Waste Management in Sugar and Ethanol Production: Evaluation of Anaerobic Co-Digestion of Sugarcane Vinasse and Bagasse for Biogas Production Under Different Parametric Conditions
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Date
2024-10
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Addis Ababa University
Abstract
In this thesis work the anaerobic co-digestion of sugarcane vinasse with bagasse was investigated under varying conditions to evaluate biogas (methane) production as well as sludge characteristics for selected batch digestors. Anaerobic digestion offers a sustainable approach for managing sugarcane residues such as vinasse & bagasse by utilizing them to generate biogas and organic fertilizer from the sludge while addressing environmental concerns related to their disposal. Sugarcane vinasse is a highly pollutant liquid due to its high organic matter content, low pH, high salt content, dark brown color and high temperature when discharged from the distillation unit. It is produced in large amount with a 1: 10-20 ratio of alcohol to vinasse from alcohol/ethanol factories. The study employs an experimental design to analyze the effects of mixing ratios of vinasse (V) to bagasse (B); (75%V:25%B, 50%V:50%B & 25%V:75%B), pH levels (6.8, 7.4 & 8.0) and temperature levels (25°C, 35°C & 45°C) on biogas production and methane yield resulting in 27 anaerobic batch digestors. Through batch experiments conducted over a period of more than 35 days (until the end of gas production), quantitative and qualitative biogas yields were measured. The results showed that the highest methane yield (203.6774ml/gVSadded) was at mixing ratio of 25%V:75%B, pH=7.4 and T=45oC. The sludge characteristics for the batch sample were determined in terms of its NPK content, TOC, TOM and C: N to compare with FAO’s recommendation for an organic fertilizer. Its TOC & TOM values are well above the minimum amount recommended by FAO (12% and 30% respectively) however the nutrient content is below the recommended value (N+P+K ≥5%). The research findings contribute for optimizing anaerobic co-digestion of sugarcane vinasse with bagasse to maximize methane production and improve sludge management practices to address energy demands, waste management challenges and limitations of inorganic fertilizers by nutrient recycling.
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Keywords
Anaerobic Co-digestion, Bagasse, Biogas, Sugarcane Vinasse, Waste management