Particulate inorganic salts and trace element emissions of a domestic boiler fed with five commercial brands of wood pellets.

Abstract

Pellet stoves arouse a real interest from consumers because they are perceived as a renewable and carbon neutral energy. However, wood combustion can contribute significantly to air pollution, in particular through the emission of particulate matter (PM). In this article, five brands of wood pellets were burnt under optimal combustion conditions and trace element and inorganic salt emission factors (EFs) in PM were determined. Results show that a significant proportion of metals such as lead, zinc, cadmium, and copper initially present in pellets were emitted into the air during combustion with 20 ± 6%, 31 ± 12%, and 19 ± 6% of the initial content respectively for Zn, Pb, and Cd. The median emission factors for Pb, Cu, Cd, As, Zn, and Ni were respectively 188, 86, 9.3, 8.7, 2177, and 3.5μgkg-1. The inorganic fraction of the PM emissions was dominated by K+, SO42-, and Cl- with respective EFs of 33, 28.7, and 11.2mgkg-1. Even taking into account a consumption of 40.1 million tons by 2030 in the EU, the resulting pollution in terms of heavy metal emissions remains minimal in comparison with global emissions in the EU.