Lünen is a town with around 86,000 inhabitants in North Rhine-Westphalia , Germany . It is located north of Dortmund , on both banks of the River Lippe . It is the largest town of the Unna district and part of the Ruhr Area .
104-422: In 2009 a biogas plant was built to provide electric power to the city. Lünen is the first city in the world to receive electricity via public utility companies that is generated on the base of animal waste. The plant produces up to 6.6 MW, supplying 26,000 homes with heat and electricity. Structure Museum Theatre The current mayor of Lünen is independent politician Jürgen Kleine-Frauns since 2015; he
208-451: A CHP gas engine , where the waste heat from the engine is conveniently used for heating the digester; cooking; space heating; water heating ; and process heating. If compressed, it can replace compressed natural gas for use in vehicles, where it can fuel an internal combustion engine or fuel cells and is a much more effective displacer of carbon dioxide than the normal use in on-site CHP plants. Raw biogas produced from digestion
312-567: A fuel ; it can be used in fuel cells and for heating purpose, such as in cooking. It can also be used in a gas engine to convert the energy in the gas into electricity and heat. After removal of carbon dioxide and hydrogen sulfide it can be compressed in the same way as natural gas and used to power motor vehicles . In the United Kingdom, for example, biogas is estimated to have the potential to replace around 17% of vehicle fuel. It qualifies for renewable energy subsidies in some parts of
416-449: A 1000-litre digester using psychrophiles harvested from "mud from a frozen lake in Alaska" has produced 200–300 liters of methane per day, about 20–30% of the output from digesters in warmer climates. The air pollution produced by biogas is similar to that of natural gas as when methane (a major constituent of biogas) is ignited for its usage as an energy source, Carbon dioxide
520-457: A Nut detailed the biogas production process from pig manure and showed how it fueled a custom-adapted combustion engine. In 2007, an estimated 12,000 vehicles were being fueled with upgraded biogas worldwide, mostly in Europe. Biogas is part of the wet gas and condensing gas (or air) category that includes mist or fog in the gas stream. The mist or fog is predominately water vapor that condenses on
624-405: A benefit to using thermophilic temperatures instead of mesophilic. Additional pre-treatment can be used to reduce the necessary retention time to produce biogas. For example, certain processes shred the substrates to increase the surface area or use a thermal pretreatment stage (such as pasteurisation) to significantly enhance the biogas output. The pasteurisation process can also be used to reduce
728-484: A biogas with a elevated methane content. The produced carbon dioxide in biogas dissolves more into the water phase under pressure then methane does. Hence the produced biogas is richer in methane. Research at the University of Groningen demonstrated that the bacterial community changes in composition under the influence of pressure. Individual bacteria species have their optimum circumstances in which they grow and replicate
832-410: A chain length greater than that of acetate must first be catabolised into compounds that can be directly used by methanogens. The biological process of acidogenesis results in further breakdown of the remaining components by acidogenic (fermentative) bacteria. Here, VFAs are created, along with ammonia, carbon dioxide, and hydrogen sulfide , as well as other byproducts. The process of acidogenesis
936-407: A domino effect of inhibition. Total ammonia nitrogen is the combination of free ammonia and ionized ammonia. TAN is produced through degrading material high in nitrogen, typically proteins and will naturally build in anaerobic digestion. This is depending on the organic feed stock fed to the system. In typical wastewater treatment practices, TAN reduction is done with via nitrification . Nitrification
1040-513: A faecal sludge treatment plant. Faecal sludge can also be co-treated with organic solid waste in composting or in an anaerobic digestion system. Biogas can be generated through anaerobic digestion in the treatment of faecal sludge. The appropriate management of excreta and its valorisation through the production of biogas from faecal sludge helps mitigate the effects of poorly managed excreta such as waterborne diseases and water and environmental pollution. The Resource Recovery and Reuse (RRR) )
1144-611: A farm-based digester that uses dairy manure as the primary feedstock, the gas production may be significantly increased by adding a second feedstock, e.g., grass and corn (typical on-farm feedstock), or various organic byproducts, such as slaughterhouse waste, fats, oils and grease from restaurants, organic household waste, etc. (typical off-site feedstock). Digesters processing dedicated energy crops can achieve high levels of degradation and biogas production. Slurry-only systems are generally cheaper, but generate far less energy than those using crops, such as maize and grass silage; by using
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#17328690169291248-474: A frozen lake in Alaska" has produced 200–300 litres of methane per day, about 20 to 30% of the output from digesters in warmer climates. Mesophilic species outnumber thermophiles, and they are also more tolerant to changes in environmental conditions than thermophiles. Mesophilic systems are, therefore, considered to be more stable than thermophilic digestion systems. In contrast, while thermophilic digestion systems are considered less stable, their energy input
1352-439: A gas-tight door. Neither approach has mixing inside the digester. The amount of pretreatment, such as contaminant removal, depends both upon the nature of the waste streams being processed and the desired quality of the digestate. Size reduction (grinding) is beneficial in continuous vertical systems, as it accelerates digestion, while batch systems avoid grinding and instead require structure (e.g. yard waste) to reduce compaction of
