Composting Systems

Project funded by the U.S. Environmental Protection Agency under Assistance Agreement No. CX824652

What is a system? drainage and proximity to surface water and A composting (or biological) toilet sys- . tem contains and processes excrement, toilet The main components of a composting paper, carbon additive, and sometimes, food toilet system (see Figure 1) are: . Unlike a septic system, a composting • a composting reactor connected to a dry or toilet system relies on unsaturated conditions micro-(s); (material cannot be fully immersed in water) • a screened air inlet and an exhaust system; where aerobic, or air-requiring, and • a means of ventilation to support the aero- fungi break down wastes, just as they do in a bic organisms in the composter; yard composter. • a means of draining and managing excess If sized and maintained properly, a com- liquid and (optional); posting toilet breaks down waste to 10 to 30% • process controls to optimize and facilitate of its original volume. The resulting soil-like management of the processes; and material, called “,” legally must be • an access door for removal of the end- either buried or removed by a licensed sep- product. tage hauler in accordance with state and local In the composting process, organic regulations. matter is transformed by naturally occurring Because they require little to no water bacteria and fungi that break down the waste and produce a usable end-product, com- into an oxidized, humus-like end-product, without the need for water or chemicals. Composting are mainly Fact Sheet Fact classified as either continuous com- posting or batch composting. Continu- Air Vent Toilet ous composters (including such brands as CTS, Clivus Multrum, Phoenix, Bi- olet, SunMar, etc.) are single chambers where excrement is added to the top, Toilet Chute and the end-product is removed from the bottom. Batch composters (such Composting Pile as Carousel, Vera, and nearly all of Inspection Hatch the site-built composters worldwide) Controller Composting Pile are actually two or more composters Box that are filled and then allowed to cure Finished while another reactor fills. Compost Access Hatch Compost What are the advantages and Liquid Storage disadvantages of using composting Compost Liquid Tank Access Port toilet systems? Advantages Figure 1: Composting Toilet • Composting toilet systems do not Adapted from: Clivus Multrum, Inc. (1994) with permission require water for flushing, and thus, reduce domestic water consumption. post-ing toilet systems have traditionally been • These systems reduce the quantity and used by public facilities, parks, cottages, and This fact sheet was developed by strength of wastewater to be disposed of remote homes. However, tightening waste- Clement Solomon, Peter Casey, onsite. water regulations, growing awareness of Colleen Mackne, and Andrew Lake. • They are especially suited for new con- sources, and compatible graywater ©1998 by the National Small struction at remote sites where conven- systems and micro-flush toilets are making Flows Clearinghouse tional onsite systems are not feasible. WWFSGN106 them a viable alternative to septic systems • Composting toilet systems have low pow- and central treatment plants in many er consumption. areas, particularly those with poor soil continued— ETI A General Overview Initiative • Self-contained systems eliminate the need for transportation of carbon for the bacteria, as well as keeping the pile porous for of wastes for treatment/disposal. proper air distribution. Periodic mixing or raking is suggested. • Composting and burying it around tree roots and In addition, the finished end-product must be removed period- nonedible plants keeps organic wastes productively cycling in ically (anywhere from every 3 months for a cottage system to the environment. every 2 years for a large central system). • Composting toilet systems can accept kitchen wastes, thus What is the cost of a composting toilet system? reducing household garbage. • In many states, installing a composting toilet system allows The cost of manufactured composting toilet systems the property owner to install a reduced-size leachfield, mini- vary. For the year-round home of two adults and two children, mizing costs and disruption of landscapes. the cost of a composting toilet system could range anywhere • Composting toilet systems divert nutrient- and -con- between $1,200 and $6,000, depending on the system. Cottage taining from soil, surface water, and groundwater. systems designed for seasonal use range from $700 to $1,500. Disadvantages How do I stay informed about composting technology? • Maintenance of composting toilet systems requires more For more information on composting toilet systems or a list responsibility and commitment by users and owners than of other fact sheets, contact the National Small Flows Clear- conventional wastewater systems. inghouse (NSFC) at West Virginia University, P.O. Box 6064, • Removing the finished end-product is an unpleasant job if the Morgantown, WV 26506-6064. Phone: (800) 624-8301 or composting toilet is not properly installed or maintained. (304) 293-4191. Fax: (304) 293-3161. World Wide Web site: • Composting toilet systems must be used in conjunction with a http://www.nsfc.wvu.edu. graywater system in most circumstances. The NSFC provides free and low-cost informational ser- • Smaller units may have limited capacity for accepting peak vices and products to help homeowners and small communities loads. address their wastewater needs. Also, information about manu- • Improper maintenance makes cleaning difficult and may lead facturers, consultants, regulations, and facilities can be obtained to health hazards and problems. from the NSFC’s databases. • Using an inadequately treated end-product as a soil amend- References ment may have possible health consequences. • There may be aesthetic issues because the excrement in some Clivus Multrum, Inc. 1994. “When nature calls... it calls Cli- systems may be in sight. vus®.” Clivus Multrum, Inc. Lawrence, Massachusetts. • Too much liquid residual (leachate) in the composter can Cook, B. 1981. “Field Evaluation of Compost Toilets.” Individ- disrupt the process if it is not drained and properly managed. ual Onsite Wastewater Systems: Proceedings of the Seventh • Most composting toilet systems require a power source. National Conference. pp. 83–98. • Improperly installed or maintained systems can produce Del Porto, D. A. and C. J. Steinfeld. 1998. The Composting and unprocessed material. Toilet Book. Chelsea Green Publishing, Inc. Whiteriver Junction, Vermont. What determines the performance of a composting toilet Felton, D. (editor). 1981. “State-Of-The Art Assessment of system? Compost Toilets and Greywater Treatment Systems.” The There are several factors that affect the rate of composting. Winthrop Rockefeller Foundation. Little Rock, Arkansas. The predominant factors are the microorganisms, temperature, Scholze, R. J. September 1985. “Innovation in Remote Site moisture, pH, carbon to ratio, and aeration. .” BioCycle. pp. 37–38. The two main parameters in the composting process that Scholze, R. J.; J. E. Alleman; S. R. Struss; and E. D. Smith. De- account for the destruction of are: cember 1986. “Technology for Waste Treatment at Remote • Antibiosis: During the process, bacterial reac- Army Sites.” USA-CERL Technical Report tions in the compost pile produce substances that are toxic to N-86/20. USA-CERL. Champaign, Illinois. most pathogens. Seabloom, R. W. and J. Engeset. March 1 & 2, 1978. “An Ap- • Time: When exposed to an unfavorable environment for an praisal of Composting Toilets.” Proceedings of the Second extended period of time, most pathogenic microorganisms Northwest On-Site Wastewater Disposal Short Course. will not survive. University of Washington. Seattle, Washington. As with all wastewater treatment systems, management is critical to the efficiency of the system. The mention of trade names or commercial products does not constitute endorsement or recommendation for use Are composting toilet systems easy to operate and maintain? by the NSFC or U.S. EPA. In general, operation and maintenance (O&M) for com- posting toilets does not require trained technicians or treatment plant operators. However, regular O&M is critical since all wastewater systems depend on responsible administration. In cold climates, all composting toilet systems should be heated to levels specified by the manufacturer or designer. Composting toilet systems may require bulking agents to be added, such as grass clippings, leaves, , or finely chopped straw. They assist composting by providing a source

2 Composting Toilet Systems