TECHNO-ECONOMIC ASSESSMENT FOR BIOGAS GENERATION FOR ENERGY USAGE FROM MUNICIPAL SEWAGE SLUDGE USING ACTI-ZYME AS DIGESTION CATALYST
M. M. MANYUCHI *
Department of Chemical and Process Systems Engineering, Harare Institute of Technology, Ganges Rd, Belvedere, Harare, Zimbabwe and Department of Chemical Engineering, Cape Peninsula University of Technology, Belleview, Western Cape, South Africa
D. I. O. IKHU-OMOREGBE
Department of Chemical Engineering, Cape Peninsula University of Technology, Belleview, Western Cape, South Africa
O. O. OYEKOLA
Department of Chemical Engineering, Cape Peninsula University of Technology, Belleview, Western Cape, South Africa
D. J. NKOMO
Department of Financial Engineering, Harare Institute of Technology, Ganges Rd, Belvedere, Harare, Zimbabwe
W. GWARIMBO
Department of Financial Engineering, Harare Institute of Technology, Ganges Rd, Belvedere, Harare, Zimbabwe
*Author to whom correspondence should be addressed.
Abstract
A sewage plant with a capacity of 19 600 m3/day was considered for techno-economic assessment, with an operating efficiency of 60% and a life span of 20 years. $5.125/day of Acti-zyme were required for production of 12 769.69 kg/day for biogas costing $1.50/kg and 672.08 kg/day of bio-solids costing $16.00/50 kg. Capital budgeting techniques were then used for techno-economic assessment of sewage treatment recovering biogas and bio-solids. A net benefit of $5 656 363.92 per annum for using the Acti-zyme technology in sewage digestion was forecasted, whilst a net energy of 1 387.33 KWh was set to be produced. An investment of $22 199 501.40 was required for kick-starting the project. A positive net present value of $1 186 239.23 was realized with an internal rate of return of 17.6% and a payback period of 5.9 years. For breakeven to be realised, only 183 059.16 KWh must be produced. The techno-economic assessment indicated it is viable to treat sewage using Acti-zyme co-harnessing biogas and bio-solids as valued added products to an extent of making 0.04% to the Zimbabwe gross domestic product.
Keywords: Acti-zyme, biogas, bio-nutrients, bio-solids, sewage treatment, techno-economic analysis