In der Landwirtschaft spielen Gerüche und die Vermeidung von Geruchsbelästigungen für die Nachbarschaft eine entscheidende Rolle. Mit dem Wandel vom Landwirt zum Energiewirt kommen dabei auch neue Geruchsemittenten wie die Blockheizkraftwerke (BHKW) mit ihren Abgasen hinzu. Der vorliegende Abschlussbericht wertet ein Messprogramm bezüglich Geruchsemissionen aus Abgasen von BHKW-Motoren aus. Insbesondere betrifft das Motoren, die Biogas einsetzen, welches aus landwirtschaftlichen Substraten gewonnen wurde. Es werden auf Grund der an mehreren Motoren vorgenommenen Messungen Geruchsemissionsfaktoren vorgeschlagen. Auf Grund der aktuellen Diskussion um die karzinogene Wirkung von Formaldehyd, werden zusätzlich die parallel dazu ermittelten Formaldehydemissionen aus den BHKW-Motoren ausgewertet.

Abgasemissionsmessungen an Biogasanlagen-BHKW zeigten Überschreitungen des gemäß TA Luft festgelegten Formaldehydgrenzwertes. Ursache sind unvollständig ablaufende Verbrennungsprozesse. Die Biogasqualität, die Motorabstimmung und die Motorenwartung sind dabei von entscheidender Bedeutung. Für die vorliegende Schriftenreihe wurden vorhandene Messergebnisse von 97 BHKW im Hinblick auf mögliche Einflüsse und Korrelationen zwischen Biogaserzeugungsprozessen, Methangehalt, BHKW-Spezifikationen, Motorprozesse und der Wartung auf die Bildung von Formaldehyd untersucht. In die Auswertung gingen neben vorhandenen Messberichten, Datenblätter von sächsischen Anlagenbetreibern und Messergebnisse aus Thüringen ein. Im Ergebnis aller Untersuchungen stellt die Studie sechs Maßnahmenvorschläge zur Minderung der Formaldehydemissionen aus Biogas-BHKW vor.

<p>During the 19-century a global warming has been observed, which includes increases in global air and ocean temperatures, widespread melting of ice and snow, and rising global sea level. There is a clear connection between emissions of greenhouse gases caused by the human and the increase in temperature. Climatic changes caused by global warming can be stopped trough decreased emission of fossil fuels, for example by an increased use of biogas. Biogas is a renewable energy source which is produced through anaerobic (oxygen free) digestion of organic material. The gas is a mixture of methane (CH4) and carbon dioxide (CO2) and can be among others used as fuel in vehicles. Greengas is biogas produced from grains.</p><p>The aim with this master’s thesis was to investigate a two-stage process for digestion of a rest by product from ethanol production, called drankvatten. Laboratory experiments were carried out with two process sets, each with two continues stirred tank reactors (CSTR). The process consisted of a thermophilic (55ºC) reactor as the first step in which the substrate was added. Afterwards there was a mesophilic (38ºC) second reactor in which the material from the first reactor was further degraded to produce more gas. The results were intended to be used for an assessment of whether a two-stage process is more efficient then a single-stage process in a full-scale production facility. One of the reasons to have a thermophilic first reactor is that the material has an average temperature around 80 ºC when it arrives to the facility today.</p><p>It was proved that a two-stage process with this type of substrate generated a higher gas production but the improvements weren’t big enough to motivate a reconstruction of the facility into a two-stage process. The thermophilic process was stable with a retention time of 15 days and a loading rate of 6 g VS/(l•dygn). This retention time was the shortest which was achieved during that loading rate. During earlier mesophilic experiments a higher loading rate was achieved however the used retention time was longer. On the basis of this work no conclusions could be drawn whether a thermophilic process could withstand a higher loading rate then a mesophilic one. Longer adaptation times is probably needed to reach higher loading rates. In this work it also has been studied if it’s necessary to have continues mixing in the biogas reactors. The conclusion of this experiment is that continues mixing isn’t necessary, which results in less mixing and in that way less energy costs.</p>

