Effect of Process Condition on the Bio-Digestion of Cow Dung for Organic Fertilizer Production

Studies were conducted on the biodigestion of cow-dung into organic fertilizer with the aim of determining the effect of process parameters on the quality of the product. The Hydrogen ion index (pH) was varied from 3.5 to 7.0 whereas the microbe: substrate (M/S) ratio was varied from 1.33 to 4.5g/kg and biodigestion time from 3 to 24hrs. The fertilizer produced was characterized by the NPK content and the production index (PI). The extent of biodigestion as indicated by the PI value, varied with the pH, ranging from 0.068 to 0.109 for pH between 3.5 to 7.0. Hydrogen ion index (pH) range of 3.5-4.0 at the temperature of 350°C, using native microbial flora were discovered to be most favorable to the biodigestion process, with PI 0.109 to 0.12. It was also discovered that the use of mixed culture (native microbe plus cultured saccharomyces cerevisiea further enhanced the result. A maximum microbe-substrate ratio of 4.5g/kg and a minimum of 2.67g/kg on mass basis were recommended. Within a bioconversion period of nine hours (9hrs), a product with N. P. K values of 2.9; 0.016, and 1.55 was obtained representing an increase in fertilizer value by 61.1% and 78.5% in Nitrogen (N) and potassium nutrient compositions respectively within the period. The fertilizer has an acceptable odour when dried and readily available to plant on application. It was also observed that the biodigestion process generated an exceeding quantity of biogas which can be trapped and upgraded for other domestic and industrial applications