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MATERIALS 53
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the problem of the low bulk density of biomass is pelletisation. pixabay.com
The great advantages of pellets in comparison to other
forms of solid biomass are reflected in the impressive growth
of pellet production, which has been occurring in the last

years, mostly in Central and Eastern Europe.
Mediterranean countries, particularly Italy, heavily rely on
extensive pellet imports to satisfy the requests of the internal
market.
Pellets are primarily produced from the residues of softwood
species, predominantly sawdust.
Softwood sawdust is the perfect substrate for pelletisation, that produce pellets on a small scale cannot afford to further
considering that it is an unprocessed residue, and that even invest time, energy, and financial resources into pre-treating
small traces of pollutants can be removed by debarking and the biomass.

washing the logs before sawing. Therefore, in the case of small-scale pellet production in
However, countries that have a forestry system which is less the Mediterranean area, the use of a poor-quality feedstock
reliant on softwood may face some challenges in producing such as hardwood with the presence of bark and leaves is
high-quality pellets. The growing demand for wood pellets and often the only affordable solution.
the limited supply of sawmill residues have sparked a great The main issues regarding fuel quality related to the
deal of interest in exploring the use of alternative sources. production of pellet from such kind of raw materials are
Just as any other biomass supply chains, pellet production associated to decreased bulk density and heating value, as

can be done on a small scale or industrial basis. well as increased ash content.
To minimise transportation expenses and environmental At the international level, pellet quality is assessed according
issues, the industrial manufacturing of pellets necessitates to the standard EN ISO 17225. This standard was released
large quantities of readily available feedstocks concentrated in 2014 and replaced the previous EN 14961.
in a small geographical area. Within EN ISO 17225, the standard EN ISO 17225-1
However, recent research has shown how crucial it is to regards the general quality requirements for pellets, while
start small-scale pellet manufacture using local raw materials EN ISO 17225-2 is about wood pellets for both residential
from one or a small number of producers. Small-scale pellet and commercial usage, and EN ISO 17225-6 regulates non-
production in rural locations can further help local small woody pellets.

agriculture and forestry businesses by increasing their income. Essentially, the standard assigns a quality class to the pellet
It is important to underline that high-value pellets are based on various parameters. For instance, considering pellets
frequently produced on an industrial scale from pure sawdust, for residential use, the top-quality class is A1, followed by A2
and other processing stages including pre-treatment and the and B. The standard provides some threshold constant values
inclusion of binders are also used. for the various parameters, i.e., to be considered a class A1
In contrast, pellets made from different feedstocks that pellets, the ash content should be ≤0.7 percent.
contain a significant amount of bark or leaves could result This approach is valid for commercial purposes but has

in worse quality. some drawbacks concerning the scientific evaluation of pellet
Small farmers, owners of sawmills, or other forest enterprises quality. The commonly applied statistical analysis techniques,