Batch Investigation of Biogas Production from Palm Oil Sludge, Bambara Nut Chaff and African Wild Mango at Varying Meteorological Conditions

Abstract

A custom response design study on the biogas production from blends of Palm oil sludge (POS), Bambara nut (VignaSubterranea) chaff (BNC) and African wild mango (AWM) was carried out. The anaerobic digestion was in the ratio of 3:1 and 2:1 of water to waste depending on the nature of the substrates as follows: System A was 100%POS; B: 100%BNC, C: 100%AWM;D: 50%POS+50%BNC and E: 60% POS+20% BNC+20% AWM. The wastes were charged into 32L capacity metal prototype digesters in a batch for 30 days retention period at an ambient temperature range of 26oC - 37°C. The cumulative gas yield from the five treatments systems (digesters) were different: the 50%POS+50%BNC had the highest cumulative gas yield (69.5L); followed by 100%BNC system (54.5L); 60%POS+20%BNC+20%AWM system (39.2L); 100%POS system (14.4L) and 100%AWM system (11.7L). 100%BNC system had the highest methane content (88.056%); followed by 60%POS+20%BNC+20%AWM system (88.007%); 100%POS system (83.025%); and 50%POS+50%BNC system (73.055%).The research has shown that 100% BNC had the least lag days (6 days), highest calorific value (25330.24KJ/Kg) and highest methane content (88.056%). African wild mango needs to be co-digested to produce flammable biogas. The TS, VS, BOD and TVC were seen to be consistently reducing throughout the digestion period. Meteorological conditions like solar radiation, air temperature and wind speed had significant effects on ambient temperature, slurry temperature, pH and daily gas yield.