Anaerobic digester types

The following is a partial list of types of anaerobic digesters. These processes and systems harness anaerobic digestion for purposes such as treatment of biowaste, animal manure, sewage and biogas generation.^[1] 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 per unit volume);^[2] by centralized plants and decentralized plants.^[3] 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.^[4] 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.^[5] The widely used UASB reactor, for example, is a suspended-growth high-rate digester, with its biomass clumped into granules that will settle relatively easily and with typical loading rates in the range 5-10 kgCOD/m³/d.^[2]

Comparison of common AD digester technology types.

Most common types of anaerobic digestion are liquid, plug-flow and solid-state type digesters.^[6]

Examples of anaerobic digesters include:

• Anaerobic activated sludge process
• Anaerobic clarigester
• Anaerobic contact process
• Anaerobic expanded-bed reactor
• Anaerobic filter
• Anaerobic fluidised bed
• Anaerobic lagoon
• Anaerobic MBRs
• Anaerobic migrating blanket reactor
• Batch system anaerobic digester
• Continuous stirred-tank reactor (CSTR)
• Expanded granular sludge bed digestion (EGSB)
• Hybrid reactor
• Imhoff tank
• Internal circulation reactor (IC)
• One-stage anaerobic digester
• Plug-flow anaerobic digester
• Submerged media anaerobic reactor
• Sintex Digester
• Solid-state anaerobic digester (SSAD)
• Two-stage anaerobic digester
• Upflow anaerobic sludge blanket digestion (UASB)
• Upflow and down-flow anaerobic attached growth

References

1. "BIOGAS AND ANAEROBIC DIGESTION: Fundamentals and Applications" (PDF). The Global Climate and Energy Project (GCEP) at Stanford University.
2. Grant, Shannon R.; Shashi Gorur; James C. Young; Robert Landine; Albert C. Cocci; C. Calvert Churn (November 2002). "An Anaerobic Exercise: A comparison of anaerobic treatment technologies for industrial wastewater". Environmental Protection: 18–26. Retrieved 4 Jan 2013.
3. Agali, Chiamaka (2018). "Overview of Biogas Production". Stanford University.
4. "War on India's Toxic Pollution". Renewable Energy World. 2020.
5. Zhou, Haoqin (January 2019). "Solid-State Anaerobic Digestion for Waste Management and Biogas Production". ResearchGate.
6. "Types of anaerobic digester". ResearchGate. January 2002.