Presentation by Prof. Reto Gieré (Penn Earth & Environmental Science Dept.)
Combustion of solid biomass for the generation of heat and electricity is in heavy demand in central Europe, mainly due to the “exit strategy”, which is aimed at abandoning nuclear and fossil-fuel energy. The main fuel type comprises wood chips and pellets from regionally available sources and is considered to be of a sustainable nature. In modern small-scale combustors, the fuel consists of standardized wood pellets. These are made from stem wood with low ash content, and the combustion products (bottom ash, fly ash) are considered non-problematic, provided that the combustion parameters are properly set. Larger facilities also burn stem wood, but the chips are not standardized and thus have variable composition, which leads to highly variable combustion products. To reduce emissions of particulate matter into the environment, the flue gas is treated with various types of air pollution control devices, but incomplete combustion can lead to impacts on air quality, especially during adverse weather conditions. The aim of this presentation is to highlight several aspects of wood combustion and draw attention to possible environmental and health impacts of the resulting particulate emissions and ashes.