composting toilet composting toilet a composting toilet is a type of dry toilet that treats human waste by a biological process called composting. this process leads to the decomposition of organic matter and turns human waste into compost-like material. composting is carried out by microorganisms (mainly bacteria and fungi) under controlled aerobic conditions. most composting toilets use no water for flushing and are therefore called "dry toilets". composting toiletcomposting toilet at activism festival 2010 in the mountains outside jerusalemposition in sanitation chainuser interface, collection/treatment (on-site)application levelhousehold, neighborhoodmanagement levelhousehold, public, shared (most common is household level)inputsfeces, urine, organics, dry cleansing materialsoutputscompost, effluenttypesslow composting (or moldering) toilets, active composters (self-contained), vermifilter toiletsenvironmental concernsnone in many composting toilet designs, a carbon additive such as sawdust, coconut coir, or peat moss is added after each use. this practice creates air pockets in the human waste to promote aerobic decomposition. this also improves the carbon-to-nitrogen ratio and reduces potential odor. most composting toilet systems rely on mesophilic composting. longer retention time in the composting chamber also facilitates pathogen die-off. the end product can also be moved to a secondary system – usually another composting step – to allow more time for mesophilic composting to further reduce pathogens. composting toilets, together with the secondary composting step, produce a humus-like end product that can be used to enrich soil if local regulations allow this. some composting toilets have urine diversion systems in the toilet bowl to collect the urine separately and control excess moisture. a vermifilter toilet is a composting toilet with flushing water where earthworms are used to promote decomposition to compost. composting toilets do not require a connection to septic tanks or sewer systems unlike flush toilets. common applications include national parks, remote holiday cottages, ecotourism resorts, off-grid homes and rural areas in developing countries. terminology schematic of the composting chamber which is located below the toilet seat the term "composting toilet" is used quite loosely, and its meaning varies by country. for example, in germany and scandinavian countries, composting always refers to a predominantly aerobic process. this aerobic composting may take place with an increase in temperature due to microbial action, or without a temperature increase in the case of slow composting or cold composting. if earth worms are used (vermicomposting) then there is also no increase in temperature. composting toilets differ from pit latrines and arborloos, which use less controlled decomposition and may not protect groundwater from nutrient or pathogen contamination or provide optimal nutrient recycling. they also differ from urine-diverting dry toilets (uddts) where pathogen reduction is achieved through dehydration (also known by the more precise term "desiccation") and where the feces collection vault is kept as dry as possible. composting toilets aim to have a certain degree of moisture in the composting chamber. composting toilets can be used to implement an ecological sanitation approach for resource recovery, and some people call their composting toilet designs "ecosan toilets" for that reason. however, this is not recommended as the two terms (i.e. composting and ecosan) are not identical. schematic of a composting toilet with urine diversion composting toilets have also been called "sawdust toilets", which can be appropriate if the amount of aerobic composting taking place in the toilet's container is very limited. the "clivus multrum" is a type of composting toilet which has a large composting chamber below the toilet seat and also receives undigested organic material to increase the carbon to nitrogen ratio. alternatives with smaller composting chambers are called "self-contained composting toilets" since the composting chamber is part of the toilet unit itself. applications this is the pedestal for a split-system composting toilet where collection/treatment chambers are located below the bathroom floor. inexpensive do-it-yourself compost toilet at dial house, essex, england, utilizing an old desk as the toilet unit. public composting toilet at a highway rest facility in sweden composting toilets can be suitable in areas such as a rural area or a park that lacks a suitable water supply, sewers and sewage treatment. they can also help increase the resilience of existing sanitation systems in the face of possible natural disasters such as climate change, earthquakes or tsunami. composting toilets can reduce or perhaps eliminate the need for a septic tank system to reduce environmental footprint (particularly when used in conjunction with an on-site greywater treatment system). these types of toilets can be used for resource recovery by reusing sanitized feces and urine as fertilizer and soil conditioner for gardening or ornamental activities. basics main article: compost components and use a composting toilet consists of two elements: a place to sit or squat and a collection/composting unit. the composting unit consists of four main parts: storage or composting chamber a ventilation unit to ensure that the degradation process in the toilet is predominantly aerobic and to vent odorous gases a leachate collection or urine diversion system to remove excess liquid an access door for extracting the compost many composting toilets collect urine in the same chamber as feces, thus they do not divert urine. adding small amounts of water that is used for anal cleansing is no problem for the composting toilet to handle. some composting toilets divert urine (and water used for anal washing) to prevent the creation of anaerobic conditions that can result from over saturation of the compost, which leads to odors and vector problems. this usually requires all users to use the toilet in a seated position. offering a waterless urinal in addition to the toilet can help keep excess amounts of urine out of the composting chamber. alternatively, in rural areas, men and boys may be encouraged just to find a tree. construction the composting chamber can be constructed above or below ground level. it can be inside a structure or include a separate superstructure. a drainage system removes leachate. otherwise, excess moisture can cause anaerobic conditions and impede decomposition. urine diversion can improve compost quality, since urine contains large amounts of ammonia that inhibits microbiological activity. composting toilets greatly reduce human waste volumes through psychrophilic, thermophilic or mesophilic