Fats, oil and grease (FOG) are generated in large amounts by cooking and food processing. Anaerobic co-digestion with municipal sewage sludge has proven to be one of best alternatives for FOG disposal due to its high potential for biogas production. However, excessive addition of long chain fatty acid, the major content of FOG, has been reported to have inhibitory effects on the anaerobic digestion process and to cause operational challenges. In this study, high purity long chain fatty acids (LCFAs) including linoleic acid, oleic acid, and a mixture of oleic acid and stearic acid were added to laboratory completed mixed anaerobic digesters. The performance of the digesters in terms of solids destruction, COD degradation, LCFAs accumulation and gas production was investigated. After reaching steady state, a large amount of palmitic acid was found in the reactors with oleic acid addition and mixture of stearic and oleic acid addition. In the meantime, no palmitic acid increase was observed in reactors where linoleic acid was added. A better solids and COD reduction and a higher biogas production were observed in reactors with higher LCFAs addition. For reactors with the same dosage of LCFAs addition, linoleic acid addition resulted in the greatest improvement in digester performance; the mixture of stearic acid and oleic acid achieved the least increase in biogas production and solids and COD reduction. A high concentration of both palmitic and stearic acid in the reactors with oleic acid addition and with 20% mixed acid addition was observed. In contrast, linoleic acid and 30% mixed acid addition did not lead to a greater palmitic or stearic acid concentrations. Up to 30% of pure linoleic acid, oleic acid and mixed acid addition are able to enhance the performance of anaerobic digesters. It is recommended that the dosage of oleic acid be below 30% to avoid LCFAs accumulation and to increase reactor stability. / Master of Science

M.Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / An enormous amount of food waste (FW) is generated worldwide. Most of this waste is discarded in landfills, where it undergoes uncontrolled anaerobic digestion (AD) process, which emits excessive amounts of greenhouse gases, (methane and carbon dioxide), thereby contributing to global warming. A controlled AD of FW is key for organic waste management with a positive impact on the environment and economy. In South Africa (SA) there is little uptake of biogas technology for FW management due to little research on biogas potential at small to large scale. Furthermore, there is an over reliance on foreign data, which leads to misfit parameters to local raw materials; consequently, producing biogas of low quality and quantity with low degradation of waste. Biogas with poor quality reduces the efficiency of biogas conversion to energy and the low production rate makes the system less feasible. Considering the challenges faced with FW management and the little uptake of the AD technology in SA, this study aimed to treat FW through AD and convert the biogas produced to electricity. A complete-mix biogas pilot plant (VUT-1000C) was designed, constructed and commissioned. The materials used for constructing the pilot plant were sourced locally to prove the applicability of the AD technology in SA. The biodigester was operated at mesophilic temperature, 37 oC, aided by a solar system. A stand-alone 1 m3 plug-flow ambient biodigester (STH-1000A) was operated semi-continuously as well as a control. Cow dung (CD) was used to inoculate the biodigesters, which were then operated semi-continuously at their optimum organic loading rate (OLR). The STH-1000A digester was operated at 0.446 kgVS/m3/day OLR, according to the manufacturer’s specification, while for VUT-1000C, the OLR was determined. The highest biogas and methane yields obtained were 582 and 332 L/kgVS/m3, respectively, at the determined optimal OLR of 1.5 kgVS/m3/day for the VUT-1000C digester this was supported by the modified Gompertz model with an R2 value of 0.9836. VUT-1000C produced 1200 L/day while STH-1000A produced 150 L/day. VUT-1000C proved to be a more effective biodigester than STH-1000A owing to the digester design and operation at mesophilic conditions. The key design findings are higher reactor working volume and high digester temperature. From the 1000 L of biogas produced from VUT-1000C, 1.8 kW of electricity was generated, which is equivalent to powering 300 6W light bulbs for 1 hour. The energy balance of the pilot plant showed that only 10 percent of the energy output was required to operate the plant. These results show that SA has a 475 GWh energy potential based on the current FW figures. Furthermore, the study has shown that biogas technology is readily available for South Africans and that the designed biogas plant was very efficient in FW-to-energy conversion.

