Anaerobic digestion (AD) is the harnessed and contained, naturally occurring process of anaerobic decomposition.^[1][2] An anaerobic digester is an industrial system that harnesses these natural process to treat waste, produce biogas that can be used to power electricity generators, provide heat and produce soil improving material.^[3] Look up Anaerobic in Wiktionary, the free dictionary. ... Biogas, typically refers to gas produced by the anaerobic digestion or fermentation of organic matter including manure, sewage sludge, municipal solid waste, or any other biodegradable feedstock, under anaerobic conditions. ... Acidogenic digestate produced from mixed municipal waste The anaerobic digestion produces two main products: digestate and biogas. ...

Twin-stage UASB anaerobic digesters adapted for waste and waste water treatment

Anaerobic digesters have been around for a long time and they are commonly used for sewage treatment or for managing animal waste. Increasing environmental pressures on waste disposal has increased the use of AD as a process for reducing waste volumes and generating useful byproducts. It is a fairly simple process that can greatly reduce the amount of organic matter which might otherwise end up in landfills or waste incinerators . Image File history File links MBT_anaerobicdigesters. ... Image File history File links MBT_anaerobicdigesters. ... UASB - Upflow Anaerobic Sludge Blanket technology normally referred to as UASB Reactor is used in the treatment of wastewater. ... jecca is very beautiful!! Environmental science is the study of the interactions among the physical, chemical and biological components of the environment; with a focus on pollution and degradation of the environment related due to human activities; and the impact on biodiversity and sustainability from local and global development. ... Environmental technology or green technology is the application of the environmental sciences to conserve the natural environment and resources, and by curbing the negative impacts of human involvement. ... Before flue gas desulfurization was installed, the emissions from this power plant in New Mexico contained excessive amounts of sulfur dioxide. ... For articles on specific fuels used in vehicles, see Biogas, Bioethanol, Biobutanol and Biodiesel Biofuel is any fuel that is derived from biomass — recently living organisms or their metabolic byproducts, such as manure from cows. ... An active compost heap, steaming on a cold winter morning. ... Ecoforestry is forestry that emphasizes holistic practices which strive to protect and restore ecosystems1 instead of traditional forestry that maximizes economic productivity. ... For the physical concepts, see conservation of energy and energy efficiency. ... // Energy development is the ongoing effort to provide sustainable, accessible energy resources through knowledge, skills, and constructions. ... Environmental design is the process of addressing environmental parameters when devising plans, programs, policies, buildings, or products. ... Future energy development faces great challenges due to an increasing world population, demands for higher standards of living, demands for less pollution and a much-discussed end to fossil fuels. ... It has been suggested that this article or section be merged with Sustainable architecture. ... This article or section is incomplete and may require expansion and/or cleanup. ... The international recycling symbol. ... Renewable energy is defined as energy derived from resources that are regenerative or for all practical purposes can not be depleted. ... Generally, remediation means giving a remedy. ... The following page contains a list of different forms of waste treatment Anaerobic digestion ArrowBio Composting Gasification Incineration In-vessel composting Landfill Mechanical biological treatment Mechanical heat treatment Plasma Pyrolysis Recycling Sewage treatment Tunnel composting UASB Windrow composting Categories: | ... This does not cite its references or sources. ... Sustainable Development is a collection of methods to create economic development which protects the environment, relieves poverty, and does not destroy natural capital in the short term at the expense of long term development. ... The following page consist of a list of waste water treatment technologies: Activated sludge Anaerobic digestion Anaerobic lagoon Cesspit Combined sewer overflow Composting toilet Constructed wetland Imhoff tank Floculation Reed bed Septic tank Sequencing batch reactor UASB Aerobic Granular Reactor This list is incomplete; you can help by expanding it. ... Water purification is the removal of contaminants from raw water to produce drinking water that is pure enough for human consumption or for industrial use. ... For the company, see Waste Management, Inc. ... Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from sewage. ... Waste inside a wheelie bin Waste, rubbish, trash, garbage, or junk is unwanted or undesired material. ... A landfill compaction vehicle in operation A landfill, also known as a dump (US) or a tip (UK), is a site for the disposal of waste materials by burial and is the oldest form of waste treatment. ... This article needs cleanup. ...