1456-639: A gaseous renewable energy source produced from raw materials such as agricultural waste , manure , municipal waste , plant material , sewage , green waste , wastewater , and food waste . Biogas is produced by anaerobic digestion with anaerobic organisms or methanogens inside an anaerobic digester , biodigester or a bioreactor . The gas composition is primarily methane ( CH 4 ) and carbon dioxide ( CO 2 ) and may have small amounts of hydrogen sulfide ( H 2 S ), moisture and siloxanes . The methane can be combusted or oxidized with oxygen. This energy release allows biogas to be used as
1560-439: A high percentage of solids (40-60%) in gas-tight chambers called fermenter boxes. It is with this understanding that mechanical biological treatment plants are designed. The higher the level of pretreatment a feedstock requires, the more processing machinery will be required, and, hence, the project will have higher capital costs. National Non-Food Crops Centre . After sorting or screening to remove any physical contaminants from
1664-472: A larger volume of the digesters (spread across several batches) to handle the same amount of waste as a continuous process digester. Higher heat energy is required in a thermophilic system compared to a mesophilic system, but the thermophilic system requires much less time and has a larger gas output capacity and higher methane gas content, so one has to consider that trade-off carefully. For solids content, low will handle up to 15% solid content. Above this level
1768-428: A liquid environment, as it enables more thorough circulation of materials and contact between the bacteria and their food. This enables the bacteria to more readily access the substances on which they are feeding, and increases the rate of gas production. Digestion systems can be configured with different levels of complexity. In a single-stage digestion system (one-stage), all of the biological reactions occur within
1872-480: A modest amount of crop material (30%), an anaerobic digestion plant can increase energy output tenfold for only three times the capital cost, relative to a slurry-only system. A second consideration related to the feedstock is moisture content. Drier, stackable substrates, such as food and yard waste, are suitable for digestion in tunnel-like chambers. Tunnel-style systems typically have near-zero wastewater discharge, as well, so this style of system has advantages where
1976-402: A number of chemical processes in converting the biomass to biogas . Gaseous oxygen is excluded from the reactions by physical containment. Anaerobes utilize electron acceptors from sources other than oxygen gas. These acceptors can be the organic material itself or may be supplied by inorganic oxides from within the input material. When the oxygen source in an anaerobic system is derived from
2080-399: A number of different configurations and can be categorized into batch vs. continuous process mode, mesophilic vs. thermophilic temperature conditions, high vs. low portion of solids, and single stage vs. multistage processes. Continuous process requires more complex design, but still, it may be more economical than batch process, because batch process requires more initial building money and
2184-772: A popular source of energy and is starting to be used in the United States more. In 2003, the United States consumed 43 TWh (147 trillion BTU) of energy from "landfill gas", about 0.6% of the total U.S. natural gas consumption. Methane biogas derived from cow manure is being tested in the U.S. According to a 2008 study, collected by the Science and Children magazine, methane biogas from cow manure would be sufficient to produce 100 billion kilowatt hours enough to power millions of homes across America. Furthermore, methane biogas has been tested to prove that it can reduce 99 million metric tons of greenhouse gas emissions or about 4% of
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#17328690169292288-421: A pressure gauge. Frequent smell checks must be performed on a biogas system. If biogas is smelled anywhere windows and doors should be opened immediately. If there is a fire the gas should be shut off at the gate valve of the biogas system. Landfill gas is produced by wet organic waste decomposing under anaerobic conditions in a similar way to biogas. The waste is covered and mechanically compressed by
2392-496: A single, sealed reactor or holding tank. Using a single stage reduces construction costs, but results in less control of the reactions occurring within the system. Acidogenic bacteria, through the production of acids, reduce the pH of the tank. Methanogenic archaea, as outlined earlier, operate in a strictly defined pH range. Therefore, the biological reactions of the different species in a single-stage reactor can be in direct competition with each other. Another one-stage reaction system
2496-532: Is twinned with: Anaerobic digestion Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen . The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the fermentation used industrially to produce food and drink products, as well as home fermentation, uses anaerobic digestion. Anaerobic digestion occurs naturally in some soils and in lake and oceanic basin sediments , where it
2600-421: Is 5% methane and the upper is 15% methane. The methane in biogas is 28 times more potent a greenhouse gas than carbon dioxide. Therefore, uncontained landfill gas, which escapes into the atmosphere may significantly contribute to the effects of global warming . In addition, volatile organic compounds (VOCs) in landfill gas contribute to the formation of photochemical smog . Biochemical oxygen demand (BOD)
2704-407: Is a function of biogas temperature; correction of measured gas volume for water vapour content and thermal expansion is easily done via simple mathematics which yields the standardized volume of dry biogas. For 1000 kg (wet weight) of input to a typical biodigester, total solids may be 30% of the wet weight while volatile suspended solids may be 90% of the total solids. Protein would be 20% of
