A COMBINED BIOGAS PLANT AND INCINERATOR SYSTEM FOR MUNICIPAL SOLID WASTE MANAGEMENT

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Department of Engineering

ABSTRACT
This study, assessed the potentials of generating biogas from the organic fraction of municipal solid wastes to fuel an incinerator which is then used to burn the residual combustible solid waste. Municipal solid waste from Ahmadu Bello University (ABU) commercial market was collected, grinded and mixed with intestinal waste from slaughtered cattle at Zango abattoir, Zaria in a 2:1 ratio by volume. The mixture was diluted with water in a 1:1 ratio by volume to form a slurry and digested anaerobically in a digester The efficacy of the digester in producing biogas were in three (3) phases. Lowest between day 3 – 11; 0.143m3 (0.018m3/kg), highest between day 15 – 55; 1.353m3 (0.034m3/kg) and medium between day 55 – 94; 1.208m3 (0.031m3/kg) Fertilizer values based on the ratios of N: P: K: Mg were 28: 1: 22: 4; 1: 971: 821: 1995 and 10: 1: 59: 104 for digestate, bottom ash and combined digestate and bottom ash respectively. Total Organic Carbon contents of the digested solid waste were0.1389 %, 0.8099 %, and 0.3008 % of the initial mass for digestate, Bottom ash and combined digestate and bottom ash respectively. A small scale incinerator was built with the capacity to burn 1.8m3 of solid waste per day burn cycle. A biogas air mixer was developed to ensure good combustion by the biogas burner. The biogas burnt with a blue flame measured at 8700C and a calorific value of 16,000J/g while the incinerator was able to achieve an average operating temperature of 9300C with a percentage waste reduction of 80 % per hour with 4.5 % as bottom ash. Biogas consumption by the incinerator’s auxiliary burner was 0.0071m3/min with adequate flame stability during the process. Ratio of gas used to the solid waste combustion was 1: 78: 1 v/v per hour.