<p>                      In this study, the bioconversion of manure and silage to biogas by an anaerobic digestion process in batch reactors was studied. Biogas is a valuable alternative energy source, mainly in rural areas. The main aim for the environment is to use biogas as a fuel instead of crude oil or natural gas. In this study, two different parameters were studied to observe the changes in methane productivity. The first three reactors were shaken once per week and the following three reactors were shaken 5 times per week. The results showed that mixing has no major effect on the methane production yield. In the second six reactors a mixture of 1% and 3% silage was added and the results were recorded. When the data from the reactors with just manure was compared to the reactors with 1% and 3% silage, it was seen that the silage increased the production rate and total gas produced. The process stabilization took a long time for digestion with the 3% silage possibly caused by release of too much fatty acids.</p>

First generation bioethanol generated from feedstocks is a sustainable alternative to fossil fuels, and the demand for fuel ethanol has promoted studies on the use of the grain as feedstock. This thesis describes various process designs and the economic feasibility for producing the main product ethanol and other by-products such as Biogas and DDGS (Distillers Dried Grains with Solubles) from the grain. The techno-economic analysis was performed by the data provided by Agroetanol industry, located in Norrköping, Sweden. The key target of this simulation work was to evaluate the influence of several process designs and the main production factors on the ethanol production process, in terms of energy efficiency, ethanol production cost and plant profitability. The main aim of this work was to simulate the current industrial process and to develop novel alternative retrofits by integrating new technologies and for investigating the effects on the plant profitability. In the base case, the cost sensitivity analysis was carried out on the grain buying price, ethanol and DDGS selling price. Along with the cost sensitivity analysis, the capacity sensitivity analysis was performed on the base case model to check the influence of different capacities on the plant profitability. While coming to the study of developing alternative retrofits, the three retrofits were developed on the base case process and they are as following: Retrofit 1) modifying the distillation and dehydration section of the base case retrofit (current process in Agroetanol), Retrofit 2) checking the impact of ethanol concentration on technical and economic aspects of the plant and Retrofit 3) installing the biogas digester.The modelling effort resulted in developing the base case model with an ethanol production rate of 41,985 ton/ year. The capital cost of the base case process was calculated to be at 68.85 million USD and the aspen economic analyzer calculated the product value of the ethanol and DDGS as 0.87 USD/litre and 0.37 USD/kg, respectively. Through cost sensitivity analysis results, it is identified that the ethanol selling price and the grain buying price have significant effects on the plant economy and it is confirmed that they are the main factors playing on the plant profitability in the base case model.The results of the alternative retrofits clearly demonstrate the importance of higher ethanol tolerant strains in ethanol production, which showed a less payback period compared to the base case. The payback periods of all the cases are showing the following patterns from the least to the highest: Retrofit 2 (17%) &gt; Base case &gt; Retrofit 3 &gt; Retrofit 2 (4%) &gt; Retrofit 1.Further retrofitting analysis results also suggested that using the stillage for biogas production will help in reducing the energy costs of the plant. The energy consumption of all the retrofits in ascending manner is as follows: Retrofit 3 &gt; Retrofit 2 (17%) &gt; Base case &gt; Retrofit 1 &gt; Retrofit 2 (4%). The energy usage result comparison of all the cases shows that, in third retrofit the overall energy consumption is decreased by 40% than the base case model.

Today 88 % of the world energy comes from fossil fuels. Greenhouse gas emissions are increasing and the fossil fuels energy sources will decrease at some point. Other alternatives must be found, to substitute and lower the usage of fossil fuels. Biogas is one of these other options. It is a versatile fossil free fuel that can be used for heat, power and fuel for vehicles. Many different substrates have been used for biogas production over the years, and now algae are examined as a substrate. Algae have advantages over the former substrates used for biogas production. Laboratory experiments were conducted to examine the co-digestion potential of algae and biosludge, which is a rest product from a wastewater treatment plant at a pulp and paper mill. The profitability aspect of using algae and biosludge for biogas production has been examined as well.The result shows that unmixed algae were the highest methane producing substrate, which produced a maximum of 203,5 Nml/g VS. An interesting result was that both algae and biosludge separately produced more methane gas than the mixtures. The profitability aspect of the thesis showed that it is not profitable to use algae primarily for biogas production, based on the conditions of today.