Anaerobic digestion (AD) is a sustainable waste management technology that primarily generates two products: biogas and digestate. The technology relies on the microorganisms' activity, which depends on several operational factors, such as pH, temperature, solid contents, and ammonia levels. Ammonia is an inorganic form of nitrogen resulting from the biodegradation of organic nitrogen. It is considered one of the major concerns for AD operations due to its inhibitory effects on some microorganisms, particularly methanogens. A common feedstock characterized by high nitrogen content is poultry manure (PM). PM is often avoided in anaerobic digesters due to the anticipated inhibition resulting from its high ammonia levels. However, since poultry manure is one of the most widely available organic wastes, researchers have extensively investigated ways to include PM as a primary feedstock for AD. One possible way to treat high ammonia levels in digestate is ammonia stripping, the physio-chemical separation of ammonia from a solution by introducing a stripping (carrier) gas. There are a few approaches to performing ammonia stripping in AD applications; the most commonly discussed in the literature are pre-hydrolysis and side-stream ammonia stripping. Pre-hydrolysis ammonia stripping is performed on raw feedstock after increasing pH and temperature and is usually not restricted in selecting the gas carrier. On the other hand, side-stream ammonia stripping is when a portion of the digester's working volume is filtered, and the filtrate is sent to a unit where pH and temperature are increased. The carrier gas in these systems is often limited to anaerobic gases such as biogas or steam. The third and most novel approach is post-hydrolysis ammonia stripping, conducted at an intermediate stage between hydrolysis and methanogenesis in a two-stage AD process. This configuration would address the shortcomings of the other two systems. However, there is minimal information on the feasibility and potential of this approach in the literature. This study aims to comprehensively investigate the post-hydrolysis ammonia stripping approach through the following four phases: Phase I) Proof of Concept; Phase II) Optimization; Phase III) Assessment of Alternative Carrier Gases; and Phase IV: Comparison of Different Ammonia Stripping Configurations. Phase I provided the proof of concept under the batch mode and compared the performance of post-hydrolysis ammonia stripping with two-stage AD and co-digestion to improve poultry manure's methane potential as the primary substrate. It was observed that ammonia stripping successfully improved methane potential by up to 150%, whereas improvements due to two-stage AD and co-digestion were limited to 41 and 9%, respectively. Phase II provided more insight into optimizing the ammonia stripping process. Different stripping conditions were tested (pH 7.8 (unadjusted), 9 and 10, temperature 25 (unadjusted), 40 and 55 °C, and flow rate 300 L/L/hour). The results showed that higher pH and temperature lead to higher removal efficiency. However, it was concluded that optimal conditions ultimately depend on the initial and target ammonia levels. Moreover, Analysis of Variance showed that pH and temperature were significant factors affecting the ammonia removal efficiency. In addition, it was observed that higher stripping temperatures (55 °C) enhanced the digestibility of PM and increased its methane potential more than stripping at 40 °C. It was concluded that the optimum stripping conditions were pH 9.5, temperature 40 or 55 °C, and flowrate of 100 L/L/hour to collectively increase ammonia removal while reducing the associated costs and material handling. In Phase III, renewable natural gas (RNG) was evaluated as a stripping medium in batch testing as a potential replacement for biogas and air. Ammonia stripping with RNG yielded promising results comparable to the application of air in terms of ammonia removal and enhancing biogas production from PM (60 and 69% ammonia removal for RNG and air, respectively). In addition, a metagenomic shotgun analysis showed that most biogas production was conducted through hydrogenotrophic methanogens instead of acetoclastic methanogens, which are more susceptible to high ammonia levels. Phase IV assessed the semi-continuous flow two-stage operation of mesophilic AD reactors coupled with different ammonia stripping configurations. Post-hydrolysis ammonia stripping successfully achieved a stable operation of PM mono-digestion at ammonia levels of 1700 and 2400 mg NH₃-N/L in the cases of stripping with air and RNG, respectively. In addition, post-hydrolysis ammonia stripping in semi-continuous flow mode may have promoted acetoclastic methanogens growth since volatile