Emission of some pollutants from biomass combustion in comparison to hard coal combustion

In the last decade biomass combustion has become one of the most important elements in the fight against global warming. For the sake of climate or environment protection people cut out large stretches of forests and burn them down It is widely believed that the combustion of wood and biomass is completely safe and does not cause any danger to people and the environment. Unfortunately, this is only a half truth. In fact, with considerably lower emissions of sulfur dioxide (SO2) from biomass combustion, significant amounts of organic micro-pollutants are emitted, among which there are more toxic compounds like polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). The aim of this paper was to assess the real situation. Seven samples of biomass were investigated, i.e. rape straw, oak bark, firewood and wood pellets, shrub willow and rape cake. Pulverized hard coal samples were used for comparison. The aim of the study was to determine and compare the pollution emission factors (per unit mass of fuel) of carbon monoxide (CO), nitrogen oxide (NO) and the sum of hydrocarbons (as total organic carbon - TOC) generated in the process of biomass combustion. Further, we compared the results obtained for coal as well as the effect of process operating conditions (temperature; air flow) on the emission factors. The investigations were carried out in a laboratory chamber furnace at five different temperatures (from 700 to 1100 °C) and at three different air flow rates providing an excess of oxygen. In many cases the determined emission indicators for biomass combustion were higher than for hard coal.