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The production of ethanol and other sustainable products including methane, limonene and pectin from citrus wastes (CWs) was studied in the present thesis. In the first part of the work, the CWs were hydrolyzed using enzymes – pectinase, cellulase and β-glucosidase – and the hydrolyzate was fermented using encapsulated yeasts in the presence of the inhibitor compound ‘limonene’. However, the application of encapsulated cells may be hampered by the high price of encapsulation, enzymes and the low stability of capsules’ membrane at high shear stresses. Therefore, a process based on dilute-acid hydrolysis of CWs was developed. The limonene of the CWs was effectively removed through flashing of the hydrolyzate into an expansion tank. The sugars present in the hydrolyzate were converted to ethanol using a flocculating yeast strain. Then ethanol was distilled and the stillage and the remaining solid materials of the hydrolyzed CWs were anaerobically digested to obtain methane. The soluble pectin content of hydrolyzate can be precipitated using the produced ethanol. One ton of CWs with 20% dry weight resulted in 39.64 l ethanol, 45 m3 methane, 8.9 l limonene, and 38.8 kg pectin. The feasibility of the process depends on the transportation cost and the capacity of CW. For example, the total cost of ethanol with a capacity of 100,000 tons CW/year was 0.91 USD/L, assuming 10 USD/ton handling and transportation cost of CW to the plant. Changing the plant capacity from 25,000 to 400,000 tons CW per year results in reducing ethanol costs from 2.55 to 0.46 USD/L in an economically feasible process. Since this process employs a flocculating yeast strain, the major concern in design of the bioreactor is the sedimentation of yeast flocs. The size of flocs is a function of sugar concentration, time and flow. A CFD model of bioreactor was developed to predict the sedimentation of flocs and the effect of flow on distribution of flocs. The CFD model predicted that the flocs sediment when they are larger than 180 micrometer. The developed CFD model can be used in design and scale-up of the bioreactor. For the plants with low CW capacity, a steam explosion process was employed to eliminate limonene and the treated CW was used in a digestion plant to produce methane. The required cost of this pretreatment was about 0.90 million dollars for 10,000 tons/year of CWs. / <p><strong>Sponsorship</strong>:</p><p>Sparbankstiftelsen Sjuhärad, Kommunalförbundet i Sjuhärad, Brämhults juice AB</p>

Published Articles / Increased waste generation and poor waste disposal strategies are a global problem. In South Africa most provinces, and the larger municipalities and metros, seems to have the waste disposal and the landfills reasonably organized. This cannot be said of the landfills in the Free State Province, which could only be called dump sites. In the Free State Province a high unemployment level exists and a lack of finances is experienced by many members of the communities, especially in rural areas. Poverty levels is shown in a study by Adventist Development and Relief Agency (ADRA SA), where it was recorded that 1.8 million (68%) of the people in the Free State Province are living in poverty and living on less than R15 per day. Data on the state of the landfill, types of waste generated which have potential to be recycled, were recorded to assess if recycling could be increased to relieve the economic burden of the poor communities. Attention was paid to the following aspects: assessing the current status of each landfill and identifying the types of waste generated in the area which ended up at the landfills. The extent of recycling and the waste handling and disposal of the waste were recorded. Non-compliance with the prescribed legislative guidelines were noted and aspects such as the state of the landfills, proper enclosure, burning of waste, recycling and products being recycled were identified and recorded. The waste disposal practices at most landfills were poor and very limited recycling was taking place. None of the landfills in the province complied with the minimum requirements for landfilling. Recommendations to improve waste disposal and identification of products with recycling potential were made. Alternative waste strategies which could be economically beneficial for the communities were recommended

Text in English / The study focused on the characterisation and management of non-formal solid waste disposal sites in Harare, the capital city of the Republic of Zimbabwe. In many developing countries, increasing urbanisation surpasses the development of urban infrastructure and this has led to the proliferation of informal settlements, illegal dumping sites and uncontrolled vending in cities like Harare. The researcher investigated the prevalence of non-formal dumping sites in Harare, including the composition, locational attributes and internal linkages of solid waste. Practices regarding the management of non-formal solid waste disposal sites were examined and areas of good practice and conformity to international standards were complemented while recommendations and suggestions were made on areas that were found wanting. An integrated management system was recommended for the sustainable management of solid waste. To support this recommendation, management window of responsibilities (EMWR) model was created so that the Harare City Council can enhance stakeholder participation. The research results show that most residents used non-conventional ways to store waste, like mealie-meal bags and sacks, and this posed a danger to human health. It also emerged that the city of Harare has not updated some of its by-laws, some of which were enacted about 33 years ago while others remained drafts for decades. This made it difficult for the city to effectively implement them. / Environmental Sciences / M.Sc. (Environmental Management)