2808-451: Is a major factor in determining the methane yield and methane production rates from the digestion of biomass. Techniques to determine the compositional characteristics of the feedstock are available, while parameters such as solids, elemental, and organic analyses are important for digester design and operation. Methane yield can be estimated from the elemental composition of substrate along with an estimate of its degradability (the fraction of
2912-806: Is a measure of the amount of oxygen required by aerobic micro-organisms to decompose the organic matter in a sample of material being used in the biodigester as well as the BOD for the liquid discharge allows for the calculation of the daily energy output from a biodigester. Another term related to biodigesters is effluent dirtiness, which tells how much organic material there is per unit of biogas source. Typical units for this measure are in mg BOD/litre. As an example, effluent dirtiness can range between 800 and 1200 mg BOD/litre in Panama. From 1 kg of decommissioned kitchen bio-waste, 0.45 m of biogas can be obtained. The price for collecting biological waste from households
3016-491: Is a subprogram of the CGIAR Research Program on Water, Land and Ecosystems (WLE) dedicated to applied research on the safe recovery of water, nutrients and energy from domestic and agro-industrial waste streams. They believe using waste as energy would be good financially and would tackle sanitation, health and environmental issues. The European Union has legislation regarding waste management and landfill sites called
3120-685: Is an anaerobic lagoon . These lagoons are pond-like, earthen basins used for the treatment and long-term storage of manures. Here the anaerobic reactions are contained within the natural anaerobic sludge contained in the pool. In a two-stage digestion system (multistage), different digestion vessels are optimised to bring maximum control over the bacterial communities living within the digesters. Acidogenic bacteria produce organic acids and more quickly grow and reproduce than methanogenic archaea. Methanogenic archaea require stable pH and temperature to optimise their performance. Under typical circumstances, hydrolysis, acetogenesis, and acidogenesis occur within
3224-479: Is an aerobic process where TAN is consumed by aerobic heterotrophic bacteria. These bacteria release nitrate and nitrite which are later converted to nitrogen gas through the denitrification process. Hydrolysis and acidogenesis can also be impacted by TAN concentration. In mesophilic conditions, inhibition for hydrolysis was found to occur at 5500 mg/L TAN, while acidogenesis inhibition occurs at 6500 mg/L TAN. The most important initial issue when considering
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3328-459: Is applied to its treatment. To use a high-solids anaerobic digester for dilute feedstocks, bulking agents, such as compost, should be applied to increase the solids content of the input material. Another key consideration is the carbon:nitrogen ratio of the input material. This ratio is the balance of food a microbe requires to grow; the optimal C:N ratio is 20–30:1. Excess N can lead to ammonia inhibition of digestion. The level of contamination of
3432-551: Is approximately €70 per ton. The composition of biogas varies depending upon the substrate composition, as well as the conditions within the anaerobic reactor (temperature, pH, and substrate concentration). Landfill gas typically has methane concentrations around 50%. Advanced waste treatment technologies can produce biogas with 55–75% methane, which for reactors with free liquids can be increased to 80–90% methane using in-situ gas purification techniques. As produced, biogas contains water vapor. The fractional volume of water vapor
3536-413: Is considered high solids content and can also be known as dry digestion. In a single stage process, one reactor houses the four anaerobic digestion steps. A multistage process utilizes two or more reactors for digestion to separate the methanogenesis and hydrolysis phases. Anaerobic digestion can be performed as a batch process or a continuous process. In a batch system, biomass is added to the reactor at
3640-578: Is higher, with more biogas being removed from the organic matter in an equal amount of time. The increased temperatures facilitate faster reaction rates, and thus faster gas yields. Operation at higher temperatures facilitates greater pathogen reduction of the digestate. In countries where legislation, such as the Animal By-Products Regulations in the European Union, requires digestate to meet certain levels of pathogen reduction there may be
3744-432: Is made as a product which is a greenhouse gas ( as described by this equation: CH 4 + 2 O 2 → CO 2 + 2 H 2 O ). The content of toxic hydrogen sulfide presents additional risks and has been responsible for serious accidents. Leaks of unburned methane are an additional risk, because methane is a potent greenhouse gas . A facility may leak 2% of the methane. Biogas can be explosive when mixed in
3848-635: Is now the GMP Cow Power Program. Customers can elect to pay a premium on their electric bill, and that premium is passed directly to the farms in the program. In Sheldon, Vermont , Green Mountain Dairy has provided renewable energy as part of the Cow Power program. It started when the brothers who own the farm, Bill and Brian Rowell, wanted to address some of the manure management challenges faced by dairy farms, including manure odor, and nutrient availability for
3952-552: Is produced by microorganisms, such as methanogens and sulfate-reducing bacteria , performing anaerobic respiration. Biogas can refer to gas produced naturally and industrially. In soil, methane is produced in anaerobic environments by methanogens, but is mostly consumed in aerobic zones by methanotrophs . Methane emissions result when the balance favors methanogens. Wetland soils are the main natural source of methane. Other sources include oceans, forest soils, termites, and wild ruminants. The purpose of industrial biogas production
