Abstract
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.
Highlights
Before the age of modern technology, demands for greater agricultural yields in Nigeria and many other nations in the world were met by shifting cultivation, irrigation and clearing of forested areas.During the primitive era in Africa, and until about the year 1900 in United States of America, the demands for high agricultural yields were met by bringing new lands into cultivation [23]
It was found that the entire slurry/sludge of the agriculture byeproducts/waste from the anaerobic digestion is an excellent source of organic fertilizer with obvious advantages over the mineral/chemical fertilizers [1, 2, 7, 13, 15, 25, 27, 31]
The optimum hydrogenionindex(pH) and microbe dosagewere determined on the basis of the process parameter that maximized the production index (PI) which is the measure of extent of biodegration/biodigestion of the cow dung
Summary
Before the age of modern technology, demands for greater agricultural yields in Nigeria and many other nations in the world were met by shifting cultivation, irrigation and clearing of forested areas. Many scholars have worked on the extraction of methane from cow dung, plants bye products, poultry droppings, goat and sheep dung and waste water From their studies, it was found that the entire slurry/sludge of the agriculture byeproducts/waste from the anaerobic digestion is an excellent source of organic fertilizer with obvious advantages over the mineral/chemical fertilizers [1, 2, 7, 13, 15, 25, 27, 31]. In the light of the above shortcomings and problems arising from continuous application of artificial (inorganic) fertilizer; the need to research and perhaps improve on the traditional method of soil nutrient enrichment (the use of manure, crop residues, animal droppings and even sewage) became obvious. The optimum hydrogenionindex(pH) and microbe dosagewere determined on the basis of the process parameter that maximized the production index (PI) which is the measure of extent of biodegration/biodigestion of the cow dung
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