National standards, best practice lists or quality assurance manuals in the field of solid biofuels have already been developed and implemented in different countries within the European Union (e. g. Austria, Finland, Germany, the Netherlands, Sweden). This has contributed to improve the matching of fuel quality and fuel provision with conversion equipment and systems, facilitate the comparison of the quality and value of different solid biofuels, and determine and assure fuel quality.

A review of the existing national standards, best practice lists or quality assurance manuals allows for some observations regarding the harmonization of standards on terminology and classification that is needed at the European level. Table 11.2 gives an overview of the various biofuel properties which are relevant for assessing biofuel quality, and which are considered within the different EU countries. First, there are fuel properties focusing on the physical and mechanical condition of the fuel and its behavior during biofuel handling (loading, transportation, storage, feeding). Second, there are fuel properties influencing the process of energy conversion (e. g. com­bustion or gasification). And last but not least, there are chemical properties needed to calculate the flow of molecules and to assess the emissions.

With regard to the intended effects of standardization procedures at the European level, there are two main relevant fields to be considered. [12]

The terminology, definitions and descriptions as well as the fuel specifications and classes which are applied in different EU countries today are the product of the traditions and characteristics, specific to the national fuel market and their information requirements. Problems of comparability of national terms and definitions can arise due to differences in the national systems of nomenclature. These nomenclature differences make fuel comparison across EU countries difficult and serve as obstacles for trade. Standards of terminology and defini­tions as well as fuel specifications and classes can make a valuable contribution towards allowing a more direct assessment of the quality and value of solid biofuels, thus fostering trade and a broader use of biofuels as an energy source throughout Europe. Standards can also provide a vital input to facilitate broad resource and market assessments (e. g. internationally comparable results and statistics for solid biofuels) which can help shape public and industrial policy.

2. Identification and classification of the most relevant biofuel properties to ensure a cheap and trouble-free conversion with low emission levels.

The number of fuel properties used in national standards, quality guidelines and assurance manuals or recommendations to classify solid biofuels varies between 3 and 90 for wood chips. The number of classes for fuel pellets and briquettes varies between 3 and 5 only because of the compression process which makes the fuel much more homogenous in size and shape, moisture content and energy density. In Germany, for example, only a wood pellet standard is available (DIN 51731, 1996).

In EU countries, only a few important fuel properties are presently used to assess fuel quality and value (among them the moisture content, the particle size and the heating value) due to practicability and costs of performing fuel property measure­ments. A review of the existing national standards and practices indicates that an intended European classification system of solid biofuels should satisfy the following criteria (Rosch et al., 2000):

• The biofuel classification system should be universal and comprehensive so that it can be used for all kinds of biomass for energy generation;

• Classification should be restricted to the biofuel properties which are most relevant in practice, being clearly defined and easy to control;

• The range and amount of classes for each of the biofuel types should take into consideration regional diversity as well as the specific demands of different provision and combustion technologies and trading practices;

• Each biofuel should be classifiable by a plain and easy code (i. e. like the classification of coal, fuel oil or steel);

• Conversion plants using solid biofuels to produce green electricity should be able to use the biofuel class code for certification of their products.