4056-499: Is produced from organic compounds containing nitrogen, such as the amino acids in proteins . If not separated from the biogas, combustion results in NO x emissions. In some cases, biogas contains siloxanes . They are formed from the anaerobic decomposition of materials commonly found in soaps and detergents. During combustion of biogas containing siloxanes, silicon is released and can combine with free oxygen or other elements in
4160-573: Is released by methanogenic archaea as methane. Populations of anaerobic microorganisms typically take a significant period of time to establish themselves to be fully effective. Therefore, common practice is to introduce anaerobic microorganisms from materials with existing populations, a process known as "seeding" the digesters, typically accomplished with the addition of sewage sludge or cattle slurry. The four key stages of anaerobic digestion involve hydrolysis , acidogenesis , acetogenesis and methanogenesis . The overall process can be described by
4264-418: Is roughly 60% methane and 39% CO 2 with trace elements of H 2 S : inadequate for use in machinery. The corrosive nature of H 2 S alone is enough to destroy the mechanisms. Methane in biogas can be concentrated via a biogas upgrader to the same standards as fossil natural gas , which itself has to go through a cleaning process, and becomes biomethane . If the local gas network allows,
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4368-406: Is similar to the way milk sours . The third stage of anaerobic digestion is acetogenesis . Here, simple molecules created through the acidogenesis phase are further digested by acetogens to produce largely acetic acid, as well as carbon dioxide and hydrogen. The terminal stage of anaerobic digestion is the biological process of methanogenesis . Here, methanogens use the intermediate products of
4472-424: Is stored under anaerobic conditions. During storage and when manure has been applied to the land, nitrous oxide is also produced as a byproduct of the denitrification process. Nitrous oxide ( N 2 O ) is 320 times more aggressive as a greenhouse gas than carbon dioxide and methane 25 times more than carbon dioxide. By converting cow manure into methane biogas via anaerobic digestion , the millions of cattle in
4576-431: Is the collection of biomethane, usually for fuel. Industrial biogas is produced either; A biogas plant is the name often given to an anaerobic digester that treats farm wastes or energy crops. It can be produced using anaerobic digesters (air-tight tanks with different configurations). These plants can be fed with energy crops such as maize silage or biodegradable wastes including sewage sludge and food waste. During
4680-474: Is the remaining inorganic matter that was not transformed into biogas. It can be used as an agricultural fertiliser. Biogas can be used as the fuel in the system of producing biogas from agricultural wastes and co-generating heat and electricity in a combined heat and power ( CHP ) plant. Unlike the other green energy such as wind and solar, the biogas can be quickly accessed on demand. The global warming potential can also be greatly reduced when using biogas as
4784-476: Is typically an agricultural anaerobic digester that accepts two or more input materials for simultaneous digestion. The length of time required for anaerobic digestion depends on the chemical complexity of the material. Material rich in easily digestible sugars breaks down quickly, whereas intact lignocellulosic material rich in cellulose and hemicellulose polymers can take much longer to break down. Anaerobic microorganisms are generally unable to break down lignin,
4888-698: Is used as part of the process to treat biodegradable waste and sewage sludge . As part of an integrated waste management system, anaerobic digestion reduces the emission of landfill gas into the atmosphere. Anaerobic digesters can also be fed with purpose-grown energy crops, such as maize . Anaerobic digestion is widely used as a source of renewable energy . The process produces a biogas , consisting of methane , carbon dioxide , and traces of other 'contaminant' gases. This biogas can be used directly as fuel, in combined heat and power gas engines or upgraded to natural gas-quality biomethane . The nutrient-rich digestate also produced can be used as fertilizer . With
4992-439: Is usually referred to as "anaerobic activity". This is the source of marsh gas methane as discovered by Alessandro Volta in 1776. Anaerobic digestion comprises four stages: The digestion process begins with bacterial hydrolysis of the input materials. Insoluble organic polymers , such as carbohydrates , are broken down to soluble derivatives that become available for other bacteria. Acidogenic bacteria then convert
5096-917: The Landfill Directive . Countries such as the United Kingdom and Germany now have legislation in force that provides farmers with long-term revenue and energy security. The EU mandates that internal combustion engines with biogas have ample gas pressure to optimize combustion, and within the European Union ATEX centrifugal fan units built in accordance with the European directive 2014–34/EU (previously 94/9/EG) are obligatory. These centrifugal fan units, for example Combimac , Meidinger AG or Witt & Sohn AG are suitable for use in Zone 1 and 2 . The United States legislates against landfill gas as it contains VOCs . The United States Clean Air Act and Title 40 of
5200-491: The combustion gas . Deposits are formed containing mostly silica ( SiO 2 ) or silicates ( Si x O y ) and can contain calcium , sulfur , zinc , phosphorus . Such white mineral deposits accumulate to a surface thickness of several millimeters and must be removed by chemical or mechanical means. Practical and cost-effective technologies to remove siloxanes and other biogas contaminants are available. High levels of methane are produced when manure
5304-467: The sugars and amino acids into carbon dioxide, hydrogen , ammonia , and organic acids . In acetogenesis, bacteria convert these resulting organic acids into acetic acid , along with additional ammonia, hydrogen, and carbon dioxide amongst other compounds. Finally, methanogens convert these products to methane and carbon dioxide. The methanogenic archaea populations play an indispensable role in anaerobic wastewater treatments. Anaerobic digestion