Almost any organic material can be processed in this manner. This includes biodegradable waste materials such as waste paper, grass clippings, leftover food, sewage and animal waste. Anaerobic digesters can also be fed with specially grown energy crops to boost biodegradable content and hence increase biogas production. After sorting or screening to remove inorganic or hazardous materials such as metals and plastics, the material to be processed is often shredded, minced, or hydrocrushed ^[4] to increase the surface area available to microbes in the digesters and hence increase the speed of digestion. The material is then fed into a airtight digester where the anaerobic treatment takes place. Rotting fruit Biodegradable waste is a waste type which comprises of waste streams that are available for biodegradation. ... An energy crop is a non-edible plant domesticated for use in agriculture, considered as a group (e. ... Inorganic chemistry is the branch of chemistry concerned with the properties and reactions of inorganic compounds. ...

Stages of anaerobic digestion

There are two conventional operational temperature levels:

• Mesophilic which takes place optimally around 37°-41°C or at ambient temperatures between 20°-45°C with mesophile bacteria
• Thermophilic which takes place optimally around 50°-52° at elevated temperatures up to 70°C with thermophile bacteria

The residence time in a digester varies with the amount of feed material, type of material and the temperature. In the case of mesophilic digestion, residence time may be between 15 and 30 days. In the case of mesophilic UASB digestion hydraulic residence times (1hour-1day) and solid retention times (<90 days) are separated. In the thermophilic phase the process can be faster, requiring only about two weeks to complete. Thermophilic digestion is more expensive, requires more energy and is less stable than the mesophilic process. Therefore, the mesophilic process is still widely in use. A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, typically between 20 and 45 °C with an optimal temperature near 37 °C, which is the normal temperature of the human body. ... A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, typically between 25 and 40 °C (68 and 113 °F). ... Thermophiles produce some of the bright colors of Grand Prismatic Spring, Yellowstone National Park A thermophile is an organism &#8211; a type of extremophile &#8211; which thrives at relatively high temperatures, up to about 60 °C. Many thermophiles are archaea. ... This article is about an organism. ...

Many continuous digesters have mechanical or hydraulic devices to mix the contents and to allow excess material to be continuously extracted to maintain a reasonably constant volume.

The digestion of the organic material involves a range of many different species of naturally occurring bacteria, all doing a different job at a different step in the digestion process. Maintaining suitable conditions in the digester is essential in maintaining a healthy bacterial population.

Four stages of anaerobic digestion have been recognised.

1. The first is hydrolysis, where complex organic molecules are broken down into simple sugars, amino acids, and fatty acids with the addition of hydroxyl groups.
2. The second stage is acidogenesis where a further breakdown into simpler molecules occurs, producing ammonia, carbon dioxide and hydrogen sulfide as byproducts.
3. The third stage is acetogenesis where the simple molecules from acidogenesis are further digested to produce carbon dioxide, hydrogen and mainly acetic acid, although higher-molecular-weight organic acids (e.g., propionic, butyric, valeric) are also produced.
4. The fourth stage is methanogenesis where methane, carbon dioxide and water are produced.

