My Two CEN/TS Worth
Woodfuel standards in the UK. The following may be dry as a ship’s biscuit, but I honestly believe that, if you can choke it down, it is all that most people in the forest industry will need to know to be able to start working with the new CEN standards for solid biofuels. Approximately 10 years ago the EU commissioned the Comité Européen de Normalisation (CEN) (the European Committee for Standardisation) to develop standards for solid biofuels. Subsequently CEN established Technical Committee 335 – Solid biofuels, which covers woody biomass, including wood from forests, plantations and landscape management.

TC/335 then created a suite of interconnected technical standards (TS) defining terminology, specification, fuel quality assurance (FQA), sampling and the range of tests required to quantify fuel properties. Ultimately the CEN/TSs for solid biofuels will be revised and upgraded
to Euro Norms (ENs) displacing all other national standards across the EU (eg ONORM & DIN). They are also being used as the basis for new ISO standards (ISO/TC 238).

Currently most of them have been published in draft form for two or three years and are now being revised prior to becoming ENs within a year or two. In the meantime the draft CEN/TSs were recognised in the UK Biomass Strategy as the UK standards for woodfuel. Standards are important for the emerging woodfuel industry as they provide a common vocabulary to
describe what consumers need or producers can deliver. Clear labelling backed by FQA and common testing methods will build the confidence that consumers need to feel if they are to be won away from the better known fossil fuel alternatives.

Also, standard sampling and testing procedures will help to prevent disputes as well as settling them. Under normal circumstances each of these draft CEN/TSs would cost between £30 and £60. Currently 25 of them can be downloaded free via the Biomass Energy Centre: www. biomassenergycentre.org.uk.

At first sight the CEN/TSs can appear daunting. However, many of those affected may simply be selling wood that will be turned into fuel. In this case it would be the work of a few moments to alter invoice layouts to comply with CEN. Quantity will probably be included already on existing invoices. The only changes may be to add the country where the wood was grown, or a more specific location, and its ‘origin’, which, in this instance, means the
type of material rather than where it comes from.

CEN classifies the origin of solid biofuels using a three or four number system. For example: Woody biomass from a forest or plantation sold as whole (deciduous) trees = 1.1.1.1. (see Table 1, page 8, CEN/ TS 14961:2005 Solid biofuels – Fuel specifications and classes (Figure 1)). Currently this system does require some interpretation: one case is arboricultural arisings, which only really fit into 1.1.6. – landscape management woody biomass; another being broadleaf branchwood which would fall into the same category as conifer harvesting
residues, 1.1.3. – logging residues, either, fresh/green (1.), stored (2.) or a mixture (3.). However, many of these issues are being addressed during the up-grading process.

Origin is important because wood from one source will be more appropriate for conversion in a particular way, for use in specific equipment, than another. For example the best wood chips for smaller combustion systems are made from clean stemwood. Conifer logging residues would be inappropriate for such use but fine when processed by a hog mill to be burned in a
large-scale installation. Although not required by CEN, it is suggested that certification is
also addressed. From April 2009 Government procurement rules will require evidence that all wood products, including woodfuels, specified by them are from independently verifiable, legal and sustainable sources or FLEGT licensed timber only (www.proforest.net/cpet/ uk-government-timber-procurementpolicy/ change/).

Also, the EU has just begun work on sustainability standards for biomass fuels through CEN/TC 383 – ‘Sustainably produced biomass for transport fuels and energy production applications’ that will formalise such efforts. So, evidence of sustainability may be a significant factor in deciding the final destination and value of woodfuels. Things are not much more complicated for those who intend to sell woodfuel direct to consumers. If they agree to supply fuel specified according to the CEN standards then they will have to label
their fuel to identify themselves and pass on the information mentioned above, see the example Fuel Quality Declaration (Figure 2). Also to be declared is the traded form of fuel
they are supplying (logs, chips or hog fuel, etc), its particle size or dimensions and that it is below particular moisture and ash contents, plus the nitrogen content if it has been chemically treated. These are called ‘normative’ properties which must be stated.

The specifications for woodfuels are presented in CEN/TS 14961:2005 Solid biofuels – Fuel specifications and classes. This document has seen considerable changes since it was published as a draft CEN/TS (which is still the version which can be downloaded from the website). The final draft of the proposed EN comes in six parts. Part 1 – General requirements is recognisable as an expanded version of the available draft CEN/TS. The other five parts
are still in development. These will cover non-industrial (domestic and community scale) wood pellets, briquettes, chips, firewood and nonwoody pellets.