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#17328690169295408-485: The Code of Federal Regulations (CFR) requires landfill owners to estimate the quantity of non-methane organic compounds (NMOCs) emitted. If the estimated NMOC emissions exceeds 50 tonnes per year, the landfill owner is required to collect the gas and treat it to remove the entrained NMOCs. That usually means burning it. Because of the remoteness of landfill sites, it is sometimes not economically feasible to produce electricity from
5512-471: The United States would be able to produce 100 billion kilowatt hours of electricity, enough to power millions of homes across the United States. One cow can produce enough manure in one day to generate 3 kilowatt hours of electricity. Furthermore, by converting cattle manure into methane biogas instead of letting it decompose, global warming gases could be reduced by 99 million metric tons or 4%. Biogas can be used for electricity production on sewage works, in
5616-399: The addition of water. The primary styles of dry digesters are continuous vertical plug flow and batch tunnel horizontal digesters. Continuous vertical plug flow digesters are upright, cylindrical tanks where feedstock is continuously fed into the top of the digester, and flows downward by gravity during digestion. In batch tunnel digesters, the feedstock is deposited in tunnel-like chambers with
5720-400: The application of anaerobic digestion as a process for reducing waste volumes and generating useful byproducts. It may either be used to process the source-separated fraction of municipal waste or alternatively combined with mechanical sorting systems, to process residual mixed municipal waste. These facilities are called mechanical biological treatment plants. Biogas Biogas is
5824-527: The application of anaerobic digestion systems is the feedstock to the process. Almost any organic material can be processed with anaerobic digestion; however, if biogas production is the aim, the level of putrescibility is the key factor in its successful application. The more putrescible (digestible) the material, the higher the gas yields possible from the system. Feedstocks can include biodegradable waste materials, such as waste paper, grass clippings, leftover food, sewage, and animal waste. Woody wastes are
5928-513: The bacterial groups responsible for the different organic matter degradation steps. The degree of the inhibition depends, among other factors, on the concentration of the inhibitor in the digester. Potential inhibitors are ammonia, sulfide, light metal ions (Na, K, Mg, Ca, Al), heavy metals, some organics (chlorophenols, halogenated aliphatics, N-substituted aromatics, long chain fatty acids), etc. Total ammonia nitrogen (TAN) has been shown to inhibit production of methane. Furthermore, it destabilises
6032-420: The biogas produced by wastewater from the brewery only. Manufacturing of biogas from intentionally planted maize has been described as being unsustainable and harmful due to very concentrated, intense and soil eroding character of these plantations. There are two key processes: mesophilic and thermophilic digestion which is dependent on temperature. In experimental work at University of Alaska Fairbanks ,
6136-450: The biomass is kept in the reactor which is then used for in-vessel composting before it is opened As the batch digestion is simple and requires less equipment and lower levels of design work, it is typically a cheaper form of digestion. Using more than one batch reactor at a plant can ensure constant production of biogas. In continuous digestion processes, organic matter is constantly added (continuous complete mixed) or added in stages to
6240-591: The chemical reaction, where organic material such as glucose is biochemically digested into carbon dioxide (CO 2 ) and methane (CH 4 ) by the anaerobic microorganisms. C 6 H 12 O 6 → 3CO 2 + 3CH 4 In most cases, biomass is made up of large organic polymers. For the bacteria in anaerobic digesters to access the energy potential of the material, these chains must first be broken down into their smaller constituent parts. These constituent parts, or monomers, such as sugars, are readily available to other bacteria. The process of breaking these chains and dissolving
6344-552: The crops they need to grow to feed the animals. They installed an anaerobic digester to process the cow and milking center waste from their 950 cows to produce renewable energy, a bedding to replace sawdust, and a plant-friendly fertilizer. The energy and environmental attributes are sold to the GMP Cow Power program. On average, the system run by the Rowells produces enough electricity to power 300 to 350 other homes. The generator capacity
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#17328690169296448-405: The digestion system. In a typical two-stage mesophilic digestion, residence time varies between 15 and 40 days, while for a single-stage thermophilic digestion, residence times is normally faster and takes around 14 days. The plug-flow nature of some of these systems will mean the full degradation of the material may not have been realised in this timescale. In this event, digestate exiting
6552-401: The discharge of digester liquids are a liability. The wetter the material, the more suitable it will be to handling with standard pumps instead of energy-intensive concrete pumps and physical means of movement. Also, the wetter the material, the more volume and area it takes up relative to the levels of gas produced. The moisture content of the target feedstock will also affect what type of system
6656-538: The emission of greenhouse gases in a number of key ways: Anaerobic digestion is particularly suited to organic material, and is commonly used for industrial effluent , wastewater and sewage sludge treatment . Anaerobic digestion, a simple process, can greatly reduce the amount of organic matter which might otherwise be destined to be dumped at sea, dumped in landfills , or burnt in incinerators . Pressure from environmentally related legislation on solid waste disposal methods in developed countries has increased
