Physical and Chemical Characterization of Municipal Solid Waste Compost in Different Particle Size Fractions

Particle size fractions, varying from 1.6 to 0.1 mm, were separated from samples of municipal solid waste (MSW) compost. Several physical and chemical parameters of the samples with different particle sizes were measured. The results indicated particle size fractionation changed the physical properties and chemical component distribution of compost. Bulk density of the compost increased as particle size decreased. However, with the decrease of particle size there is a trend to decrease some soil parameters as pH, porosity, saturated water holding capacity, organic content, and Ca, Fe, Mg, and Mn contents. Higher organic content was found in fractions of diameter exceeding 0.4 mm, and total N content was higher (P<0.05) in fractions of diameter exceeding 0.8 mm than <0.8 mm fractions. Phosphorus was mainly distributed in coarse fractions larger than 0.8 mm, but K was concentrated in fine fractions of <0.8 mm. Calcium, Fe, Mg, and Mn contents in fractions >0.8 mm were higher (P<0.05) than those in fractions < 0.4 mm and control. Heavy metal concentrations in individual particles have strong particle size dependence. Lead was largely contained in fractions <0.8 mm, 244% higher than in >0.8 mm fractions. High Cu content was observed in the size range of 0.2-0.4 mm and 0.8-0.4 mm, with the maximum of 1,317 mg·kg in the range of 0.8-0.4 mm. Zinc concentration was found to be the lowest in the range of 1.6-0.8 mm as compared to other fractions and control. No significant differences in Cd content were found between each treatment and control. Chromium and Ni were associated with the <0.8 mm particles more than any other fractions, and their concentrations were 177% and 140% higher than other particle sizes obtained, respectively. Based on the physical and chemical properties of different compost fractions used in this experiment, it is observed that coarse compost particles larger than 0.8 mm have considerable potential in agricultural applications as soil amendments.