<p>A growing interest for the climate and the environment has led to an increased interest forenvironmentally friendly and renewable energy sources, such as biogas. Planning new biogasplants requires a decision basis including facts about approximate amounts of biogas possibleto produce at the plant. The purpose of this thesis is to develop a model that calculates theapproximate biogas and digestate production from a planned or existing biogas plant.Developing the model required a literature review and studies of calculations concerningbiogas and digestate production performed by WSP Sweden AB. As a complement to themodel development, facts about substrates for biogas production were compiled through aliterature review. In addition the methane potential from selected materials was determined bybatch experiments. Two full scale experiments were also studied to compare results from themodel with results from full scale biogas production.This thesis work resulted in a model for calculating biogas, methane and digestate production,including calculations of nutrient content in the digestate, from a given amount of substrate.The model was constructed in Microsoft Office Excel and complemented by a chart,containing template facts for different biogas substrates. The template facts, together with themodel, make it possible to perform calculations of biogas production before any up-to-dateinvestigations are made of the biogas substrate.Comparing results of biogas production calculated with the model with values of biogasproduction from a full scale biogas plant showed that the calculated values where within, orjust outside, the standard deviation of the full scale values. The calculated values from themodel also turned out to be in general lower than the full scale values, which indicate that themodel doesn’t overestimate the biogas production. However, the uncertainties of the values inthe template facts chart and the simplifications made in the model both contribute in tomaking the model calculations somewhat uncertain. The calculations should thus only be seenas an indication of the possible biogas production from planned or existing biogas plants andnot as an exact prediction.</p>

<p>In order to make the biogas plant at Sobacken located 8 km west of Borås more</p><p>profitable you must become aware of flows at the plant. This not only concerning the</p><p>incoming waste to the plant but also the use of energy. Since the rebuilding in 2005 of</p><p>the plant there has been no follow up concerning the energy use. This thesis is meant</p><p>to clarify the use of electricity and heat at the plant. The work determining the use of</p><p>energy at Sobacken biogas plant has been done by collecting data from documentation</p><p>from the builder Läckeby Water but also by obtaining information from the computer</p><p>systems and frequency converters. The results of the study and its calculations shows</p><p>that the plant uses approximately 3,2 GWh of electricity per year and 3,1 GWh of</p><p>biogas, produced at the plant for heating per year. The production of biogas is</p><p>corresponding to 17,7 Gwh per year of which 14,1 GWh reaches the distribution</p><p>network. The biogas is used by the city buses but could also be used by private car</p><p>owners in Borås refuelling at the newly built tank station at Åhaga. The study does</p><p>not only show that the process consumes 6,3 Gwh per year to produce 14,1 Gwh</p><p>per year, there is also a large amount of energy being released in secondary energy</p><p>flows. These energy flows consists mostly by heat form the cooling system which</p><p>could potentially be recovered by heat exchangers and used to heat the process.</p>

Biogasprocessen är en komplex anaerob nedbrytningskedja där olika mikroorganismer är inblandade. Vanligast är att biogas produceras i mesofil rötning (cirka 38 oC), men även termofil rötning används (&gt; 50 oC). Svensk Biogas i Norrköping använder återstoden av etanoldestillationen hos en närliggande etanolproducent (drankvatten) som substrat. Substratets höga temperatur vid leverans motiverar termofilt rötningsförsök av drankvatten. Försöket genomfördes i 55 oC med två kontinuerligt omrörda tankreaktorer (CSTR) och en termofil ymp. Biogasproduktion av drankvatten undersöktes. Sätt att hantera och motverka höga ammoniumhalter, samt effekter av näringslösningstillsats undersöktes. Det tog cirka 30 dagar för ympen att acceptera det nya substratet och då hade tillsats av processhjälpmedel KMB1 samt järnklorid använts. Reaktorerna kunde belastas med 3 g VS / (L • dygn) (VS, volatile solids, glödförlust). Den specifika gasproduktionen var 0,6 – 0,7 L / g VS och metanhalten ungefär 45 %. Höga ammoniumhalter motverkades genom förkortning av uppehållstiden. Under en period tillsattes nickelklorid i en av reaktorerna och under denna period hade reaktorn med nickelkloridtillsats något bättre specifik gasproduktion jämfört med reaktorn där ingen nickelklorid tillsattes. Drankvatten kan rötas under termofila förhållanden. För att temperaturförändring vid biogasanläggningen i Norrköping ska var ekonomiskt försvarbart måste processen klara högre belastning.