Biogas, composed principally of methane, has limited use in energy generation due to the presence of hydrogen sulphide (H2S). Biogas cannot be burned directly in an engine as H2S present causes corrosion in the reaction chamber. There currently exist various technologies for the removal of H2S from a gas stream, but most are chemically based, expensive, and are limited in use. The purpose of this study was to determine a biogas purification technique suitable for a small scale farm application; including using a technology inexpensive, efficient, robust and easy to operate. As such, biofiltration was investigated for H2S removal from biogas. Factors considered in the design of the biofiltration system included the source and conditioning of inoculum, type of packing material, and general operating conditions including inlet gas flow rate and H2S loading rate to the biofilter. Activated sludge conditioned in A. ferrooxidans media was an effective inoculum source. This was tested for growth support compatibility with gravel packing material, to be used in the biofilter. The inoculated packing material was loaded into the biofilter initially during start-up and acclimatization. In this study, synthetic biogas (49.9%volCH4, 49.9%volCO2, 2000ppmv H2S) mixed with air (totalling 4%vol O2) was added at 5-10L/hr to a biofilter of 0.4L gravel packing inoculated with conditioned activated sludge. Baseline H2S removal studies in a non-inoculated biofilter were performed with anticipated operating conditions, including an inlet gas stream at 7.5L/h (25oC, 1atm), resulting in 31-56% H2S removal. A factorial test performed found that air content in the inlet gas stream was the significant factor affecting the removal of H2S in the non-inoculated biofilter. Operation of the biofilter with biogas was done for 61 days, including 41 days for start-up and acclimatization and 20 days of H2S loading tests. Start-up and acclimatization with biogas resulted in complete H2S removal after 2 days, with an average overall H2S removal of 98.1%±2.9 std deviation over 34 days. Loading tests performed on the system ranged 5-12.4L/h (25oC, 1atm), with a loading rate of 27.8 to 69.5gH2S/m3h of filter bed. Throughout this test the average H2S removal rate was 98.9%±2.1 std deviation over 20 days. Although complete H2S breakthrough studies were not performed, these results indicate that biofiltration is a promising technology for H2S removal from biogas in a small scale application.

The Swedish production of biogas was 1,5 TWh 2011. About half of the production was used as vehicle fuels. The cost for upgrading biogas depends on the size of the biogas plant and its gas production. If the gas flow is low the cost will be high. However, further development of existing upgrading technologies or development of new ones, have good potential to decrease the upgrading cost for small scale biogas plants. The aim of this master thesis is to investigate a new technology for upgrading biogas to vehicle fuel standards. The investigated technology is based on the carbonation principle, which means that carbon dioxide is fixed by calcium oxide under the formation of calcite. Wood ash, which is rich of calcium oxide, has been used for capturing carbon dioxide in biogas during the lab-scale tests. During the tests the composition of the ingoing biogas was 35 % carbon dioxide and 65 % methane. When the gas passes through the ash bed the carbon dioxide was fixed by the ash and that is the reason why the methane yields is about 95-100 % in the outgoing gas. Three different types of wood ashes have been investigated. They originate from combustion of wood pellets respectively different assortment of wood chips. Ash from combustion of wood pellets shows the best ability to capture carbon dioxide, 0,24 g CO 2/g dry ash. A Proposal on a system design has been developed based on the results from the lab-scale tests. Simplified calculations showed that the upgrading cost for the proposed system was 0,24 kr/kWh. That is about half of the cost compared to the available small-scale upgrading technologies on the market. The calculations were based on a biogas plant with the annual gas production of 1 GWh, which is a typical size for a Swedish farm-scale biogas plant

