Assessment uncertainty associated to the analysis of tar from gasification of sewage sludge

The uncertainty evaluation associated with the quantification of tar from gasification of sewage sludge is present. Each of the sources of uncertainty associated with the wet type sampling method and GC–MS analysis was identified to determine the critical stages of the analytical methodology in order to reduce them. The study shows that major contributions to the overall uncertainty are related to extraction steps. High expanded uncertainties were found for all compounds, due to the segregation of the tar in different samples because of the sampling method. However, the analytical method used was successfully applied for the evaluation of the tar cleaning filter in a real gasification plant.