fatty acid concentrations were reduced in the digesters. Phase IV also proved that the performance of post-hydrolysis ammonia stripping is superior over pre-hydrolysis and side-stream ammonia stripping. In the semi-continuous flow reactors, post-hydrolysis ammonia stripping with air achieved on average 831 L biogas/ kg VS at an organic loading rate (OLR) of 2.6 g VS/L/day, whereas side-stream ammonia stripping resulted in average of 700 L biogas/ kg VS at OLR of 1.8 g VS/L/day and higher ammonia stripping requirements. Having said that, the base scenario (no ammonia stripping) was inhibited, indicating that both ammonia stripping configurations were considered successful in alleviating inhibitory effects of ammonia from poultry manure. Phase IV results also proved that air stripping repeatedly outperformed RNG as stripping mediums by having higher ammonia removal efficiencies resulting in higher methane production. However, stripping with RNG is believed to have more practical advantages than air due to avoiding the risk of oxygen infiltration into the reactor. Moreover, renewable natural gas has proven to be an efficient stripping medium that is available on-site. The final stage of Phase IV tested pre-hydrolysis ammonia stripping using air in batch mode and compared it with post-hydrolysis ammonia stripping. Pre-hydrolysis ammonia stripping provided little to no improvement to the methane potential of PM in batch mode and therefore was excluded from the semi-continuous flow experiment. The four phases of this study demonstrated the flexibility and the superiority of post-hydrolysis ammonia stripping over the other pre-hydrolysis and side-stream ammonia stripping. In addition, post-hydrolysis ammonia stripping was proven efficient and feasible for ammonia removal and enabling the mono- or co-digestion of poultry manure. The study also showed that using RNG instead of biogas can significantly reduce the operational costs of the treatment.

Vietnam is one of the countries suffering from the most serious adverse effects due to climate change and sea level rise. The main cause of climate change is the increased activities generating greenhouse gases. Organic waste is the main source of carbon dioxide emission, which has the largest concentration among different kinds of greenhouse gases in the earth’s atmosphere. The conversion of organic waste and biomass into energy contributes not only to supply cleaner energy but also to reduce emissions of greenhouse gases. Vietnam has a large potential of biomass and agricultural by-products. The technologies to turn biomass into different kinds of bio-energies were developed and applied all over the world. Biogas was called as 'brown revolution' in the field of new energy. Biogas production technology now has been studied and applied widely in the world, particularly in developing countries with warm climate that is suitable for anaerobic fermentation of organic waste. The biogas digester can be built with any capacity, needs small investment and the input materials are widely available. The biogas energy is used for many purposes such as cooking, lighting, running engines, etc. It is a production technology quite consistent with the economy of developing countries and really brings to life more civilized and convenient to rural areas. / Việt Nam là một trong những quốc gia bị tác động nghiêm trọng nhất do biến đổi khí hậu và nước biển dâng cao. Nguyên nhân chính của biến đổi khí hậu là các hoạt động gia tăng tạo ra các khí gây hiệu ứng nhà kính. Chất thải hữu cơ là nguồn chính phát thải khí carbon dioxide có nồng độ lớn nhất trong số các loại khí gây hiệu ứng nhà kính khác nhau trong bầu khí quyển của trái đất. Việc chuyển đổi chất thải hữu cơ và sinh khối thành năng lượng góp phần không chỉ cung cấp năng lượng sạch hơn mà còn giảm phát thải khí gây hiệu ứng nhà kính. Việt Nam có một tiềm năng lớn về sinh khối và phụ phẩm nông nghiệp. Các công nghệ biến sinh khối thành các loại năng lượng sinh học khác nhau đã được phát triển và áp dụng rộng rãi trên thế giới. Khí sinh học được gọi là 'cuộc cách mạng màu nâu' trong lĩnh vực năng lượng mới. Công nghệ sản xuất khí sinh học đã được nghiên cứu và áp dụng rộng rãi trên thế giới, đặc biệt là ở các nước đang phát triển với nhiệt độ khí hậu nhiệt đới phù hợp cho quá trình lên men kỵ khí các chất thải hữu cơ để sản xuất khí sinh học. Bình phản ứng tạo khí sinh học có thể được xây dựng với công suất bất kỳ, nhu cầu đầu tư nhỏ, các nguyên liệu đầu vào sẵn có. Năng lượng khí sinh học đã được sử dụng cho nhiều mục đích như thắp sáng, nấu ăn, chạy động cơ, v.v... Đây là hoạt động sản xuất khá phù hợp với nền kinh tế của các nước đang phát triển và thực sự đem lại cuộc sống văn minh hơn và tiện lợi đến các khu vực nông thôn.