Hydrolysis is a chemical reaction or process in which a molecule is split into two parts by reacting with a molecule of water, which has the chemical formula H2O. One of the parts gets an OH- from the water molecule and the other part gets an H+ from the water. ... Monosaccharides are carbohydrates in the form of simple sugars. ... Phenylalanine is one of the standard amino acids. ... In chemistry, especially biochemistry, a fatty acid is a carboxylic acid often with a long unbranched aliphatic tail (chain), which is either saturated or unsaturated. ... Acidogenesis represents the second stage in the four stages of anaerobic digestion: Hydrolysis: Particulates are solubilized and large polymers, converted into simpler monomers; Acidogenesis: Simple monomers are converted into volatile fatty acids; Acetogenesis: Volatile fatty acids are converted into acetic acid, carbon dioxide, and hydrogen; and Methanogenesis: Acetate are converted... Ammonia is a compound of nitrogen and hydrogen with the formula NH3. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ... Flash point -82. ... Acetogenesis is a process through which acetate is produced by anaerobic bacteria from a variety of energy (for example, hydrogen) and carbon (for example, carbon dioxide) sources. ... Acetic acid, also known as ethanoic acid, is an organic chemical compound best recognized for giving vinegar its sour taste and pungent smell. ... Methanogenesis is the formation of methane by microbes. ... Methane is a significant and plentiful fuel which is the principal component of natural gas. ...

By-products of anaerobic digestion

There are three principal by-products of anaerobic digestion.

• Biogas, a gaseous mixture comprising mostly of methane and carbon dioxide, but also containing a small amount hydrogen and occasionally trace levels of hydrogen sulfide. Biogas can be burned to produce electricity, usually with a reciprocating engine or microturbine. The gas is often used in a cogeneration arrangement, to generate electricity and use waste heat to warm the digesters or to heat buildings. Excess electricity can be sold to electricity suppliers. Electricity produced by anaerobic digesters is considered to be green energy and may attract subsidies such as Renewables Obligation Certificates.

Acidogenic anaerobic digestate

• The second by-product (acidogenic digestate) is a stable organic material comprised largely of lignin and chitin, but also of a variety of mineral components in a matrix of dead bacterial cells, some plastic may be present. This resembles domestic compost and can be used as compost or to make low grade building products such as fibreboard.

• The third by-product is a liquid (methanogenic digestate) that is rich in nutrients and can be an excellent fertilizer dependent on the quality of the material being digested. If the digested materials include low levels of toxic heavy metals or synthetic organic materials such as pesticides or PCBs, the effect of digestion is to significantly concentrate such materials in the digester liquor. In such cases further treatment will be required in order to dispose of this liquid properly. In extreme cases, the disposal costs and the environmental risks posed by such materials can offset any environmental gains provided by the use of biogas. This is a significant risk when treating sewage from industrialised catchments.

Nearly all digestion plants have ancillary processes to treat and manage all of the by-products. The gas stream is dried and sometimes sweetened before storage and use. The sludge liquor mixture has to be separated by one of a variety of ways, the most common of which is filtration. Excess water is also sometimes treated in sequencing batch reactors (SBR) for discharge into sewers or for irrigation. General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Flash point -82. ... Components of a typical, four stroke cycle, DOHC piston engine. ... This machine has a single-stage radial compressor and turbine, a recuperator, and foil bearings. ... Cogeneration (also combined heat and power or CHP) is the use of a heat engine or a power station to simultaneously generate both electricity and useful heat. ... The Renewables Obligation (RO)[1] is designed to incentivise the generation of electricity from renewable sources. ... The carbon cycle is the biogeochemical cycle by which carbon is exchanged between the biosphere, geosphere, hydrosphere and atmosphere of the Earth (other astronomical objects may have similar carbon cycles, but nothing is yet known about them). ... Lignin (sometimes lignen) is a chemical compound that is most commonly derived from wood and is an integral part of the cell walls of plants, especially in tracheids, xylem fibres and sclereids. ... Structure of the chitin molecule, showing two of the N-Acetylglucosamine units that repeat to form long chains in beta-1,4 linkage. ... spreading manure, an organic fertilizer Fertilizers (British English fertilisers) are compounds given to plants to promote growth; they are usually applied either via the soil, for uptake by plant roots, or by foliar feeding, for uptake through leaves. ... A heavy metal is any of a number of higher atomic weight elements, which has the properties of a metallic substance at room temperature. ... the plane is spreading pesticide. ... PCB may refer to: Brazilian Communist Party (in Portuguese, Partido Comunista Brasileiro) Communist Party of Bolivia (in Spanish, Partido Comunista de Bolivia) Pakistan Cricket Board PCBoard, a bulletin board system software Police Complaints Board, which oversaw the system for handling complaints made against police forces in England and Wales until... Look up Industry in Wiktionary, the free dictionary. ... In chemistry, alchemy and water treatment, filtration is the process of using a filter to mechanically separate a mixture. ... Sequencing batch reactors (SBR) or sequential batch reactors are industrial processing tanks for the treatment of waste water. ... SBR may be an abbreviation for: Space-Based Radar, both the name of a specific U.S. Air Force project, and of a concept in general for placing satellites into Earth orbit with the ability to track airborne, seaborne, and land-based targets. ...

