Interlaboratory study of recovered fuels

The interlaboratory study of recovered fuels was a part of the project "Development of homogenisation and anaysis of recovered fuel samples", included in the Technology Programme Waste to REF & Energy financed by Tekes, the National Technology Agency.Samples of recovered fuel were crushed, ground and divided for the interlaboratory study at VTT Energy in Jyväskylä.In total 13 laboratories from Sweden, Norway and Finland participated in the interlaboratory study.All labortories did not perform all analyses.Only three laboratories determined metallic aluminium.Their results correlated well.The reporting limit for metallic aluminium is given 0.01 wt-% in the standard "Solid recovered fuel.Quality control system" SFS 5875.It was not possible to achieve this limit by the thermo-analytical method employed.Fairly good results were achieved in the certain analysis methods, like ash and sulphur content and calorific value.Some outliers occured.Acceptable differences in the repeatability and the reproducibility of the individual determinations, given in the international standards, were exceeded, the most significant differences being in the determinations of metals.There is a number of the digestion and dissolution methods for the determination of metals in recovered fuels e.g., flame atomic absorption spectrometry, graphite furnace atomic absorption spectrometry, ICP-AES (plasma atomic emission spectrometry), ICP mass spectrometry and DLP-AES.The mercury was analysed by a cold vapor atomic absorption spectrometry.Within the resources available in this study, it was not had not possible to identify the best method for determining metals in recovered fuels.It is evident that the standard methods would be needed for achieving smaller differences between laboratories than in this study.The standardization organisation CEN is developing standardization for the solid biofuels and a premininary work on recovered fuels is underway.