6760-434: The energy can be used for on-site generation , resulting in a reduction of losses in the transportation of energy. Typical energy losses in natural gas transmission systems range from 1% to 2%; in electricity transmission they range from 5% to 8%. Before being injected in the gas grid, biogas passes a cleaning process, during which it is upgraded to natural gas quality. During the cleaning process trace components harmful to
6864-494: The exception, because they are largely unaffected by digestion, as most anaerobes are unable to degrade lignin . Xylophagous anaerobes (lignin consumers) or high temperature pretreatment, such as pyrolysis, can be used to break lignin down. Anaerobic digesters can also be fed with specially grown energy crops , such as silage , for dedicated biogas production. In Germany and continental Europe, these facilities are referred to as "biogas" plants. A codigestion or cofermentation plant
6968-449: The fastest. Commonly known are pH, temperature, salinity etc. but pressure is also one of them. Some species have adapted to life in the deep oceans where pressure is much higher than at sea level. This makes it possible in similar vein as other process parameters such as Temperature, Retention Time, pH to influence the anaerobic digestion process. The anaerobic digestion process can be inhibited by several compounds, affecting one or more of
7072-418: The feedstock mass are potentially convertible to biogas. Low solids (wet) digesters can transport material through the system using standard pumps that require significantly lower energy input. Low solids digesters require a larger amount of land than high solids due to the increased volumes associated with the increased liquid-to-feedstock ratio of the digesters. There are benefits associated with operation in
7176-551: The feedstock material is a key consideration when using wet digestion or plug-flow digestion. If the feedstock to the digesters has significant levels of physical contaminants, such as plastic, glass, or metals, then processing to remove the contaminants will be required for the material to be used. If it is not removed, then the digesters can be blocked and will not function efficiently. This contamination issue does not occur with dry digestion or solid-state anaerobic digestion (SSAD) plants, since SSAD handles dry, stackable biomass with
7280-401: The feedstock, the material is often shredded, minced, and mechanically or hydraulically pulped to increase the surface area available to microbes in the digesters and, hence, increase the speed of digestion. The maceration of solids can be achieved by using a chopper pump to transfer the feedstock material into the airtight digester, where anaerobic treatment takes place. Substrate composition
7384-445: The feedstock. The thickness of the material may also lead to associated problems with abrasion. High solids digesters will typically have a lower land requirement due to the lower volumes associated with the moisture. High solids digesters also require correction of conventional performance calculations (e.g. gas production, retention time, kinetics, etc.) originally based on very dilute sewage digestion concepts, since larger fractions of
7488-426: The first reaction vessel. The organic material is then heated to the required operational temperature (either mesophilic or thermophilic) prior to being pumped into a methanogenic reactor. The initial hydrolysis or acidogenesis tanks prior to the methanogenic reactor can provide a buffer to the rate at which feedstock is added. Some European countries require a degree of elevated heat treatment to kill harmful bacteria in
7592-468: The flow stream because of daily and seasonal temperature fluctuations, and account for the moisture in the flow stream to produce a dry gas value. Biogas can be used in different types of internal combustion engines, such as the Jenbacher or Caterpillar gas engines. Other internal combustion engines such as gas turbines are suitable for the conversion of biogas into both electricity and heat. The digestate
7696-605: The fuel instead of fossil fuel . However, the acidification and eutrophication potentials produced by biogas are 25 and 12 times higher respectively than fossil fuel alternatives. This impact can be reduced by using correct combination of feedstocks, covered storage for digesters and improved techniques for retrieving escaped material. Overall, the results still suggest that using biogas can lead to significant reduction in most impacts compared to fossil fuel alternative. The balance between environmental damage and green house gas emission should still be considered while implicating
7800-499: The gas grid and the final users are removed. If concentrated and compressed, it can be used in vehicle transportation. Compressed biogas is becoming widely used in Sweden, Switzerland, and Germany. A biogas-powered train, named Biogaståget Amanda (The Biogas Train Amanda), has been in service in Sweden since 2005. Biogas powers automobiles. In 1974, a British documentary film titled Sweet as
7904-481: The gas. There are a variety of grants and loans the support the development of anaerobic digestor systems. The Rural Energy for American Program provides loan financing and grant funding for biogas systems, as does the Environmental Quality Incentives Program , Conservation Stewardship Program , and Conservation Loan Program . With the many benefits of biogas, it is starting to become
8008-573: The greenhouse gases produced by the United States. The number of farm-based digesters increased by 21% in 2021 according to the American Biogas Council. In Vermont biogas generated on dairy farms was included in the CVPS Cow Power program. The program was originally offered by Central Vermont Public Service Corporation as a voluntary tariff and now with a recent merger with Green Mountain Power