Digestion can be either wet or dry. Dry digestion refers to mixtures which have a solid content of 30% or greater, whereas wet digestion refers to mixtures of 15% or less.

Reactor types

There is a range of types of anaerobic digesters, however the two main types of operations are continuous and batch.

Batch is the simplest, with the biomass added to the reactor at the beginning and sealed for the duration of the process. In the continuous process, which is the more common type, organic matter is constantly added to reactor and the end products constantly removed, resulting in a much more constant production of biogas.

Although there will always be a net loss in energy in the whole system (the energy to grow the biomass is more than the output of the reactor), for the processing of waste organic material, anaerobic digestion is the preferable choice because it is environmentally friendly. The biggest impacts on the environment include the energy and materials used to build the plant, transport costs and fuel use in transporting material to site and visual and audible impacts of the site operation. Odour can be a severe problem during emptying cycles. This is a particularly difficult issue for batch reactors. |0. ... The phrase environmentally friendly is used to refer to goods or services considered to inflict little harm on the environment. ...

Considerations

To be economically viable, there must be a market for the end products. Biogas can be sold or used in almost all parts of the world, where it will offset demand on fossil fuel stocks. The digester liquor is suitable for use as a fertilizer, although frequently supplemental nutrients need to be added.

The sludge component, even when dried and available as a soil conditioner, is not easily disposed of. However, it has its uses in non-agricultural areas, such as golf courses, and as cover for landfills. In some localities, the sludge itself is used as a fuel in heating systems, and the residual ash is disposed of in a landfill. Soil conditioners, also called soil amendments, are materials added to soil to improve plant growth and health. ... This article is about the sport of golf. ...

Contribution to prevention of climate change

Production of Renewable Fuel

Processing biodegradable waste using anaerobic digestion helps to reduce global warming. The carbon in biodegradable waste is part of a complete carbon-cycle: the carbon released from the combustion of biogas was removed by plants in the recent past, and does not contribute to the global accumulation of carbon in the same manner that fossil fuels do. Furthermore, if this waste was landfilled it would break down naturally and the biogas would escape directly into the atmosphere. Using the biogas for energy is an intermediate use that does not affect the overall cycle. In this way anaerobic digestion is considered to be a sustainable technology and biogas is considered to be a renewable fuel. Renewable energy is defined as energy derived from resources that are regenerative or for all practical purposes can not be depleted. ...

Associated technologies

Mechanical biological treatment

Main article: mechanical biological treatment

New developments in anaerobic digestion have led to systems being integrated with sorting units. Mixed waste streams such as unsorted household waste can undergo a mechanical pretreatment stage. These systems come under the category of mechanical biological treatment. They enable the recovery of the organic fraction of the waste in a form that can be processed in anaerobic digesters. Mechanical Biological Treatment (MBT) is a form of waste processing. ... A materials recovery facility or materials reclaimation facility (MRF -- pronounced murf) is a specialized plant that receives, separates and prepares recyclable materials for marketing to end-user manufacturers. ... Mechanical Biological Treatment (MBT) is a form of waste processing. ...

