Challenges surrounding energy have gained increased attention, which is not least reflected in the 2030 Agenda for Sustainable Development and the Sustainable Development Goals (SDGs). Energy issues have also become a pressing matter for most countries in the last decades. The reasons for this are not only related to the effects of the emission of greenhouse gases (GHG) from fossil fuels and their impact in climate change, but also span through other issues such as security of energy supply with geopolitical considerations and competitiveness of industry. To address these issues, a collection of public policies ranging from the international to local levels have been implemented. Sweden has historically had lower energy prices than its European counterparts, which has resulted in its industry having a relatively higher share of electricity in the total energy use by industry. The share of electricity accounts for 35% of total energy use in Swedish industry. This has led to efficiency measures being overlooked by industry, and the pulp and paper industry is by far the biggest energy user, with a share of 51% of the total energy use by industry. The variation of energy prices, and particularly electricity prices have obvious implications on the competitiveness of this sector. Production of biogas in pulp and paper mills has been gaining attention, and is now the target of an increasing number of scientific studies. The interest for this industry is not only related to security of energy supply and the environmental performance of the biogas itself, but there are also considerations regarding the biogas plant as an alternative to treat the large flows of wastewaters and other waste stream in this sector. There is an estimated biogas production potential of 1 TWh within this industry in Sweden, which accounts for 60% of the current biogas production in the country. Pulp and paper mills commonly rely on aerated biological treatment to deal with waste streams with high organic content This biological process has a high energy demand, and the integration of an anaerobic treatment, along with the use of the biogas for heat and electricity can yield a net positive energy recovery for the combined plant. This project analyses the current energy and material performance of an anaerobic biological treatment combined with an aerobic biological treatment in a recycled board mill. The anaerobic treatment is performed upstream of the aerobic one and removes most of the chemical oxygen demand of the wastewater. Energy and material balances for the plant are presented, and a comparison of the wastewater treatment plant running before and after the start-up of the biogas plant is made. The plant operation with the anaerobic digestion has shown an increased energy use of 9.4% coupled to an increased flow of wastewater of 7.7%. The average biogas production is 72 Nm³/h, which accounts for 440 kWh and is currently being flared. The introduction of AD has largely decrease the organic load in the aerobic treatment, by nearly 50%. This project ends with an optimisation model implemented with the optimisation tool reMIND to investigate potential optimisation strategies for the operation of the combined plant. The model has shown to be adequate to describe electricity use with mean error below 10%. For the biogas production, the mean error was of 16%.

Economic utilisation of biogas arising from sewage sludge is hampered by the need to remove siloxanes, which damage gas engines upon combustion. This thesis applies on-line Fourier transform infrared spectroscopy to measure siloxanes in biogas upstream and downstream of the activated carbon vessels designed to adsorb siloxanes. On-line analysis provides accurate measurement of siloxane concentrations with a detection limit below the siloxane limits set by engine manufacturers, high data intensity and timely identification of breakthrough. Cost savings of up to £0.007 kWh- 1 may be realised compared to existing grab sampling. Using on-line analysis, the performance of full-scale and bench-scale carbon vessels were measured. Full-scale carbon contactors are typically operated at Reynold’s numbers close to the boundary between the laminar and transitional regimes (Re = 40 - 55). This thesis demonstrates, at full- and bench-scale, that increasing the Reynold’s number to site the adsorption process in the transitional regime increases media capacity, by 36% in dry gas and by 400% at 80% humidity. It is postulated that the change in gas velocity profile which occurs as Reynold’s number increases reduces the resistance to siloxane transport caused by gas and water films around the carbon particles, and therefore increases the rate of the overall adsorption process. In the laminar regime (Re = 31) increasing humidity from zero to 80% led to the classical stepwise reduction in adsorption capacity observed by other researchers, caused by the increasing thickness of the water film, but in the transitional regime (Re = 73) increasing humidity had no effect as no significant water film develops. It is therefore recommended that siloxane adsorption vessels should be designed to operate at Reynold’s numbers above 55. By choosing a high aspect ratio (tall and thin) both Reynold’s number and contact time can be optimised.

