DESIGN AND CONSTRUCTION OF A DIGESTER FOR BIOGAS AND ORGANIC FERTILIZER GENERATION

Abstract

In the present work the design and construction of a fixed dome biogas plant for the treatment of pig droppings through anaerobic digestion is shown. The methodology to calculate the dimensions of the plant is described; the plant is able to process 200 kg/day of dung, and 6,1 m3 of biogas and 3,4 t/year of fertilizer are obtained. The elements of the biogas plant and constructing materials are specified. The biogas is used for cooking foods which substitute firewood and petroleum liquefied gas (PLG), with the compost produced every month 0,72 ha/year of soil is fertilized, protecting it from erosion and giving it back the fertility. It has been estimated that agricultural production raised 10% due to organic fertilizer application, especially vegetables; in other agricultural crops the increment has been lower. The cash flow methodology gave up a positive net present value (NPV) of 43 634,89 CUP at a discount rate of 10%, internal rate of return (IRR) of 30%, and payback period of 3,72 years.