Inhibition of methanogenesis & production of alcohols

Main article: bioconversion of biomass to mixed alcohol fuels

Anaerobic digestion can be inhibited from reaching the methanogenic stage. The organic acids (i.e., carboxylic acids) from the acidogenic and acetogenic stages of the digestion can be recovered. The acids can then undergo further chemical transformations into useful chemicals or fuels. The bioconversion of biomass to mixed alcohol fuels can be accomplished using the MixAlco process. ... In chemistry, carboxylic acids (also called alkanoic acids) are organic acids characterized by the presence of a carboxyl group. ... Acidogenesis represents the second stage in the four stages of anaerobic digestion: Hydrolysis: Particulates are solubilized and large polymers, converted into simpler monomers; Acidogenesis: Simple monomers are converted into volatile fatty acids; Acetogenesis: Volatile fatty acids are converted into acetic acid, carbon dioxide, and hydrogen; and Methanogenesis: Acetate are converted... Acetogenesis is a process through which acetate is produced by anaerobic bacteria from a variety of energy (for example, hydrogen) and carbon (for example, carbon dioxide) sources. ...

Potential in the Hydrogen Economy

Main article: steam methane reforming

As anaerobic digestion is a renewable source of methane it offers the potential to contribute to the hydrogen economy: A hydrogen economy is a hypothetical future economy in which energy, for mobile applications (vehicles, aircraft) and electrical grid load balancing (daily peak demand reserve), is stored as hydrogen (H2). ...

Steam methane reforming (SMR) is the most common method of producing commercial bulk hydrogen. It is also the least expensive method. At high temperatures (700 – 1100 °C) and in the presence of a metal-based catalyst, steam reacts with methane to yield carbon monoxide and hydrogen.

CH₄ + H₂O → CO + 3 H₂

The United States produces nine million tons of hydrogen per year, mostly with steam reforming of natural gas. This process is different from catalytic reforming, an oil refinery process that also produces significant amounts of hydrogen along with high octane rating gasoline.

See also

• Category:Anaerobic digestion
• Anaerobic decomposition
• Anaerobic digester types
• Anaerobic lagoon

• Biogas powerplant
• Ecological sanitation
• List of solid waste treatment technologies
• List of waste water treatment technologies
• Mechanical biological treatment
• Sewage treatment

A photo of the anaerobic lagoon at the Cal Poly Dairy taken in 2003. ... Biogas Powerplant Small Gas turbines (GT) can be powered by Biogas and create free Steam and hotwater . ... Ecological Sanitation One person produces about 500 litres of urine and only 50 litres of faeces per year. ... The following page contains a list of different forms of waste treatment Anaerobic digestion ArrowBio Composting Gasification Incineration In-vessel composting Landfill Mechanical biological treatment Mechanical heat treatment Plasma Pyrolysis Recycling Sewage treatment Tunnel composting UASB Windrow composting Categories: | ... The following page consist of a list of waste water treatment technologies: Activated sludge Anaerobic digestion Anaerobic lagoon Cesspit Combined sewer overflow Composting toilet Constructed wetland Imhoff tank Floculation Reed bed Septic tank Sequencing batch reactor UASB Aerobic Granular Reactor This list is incomplete; you can help by expanding it. ... Mechanical Biological Treatment (MBT) is a form of waste processing. ... Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from sewage. ...