The anaerobic biodegradability of food waste (FW), meat waste and FOG (fats, oils and greases) with municipal primary sewage sludge was assessed using a laboratory scale anaerobic digester and by ultimate sludge digestibility, at mesophilic conditions by varying the inoculum to feedstock ratio (1:2-1:10) and solids retention time (SRT). Preliminary analysis assessed the anaerobic digestion of food waste and meat at a biogas production over 30 days at 1000 mL and 1400 mL, respectively. The maximum methane yield was 0.18 m3/kg VS and 0.50 m3/kg VS for 1:10 in meat and FOG, respectively in 28 days with 56-61% volatile solids of destruction and first order methane generation rate of 0.15 d-1 for both meat and FOG. The optimal ratio for meat and FOG was determined to be beyond highest ratio tested (1:10), and longer SRT should be considered to investigate the impact of feedstock on methane yield. Preliminary modeling suggests that for one 1.74 MG digester, diverting just 0.6% of the food waste generated in one-third of Palm Beach County could produce enough methane to power 130-360 homes for one full month. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Research was conducted using algal biomass obtained from the surface of a secondary clarifier at Bridge City Wastewater Treatment Plant and subsequently sent through an electrochemical (EC) batch reactor at various concentrations. The first objective was to achieve maximum cell wall destruction electrochemically using the EC batch reactor and determine the optimal detention time and voltage/current relationship at which this occurred. The second objective was to subject two algal mediums to anaerobic digestion: the algal medium without electrochemical disinfection and the algal medium after disinfection. Every three days, for 12 days, total solids were measured from each apparatus to determine if cell destruction increased, decreased or did not change the consumption rate of algae by anaerobic bacteria. The consumption rate of algae is directly proportional to the production of methane, which can be used as a source of biofuel.

With an ever increasing concern for the environment, different methods of managing organic waste on dairy farms have been explored and analyzed. Anaerobic digestion has long been a popular method of managing organic waste. Its popularity stems from the potential to decrease greenhouse gases, improve air quality and provide a source of additional revenue for the farm. Problems with implementing anaerobic digestion arise from high failure rates, high start-up costs and continuous maintenance and equipment replacement. Subsidies for the initial investment and improved technology have increased the possibility of large-scale dairy farms to adopt anaerobic digestion. Due to economies of scale large-scale dairy farms are more able to adopt anaerobic digestion, but small-scale dairies struggle to finance the investment, maintain the digester system and provide sufficient organic waste to continuously feed the microorganisms inside the digester system. The increasing impact of urbanization greatly impacts the demand for anaerobic digestion on small-scale farms to mitigate the negative effects of organic waste produced by dairy farms. Dr. Conly Hansen at Utah State University suggested we use an IBR digester model to analyze the feasibility of adopting anaerobic digestion on small-scale farms. The IBR digester system is more conducive to small-scale dairies located in regions with varying temperature (i.e., Utah), and may be the solution to mitigate the negative effects of organic farm waste. Dr. Donald McMahon also suggested we analyze the potential of implementing a digester on a dairy farm that produces artisan cheese. We predicted that this would improve the feasibility due to the need to dispose of whey from the cheese production. To determine the feasibility of implementing a digester system on a small-scale dairy farm the net present value and the internal rate of return were calculated to estimate the success of the investment. These financial measures were calculated from equipment price quotes, estimations from the literature review and from using estimated annual receipts and costs for a dairy farm, artisan cheese plant and anaerobic digester system. The feasibility also depends on the success of marketing the products produced from the digester system and the farmer’s participation in incentive programs for digester systems. The products produced vary from electricity to waste disposal services, and marketing an array of diverse products and services is important to the success of the digester system. The feasibility determined by this study was estimated using generalized assumptions from various sources and should be analyzed by individual operations to determine specific farm feasibility.