This dissertation determines theoretical targets for producing biogas. Calculations were based on the relationship between the mass of substrate used (assumed to be glucose) versus the amount and composition of gas produced. Methane, hydrogen and carbon dioxide were considered as gases produced by biogas processes. The calculations undertaken to determine the production rates and environmental targets of the biogas production system were based on mass and energy balances as well as the second law of thermodynamics. These were applied to determine the limits of performance of the process. These limits are important due to the fact that they cannot be exceeded even if we genetically engineer organisms or change the equipment design or operation. Combining the results enabled us to plot an attainable region that showed the achievable composition of the gas as well as the minimum work and energy requirements for biogas production. It shows that the process is hydrogen and enthalpy (heat) limited. Furthermore the results show that a maximum of 3 moles of methane per mole of glucose are produced sustainably which in turn produces a large heat load of 142 kJ/mol of glucose. / Physics / M. Sc. (Physics)

The UK buries about 100 million tonnes of waste a year, of which 25% is municipal solid waste (refuse). The environmental impacts from gas and leachate releases are known and direct risks to health from landfill are reported. Europe has agreed to a Landfill Directive which has set targets for the stepwise reduction in biodegradable municipal waste going to landfill. The anaerobic digestion of municipal solid waste in controlled bioreactors is an area that could play an important role in overall evolution towards sustainability by recovering biogas and organic matter. Separated hydrolysis and subsequent anaerobic codigestion was demonstrated from the literature review to have the best potential for biodegradable municipal waste diverted from landfill. The rate of hydrolysis of solids wastes remains an outstanding problem. In this research, firstly the codigestion of industrial effluent (coffee wastewater), food wastes and garden wastes were investigated for their impact on hydrolysis and digestion. The results show that there were no treatability problems for coffee wastes up to 37.5% of volume feed per day at the HRT of 9 days. The results supported the view that dilute biodegradable streams such as coffee waste may improve digestion by promoting mixing. Fruit and vegetable wastes were highly biodegradable and can have a major improvement in biogas production of the whole codigestion process, whereas garden waste was not as successful as a cosubstrate, probably because of the predominant celluloses and lignocelluloses with a low biodegradability. The literature review also revealed that washing or elutriation can remove organic matter from municipal waste. This is an important hydrolytic process in which a solubilised acidic organic matter is obtained. The codigestion of refuse hydrolysate with sewage sludge was therefore studied. A control digester treating sewage sludge only was compared with an experimental reactor fed mixed refuse hydrolysate with sewage sludge. It was possible to add the solubilised hydrolysate to existing anaerobic digesters designed at a standard sludge solids loading rate without causing overloading. (Continues...).