External links

• Digestion archives
• European Anaerobic Digestion Network
• Independent Anaerobic Digestion Website
• Methane (Biogas) from Anaerobic Digesters
• Application of anaerobic digesters

References

1. ^ Friends of the Earth FOE (2004 Anaerobic digestion Briefing of the breakdown of organic matter by anaerobic organisms in environments lacking oxygen
2. ^ Anaerobic Digestion Cardiff University Anaerobic Digestion Page
3. ^ Anaerobic Digestion Remade Scotland Anaerobic Digestion Page
4. ^ ArrowBio Reference Finstein, M. S., Zadik, Y., Marshall, A. T. & Brody, D. (2004) The ArrowBio Process for Mixed Municipal Solid Waste – Responses to “Requests for Information”, Proceedings for Biodegradable and Residual Waste Management, Proceedings. (Eds. E. K. Papadimitriou & E. I. Stentiford), Technology and Service Providers Forum, p. 407-413

Sustainability and Development of Energy   Edit Conversion | Development and Use | Sustainable Energy | Conservation | Transportation

An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... In physics and engineering, energy conversion is any process of converting energy from one form to another. ... Solar power describes a number of methods of harnessing energy from the light of the sun. ... Active solar is a term which refers to the use of solar energy to actively convert the energy in sunlight into other forms. ... The Barra system, developed by Horazio Barra in Italy, is a passive solar building technology. ... Central solar heating is the provision of central heating and hot water from solar energy by a system in which the water is heated centrally by arrays of solar thermal collectors (central solar heating plants - CSHPs) and distributed through district heating pipe networks (or block heating systems in the case... An Energy tower is a new concept for producing electrical power for consumer consumption, the brainchild of Professor Dan Zaslavsky. ... Photovoltaics, or PV for short, is a solar power technology that uses solar cells or solar photovoltaic arrays to convert energy from the sun into electricity. ... A solar cell, made from a monocrystalline silicon wafer A solar cell (or a photovoltaic cell) is a device that converts photons from the sun (solar light) into electricity. ... A solar combisystem is a solar heating system that provides both space heating and hot water from a common array of solar thermal collectors, normally linked to an auxiliary non-solar heat source. ... A photovoltaic (PV) module that is composed of multiple PV cells. ... A Solar pond is large-scale solar energy collector with integral heat storage for supplying thermal energy. ... A solar power tower is a solar power station based on a tower. ... The major applications of solar thermal energy at present are heating swimming pools, heating water for domestic use, and space heating of buildings. ... A backyard installation of passive single–axis trackers, DC rated at 2340 watts. ... Schematic of a Solar updraft tower This article is about a type of power plant. ... Solar panels are used in passive and active solar hot water systems Passive solar is a term referring to those technologies that can be employed to convert sunlight into usable heat, to cause air-movement for ventilation or cooling, or to store the heat for future use, without the use... 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Wave power refers to the energy of ocean surface waves and the capture of that energy to do useful work - including electricity generation, desalination, and the pumping of water (into reservoirs). ... Mechanical Biological Treatment (MBT) is a form of waste processing. ... |0. ... Blue energy is the energy retrieved from the difference in the salt concentration between seawater and river water with the use of osmosis or reverse electro dialysis (RED) with ion specific membranes. ... A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ... Hydrogen production is done in bulk today from hydrocarbon fossil fuels via a chemical path. ... Geothermal power plant in the Philippines Look up geothermal in Wiktionary, the free dictionary. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Deep lake water cooling uses cold water pumped from the bottom of a lake as a heat sink for climate control systems. ... Electricity generation is the first process in the delivery of electricity to consumers. ... Distributed generation is a new trend in the generation of heat and electrical power. ... Microgeneration is the generation of zero or low-carbon heat and power by individuals, small businesses and communities to meet their own needs. ... A sustainable community energy system is an integrated approach to supplying a local community with its energy requirements from renewable energy or high-efficiency co-generation energy sources. ... A seasonal thermal store (also known as a seasonal heat store or inter-seasonal thermal store) is a store designed to retain heat deposited during the hot summer months for use during colder winter weather. ... Image File history File links Crystal_128_energy. ... In physics and engineering, energy conversion is any process of converting energy from one form to another. ... // Energy development is the ongoing effort to provide sustainable, accessible energy resources through knowledge, skills, and constructions. ... This does not cite its references or sources. ... For the physical concepts, see conservation of energy and energy efficiency. ...