Mathematical Modelling for Organic Waste Resources Targeting and Optimization using Carbon-to-Nitrogen Ratio

Abstract

Organic waste is one of the major components found in solid waste disposal. The increasing production of solid wastes reflects the great potential of organic wastes as one of the green energy resources. The organic wastes can be used to generate green energy resources such as biomethane via designated bioprocesses. Each bioprocess is unique and requires an optimum range of carbon-to-nitrogen ratio to obtain the optimum production energy resources. The composition of organic wastes varies across different origins and different types. A non-linear programming mathematical model was developed to allocate the resources and satisfy the carbon-to-nitrogen ratio among the sources and sinks via General Algebraic Modelling System. The objective function of the model is to minimize the utilization of external supply to reduce the necessary of transporting external resources from a distant location. To satisfy a biomethane digester demanding daily 40 kg/d feedstock with carbon-to-nitrogen ratio of 28.1, 193.387 kg/week of external supplies were required to mix with 2212.572 kg/week of organic waste locally available to produce 115.2 m3 CH4/d. A biogas storage with capacity of 52.86 m3 was determined from the model. A storage with a capacity of 689.43 m3 was identified to store the unutilized corn stover but the storage does not show practical usage as the daily accumulation of corn stover increases from day 1 to day 7, where the unutilized organic waste will be disposed at the end of the week due to unavoidable composition change during biodegradation. The results obtained from the developed mathematical mode can be a preliminary analytic tool that provides governments, agencies and industries intended to invest and contribute to the green and sustainable waste management sectors.