<p>As a part of a large project at Norrmejerier, a biogas production plant has been constructed at Umeå Dairy. In this plant wastewater, residual milk and whey are decomposed and biogas is produced. The biogas is burned in a steam boiler. The biogas plant is designed as an anaerobic contact process, with sludge separation and recirculation by a clarifier. The fat in the substrate is treated in a separate reactor.</p><p>The purpose of this study is to evaluate the design and start-up of this biogas production plant. Further, the interaction with the contractor responsible for construction and start-up is evaluated.</p><p>The plant is generally well designed, the process conditions are suitable and the objectives are realistic. However, the seed sludge is unsuitable and the time plan is too optimistic.</p><p>At the end of the period of this study, the plant was running and all central components are performing as intended. Still, the objectives have not been reached. This is mainly attributed to the poor quality of the seed sludge.</p><p>The management of the plant and the interaction with the contractor has generally been good. Most problems that arose were of typical start-up nature. Others were due to insufficient planning or lack of communication. Further, several design flaws were identified during start-up.</p><p>Washout of sludge has been one of the most significant drawbacks during start-up. This inconvenience seems to be the result of improper seed sludge and a too hasty increase of the organic loading rate.</p> / <p>Norrmejerier har som en del av ett större projekt låtit uppföra en anläggning för biogasproduktion vid Umeå mejeri. I anläggningen, som är utformad som en anaerob kontaktprocess, behandlas avloppsvattnen och andra organiska restprodukter från mejeriet tillsammans med vassle från både Umeå och Burträsk mejeri. Fettet i substratet avskiljs och behandlas separat. Den biogas som produceras vid nedbrytningen av det organiska materialet bränns i en brännare och ånga produceras.</p><p>Syftet med den här studien är att utvärdera anläggningens design, valda processförhållanden och förfarandet under uppstarten av biogasanläggningen. Dessutom utvärderas interaktionen med den tyska entreprenör som är ansvarig för konstruktion och uppstart.</p><p>Anläggningens utformning och valda processbetingelser är passande och de uppsatta målen är rimliga. Däremot är valet av ymp olämpligt och tidsplanen för uppstarten är för optimistisk.</p><p>När denna studie avslutades var anläggningen i bruk och biogas producerades. Alla de mål för som formulerats hade dock inte uppnåtts. Ympens dåliga kvalitet är den mest bidragande orsaken till att uppstartsperioden har blivit förlängd.</p><p>Arbetet under uppstarten och samarbetet med entreprenören har generellt sett varit lyckat. Man har dock stött på många komplikationer, varav de flesta har varit av typisk uppstartsnatur. Andra har varit resultatet av bristande planering och kommunikation. En rad konstruktions- och designfel har också identifierats under uppstarten.</p><p>Slamflykt från reaktorerna har varit det mest betydande problemet hos den biologiska processen. Denna förlust av slam förmodas bero på olämpligt val av ymp och en alltför hastig ökning av den organiska belastningen i reaktorerna under uppstarten.</p>

<p>Two species of emergent macrophytes, Typha latifolia (common cattail) and Phalaris arundinacea (reed canary grass) were evaluated as substrates for biogas production. The specific methane yield for each plant was obtained by batch wise anaerobic digestion in 300-mL bottles. Three different pretreatments were evaluated for increased biogas production; mechanical milling, alkaline treatment with lime and fungal degradation with Pleurotus ostreatus (oyseter mushroom).The methane yield for Typha latifolia and Phalaris arundinacea was determined to 300 and 323mL methane per g VS, respectively. There was no statistical difference in methane yield between the two species. Milling pretreatment increased the biogas yield with 16 % by average compared to untreated plant. Alkaline pretreatment with lime increased the biogas yield with 27 % at roomtemp. and 22 % at 55 °C. The fungal pretreatment decreased the biogas production by 20 % and is probably not suitable for this kind of substrate.The results showed that emergent macrophytes have a biogas yield similar to other plants already tested (grasses) and commonly used (pasture crops) in large scale reactors. However, emergent macrophytes and grasses cause mechanical problems in a reactor due to their structure. Probably some kind of milling must be done to decrease the fiber length of the emergent macrophytes. The costs for harvest, transport, handling and possible pretreatment of the emergent macrophytes have to be estimated and included in the overall cost calculations. This can tell if emergent macrophytes should be used as a substrate for biogas production.</p>

