Compost properties related to particle size

Abstract

Several properties (pH, electrical conductivity, contents of organic matter, nutrients, heavy metals, glass and impurities) were determined in different particle size fractions (0-0.5, 0.5-2, 2-5, 5-10, 10-25 and >25 mm) of various MSW composts produced in two composting facilities located at SW Spain (Montemarta-Sevilla and Villarrasa-Huelva). Mean percentages of the first five fractions were 9.6, 22.7, 29.2, 23.4 and 15.1 respectively. The MSW compost properties depended on particle size. Fine fractions (<2 mm) shown better quality than the mean compost: lower EC, Na content, C/N ratio, less glass and impurities indicated higher maturity and cleanness. Though this fine fraction had lower nutrient contents and the 0.5-2 mm fraction accumulated heavy metals, separation of the fine fraction would produce a compost more suitable for applications which require high stability compost, such as component for pot substrates. On the other hand, the >2 mm fractions tended to be richer in fertilizing elements, probably in relation with OM mineralization.