composting. keeping the composting chamber insulated and warm protects the composting process from slowing due to low temperatures. odorous gases the following gases may be emitted during the composting process that takes place in composting toilets: hydrogen sulfide (h2s), ammonia, nitrous oxide (n2o) and volatile organic compounds (vocs). these gases can potentially lead to complaints about odours. some methane may also be present, but it is not odorous. pathogen removal waste-derived compost recycles fecal nutrients, but it can carry and spread pathogens if the process of reuse of waste is not done properly. pathogen destruction rates in composting toilets are usually low, particularly of helminth eggs (such as those from the genus ascaris). this carries the risk of spreading disease if a proper system management is not in place. compost from human waste processed under only mesophilic conditions or taken directly from the compost chamber is not safe for food production. high temperatures or long composting times are required to kill helminth eggs, the hardiest of all pathogens. helminth infections are common in many developing countries. in thermophilic composting bacteria that thrive at temperatures of 40–60 °c (104–140 °f) oxidize (break down) waste into its components, some of which are consumed in the process, reducing volume and eliminating potential pathogens. to destroy pathogens, thermophilic composting must heat the compost pile sufficiently, or enough time (1–2 years) must elapse since fresh material was added that biological activity has had the same pathogen removal effect. one guideline claims that pathogen levels are reduced to a safe level by thermophilic composting at temperatures of 55 °c for at least two weeks or at 60 °c for one week. an alternative guideline claims that complete pathogen destruction may be achieved already if the entire compost heap reaches a temperature of 62 °c (144 °f) for one hour, 50 °c (122 °f) for one day, 46 °c (115 °f) for one week or 43 °c (109 °f) for one month, although others regard this as overly optimistic. design considerations composting toilet with a seal in the lid in germany environmental factors four main factors affect the decomposition process: sufficient oxygen is necessary for aerobic composting moisture content from 45 to 70 percent (heuristically, "the compost should feel damp to the touch, with only a drop or two of water expelled when tightly squeezed in the hand".) temperature between 40 °c (104 °f) and 50 °c (122 °f), which is achieved through proper chamber dimensioning and possibly active mixing carbon-to-nitrogen ratio (c:n) of 25:1 additives and bulking material human waste and food waste do not provide optimum conditions for composting. usually the water and nitrogen content is too high, particularly when urine is mixed with feces. additives or "bulking material", such as wood chips, bark chips, sawdust, shredded dry leaves, ash and pieces of paper can absorb moisture. the additives improve pile aeration and increase the carbon to nitrogen ratio. bulking material also covers feces and reduces insect access. absent sufficient bulking material, the material may become too compact and form impermeable layers, which leads to anaerobic conditions and odour. leachate management leachate removal controls moisture levels, which is necessary to ensure rapid, aerobic composting. some commercial units include a urine-separator or urine-diverting system and/or a drain at the bottom of the composter for this purpose. aeration and mixing microbial action also requires oxygen, typically from the air. commercial systems provide ventilation that moves air from the bathroom, through the waste container, and out a vertical pipe, venting above the roof. this air movement (via convection or fan forced) passes carbon dioxide and odors. some units require manual methods for periodic aeration of the solid mass such as rotating the composting chamber or pulling an "aerator rake" through the mass. comparisons with other types of toilets pit latrines main article: pit latrine composting toilets convert feces into a dry, odorless material which is very different to the wet fecal sludge produced in pit latrines which has to be taken care of through a fecal sludge management system. composting toilets do not cause groundwater pollution due to their safe containment of feces in above-ground vaults compared to pit latrines, allowing composting toilets to be sited in locations where pit-based systems are not appropriate. composting toilets have higher capital costs than pit latrines, but lower lifecycle costs. they require more involvement by the user than the "drop and forget" approach of pit latrines. flush toilets main article: flush toilet unlike flush toilets, composting toilets do not require a sewerage system and do not mix flushing water with urine and feces. they require more involvement by the user than the "flush and forget" approach of flush toilets connected to sewage treatment plants. urine-diverting dry toilets main article: urine-diverting dry toilet composting toilets, although similar to and sharing many advantages and disadvantages with urine-diverting dry toilets (uddt), are more complex and require more maintenance to keep a consistent and relatively high moisture content. some composting toilets are designed with urine diversion. types external composting chamber of a composting toilet at a house in france commercial units and construct-it-yourself systems are available. variations include number of composting vaults, removable vault, urine diversion and active mixing/aeration. slow composting (or moldering) toilets most composting toilets use slow composting which is also called "cold composting". the compost heap is built up step by step over time. the finished end product from "slow" composting toilets ("moldering toilets" or "moldering privies" in the us), is generally not free of pathogens. world health organization guidelines from 2006 offer a framework for safe reuse of waste, using a multiple barrier approach. slow composting toilets employ a passive approach. common applications involve modest and often seasonal use, such as remote trail networks. they are typically designed such that the materials deposited can be isolated from the operational part. the toilet can also be closed to allow further mesophilic composting. slow composting toilets rely on long retention times for pathogen reduction and for decomposition of waste or on the combination of time and/or the addition of red wriggler worms for vermi-composting. worms can be introduced to accelerate composting. some jurisdictions of the us consider these worms as invasive species. active composters (self-contained) "self-contained" composting toilets compost in a container within the toilet unit.