8112-414: The input waste. In this instance, there may be a pasteurisation or sterilisation stage prior to digestion or between the two digestion tanks. Notably, it is not possible to completely isolate the different reaction phases, and often some biogas is produced in the hydrolysis or acidogenesis tanks. The residence time in a digester varies with the amount and type of feed material, and with the configuration of
8216-428: The level of solids in the material, to mix the contents, enabling the bacteria and the food to be in contact. They also allow excess material to be continuously extracted to maintain a reasonably constant volume within the digestion tanks. A recent development in anaerobic reactor design is High-pressure anaerobic digestion (HPAD) also referred to a Autogenerative High Pressure Digestion (AHPD). This technique produces
8320-415: The microbial community, impacting the synthesis of acetic acid. Acetic acid is one of the driving forces in methane production. At an excess of 5000 mg/L TAN, pH adjustment is needed to keep the reaction stable. A TAN concentration above 1700– 1800 mg/L inhibits methane production and yield decreases at greater TAN concentrations. High TAN concentrations cause the reaction to turn acidic and lead to
8424-411: The organic material itself, the 'intermediate' end products are primarily alcohols , aldehydes , and organic acids, plus carbon dioxide. In the presence of specialised methanogens, the intermediates are converted to the 'final' end products of methane, carbon dioxide, and trace levels of hydrogen sulfide . In an anaerobic system, the majority of the chemical energy contained within the starting material
8528-413: The organic matter has completed. There can be severe odour issues if a batch reactor is opened and emptied before the process is well completed. A more advanced type of batch approach has limited the odour issues by integrating anaerobic digestion with in-vessel composting . In this approach inoculation takes place through the use of recirculated degasified percolate. After anaerobic digestion has completed,
8632-565: The pathogenic concentration in the digestate, leaving the anaerobic digester. Pasteurisation may be achieved by heat treatment combined with maceration of the solids. In a typical scenario, three different operational parameters are associated with the solids content of the feedstock to the digesters: High solids (dry) digesters are designed to process materials with a solids content between 25 and 40%. Unlike wet digesters that process pumpable slurries, high solids (dry – stackable substrate) digesters are designed to process solid substrates without
8736-437: The preceding stages and convert them into methane, carbon dioxide, and water. These components make up the majority of the biogas emitted from the system. Methanogenesis is sensitive to both high and low pHs and occurs between pH 6.5 and pH 8. The remaining, indigestible material the microbes cannot use and any dead bacterial remains constitute the digestate. Anaerobic digesters can be designed and engineered to operate using
8840-428: The process, the micro-organisms transform biomass waste into biogas (mainly methane and carbon dioxide) and digestate . Higher quantities of biogas can be produced when the wastewater is co-digested with other residuals from the dairy industry, sugar industry, or brewery industry. For example, while mixing 90% of wastewater from beer factory with 10% cow whey, the production of biogas was increased by 2.5 times compared to
8944-441: The producer of the biogas may use their distribution networks. Gas must be very clean to reach pipeline quality and must be of the correct composition for the distribution network to accept. Carbon dioxide , water , hydrogen sulfide , and particulates must be removed if present. There are four main methods of upgrading: water washing, pressure swing absorption, selexol absorption, and amine gas treating . In addition to these,
9048-419: The ratio of one part biogas to 8–20 parts air. Special safety precautions have to be taken for entering an empty biogas digester for maintenance work. It is important that a biogas system never has negative pressure as this could cause an explosion. Negative gas pressure can occur if too much gas is removed or leaked; Because of this biogas should not be used at pressures below one column inch of water, measured by
9152-481: The re-use of waste as a resource and new technological approaches that have lowered capital costs , anaerobic digestion has in recent years received increased attention among governments in a number of countries, among these the United Kingdom (2011), Germany, Denmark (2011), and the United States. Many microorganisms affect anaerobic digestion, including acetic acid-forming bacteria ( acetogens ) and methane-forming archaea ( methanogens ). These organisms promote
9256-507: The reactor (continuous plug flow ; first in – first out). Here, the end products are constantly or periodically removed, resulting in constant production of biogas. A single or multiple digesters in sequence may be used. Examples of this form of anaerobic digestion include continuous stirred-tank reactors , upflow anaerobic sludge blankets , expanded granular sludge beds , and internal circulation reactors . The two conventional operational temperature levels for anaerobic digesters determine
9360-458: The recalcitrant aromatic component of biomass. Anaerobic digesters were originally designed for operation using sewage sludge and manures. Sewage and manure are not, however, the material with the most potential for anaerobic digestion, as the biodegradable material has already had much of the energy content taken out by the animals that produced it. Therefore, many digesters operate with codigestion of two or more types of feedstock. For example, in
9464-608: The sides of pipes or stacks throughout the gas flow. Biogas environments include wastewater digesters, landfills, and animal feeding operations (covered livestock lagoons). Ultrasonic flow meters are one of the few devices capable of measuring in a biogas atmosphere. Most of thermal flow meters are unable to provide reliable data because the moisture causes steady high flow readings and continuous flow spiking, although there are single-point insertion thermal mass flow meters capable of accurately monitoring biogas flows with minimal pressure drop. They can handle moisture variations that occur in