Each year, the coffee machines at Ericsson in Kista produce around 100 tons of ground coffee waste. The companies Coor Service Management, Löfbergs Lila and Selecta are all responsible for different stages in the logistical chain in delivering coffee and, together with Ericsson, they want to increase their environmental benefit. The plan is to produce biogas through anaerobic digestion instead of incinerating the coffee waste in a heating plant. The results are to be presented as different business cases in which different biogas plants are compared with the reference case (heating plant), comparing costs and environmental impacts. There are two major environmental benefits from producing biogas; reduced carbon dioxide emissions from when fossile fule is replaced by carbon neutral biogas, and reduced emissions from returning digestate from the bio reactor to farmland instead of using industrial fertelizer. In order to determine the biogas potential in coffee waste, a couple of properties had to be determined in a laboratory. Properties such as the dry substance content, heating value, moisture content and ash content. The results show that 100 tons coffee waste could produce around 16 500 Nm3 biogas which would contain 163 MWh. The biogas reactor and upgrade plant both need energy gas to function and uses around 14 MWh of the produced gas. In the end, the resulting upgraded biogas contains 149 MWh energy. Such an amount of gas can replace 15,1 m3 of diesel and thus reduce carbon dioxide emissions by 39,4 ton. The emissions from running the reactor and upgrade plant, combined with methane leakage amounts to 4,8 ton carbon dioxide. All of the biogas plants that were examined returns digestate and nutrients to farmlands which reduces the need for industrial fertelizer. The production of fertelizer uses alot of energy, and by returning digestate a reduction of 58 GJ energy and 3 ton CO2 can be achieved. This is not the case with the heat plant which instead has to place some of its produced ashes in landfills. If the exergy content in the biogas is compared to that of the heat it shows that there is a point to making gas instead of incinerating the waste. The biogas has about 50 % higher exergy content than the heat has and therefore it is possible to utilize the substrate more efficiently. Transporting coffee waste from Ericsson to different biogas plants will result in increased carbon dioxide emissions. The three plants investigated in this thesis are Henriksdals sewage treatment plant, the Himmerfjärd plant and Uppsala biogas plant. For each plant, drivning distance, pre treatment requirements of the coffee waste, and related costs were determined. Using methods from the Network for transportation and enviroment, the emissions for each case were calculated. The results show that the Henriksdal case will increase carbon dioxide emissions by two tons per year, and the other cases will increase emissions by four tons. The result from combining laboratory work, simulations and calculations show that the case where Henriksdal recives the coffee waste will reduce carbon dioxide emissions by 15,1 ton at a cost of 72 000 kr per year. The case with the Himmerfjärd plant will reduce emissions by 13,8 ton at a cost of 74 000 kr per year. The final case with Uppsala biogas plant will reduce emissions by 13,7 ton at the cost of 107 000 kr per year. And thus there are environmental benefits from producing biogas from the coffee waste, but they do come at a cost.

Access to modern energy is essential to achieve sustainable development and poverty reduction. However, with about 321 kWh per capita, Rwanda is ranked among the countries that have a lower consumption of primary energy in the world. More than 86 percent of its total energy comes from the traditional biomass energy such as forests, agricultural residues and by-products from crops that lead to environmental degradation and ecological imbalance and negative impacts on human health as well. In addition, only 301,500 ha of forest are available for fuel wood and other uses such as construction for a total population of 10.5 million. Therefore, decentralized energy sources in small-scale are presented to improve access to "appropriate" energy, which are beneficial to human health and environmental perspectives. The anaerobic digestion of biomass, popularly called “biogas”, is one of the appropriate energy technologies for cooking and/or lighting purposes (both in households and in institutions), which receives special attention in Rwanda since 2007. Three main objectives of this study were to assess the current biogas sector in Rwanda, to make projections of biogas development by 2020 and finally to analyze the socio-economic and environment benefits of biogas use to the Rwandan community. The fieldwork conducted in two districts per province in addition to services that are in the capital, was based on the structured questionnaire, discussion with key people and see the state of biogas built. Therefore, in this study we used the "Appropriate Energy Model” to measure the degree of biogas dissemination, which educates for “geographical, institutional, entrepreneurial and socio-cultural “aspects. The results showed that the temperature conditions in the country are generally conducive to the operation of a digester. However, the drought period between June and August, water scarcity in some regions and a low potential for digester feeding impede the propagation of biogas to a large number of people.  The Rwandan entrepreneurs do not face institutional barriers to start-up biogas companies since the bureaucratic system in registration of a company is transparent. The installation costs of biogas plant are so high that they hamper the dissemination of biogas; however biogas technology does not contradict the socio-cultural conditions of Rwandans. Based on projections of potential biogas in Rwanda in 2020, following three scenarios for 2020 biogas development were identified: 1,135,000 biogas plants can be built in 2020 by considering a global basis the potential biogas available If 70% of the population will live in grouped settlements in 2020, 70% of Rwandan households will use biogas if additional resources as livestock and subsidies were provided to the poor families. Only 10% of the population (251,000households) will be eligible for biogas installation Reducing the consumption of firewood after biogas operation provides annual coverage of approximately 0.306 ha of forest area per household. Therefore, each household biogas would reduce annual GHG emissions of about 4.1 tonnes of CO2 and could possibly lead to Rwanda an annual income of about USD 21 due to the reduction of CO2 emissions in a hypothetical rate USD 5 per ton of CO2 if registered under the CDM.