Anaerobic digestion

Methane ( , ) is a chemical compound that has the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes it an economically attractive fuel, although capturing and storing it is difficult because it is a gas at standard temperature and pressure. In the Earth's atmosphere methane is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas. Methane is an organic hydrocarbon, and among the simplest of organic compounds.

thumb|Phylogenetic tree of bacteria and archaea, highlighting those that carry out fermentation. Their end products are also highlighted. Figure modified from Hackmann (2024). Fermentation is a type of anaerobic metabolism that harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and their electrons are transferred to other organic molecules (cofactors, coenzymes, etc.). Anaerobic glycolysis is a related term used to describe the occurrence of fermentation in organisms (

thumb|upright|A sample of biodiesel

thumb|270px|Simple sketch of household biogas plant

thumb|Silage underneath plastic sheeting is held down by scrap tires. Concrete beneath the silage prevents fermented juice from leaching out.thumb|right|Cattle eating silage Silage is fodder made from green foliage crops which have been preserved by fermentation to the point of souring. It is fed to cattle, sheep and other ruminants. The fermentation and storage process is called ensilage, ensiling, or silaging. The exact methods vary, depending on available technology, local tradition and prevailing climate.

thumb|Yellow slime mold growing on a bin of wet paper

thumb|Decomposition of strawberries, reverse time lapse alt=African buffalo skull decomposing in the Serengeti National Park, Tanzania|thumb|African buffalo skull decomposing in the [[Serengeti National Park, Tanzania]] thumb|A rotten apple after it fell from a tree thumb|Decomposing fallen nurse log in a forest

processes by which microorganisms break down biodegradable material in the absence of oxygen

oxygen needed to remove organics from water

The enzymatic release of energy from inorganic and organic compounds (especially carbohydrates and fats) which uses compounds other than oxygen (e.g. nitrate, sulfate) as the terminal electron acceptor.

right|thumb|300px|Thermophiles produce some of the bright colors of Grand Prismatic Spring, [[Yellowstone National Park]] A thermophile is a type of extremophile that thrives at relatively high temperatures, between . Many thermophiles are archaea, though some of them are bacteria and fungi. Thermophilic bacteria are suggested to have been among the earliest bacteria.

measure of the amount of oxygen that can be consumed by reactions in a solution

Methanogens are anaerobic archaea that produce methane as a byproduct of their energy metabolism, i.e., catabolism. Methane production, or methanogenesis, is the only biochemical pathway for ATP generation in methanogens. All known methanogens belong exclusively to the domain Archaea, although some bacteria, plants, and animal cells are also known to produce methane. However, the biochemical pathway for methane production in these organisms differs from that in methanogens and does not contribute to ATP formation. Methanogens belong to various phyla within the domain Archaea. Previous studies

A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from . The optimum growth temperature for these organisms is 37 °C (about 99 °F). The term is mainly applied to microorganisms. Organisms that prefer extreme environments are known as extremophiles. Mesophiles have diverse classifications, belonging to two domains: Bacteria, Archaea, and to kingdom Fungi of domain Eukarya. Mesophiles belonging to the domain Bacteria can either be gram-positive or gram-negative. Oxygen requirements for mesophiles can be aerobi

Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from residences and from commercial, institutional and public facilities that exist in the locality. Sub-types of sewage are greywater (from sinks, bathtubs, showers, dishwashers, and clothes washers) and blackwater (the water used to flush toilets, combined with the human waste that it flushes away). Sewage also contains soaps and detergents. Food waste may be prese

thumb|Microbial hydrogen production. Biohydrogen is H2 that is produced biologically. Interest is high in this technology because H2 is a clean fuel and can be readily produced from certain kinds of biomass, including biological waste. Furthermore some photosynthetic microorganisms are capable of producing H2 directly from water splitting using light as energy source.

gas produced naturally within marshes, swamps and bogs

Crops grown solely for energy production by combustion

complex mix of different gases created by the action of microorganisms within a landfill

Acetogenesis is a process through which acetyl-CoA or acetic acid is produced by anaerobic bacteria through the reduction of Carbon dioxide| via the Wood–Ljungdahl pathway. Other microbial processes that produce acetic acid (like certain types of fermentation or the oxidative breakdown of carbohydrates or ethanol by acetic acid bacteria) are not considered acetogenesis. The diverse bacterial species capable of acetogenesis are collectively called acetogens.

species of fungus

Russian academician and physician (1867-1928)

ponds designed and built for wastewater treatment

Acidogenesis is the second stage in the four stages of anaerobic digestion: Hydrolysis: A chemical reaction where particulates are solubilized and large polymers converted into simpler monomers; Acidogenesis: A biological reaction where simple monomers are converted into volatile fatty acids; Acetogenesis: A biological reaction where volatile fatty acids are converted into acetic acid, carbon dioxide, and hydrogen Methanogenesis: A biological reaction where acetates are converted into methane and carbon dioxide, while hydrogen is consumed. Anaerobic digestion is a complex biochemical proce

3-Nitrooxypropanol (abbreviated as 3-NOP or 3NOP, commercially known as Bovaer) is a synthetic organic compound with the formula HOCH2CH2CH2ONO2. It is the mononitrate ester of 1,3-propanediol and acts as an enzyme inhibitor that specifically targets methyl coenzyme M reductase (MCR), the enzyme that catalyzes the final step of methanogenesis in microbes living in the digestive system of ruminants, such as cows and sheep.

water quality measurement

right|thumbnail|300px|Acidogenic digestate produced from mixed municipal waste Digestate is the material remaining after the anaerobic digestion (decomposition under low oxygen conditions) of a biodegradable feedstock. Anaerobic digestion produces two main products: digestate and biogas. Digestate is produced both by acidogenesis and methanogenesis and each has different characteristics. These characteristics stem from the original feedstock source as well as the processes themselves.

used to dispose of animal waste, particularly that of cows and pigs

The anaerobic chemical reactions and pathways resulting in the breakdown of glucose into ethanol, lactate, formate, succinate, and acetate, yielding energy in the form of ATP.

An acetogen is a microorganism that generates acetate (CH3COO−) as an end product of either anaerobic respiration or fermentation. In a narrower sense, a homoacetogen is a bacterial or archaeal microorganism that performs anaerobic respiration and carbon fixation simultaneously through the reductive acetyl coenzyme A (acetyl-CoA) pathway – also known as the Wood-Ljungdahl pathway; they can produce acetyl-CoA (and from that, in most cases, acetate as the end product) from two molecules of carbon dioxide (CO2) and four molecules of molecular hydrogen (H2). This process is known as acetogenesis,

class of enzymes