Biogas Potentials Evaluation of Household Wastes in Johannesburg Metropolitan Area Using the Automatic Methane Potential Test System (AMPTS) II

Abstract

A work on biogas potentials evaluation of household wastes in Johannesburg metropolitan area using the Automatic Methane Potential Test System (AMPTS) II is presented. The AMPTS II consists of three units — the sample incubation unit, CO2 absorption unit and the gas volume measuring device. Organic fraction of wastes collected from households within Johannesburg metropolis were sorted, ground and prepared into slurry by mixing with water. Microcrystalline cellulose powder with 3.5% loss on drying and 0.28g/cc density was used as control substrate while anaerobic sludge collected from a functional biogas reactor was used as inoculum. Anaerobic sludge was classified as sample A, household waste containing mainly non-food waste was labelled sample B, sample C was microcrystalline cellulose used as positive control while household waste composing of mainly food waste was classified as sample D. Each sample was fed into a 50 mL bottle reactor in triplicates and stirred in a clockwise direction continuously for 5 minutes with a pulse interval of 1 minute at a set temperature of 37°C for 30 days retention time. NaOH solution was prepared into solution following standard procedure and mixed with a prepared 0.4 % Thymolpthalein solution. The resultant solution was poured into the 100 mL bottles of the CO2 unit. Produced biogas was measured through water displacement in the volumetric bath and values read off through a data-logger connected to a laptop. Results indicated biochemical methane potential (BMP) of 69–800 NmL/gvs and biogas composition with more than 50% methane before CO2 fixing and over 80% after CO2 fixing. Given that the average amount of waste generated per person per day in South Africa is over 0.7 kg, there is huge potentials for biogas production from household wastes in Johannesburg.