Em muitas Estações de Tratamento de Esgoto Sanitário (ETE) no Brasil, reatores anaeróbios de manta de lodo (UASB) têm sido utilizados para tratamento de esgoto doméstico, embora apresentem baixa eficiência de remoção de demanda química de oxigênio (DQO) e alta quantidade de sólidos no efluente para esse substrato. Ademais, a digestão anaeróbia do esgoto sanitário em reatores UASB tem apresentado baixa produção do biogás, em razão da baixa concentração de matéria orgânica no afluente. No entanto, a produção de biogás pode ser aumentada pelo processo de codigestão anaeróbia, com a adição de um cossubstrato para aumentar a concentração inicial de matéria orgânica. O glicerol tem se destacado como cossubstrato de elevado potencial de geração de metano devido à sua alta concentração de matéria orgânica prontamente biodegradável. Nesse trabalho foi avaliada a possibilidade de utilização do potencial de produção de metano de reatores UASB já instalados no Brasil, por meio da adição de glicerol ao esgoto afluente. A pesquisa foi realizada em duas etapas, usando reatores UASB híbrido, com volumes de 24,75 L na primeira etapa, e 1,46 L na segunda etapa. Os reatores alimentados com esgoto sanitário e efluente de reator UASB, respectivamente, mantendo-se o tempo de detenção hidráulica (TDH) constante em 8 horas e variando-se a dosagem de glicerol afluente. A melhor fase de operação considerando eficiência de remoção de DQO, produção de metano e estabilidade do sistema biológico, foi operada com COV de 2,09 ± 0,22 kgDQO.m-3.d-1 e rendimento de metano de 75 ± 68 mLCH4.gDQOremovida-1. / In many sewage treatment plants in Brazil, up-flow sludge blanket (UASB) reactors have been used to treat domestic sewage, although they have a low removal efficiency of chemical oxygen demand (COD) and high amount of solids in the effluent for this substrate. In addition, most of the installed UASB reactors has presented small biogas production due to the low influent organic matter concentration. However, biogas production can be increased by the anaerobic codigestion process, by adding a co-substrate to increase the influent organic matter concentration. Glycerol has been highlighted as a co-substrate for high methane generation potential due to its high concentration of readily biodegradable organic matter. It is intended to evaluate the possibility of using the methane production potential of UASB reactors already installed in Brazil, through the addition of glycerol to the influent sewage. The research was conducted in two stages, using UASB hybrid reactors, with volumes of 24.75 L in the first stage, and 1.46 L in the second stage. They were fed with sanitary sewage and UASB reactor effluent, respectively, maintaining the hydraulic holding time (TDH) constant at 8 hours and varying the dosage of affluent glycerol. The best phase of operation considering COD removal efficiency, methane production and biological system stability was operated with OLR of 2.09 ± 0.22 kg CODm-3.d-1 and methane yield of 75 ± 68 mLCH4.gCODremoved-1.

N-methylmorpholine-N-oxide has shown a positive effect for the pretreatmentof lignocelluloses. Pretreatment by NMMO was developed to enhance thedigestibility of lignocellulosic biomass.Barely straw and forest residue were pretreated by N-methylmorpholine-Noxide(NMMO) prior to anaerobic digestion. The effectiveness of NMMOtreatmenton straw and forest residue was examined as well as the recycling andreuse of NMMO for the next pretreatment process. During the first experimentalseries pretreatments were performed at 90 °C for 3h and 30h, followed bydigestion of the pretreated material for 41 days. Low methane yield was found inthese experiments due to high organic loading rate. In the second series therecycling and reuse of NMMO was investigated on straw. The pretreatmentswere carried out at 90 °C for 30 hr and the recycling and reuse were performedin three times. After treatments with fresh, as well as 1, 2, 3 times recycledNMMO methane yield of 0.45, 0.42, 0.38 and 0.4 Nm3/kg VS were obtained. / Program: Masterutbildning i energi- och materialåtervinning - industriell bioteknik

Submitted by Deyse Queiroz (deysequeirozz@hotmail.com) on 2018-05-28T14:27:42Z No. of bitstreams: 1 DAMIÃO JUNIOR GOMES - DISSERTAÇÃO PPGSA PROFISSIONAL 2014..pdf: 1021631 bytes, checksum: 9d3b509edbbf52efa1db00de496731a6 (MD5) / Made available in DSpace on 2018-05-28T14:27:42Z (GMT). No. of bitstreams: 1 DAMIÃO JUNIOR GOMES - DISSERTAÇÃO PPGSA PROFISSIONAL 2014..pdf: 1021631 bytes, checksum: 9d3b509edbbf52efa1db00de496731a6 (MD5) Previous issue date: 2014-12-19 / Este estudo analisa o comportamento físico químico e microbiológico, referente à mistura de resíduos suínos com e sem adição de meios de cultura descartados, durante o processo de biodigestão anaeróbia, em biorreator tipo batelada. Montaram-se dois biorreatores, para fim de comparação, com capacidade de 50L cada. Os biorreatores foram ativados com a mesma diluição, razão de 1:2 (mistura biomassa/água, em m/m), no entanto, em um deles foi acrescidos 10% (m/m) de meios de culturas usados oriundos de um laboratório microbiológico. O monitoramento destes procedera por 56 dias, sendo coletadas