On the limits of empirical partition coefficients for modeling material recovery facility unit operations in municipal solid waste management

Material recovery facilities and mechanical biological treatments play an important role in current municipal solid waste systems, by providing a way to separate the different municipal solid waste fractions according to their main physical properties. However, the composition of their outputs streams is directly impacted by the composition of the input stream and by the sequence of unit operations considered, rending it particularly difficult to predict. Some authors have analyzed the sorting efficiency of the different unit operations commonly found in these processes and have derived partition coefficients. The main available coefficients were reviewed to identify the differences on both the methodological and numerical levels. Results showed large discrepancies for both cases amongst literature data but also with experimental data derived from an MRF plant located in Canada. A sensitivity analysis realized on a typical MRF plant showed the strong influence of the partition coefficient differences on the potential recovery of these plants. The trommel was identified as the unit operation having the largest impact on the modeling results. According to the sensitivity of the recovery of these kind of plants for each unit operation, a modeling approach is proposed for three groups of unit operations.