Comparison of common biogas technologies

The following is a partial list of types of anaerobic digesters. These processes and systems harness

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 ferm ...

for purposes such as treatment of biowaste, animal manure,

sewage 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 residenc ...

and

biogas Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. It is a ...

generation. Anaerobic digesters can be categorized according to several criteria: by whether the biomass is fixed to a surface ("attached growth") or can mix freely with the reactor liquid ("suspended growth"); by the organic loading rate (the influent mass rate of

chemical oxygen demand In environmental chemistry, the chemical oxygen demand (COD) is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed in mass of oxygen consumed over volume of solution whic ...

per unit volume); by centralized plants and decentralized plants. Most anaerobic digesters worldwide are built based on wet-type anaerobic digestion, wherein biomass (usually animal dung) and water are mixed in equal amounts to form a slurry in which the content of total solids (TS) is about 10-15%. While this type is suitable for most regions, it becomes a challenge in large plants where it necessitates the use of large quantities of water every day, often in water-scare areas. Solid-state type digesters, as opposed to the wet-type digesters, reduces the need to dilute the biomass before using it for digestion. solid-state type digesters can handle dry, stackable biomass with a high percentage of solids (up to 40%), and consists of gas-tight chambers called fermenter boxes working in batch-mode that are periodically loaded and unloaded with solid biomass and manure. The widely used UASB reactor, for example, is a suspended-growth high-rate digester, with its biomass clumped into granules that will

settle Settle or SETTLE may refer to: Places * Settle, Kentucky, United States * Settle, North Yorkshire, a town in England ** Settle Rural District, a historical administrative district Music * Settle (band), an indie rock band from Pennsylvania * ''S ...

relatively easily and with typical loading rates in the range 5-10 kgCOD/m³/d. Most common types of anaerobic digestion are liquid, plug-flow and solid-state type digesters. Examples of anaerobic digesters include: * Anaerobic activated sludge process *

Anaerobic clarigester The anaerobic clarigester is a form of anaerobic digester. It is regarded as being the ancestor of the upflow anaerobic sludge blanket digestion (UASB) anaerobic digester.

Anaerobic contact process The anaerobic contact process is a type of anaerobic digester. Here a set of reactors are created in series, where biomass is separated and returned to the complete mixture. This recycled material is pumped up into the bottom of the first reactor, ...

* Anaerobic expanded-bed reactor *

Anaerobic filter Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: * Anaerobic adhesive, a bonding a ...

* Anaerobic fluidised bed *

Anaerobic lagoon An anaerobic lagoon or manure lagoon is a man-made outdoor earthen basin filled with animal waste that undergoes anaerobic respiration as part of a system designed to manage and treat refuse created by concentrated animal feeding operations (CAFOs). ...

* Anaerobic MBRs *

Anaerobic migrating blanket reactor Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: * Anaerobic adhesive, a bonding a ...

* Batch system anaerobic digester *

Continuous stirred-tank reactor The continuous stirred-tank reactor (CSTR), also known as vat- or backmix reactor, mixed flow reactor (MFR), or a continuous-''flow'' stirred-tank reactor (C''F''STR), is a common model for a chemical reactor in chemical engineering and environmen ...

(CSTR) *

Expanded granular sludge bed digestion An expanded granular sludge bed (EGSB) reactor is a variant of the upflow anaerobic sludge blanket digestion (UASB) concept for anaerobic wastewater treatment. The distinguishing feature is that a faster rate of upward-flow velocity is designed f ...

(EGSB) *

Hybrid reactor :''See Hybrid nuclear fusion for the proposed nuclear reactor.'' A hybrid biological reactor (HBR) was developed which involved the introduction of a new phase of attached-biomass into a regular suspended-growth system (activated sludge process) b ...

Imhoff tank The Imhoff tank, named for German engineer Karl Imhoff (1876–1965), is a chamber suitable for the reception and processing of sewage. It may be used for the clarification of sewage by simple settling and sedimentation, along with anaerobic dige ...

* Internal circulation reactor (IC) * One-stage anaerobic digester * Plug-flow anaerobic digester *

Submerged media anaerobic reactor Submerge (and its variants) means to be covered by something (usually a liquid), such as being underwater: * Submerged arc welding * Submerged continent * Submerged forest * Submerged floating tunnel * Submerged specific gravity * Submergent ...

Sintex Digester Sintex group, formerly known as The Bharat Vijay Mills Ltd and Sintex Industries Ltd, is the world's largest producer of plastic water tanks and Asia's largest manufacturer of corduroy fabrics. Sintex operates in Europe, America, Africa, and A ...

*Solid-state anaerobic digester (SSAD) * Two-stage anaerobic digester *

Upflow anaerobic sludge blanket digestion Upflow anaerobic sludge blanket (UASB) technology, normally referred to as UASB reactor, is a form of anaerobic digester that is used for wastewater treatment. The UASB reactor is a methanogenic (methane-producing) digester that evolved from th ...

(UASB) * Upflow and down-flow anaerobic attached growth

References

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