Gaseous and particulate emissions from the combustion of hard and soft wood for household heating: Influence of boiler type and heat output

Abstract

Comparison of gaseous and particulate emissions from the combustion of hard (beech) and soft (spruce) wood in four types (old and modern) boilers used for household/residential heating was studied. The boilers were run with three different heat outputs, i.e. nominal (85–100%) and two reduced outputs (60–70% and 35–45%), to cover the expected usage of these boilers in real households during different outdoor air winter temperatures. Gaseous emission factors (CO2, CO, NOx, OGC – organic gaseous compounds), particulate pollutants (n-alkanes and polycyclic aromatic hydrocarbons) and particulate organic markers (monosaccharide anhydrides, methoxyphenols and diterpenoids) were determined. In general, modern-type boilers emitted lower amounts of products of incomplete combustion than those old-type boilers. The emission factors (EFs) of total suspended particles varied between 562 and 2150 mg kg−1 (beech logs, the oldest-type boiler), and 69.1 and 118 mg kg−1 (spruce pellets, the modern-type boiler). The trends between the heat outputs of boilers and the EFs of particulate organic compounds/markers were observed for all boilers (especially the automatic boiler) with some exceptions and mostly increased with a decreasing output of boilers. The ratios levoglucosan/mannosan varied in the range of 13.4–18.6 for the combustion of beech, and 2.11–4.16 for the combustion of spruce.