Selected characteristics of leachate, condensate and runoff released during composting of biogenic waste

During composting, depending on the feedstock and the chosen composting technology, leachate, condensate and runoff are generated. To determine pollution loads of these liquid by-products of composting, selected chemical, physical and biological characteristics of leachates, condensates and runoff from full-scale composting facilities and lab-scale experiments were evaluated using biogenic waste (source-separated food and yard waste) as feedstock. Parameters included settleable solids, pH, conductivity, biological oxygen demand (BOD₅), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), NH₄⁺-N, NO₃^--N, NO₂^--N; Cl^-, Zn, Pb, Cd, As and volatile fatty acids (VFA). The measurements showed that, as stipulated by German regulations, leachates and some condensates need to be pretreated before released into public sewers unless diluted with other waste streams. The effect of different biogenic waste fractions on leachate and condensate quantity and quality are described.