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Anaerobic digester types

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File:Comparison of common biogas technologies.jpg

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.{{Cite web|url=https://gcep.stanford.edu/pdfs/energy_workshops_04_04/biomass_wilkie.pdf|title=BIOGAS AND ANAEROBIC DIGESTION: Fundamentals and Applications|website=The Global Climate and Energy Project (GCEP) at Stanford University}} 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); by centralized plants and decentralized plants.{{Cite web|url=http://large.stanford.edu/courses/2018/ph240/agali1/|title=Overview of Biogas Production|last=Agali|first=Chiamaka|date=2018|website=Stanford University}} 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.{{Cite news|url=http://finance.renewableenergyworld.com/pennwell.renewableenergy/news/read/39424925/|title=War on India’s Toxic Pollution|date=2020|work=Renewable Energy World}} 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.{{Cite web|url=https://www.researchgate.net/publication/331278955_Solid-State_Anaerobic_Digestion_for_Waste_Management_and_Biogas_Production|title=Solid-State Anaerobic Digestion for Waste Management and Biogas Production|last=Zhou|first=Haoqin|date=January 2019|website=ResearchGate}} 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.{{cite journal|last=Grant|first=Shannon R.|author2=Shashi Gorur |author3=James C. Young |author4=Robert Landine |author5=Albert C. Cocci |author6=C. Calvert Churn |title=An Anaerobic Exercise: A comparison of anaerobic treatment technologies for industrial wastewater|journal=Environmental Protection|date=November 2002|pages=18–26|url=http://eponline.com/Articles/2002/11/01/An-Anaerobic-Exercise.aspx?admgarea=ht.water.wastewater|access-date=4 Jan 2013}}

Most common types of anaerobic digestion are liquid, plug-flow and solid-state type digesters.{{Cite web|url=https://www.researchgate.net/publication/254469763_Types_of_anaerobic_digester_for_solid_wastes|title=Types of anaerobic digester|date=January 2002|website=ResearchGate}}

Examples of anaerobic digesters include:

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