Kinetic Evaluation of Composting of Agricultural Wastes

Abstract

Composting as a biological waste treatment process holds a lot of promise in Malaysia. Although composting has a long history of application, it is difficult to find published work in the area of kinetics, which is regarded as important from the engineering point of view. As composting operates on the same general biochemical principles as all biological systems, enzyme kinetics concepts could be applicable in the formulation of kinetic model of the composting process In this study, composting experiments were performed on oil palm empty fruit bunches, garden wastes, chicken dung and garden waste together with municipal sewage sludge. A commercial compost starter was evaluated for its efficacy to speed up the composting process. The kinetic rate constants Km, K′m, Rm and R′m were determined experimentally. It was observed that the Michealis constant (Km) values were fairly constant (between 1.20 to 1.84) for each waste irrespective of whether compost starter was added. As for the maximum or limiting velocity, Rm and R′m values, it was observed that the values were higher with the addition of compost starter, the increase depending on the type of agro-waste and in the case of garden waste and EFB it was almost double when compared to control. The growth characteristics of actinomycetes, bacteria and fungi involved in composting were also evaluated and based on μm and Ks the addition of compost starters showed a positive effect on the growth rate of these microorganisms.