A comparison of backcountry waste management methods
Introduction
Human waste management in backcountry recreational areas has long been a challenge for trail maintaining organizations. In the 1970s, a surge in hiking in the Green Mountains led to serious waste problems; popular sites were littered with trash, and hikers were defecating wherever they could find a clean spot. The lack of proper waste management posed severe environmental and health risks. Historically, pit privies were the primary method of handling human waste in the backcountry. These were simple outhouse structures built over a hole in the ground where waste accumulated and decomposed anaerobically. This anaerobic system increased risk of groundwater contamination, created unpleasant odors, and required frequent site relocations. Recognizing these issues, organizations like the Green Mountain Club (GMC) sought more sustainable and environmentally responsible solutions including moldering privies and batch bin composting systems. The following analysis considers the design, advantages, and overall effectiveness of moldering privies and batch bin systems in backcountry waste management.
Moldering Privy
A moldering privy, first ideated and constructed by GMC volunteer Dick Andrews in 1997, consists of a shelter or outhouse built on top of a foundation known as a crib (figure 1). The crib is situated on a shallow depression to facilitate liquid percolation into the soil. Human waste is collected in the crib and mixed with a bulking agent, typically wood shavings, which aids in aeration and decomposition. The crib is enclosed with hardware cloth and insect screening to keep rodents and insects out while maintaining airflow. Native microorganisms and invertebrates, such as red wiggler worms, can be added to the crib to contribute to the composting process. The worms aerate the pile by burrowing, which enhances oxygen delivery to aerobic bacteria, expediting decomposition. In the crib, a slow, cool composting process takes place, operating at temperatures between 4 and 37 degrees Celsius (Hardy et al. 2015). Due to dissolved salts and minerals, the compost pile does not freeze until temperatures dip below -2 degrees Celsius (Hardy et al. 2015), allowing microbial activity to become dormant in the winter and resume once conditions become favorable again. Throughout the year, maintainers visit the site about three to four times to monitor capacity and moisture levels in the crib (figure 2), adding water if conditions are too dry or additional bulking agent if urine levels create odor issues. The GMC typically constructs a double-crib system, allowing for alternating use. While one chamber is in use, the other continues composting. The longer waste is left to compost, the more pathogens break down, making the final product safe for disposal. Once fully composted, the material can be spread on the forest floor at a safe distance from water sources, campsites, and trails.
Batch Bin Composting
Batch bin composting, introduced in the 1970s, was designed to provide an alternative human waste management solution in high-altitude areas where pit privies are impractical due to thin or saturated soils. This method relies on hot composting, which requires active human intervention to maintain optimal conditions. A batch bin system includes a conventional outhouse with a polyethylene, leak-proof 70-gallon container, known as the catcher, placed beneath the toilet seat. When full, a maintainer transfers the raw sewage from the catcher to 32-gallon storage containers (figure 3). Then, when all storage containers are full, the maintainer moves all the sewage into a large cylindrical composting bin (approximately 4 feet in diameter and 2.5 feet high) where the composting run begins. Each compost run lasts four to six weeks, during which bacteria and fungi actively break down waste, increasing the temperature of the pile. At 90 degrees Fahrenheit, human pathogens are effectively killed (Antos-Ketcham and Manikan, 2015). Once the composting phase concludes, the material is transferred to a drying rack for an additional six to twelve months of decomposition. Some finished compost is retained to inoculate future batches with beneficial organisms, while the remainder is dispersed across the forest floor, distant from water sources, trails, and campsites.
To optimize decomposition, a carbon-to-nitrogen ratio of 30:1 is most desirable (Fay and Walker, 1977), achieved by mixing two parts bark mulch with one part waste. When using the privy, users are asked to add a handful of mulch. The supply of mulch at sites depends on volunteer maintainers or seasonal field staff to hike them in on pack boards. Some sites may be accessible by ATV or a ski lift/gondola. Users are also requested to avoid urinating in batch bin privies as excess urine increases nitrogen levels, requiring additional bark mulch to maintain the ideal ratio. Inevitably, some urine is added to the catcher, especially at high-use sites, so a Beyond-the-Bin (BTB) liquid management system is often incorporated to separate excess liquid (figure 4). A drain plug is installed on the catcher, allowing liquid waste to flow into a filtration vessel containing a strainer plate to catch large solids. The effluent liquid is then filtered through a layer of anthracite coal and septic stone before being dispersed into the soil. Removing as much urine as possible in the system reduces odors, minimizes spillage, and lowers the risk of pathogen exposure for maintainers. After the final compost run of the season, the pipe fittings and filters must be disconnected in order to prevent damage from freezing in the winter.
Analysis
Unlike pit privies which often get submerged in seasonal high water tables and consequently contaminate groundwater, moldering privies and batch bins keep waste above ground, preventing waterlogging and proliferation of pathogens. While both systems are preferred over the traditional pit toilet, batch bin systems are less efficient than moldering privies, demanding more frequent maintenance, transport of bark mulch, and direct handling of raw waste. On the other hand, moldering privies offer a lower maintenance alternative that minimizes human exposure to pathogens with the same waste-handling capacity. The moldering privy’s reliance on ambient microbial activity makes it an environmentally sustainable and low-maintenance choice for backcountry waste management.
References
Antos-Ketcham, P., & Manikan, S. (2015). Batch-bin composting. In Green Mountain Club, The Appalachian Trail Conservancy, National Park Service, & US Forest Service (Eds.), Backcountry sanitation manual, Second edition (pp. 71-94).
Fay, S.C., & Walke, R.H. (1977). The composting option for human waste disposal in the backcountry.USDA Forest Service Research Note NE-246. The Northeastern Forest Experiment Station & Forest Service, US Department of Agriculture. Upper Darby, PA.
Hardy, D., Antos-Ketcham, P., & Andrews, D. (2015). The moldering privy. In Green Mountain Club, The Appalachian Trail Conservancy, National Park Service, & US Forest Service (Eds.), edition Backcountry sanitation manual, Second edition (pp. 52-70).