Between and Betwixt Soil Fertility Improvement and Disease Transmission: An Assessment of the Suitability of Anaerobic Digestion Effluent for Direct Application as Fertilizer

Abstract

Although anaerobic digestate has been identified as a rich source of essential plant nutrients, its safety measured by the concentration of pathogen present is of great concern to end users. This research explored the efficiency of the mesophilic biodigestion process in the stabilization and sanitization of cow dung and chicken droppings. 6kg each of cow dung and chicken droppings were collected fresh and free from impurities, pre-fermented, mixed with water in the ratio 1:1 by volume to form slurry, fed into the respective reactors and digested for 30 days at an average daily ambient temperature of 37oC. The pH of the medium fluctuated between 6.5 and 8.0. The analysis of the feedstock and effluent of the digesters showed that a total solids reduction of 75.3% and 60.1% were recorded for cow dung and chicken droppings respectively while the reductions in total coliforms were 95% and 70% respectively. E.coli and Shigella spp., were removed while Salmonella spp. and Klebsiella spp. where still present in the digestate. Notwithstanding these results, the digestate still requires further treatment for it to be suitable for application on unrestricted crops either as fertilizer; otherwise a health problem would be created as attempt is made to improve soil fertility.