EFFECT OF LEACHATE ADDITION ON BIOGAS PRODUCTION FROM WASTE UNDER MESOPHILIC CONDITION

Abstract

Energy crisis is the main hindrance in economic development of Pakistan. Fortunately, Pakistan has enormous biomass resources available in the form of crop residues, sugarcane bagasse, food waste, wood, dung, feces and poultry litter etc. which could be used to produce biogas, an alternative renewable fuel. The present study was conducted to examine the potential for biogas production from cow dung and vegetable waste with the objective of increasing the biogas production through the addition of municipal solid waste leachate in different proportion under mesophilic conditions. For this reason batch digestion was performed in the laboratory of IESE, NUST. In this experiment eight digesters having working volume of 1.2 liters were used. First four digesters were filled with vegetable waste and other four with cow dung. Different proportions of leachate with water (0, 33, 66 & 100 percent respectively) was used as liquid content in the digesters. For both the substrates Na2CO3 was used to buffer any sharp drop in the pH. Results showed that biogas production was increased with the increase in leachate content. Digesters containing highest leachate content of both vegetable waste and cow dung cumulatively produced highest amount of biogas which was approximately 700 L/kg of VS and 708 L/kg of VS while digesters having no leachate content produced 618 L/kg of VS and 437 L/kg of VS respectively. The percentage increase in the gas production was found to be 13% for vegetable waste and 62% for cow dung. Average methane content in biogas after attaining stability was 69% for vegetable waste while 64% for cow dung. From the results it was concluded that leachate addition had a positive effect on biogas production from both type of waste but this effect was more considerable in cow dung as compared to vegetable waste.