Evaluation of urban wastes for agricultural use

Three different groups of municipal wastes: The organic fraction of municipal solid wastes, sewage sludges, and composts of these materials were characterized in order to evaluate their suitability as fertilizers. The parameters determined were: pH, contents of N, P, K, total organic C, water-soluble C, extractable C, pH 2-soluble C, pH 2-precipitated C, heavy metals, and organic phytotoxic substances as well as microbiological activity (respiration). The physiological effect of these wastes on seed germination was also studied. Sewage sludges showed the highest N and P contents while NO3- content was higher in composts. The fresh wastes exhibited a higher organic matter content than composts but the organic matter of the latter was most stable and humified. Aqueous extracts of the fresh products (municipal solid wastes and sewage sludges) inhibited the germination of Lepidium sativum seeds.