The concept of Sustainable Development is an interdisciplinary science. Transcending various academic fields the concept shows paths how the needs of present and future generations can be met through economic development on a finite natural resource base. Global warming and rising sea levels are just two of a series of phenomena that are directly attributable to human-induced increasing greenhouse gas levels in the atmosphere as consequence of the combustion of fossil fuels. Therefore, reducing greenhouse gas emissions through the use of renewable resources such as bioenergy are of vital importance if detrimental environmental effects are to be mitigated. The production of biogas in a decentralized context is receiving much attention in Germany as a means to reduce greenhouse gases and to counteract correlated negative environmental effects, respectively. In addition, socio-economic benefits such as local employment creation have the potential to empower rural communities. Subsidised by the German Renewable Sources Act and its various remuneration schemes, two 500kWel CHP biogas plants are producing through anaerobic digestion of maize silage and manure electricity and heat in the East German village Bollewick, which is the case study. The sustainability of this decentralized system is analyzed by applying a set of indicators. Socio-economic benefits for the population, economic efficiency of the digestion process and impacts of substrate costs on the profitability, greenhouse gas emissions due to land use change and biodiversity loss being some of these indicators. The thesis concludes that none of the sustainability indicators are sufficiently fulfilled in Bollewick. Especially the cultivation of the energy crop maize has despite crop rotations immense negative environmental effects. Therefore, the decentralized biogas production in the rurally coined village Bollewick is not sustainable.

Technologies for pretreatment of waste activated sludges (WAS) prior to digestion are of increasing interest to wastewater treatment utilities because of their promise for improving sludge digestibility and reducing the mass of biosolids remaining after digestion. While there has been considerable study of pretreatment processes, a common approach to describing the impact of pretreatments on sludge biodegradability has not been developed. The overall objective of this study was to develop protocols that can be employed to characterize the impact of pretreatment processes on WAS digestion. Sonication and ozonation were employed as models of physical and chemical pretreatment technologies respectively. A range of physical, chemical and biological responses were evaluated to assess the impact of pretreatment on WAS properties as well as digestibility. WAS samples that were generated over a range of solids residence times (SRTs) under controlled operating conditions were employed to facilitate an assessment of the interaction between pretreatment and WAS properties on digestibility. The VS, COD and soluble TKN responses indicated that a significant fraction of the WAS solids were solublized by sonication and ozonation, however, it appeared that the types of materials which were solublized was affected by the SRT at which the WAS was generated and the level of pretreatment. The results indicated that the impact of pretreatment on biodegradability of WAS was not described by solublization values exclusively without considering the SRT of the sludge and the level and type of pretreatment. A higher level of proteinaceous materials was preferentially solublized as the result of pretreatment. Respirometry revealed that both sonication and ozonation substantially reduced the viable heterotrophs in the sludge and modestly increased the readily biodegradable fraction of COD. The ultimate yields of CH4 and NH4 in BMP tests and VFAs in BAP tests revealed that pretreatment marginally increased the ultimate digestibility of the sludges. Only a high dose of ozonation substantially increased the digestibility of the 15 day SRT sludge. However, both sonication and ozonation substantially increased the rate of hydrolysis which is typically the rate limiting process in WAS digestion. The BMP test was not a useful test to evaluate the rate of methane generation due to inhibition of methanogens in the early days of BMP test for pretreated sludges. The comparison between VFA and ammonia responses in day 10 of BAP test and ultimate values of these responses after 60 days in BMP test revealed linear relationships between these responses. According to these relationships, a set of models were introduced in this study. The models can be employed to predict the ultimate methane and ammonia generation using soluble COD, VFA or ammonia responses in day 10 of BAP tests. The BAP test was determined to be a shorter test (10 days) than the BMP (55 to 60 days) test and could provide information on the rates of hydrolysis and acidification/ammonification processes. Characterization of biodegradable and non-biodegradable material in WAS samples was conducted using a simplified ADM1 model. The characterization also revealed that proteins are a substantial fraction of biodegradable materials. The estimated ammonia, VFA and methane values from the stoichiometric model were similar to the corresponding values from the experiments. This supported the validity of the simplified model for all sludges employed in this study.

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