Mono-fermentation of shea waste in anaerobic digesters - laboratory investigations

Abstract

With an estimate of 45,000 metric tons of shea waste produced annually and in order to utilize the waste in an appropriate way and to reduce its negative impact on the environment, there is the need for research in the field of waste treatment. For the purpose of understanding the characteristics in performance of the shea waste and to provide the necessary input parameters towards the design of biogas plants, mono-fermentation as an option in anaerobic digestion for energy (methane) generation was investigated. Six horizontal reactors with a liquid volume of 74 litres were used. All experiments proceeded at ambient temperatures in the laboratory. Monofermentation of shea-waste was found not to be a suitable option in anaerobic digestion for thepurpose of methane production. Irrespective of the hydraulic retention times (HRTs) and volatile solids (VS) content of the substrates the experiments under mono-fermentation showed processinstability and at one point or the other the experiment had to be terminated due to decreasing pH-values of substrate which influenced negatively on the biogas production. However, an interestingobservation was the potential of the shea waste to generate substantial amount of methane.