Effects of season and population density on source-separated waste composts

A German federal law, enacted in 1993, requires that biogenic wastes be source-separated for re-use in most circumstances. This has resulted in the collection of over 4 million metric tons of biogenic waste per year, most of which is composted. The purpose of this study is to examine the potential to control and to optimize the chemical and physical properties of biogenic waste composts from suburban and urban communities during different seasons. Therefore, the composition of the biogenic waste stream in the City of Hamburg, Germany was determined and the chemical and physical properties of the resulting composts were analysed. The most dramatic differences were found for trace metals, especially in urban areas. Although some trace metals cannot be avoided, careful analysis of typical waste stream fractions can permit moderation of end-product contamination levels.