Thesis (M.S.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references (leaves 84-87).

Submitted in fulfillment of the requirements of the degree of Masters of Engineering: Chemical Engineering, Durban University of Technology, Durban, South Africa, 2018. / The anaerobic process is increasingly becoming a subject for many as it reduces greenhouse gas emissions and recovers carbon dioxide energy as methane. Even though these benefits are attainable, proper control and design of the process variables has to be done in order to optimize the system productivity and improve stability. The aim of this research was to optimize methane and biogas yields on the anaerobic co-digestion of sewage sludge using bio-chemical substrates as co-substrates. The first objective was to find the bio-chemical substrate that will generate the highest biogas and methane yields. The anaerobic digestion of these substrates was operated using 6 L digesters at 37.5℃. The substrate which generated the highest biogas and methane yield in the first batch experiment was then used for the second batch test. The objective was to optimize the anaerobic conditions (substrate to inoculum ratio, co-substrate concentration and temperature) in-order to optimize the biogas and methane yields. The second batch test was achieved using the conventional One-Factor-At-A-Time (OFAT) and the Design of Experiment (DOE) methods. Final analysis showed that the bio-chemical substrates could be substrates of interest to biogas generators. Amongst the substrates tested in the first batch experiment glycerol (Oleo-Chemical Product waste) generated the highest methane and biogas yields of 0.71 and 0.93 L. (g volatile solids added)-1, respectively. It was believed that glycerol contains significant amount of other organic substances such as lipids that have higher energy content than the other bio-chemical substrates, thus generating larger biogas and methane yields. Moreover, digestion of sewage sludge alone produced biogas yields of 0.19 L /g VS and 0.33 L/g COD, and methane yields of 0.16 L/g VS and 0.28 L/g COD. Generally, co-digestion yields were higher than digestion yields of sewage alone. Using the OFAT method the results of the second batch test on glycerol demonstrated highest amounts of volatile solids (VS) reduction, chemical oxygen demand (COD) reduction, biogas yield and methane yield of 99.7%, 100%, 0.94 L (g VS added)-1 and 0.75 L (g VS added)-1 at a temperature, substrate to inoculum ratio and glycerol volume of 50℃, 1 (on VS basis) and 10 mL, respectively. Above 22 mL and substrate to inoculum ratio of 1, the process was inhibited. The DOE results suggested that the highest methane and biogas yields were 0.75 and 0.94 L (g VS added)-1, respectively. These results were similar to the OFAT results, thus the DOE software may be used to define the biogas and methane yields equations for glycerol. In conclusion, anaerobic co-digestion of bio-chemical substrates as co-substrates on sewage sludge was successfully applied to optimize methane and biogas yields. / M

PhD (Geography) / Department of Geography and Geo-Information Sciences / Improved access to modern affordable, sustainable and reliable energy supply is fundamental in the development of any economy and in the achievement of sustainable development goals. However, energy as a resource is increasingly and becoming scare in many countries and subsequently expensive, with a substantial impact on the socio-economic progress, especially in any country that lacks the financial, physical, social and human capital to secure its energy supply. Energy can also be produced though the anaerobic fermentation of biological waste, such as animal excrement, which is methane-rich. Fermentation also produces a nutrient-rich digestate. Biogas can be used for domestic purposes, such as cooking and heating. Furthermore, it can be converted into electricity. Biogas technology is of particular significance in rural households, where energy crisis are common. This thesis therefore aimed at developing an adoption and sustainable utilisation framework of biogas as an alternative source of energy for greenhouse gases emission reduction in the Limpopo Province. The sample involved 72 households with biogas digesters, which were purposively sampled and 128 households without digesters, which were randomly selected. The study was based on the primary data that were elicited using open and closed-ended questionnaires. Empirically, the results of this thesis developed a sustainable, simplified, appropriate and comprehensive framework for biogas adoption and utilisation, including an analysis of important factors that could influence the adoption of this desired technology, for cost-effectiveness and sustainability. / NRF

MENVSC / Department of Ecology and Resource Management