9568-452: The smaller molecules into solution is called hydrolysis. Therefore, hydrolysis of these high-molecular-weight polymeric components is the necessary first step in anaerobic digestion. Through hydrolysis the complex organic molecules are broken down into simple sugars , amino acids, and fatty acids . Acetate and hydrogen produced in the first stages can be used directly by methanogens. Other molecules, such as volatile fatty acids (VFAs) with
9672-454: The species of methanogens in the digesters: A limit case has been reached in Bolivia , with anaerobic digestion in temperature working conditions of less than 10 °C. The anaerobic process is very slow, taking more than three times the normal mesophilic time process. In experimental work at University of Alaska Fairbanks , a 1,000-litre digester using psychrophiles harvested from "mud from
9776-439: The stacked pile. Continuous vertical dry digesters have a smaller footprint due to the shorter effective retention time and vertical design. Wet digesters can be designed to operate in either a high-solids content, with a total suspended solids (TSS) concentration greater than ~20%, or a low-solids concentration less than ~15%. High solids (wet) digesters process a thick slurry that requires more energy input to move and process
9880-400: The start of the process. The reactor is then sealed for the duration of the process. In its simplest form batch processing needs inoculation with already processed material to start the anaerobic digestion. In a typical scenario, biogas production will be formed with a normal distribution pattern over time. Operators can use this fact to determine when they believe the process of digestion of
9984-552: The substrate that is converted to biogas in a reactor). In order to predict biogas composition (the relative fractions of methane and carbon dioxide) it is necessary to estimate carbon dioxide partitioning between the aqueous and gas phases, which requires additional information (reactor temperature, pH , and substrate composition) and a chemical speciation model. Direct measurements of biomethanation potential are also made using gas evolution or more recent gravimetric assays. Using anaerobic digestion technologies can help to reduce
10088-448: The system will be darker in colour and will typically have more odour. In the case of an upflow anaerobic sludge blanket digestion (UASB), hydraulic residence times can be as short as 1 hour to 1 day, and solid retention times can be up to 90 days. In this manner, a UASB system is able to separate solids and hydraulic retention times with the use of a sludge blanket. Continuous digesters have mechanical or hydraulic devices, depending on
10192-460: The system. Projects such as NANOCLEAN are nowadays developing new ways to produce biogas more efficiently, using iron oxide nanoparticles in the processes of organic waste treatment. This process can triple the production of biogas. Faecal Sludge is a product of onsite sanitation systems. Post collection and transportation, Faecal sludge can be treated with sewage in a conventional treatment plant, or otherwise it can be treated independently in
10296-399: The system. It takes roughly between 3% and 6% of the total energy output in gas to run a biogas upgrading system. Gas-grid injection is the injection of biogas into the methane grid ( natural gas grid ). Until the breakthrough of micro combined heat and power two-thirds of all the energy produced by biogas power plants was lost (as heat). Using the grid to transport the gas to consumers,
10400-451: The use of membrane separation technology for biogas upgrading is increasing, and there are already several plants operating in Europe and USA. The most prevalent method is water washing where high pressure gas flows into a column where the carbon dioxide and other trace elements are scrubbed by cascading water running counter-flow to the gas. This arrangement could deliver 98% methane with manufacturers guaranteeing maximum 2% methane loss in
10504-548: The volatile solids, carbohydrates would be 70% of the volatile solids, and finally fats would be 10% of the volatile solids. Toxic and foul smelling Hydrogen sulfide ( H 2 S ) is the most common contaminant in biogas, but other sulfur-containing compounds, such as thiols may be present. Left in the biogas stream, hydrogen sulfide is corrosive and when combusted yields sulfur dioxide ( SO 2 ) and sulfuric acid ( H 2 SO 4 ), also corrosive and environmentally hazardous compounds. Ammonia ( NH 3 )
10608-426: The weight of the material that is deposited above. This material prevents oxygen exposure thus allowing anaerobic microbes to thrive. Biogas builds up and is slowly released into the atmosphere if the site has not been engineered to capture the gas. Landfill gas released in an uncontrolled way can be hazardous since it can become explosive when it escapes from the landfill and mixes with oxygen. The lower explosive limit
10712-442: The world. Biogas can be cleaned and upgraded to natural gas standards, when it becomes bio-methane. Biogas is considered to be a renewable resource because its production-and-use cycle is continuous, and it generates no net carbon dioxide. From a carbon perspective, as much carbon dioxide is absorbed from the atmosphere in the growth of the primary bio-resource as is released, when the material is ultimately converted to energy. Biogas
10816-473: Was originally elected as a member of Together for Lünen (German: Gemeinsam für Lünen = GFL), but later left the party. The most recent mayoral election was held on 13 September 2020, with a runoff held on 27 September, and the results were as follows: The Lünen city council governs the city alongside the Mayor. The most recent city council election was held on 13 September 2020, and the results were as follows: Lünen
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