In-vessel composting generally describes a group of methods that confine the
composting
Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting ...
materials within a building, container, or vessel. In-vessel composting systems can consist of metal or plastic tanks or concrete bunkers in which air flow and temperature can be controlled, using the principles of a "
bioreactor
A bioreactor refers to any manufactured device or system that supports a biologically active environment. In one case, a bioreactor is a vessel in which a chemical process is carried out which involves organisms or biochemically active substances ...
". Generally the air circulation is metered in via buried tubes that allow fresh air to be injected under pressure, with the exhaust being extracted through a
biofilter, with temperature and moisture conditions monitored using probes in the mass to allow maintenance of optimum
aerobic decomposition conditions.
This technique is generally used for municipal scale
organic waste processing, including final treatment of sewage
biosolids, to a stable state with safe pathogen levels, for reclamation as a soil amendment. In-vessel composting can also refer to
aerated static pile composting with the addition of removable covers that enclose the piles, as with the system in extensive use by farmer groups in Thailand, supported by the National Science and Technology Development Agency there. In recent years, smaller scale in-vessel composting has been advanced. These can even use common roll-off waste dumpsters as the vessel. The advantage of using roll-off waste dumpsters is their relatively low cost, wide availability, they are highly mobile, often do not need building permits and can be obtained by renting or buying.
Evaluation is ongoing with regard to the health risks associated with compost derived from sewage biosolids—including identifying safe levels of contaminates such as
PFASs
Per- and polyfluoroalkyl substances (PFASs) are synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. An early definition, from 2011, required that they contain at least one perfluoroalkyl mo ...
("forever chemicals").
Offensive
odor
An odor (American English) or odour (Commonwealth English; see spelling differences) is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive via their sense ...
s are caused by putrefaction (
anaerobic decomposition) of nitrogenous animal and vegetable matter gassing off as
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogeno ...
. This is controlled with a higher
carbon to nitrogen ratio, or increased aeration by ventilation, and use of a coarser grade of carbon material to allow better air circulation. Prevention and capture of any gases naturally occurring (
volatile organic compounds
Volatile organic compounds (VOCs) are organic compounds that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, ...
) during the hot aerobic composting involved is the objective of the biofilter, and as the filtering material saturates over time, it can be used in the composting process and replaced with fresh material.
A more advanced systems design is able to limit the odor issues considerably, and it is also able to raise the total energy and resource output by integrating in-vessel composting with
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 ...
. Through anaerobic decomposition it is also possible to reduce pathogen levels similarly to that of traditional aerated composting when the anaerobic bioreactors operate at thermophilic temperatures, between 41 and 122 °C (106 and 252 °F).§
Gallery
Image:CVRD1loader.5bays.jpg, Biosolids composting facility - receiving and mixing bays and 5 reactor chambers
Image:CVRD2week1bay.jpg, Composting chamber material after 1 week
Image:CVRD3week2.bay.jpg, Composting chamber material after 2 weeks
Image:CVRD4chamber.air.jpg, Air supply and exhaust system for enclosed composting
Image:CVRD5biofilter.air.exhaust.jpg, Exhaust biofilter mound
See also
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Aerated static pile composting
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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 ...
*
Compost
Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting ...
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List of solid waste treatment technologies
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Mechanical biological treatment
A mechanical biological treatment (MBT) system is a type of waste processing facility that combines a sorting facility with a form of biological treatment such as composting or anaerobic digestion. MBT plants are designed to process mixed househ ...
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Waste management
Waste management or waste disposal includes the processes and actions required to manage waste from its inception to its final disposal.
This includes the collection, transport, treatment and disposal of waste, together with monitori ...
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Windrow composting
References
External links
Composting Association UK
{{Environmental technology
Industrial composting
Waste treatment technology