Definition of an emission factor for VOC emitted from Italian and European refineries

Refineries are a major source of atmospheric emissions, which typically include CO, SO2, NOX, particulates, and volatile organic compounds (VOCs). There has been an increasing level of attention toward the emissions of VOCs related to their environmental impact as well as their potential to cause adverse effects on human health and the discomfort associated with their unpleasant odor. In general, an emission factor (EF) represents a model for a first order estimate of emissions, which correlates the quantity of pollutant released into the atmosphere with a so-called "activity index" related to the release of that pollutant. Based on the study of the scientific and technical literature regarding the Italian and European refining scenarios, an attempt was made to verify the existence of a correlation between the size of a refinery and the related total VOC emissions. Once this correlation was evaluated, it was possible to develop an emission factor for VOC emissions considering the plant capacity as the related activity index. After collecting and analyzing data concerning operative capacity and total VOCs emitted from 15 refineries in 2018, the resulting emission factor turned out to be equal to 188 ± 166 g per ton of crude oil processed. This value is in agreement with the range of 50-1000 g/ton reported in the European Best Available Techniques Reference Document for the Refining of Mineral Oil and Gas.