Submitted in fulfillment of the requirements of the degree of Master of Engineering: Chemical Engineering, Durban University of Technology, Durban, South Africa, 2015. / The implementation of new water regulations from the local government has been a motivation for most industries to treat the effluent before disposal or reuse within the plant, in order to save costs and avoid sanctions. Tongaat-Huletts sugar refinery has therefore invested in this collaborative research with the Durban University of Technology in order to investigate new technologies for wastewater treatment and water recovery using an organic coagulant called chitosan. Chitosan is a natural non-toxic polymer extracted from the exoskeleton of crustaceans. Chitosan has gained extensive attention as a coagulant in the treatment of wastewaters from various industries. However, no attention has been given to the coagulation of effluents from the sugar industry using this polymer. In this work, chitosan coagulant (CCo) was prepared by dissolution of known amounts of chitosan powder in aqueous acid at 50℃. The solution was diluted to desired concentrations using distilled water at room temperature. The removal of impurities using chitosan was investigated for two effluent streams from the sugar refinery, namely the final effluent (FE) and the resin effluent (RE) by applying the one-factor-at-a-time (OFAT) method. The optimum chitosan loading was found to be 138 mg/l for the RE and 7.41 mg/l for the FE, beyond which the efficiency of the coagulant decreased. The coagulation of FE removed 97% of the total suspended solids (TSS), 61% colour and 35% chemical oxygen demand (COD). The treatment of RE resulted in the removal of 68% TSS, 30% colour and 15% COD due to its high content of impurities. Therefore, RE was not considered for statistical studies. The Box-Behnken (BBD) design, which is a statistical response surface methodology (RSM) model was used to study the simultaneous effect of pH, coagulant loading and settling time on the removal of the COD, TSS and colour, with the help of an overlay plot for the FE. The optimum values from the overlay plot were 92% for TSS, 83% for colour and 29% for COD. The model equations generated by the BBD for individual responses involved all the manipulated variables contrary to the OFAT which only considered one manipulated parameter per response. Moreover, the BBD allowed the simultaneous analysis of all the parameters and the identification of interactions which occur when the effect of one factor is dependent on the level of another. The most important interaction for the removal of TSS was the combination of the variation in pH and coagulant dosage. The COD removal was mostly affected by the interaction between the coagulant loading and the settling time. The colour removal increased with the simultaneous increase of the pH and the settling time. A comparative study between the wastewaters from the sugar industry, the brewery industry and milk processing industry revealed that the performance of the chitosan was also affected by the amount of total dissolved solids (TDS) in the wastewater. A model was developed relating the TSS, COD and TDS from all these wastewaters, and was used to predict the TSS removal for the effluent from the olive oil mills and the wastewater from the winery. Chitosan can be considered as a good alternative to inorganic and synthetic coagulants for the pre-treatment of the FE due to its ability to efficiently remove the levels of TSS and colour. Furthermore, the production of chitosan from crustacean shells is a good method of reducing pollution from the fishery industry. Chitosan can be produced locally at low cost due to both the abundance of crustacean shells in the coastal regions of South Africa and the simplicity of its preparation process. It is recommended that a mathematical model be developed to accurately predict the influence of chitosan on all types of effluent. Such a model will provide an indication of the performance of the chitosan and guide experimenters. It is further recommended that the effect of the use of organic coagulants on the destabilization of dissolved solids in wastewater be given greater attention.

Bibliographical refernces appear at the end of each chapter / This study reviews solid waste management practices in Polokwane City. The study area covered some of the residential areas in Polokwane City; namely; Ivy Park, Fauna Park, Welgelegen, Westernburg and the City Centre. This article describes two main methods that were used to collect data; that is Qualitative and Quantitative method. Field survey was also made to validate data obtained from the participants that were interviewed during qualitative data process. After framing the problem, the objectives of Solid Waste Management Practices in Polokwane City were briefly outlined as follows: • Assess solid waste management practices in Polokwane City. • Make comparison on how households and the municipality take responsibility in storing, collecting, transporting, treating and disposing solid waste. • Investigate what problems the City encounters in managing solid waste. • Make relevant recommendations aimed at improving solid waste management practices within the City. The service management was administered by the municipality and private sector. From the five study residential areas, the Municipality manages waste in the City Centre while the private sector manages waste in the other residential areas. However, the City continues to play an administrative role over the contracted service provider. Statistical results were presented in figures and tables. The results showed the storage habits, frequency of collection, mode of transport and methods of disposal for solid waste in Polokwane City. The only method of disposal in the city was found to be landfilling. Activities that took place at the landfill site, such as reclaiming were outlined together with the economic values that these activities add to the City. The study also revealed that as population increases, the amount of solid waste generated also increased. / Environmental Sciences / M. Sc. (Environmental Management)

