History in Vermont
• Concept introduced to Long
Trail/Appalachian Trail System in 1997 by
Green Mountain Club Volunteer Dick
site was Little Rock Pond
Shelter in 1997.
• Concept based on Andrew’s Clivus
Multrum composting toilet in his home –
same composting techniques used.
• Moldering method of composting employs
mesophilic temperature range (68° to
112°F). AKA “Slow Composting.”
• Not hot enough to kill disease-causing
• Moldering toilets substitute long retention
time of waste to ensure pathogen
destruction – minimum of 2 years. The
longer the better.
Moldering – Where to use?
• At low to medium use sites.
• Defined as a site where it will take a minimum of 2+
years for one crib to fill up. If it fills faster than this a
batch-bin or commercial system is called for. Alternately
you can build more cribs – you as a manager need to
determine how many cribs you can accept
environmentally and aesthetically. GMC limit is two cribs.
• GMC recommends you choose a site where you believe
you have low use and where you can measure the use.
See how long it takes to fill a crib – use this data to
define your “use threshold.”
Original Crib design circa
1999 – Single Crib, 6x6
Finished Single Crib
unit. Privy attached to
crib with angle
The finished unit is
tall. Stairs or an
ramp/stair system is
• Basic Crib Capacity is 4’x4’x3’ (w/l/d).
• Shallow depression is made in the ground
below the crib to focus blackwater into
biologically active soil.
• Air Slots are covered on both sides with
hardware cloth and externally with dark
insect screening to prevent waste escape
and vector access.
• Original design utilized 6x6 timbers (treated and
• Easy to design and build but very heavy to pack to
remote backcountry campsites. A second or third crib
would need to be packed in when the first one was full.
• Current design is a two-chambered unit built with 4x4
uprights held together with 1x6 horizontal members. The
composting crib is covered with a removable roof
system. This unit is much lighter, easier to pre-build in
the frontcountry, and is more readily adaptable to double
and triple-chambered units.
The new design is a double-
chambered unit. The basic
frame is composed of six
4x4’s each 3 feet tall.
construction – new
privy and cribs.
Note strapping used to
reinforce hardware cloth to
Modified Moldering System w/
• Installed at AMC’s Upper Goose Pond
• A caretaker periodically homogenizes the
waste and adds bulking agent as needed.
• Crib is shallower and thus requires regular
tending to prevent overflow.
• Liquid separator requires a separate seat
and drains to a modified French Drain.
Clivus-Style Moldering Privy
• Constructed on the Appalachian Trail in
Maryland and Pennsylvania.
• Utilizes large sloping chamber.
• Dual Chambered Units create long retention
time for waste.
• No contact with soil – needs large base of
bulking agent added to create composting “bed.”
• System improvement needed: liquid drainage
system to French Drain or Beyond the Bin
Current Design – Lessons Learned
• Bulking agent (carbon source) must be brought in.
Reliance on area leaves and duff proved hard on the
resource. GMC has had the most success with dry
softwood planer shavings – most absorbent.
• A base of 4 to 6 inches of bulking agent should be added to
bottom of the crib to create a composting bed. This assists
in aeration and increases percolation of liquids by providing
• An access lid must be incorporated into the design so the
cone can be knocked over periodically and the waste pile
homogenized. Access through the seat is unsanitary.
• Pile can and will dry out if the manager does not monitor
pile moisture and add water as needed. A dry pile will not
compost – pathogens go dormant and persist.
Current Design – Lessons Learned
• GMC has begun to perforate the roof cover that goes
over the composting crib so that rain water can percolate
in and keep pile moist. For the active pile we ask users
to urinate on the pile – unless use levels create an
• GMC has added a sloping metal roof cover to
the composting chamber to prevent excessive
moisture and reduce the chance of cave-in from
heavy snow load.
Appalachian Trail Conservancy and Green
Mountain Club’s Backcountry Sanitation