Characterization and combustion behaviour of commercial and experimental wood pellets in South West Europe

In this work four types of wood pellets were analyzed, with the aim of assessing their characteristics and behaviour during combustion in a domestic pellet stove. With this purpose, several comparisons among four kinds of biomass were carried out: commercial pellets from fruit tree pruning, another two commercial pellets from pine wood and different manufacturing industries and pellets manufactured in our laboratory from Pyrenean Oak by using semi-industrial equipment. In addition, their characteristics and emission rates were compared to the limits recommended by the European standards regarding solid biofuels. Proximate and ultimate analyses, heating value, durability, bulk density, ash characterization and ash melting temperature were determined in order to carry out a thorough analysis of physical and chemical characteristics. In order to study the combustion behaviour, the essays were carried out in a domestic pellet stove. Pellets from pine wood presented better characteristics for their domestic use in small-sized stoves, due to the fact that they have lower ash percentage and higher high heating value compared to the rest of pellets in study. Additionally, less NOx and SO2 emissions were reported during the combustion of pine wood samples. Commercial pellets from fruit tree pruning presented physical characteristics similar to pine pellets', although the former have a composition that restrict their use in small equipments (high ash percentage and NOx and SO2 emissions, among others). Experimental pellets presented similar characteristics compared to commercial pellets, except for some properties, such as ash percentage, due to its high value on account of the fact that the waste was gathered by hand and the bark was not stripped from the tree. Concerning their physical properties, such as durability, they presented high values but lower than commercial pellets. These properties could be improved by optimizing manufacturing process. Generally, the essays carried out during the combustion in a pellet stove pointed out that these types of pellets could be a suitable product for domestic use. However, further research is needed in order to optimize pellet manufacturing and commercialization in Europe. Consequently, further and exhaustive studies are needed to improve and develop the production process of wood pellets. (C) 2014 Elsevier Ltd. All rights reserved.