Biodegradable wastes cause high emissions of greenhouse gases (GHG) if not properly treated. The emissions can be reduced by the development of an effective waste management strategy. Waste-to-energy technologies, such as anaerobic digestion (AD) can be utilised for this purpose. Biomass energy from wastes is of particular interest to Cyprus that has to meet legal commitments for reducing its GHG emissions by 5% compared to 2005 levels and increase the contribution of renewable energy sources to 13% by 2020. This research project is making a significant contribution to this effort. The research considered the quantities and distribution of biodegradable waste in Cyprus and developed the necessary methodologies and tools for their estimation and determination of the potential for energy production through AD. The study identified that the predominant biodegradable wastes in Cyprus are the biodegradable fraction of municipal solid waste (MSW), sewage sludge, solid and liquid agricultural residues and solid and liquid wastes from the food and drinks industries. According to the estimated amount of solid and liquid biomass from these waste streams, at least 4,200 TJ of energy can be produced through AD, which represents 4% of the national energy demand. Livestock production is a very important source of waste due to the high potential of biogas production with the aid of AD. The produced energy can satisfy the needs of a farm, reduce the consumption of fuel and provide renewable energy to the national grid. Simple methodologies were developed and implemented for the estimation of energy consumption of the farm and the respective GHG emissions. It was found that in Cyprus the annual energy consumption per animal is lower than most other countries, due to favourable weather conditions which reduce the energy needs for heating. The emissions from energy use in livestock production contribute 16% to the total agricultural energy emissions. Literature review on AD, confirmed the complexity of the process, due to the many microorganisms involved. To estimate the potential of biogas production from animal waste through AD, three methods were developed based on the accepted relations that exist between Chemical Oxygen Demand (COD), volatile solids (VS), waste digested and biogas production. The results show that livestock production could cover the complete agricultural energy demand and make a considerable contribution to the renewable energy targets of Cyprus. Due to the identified importance that AD could have for Cyprus and to overcome deficiencies of existing models, the software FARMS was developed. The tool can be used by any farmer, consultant or policy maker for the estimation of the potential of biogas production, associated costs, reduction in GHG emissions and comparison of scenarios for waste management. Furthermore, the validation of the tool is presented. This was done through comparison against data collected from existing AD plants and through testing by potential users.

The state of solid waste management in cities of most developing countries is fast assuming the scale of a major social and environmental challenge. In Sub-Saharan Africa in particular, the combined influence of poverty, population growth and rapid urbanization has tended to worsen the situation. The gravity of this problem is perhaps best reflected in the level of attention given to it in the United Nations (UN) Millennium Declaration. Three of the eight Millennium Development Goals (MDGs) outlined in the declaration have waste or resource efficiency implications. In response to the waste challenge many developed countries have embarked upon ambitious environmental reforms, recording remarkable advances in best practises and sustainable management of their Municipal Solid Waste (MSW). However, many developing countries such as Nigeria have fared less well in this regard as a result of several barriers militating against sustainable management of MSW. The principal aim of this research is therefore to carry out a critical analysis of the various barriers as well as success factors that affect the sustainable management of MSW using Abuja, Nigeria, as a case study. The study adopts a largely quantitative methodological approach, employing waste composition analysis of samples from the case study area, questionnaire survey and focus group interviews of stakeholders in MSW management as key methods for generation of data. Results from analysis of data, using the Statistical Programme for the Social Sciences (SPSS), indicate that between 65-70% of MSW samples from Abuja is biodegradable, mostly comprising of high wet weight and high moisture content kitchen wastes. On the other hand between 11%-30% of MSW samples from the City comprises mostly of non-degradable but recyclable materials such as glass, metals and cans, non-ferrous metals and waste electrical and electronic equipment. The implication of the high levels of moisture content in the biodegradable components is that samples are not suitable for incineration but are ideal for composting and other mechanical and biological management options. Data analysis also reveals that the main barriers to sustainable MSW management in the City include low public awareness/education on MSW management, obsolete and insufficient equipment and funding limitations. On the other hand, the most important success factor affecting sustainable MSW management in Abuja was found to be the bourgeoning City population which has a huge potential for uptake of recycled products. In summary, this research concludes that the factors affecting MSW management in Abuja are typical of many tropical urban environments. Fundamental shifts in current practises towards waste prevention; driven by a structured public education programme in MSW management is recommended, so as to bring about a more sustainable management regime. As a result of resource and time limitations, it was not possible to complete several potential lines of investigation related to this study. To fully understand the character of the Abuja waste stream however, further chemical characterization including proximate and ultimate analysis is required. Future research in this genre must endeavour to collect data from a larger sample to increase the precision of the analysis and to enable firmer conclusions to be drawn.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management