Ultrafine particle emissions for municipal waste-to-energyplants and residential heating boilers

Most recent air quality issues related to particulate matter pollution address ultrafine (UFP < 0.1 microns) and nanoparticle (NP<0.05 microns) size fractions and their involvement in health related issues. Consequently, large efforts have been dedicated to the evaluation of their concentration levels in ambient air, with particular reference to those situations typically representative of the highest expected human exposures (urban sites with high traffic density, indoor domestic environments, industrial workplaces). Similar investigations for assessing emissions arising from outdoor sources responsible of their origin have been mostly confined to vehicle emissions, particularly light and heavy duty diesel engines, with very limited informations for stationary combustion activities, yet considered of potential significance in the whole emissions budget. Still less attention has been attracted by some specific sources like waste to energy (WTE) plants and small scale residential heating boilers, despite their large utilization in or near heavily populated areas and their interest in public stakeholders for health related concerns. Present paper reports on the available data of UFP and NP emissions from full scale WTE plants and from small scale boilers fired with fuels typical of heat generation in the residential sector (wood pellets, light oil, natural gas), with particular reference on measurements conducted with those sampling techniques proposed recently for investigating also the contribution of the condensable fraction from semivolatile flue gas components on primary UFP concentrations and corresponding size distributions.