically; - vegetable waste, fibrous waste from virgin pulp production and from production of paper from pulp that has been dewatered; - thermally treated and densified biomass materials; - roundwood. ISO 18135:2017 is not applicable to airborne dust from solid biofuels. It may be possible to use this document for other solid biofuels. The methods described in this document may be used, for example, when the samples are to be tested for moisture content, ash content, calorific value, bulk density, durability, particle size distribution, ash melting behaviour and chemical composition.

ISO 18134-2:2017 describes the method of determining the total moisture content of a test sample of solid biofuels by drying in an oven and is used when the highest precision is not needed, e.g. for routine production control on site. The method described in ISO 18134 (all parts) is applicable to all solid biofuels. The moisture content of solid biofuels (as received) is always reported based on the total mass of the test sample (wet basis).

ISO/TS 17225-8:2016 determines the fuel quality classes and specifications of graded densified solid biofuels produced from thermally treated biomass for non-industrial and industrial use. This document covers pellets and briquettes produced from the following raw materials (see ISO 17225‑1:2014, Table 1): - 1.1 Forest, plantation and other virgin wood; - 1.2 By-products and residues from wood processing industry; - 1.3.1 Chemically untreated used wood; - 2. Herbaceous biomass; - 3. Fruit biomass; - 4. Aquatic biomass. Subcategories of the above stated raw materials are included. ISO/TS 17225-8:2016 does not consider products, which are marketed as charcoal or as charcoal products. For these products, ISO 17225‑1:2014, Table 14 shall apply. NOTE 1 For thermally treated powder, ISO 17225‑1:2014, Table 15 or Table 16 may be used for specification. NOTE 2 Health, safety and environmental issues for solid biofuels are important and need special attention; however, they are outside the scope of this document.

ISO 18847:2016 specifies the method for determining the particle density of compressed fuels such as pellets or briquettes. Particle density is not an absolute value and conditions for its determination have to be standardized to enable comparative determinations to be made.

ISO 18846:2016 specifies a method for determining the amount of material passing through a sieve with 3,15 mm diameter round hole.

ISO 16993:2016 gives formulae which allow analytical data relating to solid biofuels to be expressed on the different bases in common use. Consideration is given to corrections that can be applied to certain determined values for solid biofuels prior to their calculation to other bases. In Annex A, tools for integrity checks of analytical results are given. In Annex B, conversion factors for calculation into other units are given. Annex C is a guideline for the use of validation parameters as can be found in ISO/TC 238 analytical standards.

ISO 16994:2016 describes methods for the determination of the total sulfur and total chlorine content in solid biofuels. It specifies two methods for decomposition of the fuel and different analytical techniques for the quantification of the elements in the decomposition solutions. The use of automatic equipment is also included in ISO 16994:2016, provided that a validation is carried out as specified and that the performance characteristics are similar to those of the method described in ISO 16994:2016.

ISO 17827-2:2016 specifies a method for the determination of the size distribution of particulate biofuels by the vibrating screen method. The method described is meant for particulate biofuels only, namely, materials that either have been reduced in size, such as most wood fuels, or are physically in a particulate form. This part of ISO 17827 applies to particulate uncompressed fuels with a nominal top size of 3,15 mm and below (e.g. sawdust).

ISO 17827-1:2016 specifies a method for the determination of the size distribution of particulate biofuels by the horizontally oscillating screen method. It applies to particulate uncompressed fuels with a nominal top size of 3,15 mm and above, e.g. wood chips, hog fuel, olive stones, etc. The method is intended to characterize material up to a particle size class of P63. For larger P-classes, the characterization is mainly done by hand sorting.

ISO 17830:2016 aims to define the requirements and method used to determine particle size distribution of disintegrated pellets. It is applicable for pellets that fully disintegrate in hot water.

ISO 17828:2015 defines a method of determining bulk density of solid biofuels by the use of a standard measuring container. This method is applicable to all pourable solid biofuels with a nominal top size of maximum 100 mm. Bulk density is not an absolute value; therefore, conditions for its determination have to be standardized in order to gain comparative measuring results. NOTE Bulk density of solid biofuels is subject to variation due to several factors such as vibration, shock, pressure, biodegradation, drying, and wetting. Measured bulk density can therefore deviate from actual conditions during transportation, storage, or transhipment.

ISO 17831-1:2015 defines a determination method for testing the mechanical durability of pellets. The mechanical durability is a measure of the resistance of compressed fuels towards shocks and/or abrasion as a consequence of handling and transportation.

ISO 17831-2:2015 defines a method for determining the mechanical durability of briquettes. The mechanical durability is a measure of the resistance of compressed fuels towards shocks and/or abrasion as a consequence of handling and transportation.

ISO/TS 16996:2015 specifies the procedure for a determination of major and minor element concentrations in biomass material by energy dispersive X-ray fluorescence (EDXRF) spectrometry or wavelength dispersive X-ray fluorescence (WDXRF) spectrometry using a calibration with biomass reference materials. A semi-quantitative determination may be carried out using matrix independent standards. ISO/TS 16996:2015 is applicable for the following elements: Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Br, Mo, Cd, Sb, and Pb. Concentrations from approximately 0,000 1 % and above can be determined depending on the element, the calibration materials used and the instrument used.