Production of biogas through anaerobic digestion (AD) from the organic fraction of minucipal solid waste (OFMSW) was compared to incineration of the waste. At the moment, almost all of the OFMSW in Singapore is incinerated. Three different scales of biogas plants were compared to incineration: one large-scale biogas plant that can treat half of all OFMSW in Singapore; one medium- scale biogas plant about 15 times smaller than the large one; and one small-scale biogas plant that can treat waste from e.g. a shopping centre or food centre. Two alternatives for utilization of the biogas were also compared, generation of electricity and the use of the biogas in heavy vehicles. The combination of the different scales and the different utilization gives the six different scenarios. By using life cycle assessment (LCA) the different scenarios were compared in terms of global warming potential (GWP), acidification, eutrophication, energy use and land use. The results show that biogas production creates less environmental impact than incineration. The use of the gas as a vehicle fuel creates a bigger decrease of GWP, acidification and eutrophication than when using the gas for electricity generation. The prevention of leakage of biogas during production and upgrading is crucial for the environmental impact on GWP. A leakage of only a few percent of the produced gas will lead to a loss of all the gain in saved GHG-emissions.

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.

This thesis examines the characteristics of a community that positively influence the success of a community renewable energy project. As the first stage of a two-stage inductive research process, a review of relevant bodies of literature results in the development of 5 characteristics of a community that?based on the literature?have the potential to positively affect the success of a community renewable energy project. Those characteristics are: a large stock of social capital and a strong sense of community; effective leadership from local government and local organizations; past experience with cooperation and innovation, and access to technical resources; economic perceptions and realities; and biophysical resources appropriate to the technologies being used. <br /><br /> Following an examination of how these characteristics might manifest themselves in a Chinese context, the five characteristics were used as a heuristic to guide the second stage of the research process: a case study of a community biogas project in Cang Dong Village in China's Hainan province. This case study suggests that the success of Cang Dong's biogas project was directly influenced by four main factors: effective leadership from local government, access to technical resources, economic perceptions and realities, and biophysical resources appropriate to the technologies being used. The impact of the community's past experience with innovation & cooperation and their strong stock of social capital were more ambiguous; although the community had past experience with cooperative and innovative projects, along with a high stock of social capital, a direct link between these characteristics and the success of the biogas project could not be conclusively determined. <br /><br /> As a result of the case study, this thesis concludes with an outline of a general framework that could be used to evaluate the suitability of a community for a community renewable energy project. This outline is presented acknowledging the exploratory nature of this research and follows the need for more research on this topic.

A growing interest for the climate and the environment has led to an increased interest forenvironmentally friendly and renewable energy sources, such as biogas. Planning new biogasplants requires a decision basis including facts about approximate amounts of biogas possibleto produce at the plant. The purpose of this thesis is to develop a model that calculates theapproximate biogas and digestate production from a planned or existing biogas plant.Developing the model required a literature review and studies of calculations concerningbiogas and digestate production performed by WSP Sweden AB. As a complement to themodel development, facts about substrates for biogas production were compiled through aliterature review. In addition the methane potential from selected materials was determined bybatch experiments. Two full scale experiments were also studied to compare results from themodel with results from full scale biogas production.This thesis work resulted in a model for calculating biogas, methane and digestate production,including calculations of nutrient content in the digestate, from a given amount of substrate.The model was constructed in Microsoft Office Excel and complemented by a chart,containing template facts for different biogas substrates. The template facts, together with themodel, make it possible to perform calculations of biogas production before any up-to-dateinvestigations are made of the biogas substrate.Comparing results of biogas production calculated with the model with values of biogasproduction from a full scale biogas plant showed that the calculated values where within, orjust outside, the standard deviation of the full scale values. The calculated values from themodel also turned out to be in general lower than the full scale values, which indicate that themodel doesn’t overestimate the biogas production. However, the uncertainties of the values inthe template facts chart and the simplifications made in the model both contribute in tomaking the model calculations somewhat uncertain. The calculations should thus only be seenas an indication of the possible biogas production from planned or existing biogas plants andnot as an exact prediction.