alíquotas dos substratos nos tempos 0, 7, 21, 28, 35, 42, 49 e 56 dias, e submetidos à caracterização físico-química e microbiológica, bem como, verificou-se a influência dos meios de cultura na produção de biogás. Durante o desenvolvimento não se realizou nenhuma suplementação nos biodigestores. Os dados experimentais apontaram que durante o processo da biodegradação anaeróbia dos substratos, o biorreator A (com presença de meios de cultura) desempenhou melhores resultados, em relação ao biorreator B (com ausência de meios de cultura). Como por exemplo, pH’s próximos da alcalinidade, propiciando o desenvolvimento das bactérias metanogênicas, e consequentemente, maior liberação de gases. No que concerne aos valores de concentração de coliformes totais (35 ºC), termotolerantes (45 ºC) e E. coli entre os afluentes e efluentes dos biorreatores, estes foram reduzidos, principalmente no biodigestor A, em que apresentou maior concentração de macronutrientes (NPK). Por fim, pode ser inferido que os resultados foram bastante relevantes, fazendo entender que a introdução de meios de cultura potencializa as reações de biodigestão anaeróbia, favorecendo maior produção de biogás, além de incorporar ao efluente (biofertilizante) maior concentração de nutrientes. / This study analyzes the chemical and physical behavior microbiological, regarding the mixture of swine residues with and without addition of discarded culture means, during the process of anaerobic digestion, in bioreactor boat-load type. Two bioreactors were set up, for comparison end, with capacity of 50L each. The bioreactors were activated with the same dilution, reason of 1 : 2 (it mixes biomass / water, in m/m), however , in one of them was added 10 % (m/m) of means of cultures used originating from of the microbiological laboratory . The monitoring of these it had proceeded for 56 days , being collected brackets of the substrata in the times 0, 7, 21, 28 , 35, 42, 49 and 56 days, and submitted to the physiochemical characterization and microbiological, as well as, the influence of the culture means was verified in the biogas production. During the development it did not take place any supplementation in the digesters. The trial date appeared that during the process of the anaerobic biodegradation of the substrates, the bioreactor (with presence of culture means) it carried October better results, in relation to the bioreactor B (with absence of culture means). For example, close pH 's of the alkalinity , propitiating the development of the methanogenic bacteria , and consequently , larger liberation of gases. In what it concerns to the values of concentration of the total coliforms (35 ° C), thermophilic (45 ° C) and E. coli between the tributaries and effluents of the bioreactors, these were reduced, mainly in the digester, in that It presented larger macronutrient concentration (NPK ). Finally, it can be inferred which the results were quite relevant, making that to understand the introduction of culture means potentiates the reactions of anaerobic digestion , favoring larger biogas production, fouled Incorporating to the effluent (biofertilizer) larger concentration of nutritious.

The thesis analyzes the conditions for biogas in the Swedish transport sector. Biogas can contribute to the achievement of Sweden’s ambitious targets of decreased emissions of greenhouse gases and an increased share of renewables in the transport sector, a sector that encompasses the major challenges in the phase-out of fossil fuels. Biogas development has stagnated during recent years and there are several factors that have contributed to this. The use of biogas in transport has developed in niches strongly affected by policy instruments and in this thesis, the progress is understood as a policy-driven systemic transition. Biogas has (started to) become established at the regime level and has begun to replace fossil fuels. The major obstacles for continued biogas development are found to be the stagnated vehicle gas demand, the low predictability of Swedish policy instruments, and electric car development. Moreover, the current prolonged period of low oil prices has also contributed to a lack of top-down pressure. A large share of the cheap and easily accessible feedstock for conventional biogas production is already utilized and an increased use of vehicle gas could enable a commercial introduction of forest-derived methane. However, the technologies to produce forest-derived methane are still not commercial, although there are industrial actors with technological know-how. Future biogas development depends on how the policy framework develops. Policy makers should consider the dynamics of biogas as a young sociotechnical system where different system fronts develop at a varying pace. Currently the demand side is lagging behind. However, it is necessary to maintain predictable policy support throughout the entire biogas value chain, since the system fronts that lag can vary over time. The low predictability of Swedish policy instruments indicates that policy makers should exercise care in their design to create a more robust policy framework moving forward. / <p>QC 20170508</p>