ISO 17829:2015 specifies the methods for the determination of diameter and length of pellets. Concerning the pellet length methods for both determination of the proportion of oversized pellets and for determination of the average length are included.

ISO 18123:2015 aims to define the requirements and method used to determine the volatile matter content of solid biofuels. It is intended for persons and organisations that manufacture, plan, sell, erect or use machinery, equipment, tools, and entire plants related to solid biofuels, and to all persons and organisations involved in producing, purchasing, selling, and utilizing solid biofuels. The volatile matter content is determined as the loss in mass, less that due to moisture, when solid biofuel is subject to partial pyrolysis under standardized conditions.

ISO 18122:2015 specifies a method for the determination of ash content of all solid biofuels.

ISO 18134-3:2015 describes the method of determining the moisture in the analysis test sample by drying in an oven. It is intended to be used for general analysis samples in accordance with EN 14780. The method described in this part of ISO 18134-3:2015 is applicable to all solid biofuels. The moisture content of solid biofuels (as received) is always reported based on the total mass of the test sample (wet basis). Since biofuels in small particle size are very hygroscopic, their moisture content will change with humidity in the atmosphere and therefore, the moisture of the test portion is determined simultaneously with determination of for example calorific value, carbon content, and nitrogen content. NOTE The term moisture content when used with biomass materials can be misleading since untreated biomass frequently contains varying amounts of volatile compounds (extractives) which can evaporate when determining the moisture content by oven drying (see References [1] and [2]).

ISO 18134-1:2015 describes the method of determining the total moisture content of a test sample of solid biofuels by drying in an oven and may be used when high precision of the determination of moisture content is necessary. The method described in this International Standard is applicable to all solid biofuels. The moisture content of solid biofuels (as received) is always reported based on the total mass of the test sample (wet basis). NOTE The term moisture content, when used with biomass materials, can be misleading since untreated biomass frequently contains varying amounts of volatile compounds (extractives) which might evaporate when determining moisture content by oven drying (see References [2] and [3]).

ISO 16968:2015 is intended for the determination of the minor elements Arsenic, Cadmium, Cobalt, Chromium, Copper, Mercury, Manganese, Molybdenum, Nickel, Lead, Antimony, Vanadium, and Zinc in all solid biofuels. Further, it describes methods for sample decomposition and suggests suitable instrumental methods for the determination of the elements of interest in the digests. The determination of other elements such as Selenium, Tin, and Thallium is also possible with the method described in this International Standard.

ISO 16948:2015 describes a method for the determination of total carbon, hydrogen and nitrogen contents in solid biofuels.

ISO 16967:2015 describes methods for the determination of major elements of solid biofuels respectively of their ashes, which are Al, Ca, Fe, Mg, P, K, Si, Na, Ti. The determination of other elements such as barium (Ba) and manganese (Mn) is also possible with the methods described in ISO 16967:2015. ISO 16967:2015 includes two parts: Part A describes the direct determination on the fuel, this method is also applicable for sulfur and minor elements, Part B gives a method of determination on a prepared 550 °C ash.

ISO 16995:2015 describes a method for the determination of the water soluble chloride, sodium and potassium content in solid biofuels by extraction with water in a closed container and their subsequent quantification by different analytical techniques.

This document determines the fuel quality classes and specifications of graded hog fuel and wood chips for industrial use. It covers only hog fuel and wood chips produced from the following raw materials (see ISO 17225-1:—, Table 1): — 1.1 forest, plantation and other virgin wood; — 1.2 by-products and residues from wood processing industry; — 1.3.1 chemically untreated used wood; — 1.4 blends and mixtures. This document covers hog fuel, which is produced with blunt tools, and wood chips, which are produced with sharp tools. NOTE 1 1.2.2 By-products and residues from wood processing industry, which can include chemically treated material (e.g. glued, painted, laminated) are not allowed include halogenated organic compounds or heavy metals at levels higher than those in typical virgin material values (see Annex B in ISO 17225-1) or higher than typical values of the country of origin. NOTE 2 If class I4 includes chemically treated used wood (1.3.2), it can be only used in the installations permitted to use 1.3.2.

ISO 18134-2:2015 describes the method of determining the total moisture content of a test sample of solid biofuels by drying in an oven and may be used when the highest precision is not needed, e.g. for routine production control on site. The method described in this International Standard is applicable to all solid biofuels. The moisture content of solid biofuels (as received) is always reported based on the total mass of the test sample (wet basis). NOTE The term moisture content, when used with biomass materials, can be misleading since untreated biomass frequently contains varying amounts of volatile compounds (extractives) which might evaporate when determining moisture content by oven drying (see References [2] and [3]).

ISO 16993:2015 gives formulae which allow analytical data relating to solid biofuels to be expressed on the different bases in common use. Consideration is given to corrections that can be applied to certain determined values for solid biofuels prior to their calculation to other bases.

ISO 16994:2015 describes methods for the determination of the total sulfur and total chlorine content in solid biofuels. ISO 16994:2015 specifies two methods for decomposition of the fuel and different analytical techniques for the quantification of the elements in the decomposition solutions. The use of automatic equipment is also included in ISO 16994:2015, provided that a validation is carried out as specified and that the performance characteristics are similar to those of the method described in ISO 16994:2015.