Early drafts of Part 4 – Non-industrial woodchip product standard almost look as if they were
designed to challenge small producers. The number of normative properties that must be stated on the label is increased from the 4 shown in the draft CEN/TS to 19, including the amounts of nitrogen, sulphur, chlorine, chromium, nickel, zinc, copper, arsenic, cadmium, lead and mercury contained in the fuel. The responsibilities of the producer are clearly stated in the final draft of the proposed Fuel specifications and classes EN: “To minimise
resources needed, one of the measures in the following order is recommended: “Using typical values, eg laid down in Annex B, or obtained by experience.

“Calculation of properties, eg by using typical values and considering documented specific values. “Carrying out of analysis: a. With simplified methods if available, b. With reference methods. “The responsibility of the producer or supplier to provide correct and accurate information is exactly the same whether laboratory analysis is performed or not.” Also, “Typical values… cannot be used for the limitation of the fuel parameters.”
Only time will tell how woodfuel suppliers will deal with the above in practice. This uncertainty may lead them to create their own certification scheme(s). Such a scheme should perhaps be born out of the realities of actually making woodfuels and monitoring them day-to-day
rather than something imposed by an outside body to give potential consumers unrealistic expectations.

The details of labelling requirements are given in CEN/TS 15234:2006 Solid biofuels – Fuel
quality assurance. This also includes guidance on the FQA measures and documentation required to prove that suppliers are delivering what they promised to deliver. This is due to be expanded into a six-part document to match the changes in Fuel specifications and classes. FQA necessarily involves sampling and some testing. Sampling is covered by three standards, which are expected to be amalgamated into one or two before final publication:

• CEN/TS 14778 – 1: 2005 Solid biofuels – Sampling – Part 1: Methods for sampling.

• CEN/TS 14778 – 2: 2005 Solid biofuels – Sampling – Part 2: Methods for sampling particulate materials transported in lorries.

• CEN/TS 14779: 2005 Solid biofuels – Sampling – Methods for preparing sampling plans and sampling certificates.

• CEN/TS 14780: 2005 Solid biofuels – Methods for sample preparation.

Testing is more problematic. The most important properties for log, chip or hog fuels are arguably particle size, moisture content and ash content for all of them plus species for logs. Taking particle size first, the manual testing procedure currently included in CEN/TS 15149-1:2005 Solid biofuels – Methods for the determination of particle size distribution – Part 1: Oscillating screen method using sieve apertures of 3.15mm and above, for chipped or hogged fuels, has been withdrawn in the latest draft as experiments carried out under the BioNorm project showed that readings do not stabilise until sieves are oscillated for 15 minutes.

Five sieves are recommended for each test and it was not thought reasonable to suggest that people should oscillate heavy sieves manually for up to an hour and a quarter per test. The manual procedure shown in the draft may be useful for FQA purposes but definitive tests
will require laboratory equipment. Similarly, testing moisture content requires an oven that can maintain a temperature of 105ºC (±2ºC) and in which the air atmosphere changes between 3 and 5 times per hour without dislodging particles from their drying container.

This may be possible in a domestic oven but it might be difficult to prove that the equipment used meets the required specifications. Determination of ash content calls for a furnace and ‘rigidly controlled conditions’. As with ash content, many other properties are beyond the resources of most smaller operations to test. The results of standard tests must be repeatable (using the same sample in the same lab) to a high degree and preferably reproducible (using sub-samples of the same combined sample in different labs) or they will not have the credibility to prevent or solve disputes. As a result of the repeatability/reproducibility issue there will not be many standard tests that can be performed in-house in the final ENs.

However, this should not be too much of a problem where good practice is the norm and testing is only required to confirm expected results. Problems may arise where time is short and there is uncertainty over whether material will meet specified criteria, particularly moisture content (or the range of properties required by the ‘non-industrial’ standards when
they begin to apply). In practice, if woodfuel suppliers document where their wood is
coming from and its origin, keep it clean, select a chipper (or firewood processor, hog mill, etc) that makes the particle size range their customers require, maintain it, and record
all of these steps, then the only fuel property of real concern should be moisture content. When the new ‘non-industrial’ standards arrive, those who use them to specify fuel will probably have to accept the additional costs of the tests and delays necessary to meet them and may struggle to find a supplier who wants to go to such lengths.

This may provide a market advantage for those who sell heavily processed fuels like pellets who may routinely test every batch of raw material they accept and can pass back the costs to their suppliers. All of the draft standards begin with a foreword requesting feedback from users and instructions on how to have your views taken into account through BSI Technical Committee PTI/17, which mirrors the work of CEN/TC 335. It is late in the process but the standards will be continuously reviewed, so it is always worth pointing out any
errors. Phil Potter


(below) Classifying the origin of solid biofuels using a three or four digit number.

(Below) Figure 2: An example fuel quality declaration.



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