GC: n
CT: Anaerobic digestion is the natural breakdown of organic materials into methane and carbon dioxide gas and fertiliser. This takes place naturally, or in an anaerobic digester.
A typical anaerobic digester is a sealed vessel, or series of vessels, in which bacteria act without oxygen. The organic material contents need to be fully mixed and warmed, usually to blood temperature.
S: http://www.organic-power.co.uk/what_is_anaerobic_digestion.aspx (last access: 27 December 2014)
N: 1. – anaerobic (adj): “capable of living without oxygen,” 1879 (as anaerobian; modern form first attested 1884), from French anaérobie, coined 1863 by French bacteriologist Louis Pasteur (1822-1895), from Greek an- “without” + aer “air” + bios “life”.
– digester (n): Origin: to digest (From Middle English digesten, from Latin digestus, past participle of dīgerō (“carry apart”), from dī- (for dis- (“apart”)) + gerō (“I carry”), influenced by Middle French digestion) + -er (From Middle English -er, -ere, from Old English -ere (agent suffix), from Proto-Germanic *-ārijaz (agent suffix). Usually thought to have been borrowed from Latin -ārius. Cognate with Dutch -er and -aar, Low German -er, German -er, Swedish -are, Icelandic -ari, Gothic (-areis). Compare also Ancient Greek -ήριος (-ḗrios), Old Church Slavonic -арь (-arĭ).
Reinforced by the synonymous but unrelated Old French -or, -eor (Anglo-Norman variant -our), from Latin -(ā)tor, from Proto-Indo-European *-tōr). Also digestor.
2. Many different anaerobic digester systems are commercially available. The following is an overview based on organic waste stream type (manure, municipal wastewater treatment, industrial wastewater treatment and municipal solid waste): Manure: Anaerobic digestion systems for livestock manure operate to reduce methane emissions, odors, pathogens and weed seeds and produce biogas. They fall into four general categories:
- Covered anaerobic lagoon digester: Sealed with flexible cover, with methane recovered and piped to the combustion device. Some systems use a single cell for combined digestion and storage.
- Plug flow digester: Long, narrow concrete tank with a rigid or flexible cover. The tank is built partially or fully below grade to limit the demand for supplemental heat. Plug flow digesters are used at dairy operations that collect manure by scraping.
- Complete mix digester: Enclosed, heated tank with a mechanical, hydraulic, or gas mixing system. Complete mix digesters work best when there is some dilution of the excreted manure with water (e.g., milking center wastewater).
- Dry Digestion: Upright, silo-style digesters made of concrete and steel with rigid cover. Dry digesters operate at 20 to 42 percent total solids, which allows them to combine high dry matter manure and crop residuals with very dilute liquid manures or co-substrates.
3. Biogas recovery systems are sometimes known as anaerobic digesters, because they use a process called anaerobic digestion. (Conventional lagoons operate on the same biological principle.) During anaerobic digestion, bacteria break down manure in an oxygen-free environment. One of the natural products of anaerobic digestion is biogas, which typically contains between 60 to 70 percent methane, 30 to 40 percent carbon dioxide, and trace amounts of other gases.
S: 1. OED – http://www.etymonline.com/index.php?allowed_in_frame=0&search=anaerobic&searchmode=none (last access: 27 December 2014); http://www.memidex.com/digester (last access: 27 December 2014); MW – http://www.merriam-webster.com/dictionary/digester (last access: 27 December 2014). 2. http://www.americanbiogascouncil.org/biogas_what.asp (last access: 27 December 2014). 3. EPA – http://www.epa.gov/agstar/anaerobic/ (last access: 27 December 2014).
SYN: digester, digestion tank, sludge digestion tank, sludge digester, methanizer.
S: GDT – http://www.granddictionnaire.com/ficheOqlf.aspx?Id_Fiche=26500603 (last access: 28 February 2018); http://www.biofuelsdigest.com/bdigest/2016/10/17/bossie-the-climate-warrior-new-approaches-may-unlock-dairy-methanes-value/ (last access: 28 February 2018).
CR: acetogenesis, acidogenesis, anaerobic digestion, biogas, biomass, biomass energy, manure.