In order to make the biogas plant at Sobacken located 8 km west of Borås more profitable you must become aware of flows at the plant. This not only concerning the incoming waste to the plant but also the use of energy. Since the rebuilding in 2005 of the plant there has been no follow up concerning the energy use. This thesis is meant to clarify the use of electricity and heat at the plant. The work determining the use of energy at Sobacken biogas plant has been done by collecting data from documentation from the builder Läckeby Water but also by obtaining information from the computer systems and frequency converters. The results of the study and its calculations shows that the plant uses approximately 3,2 GWh of electricity per year and 3,1 GWh of biogas, produced at the plant for heating per year. The production of biogas is corresponding to 17,7 Gwh per year of which 14,1 GWh reaches the distribution network. The biogas is used by the city buses but could also be used by private car owners in Borås refuelling at the newly built tank station at Åhaga. The study does not only show that the process consumes 6,3 Gwh per year to produce 14,1 Gwh per year, there is also a large amount of energy being released in secondary energy flows. These energy flows consists mostly by heat form the cooling system which could potentially be recovered by heat exchangers and used to heat the process.

Detta arbete innefattar planering, uppbyggnad och inkörning av teströtningsanläggning för biogasproduktion, bestående av batch- och tankreaktorsystem. Arbetet inbegriper även utförandet av experiment, på batchreaktorsystem, som syftar till att ge en första inblick och vägledning för vidare studier kring optimering av processen med inriktning på tillsats av kolkälla och justering av kvoten mellan kol och kväve. Utifrån de resultat som erhållits vid försök på batchreaktorsystemet observerades en positiv effekt, gällande ökad nedbrytning av VFA, vid tillsats av glukos till systemet. Igångkörning av tankreaktorsystemet gav erfarenheter gällande handhavandet av anläggningen samt driftsäkerheten, vad gäller t.ex. återstart efter strömavbrott, loggning av gasflödesdata, pålitlig substratdosering och substratuttag utan syreläckage in i systemet.

Stockholm Water is a water and sewage company with Henriksdal as one of two wastewater treatment plants (WWTPs). At Henriksdal wastewater sludge generated in the wastewater treatment process is digested which generate biogas; a mixture of mainly methane and carbon dioxide. If purified to methane content of 96 - 98 % this gas is called biomethane. Biogasmax is a project aiming to reduce the use of fossile fuels in Europe by providing that biogas is a good technical, economical and environmental alternative as vehicle fuel. The specific aim for Stockholm Water is to increase the biogas production at the existing plant in Henriksdal. Enzymatic treatment of wastewater sludge is an innovative technique earlier proofed to increase the biogas production from wastewater sludge with up to 60 %. The enzyme activity is in turn proven to significantly increase in the presence of a cation binding agent. One aim with this thesis was to investigate if the sludge from Henriksdal wastewater treatment process at all is affected of enzymatic treatment in presence of a cation binding agent since this has shown to have some significance. The chemical oxygen demand (COD) was measured in the liquid phase of sludge after treatment and used as a measurement of treatment effect. Another aim of this thesis was to look into the possibility to increase the methane production from sludge at Henriksdal WWTP. This was investigated through batch laboratory digestion tests. The sludge from Henriksdal WWTP was shown to be a good substrate for the enzymes added. COD in the liquid phase was increased with 17 – 32 % depending on the dose of enzymes and sodium citrate added. Digestion of sludge with a total addition of 18.6 mg enzymes per 1 g total solids (TS) and a concentration of 5 mM sodium citrate increased the methane production with almost 18 % compared to untreated sludge. This equals an increase of 18.3 % when converted to represent a totally blended and continuous digestion chamber at Henriksdal WWTP. The increased methane production also results in a sludge reduction out from the digestion chambers. The increased methane production and sludge reduction though does not fulfil the increased costs for the enzymes and sodium citrate applied. These doses must be decreased and the costs for both enzymes and sodium citrate must be reduced for this technique to be economically feasible in a full scale operation.