Quality Analysis of Commercially Available Wood Pellets and Correlations between Pellets Characteristics

In this study, the quality of wood fuel pellets, commercially available in the Greek market, was evaluated using the ISO 17225 Standard Requirement Thresholds as a benchmark. The examined quality criteria were calorific value, ash content, mechanical durability, bulk density and moisture content. The reliability of the information on packages was evaluated. Meanwhile, the potential correlation between the most crucial qualitative properties of pellets was investigated to elucidate their potential contribution to pellets' quality estimation. Most of the pellet brands showed low moisture and ash content and acceptable calorific values for residential use-although the quality of half of the pellet brands was found to be lower than that reported, mainly with regard to the mechanical durability and bulk density. The application of two different collection periods highlighted a stability in quality over time. Higher calorific value seemed to be provided by pellets which had low ash and low moisture content and were mechanically durable. As regards the specific samples, a dark colour and high roughness were correlated with lower fuel quality (impact of 56.2% and 43.6%, respectively).