Many years ago Sun-Mar engineers realized that to work properly,
these three tasks required independent chambers, each with its own
separate environment. This revolutionary new three chamber approach
first developed in 1979 proved so successful that today it is incorporated
into all Sun-Mar units.
Our commitment to superior design
makes Sun-Mar the wise choice for anyone who wants a durable and
high quality product. Read on to learn the technology behind our
composting toilets and the advantages of these exclusive Sun-Mar
Sun-Mar engineers found that the ideal conditions for fast, odorless
composting were best provided in a rotating drum, (we call it the
Bio-drum), where the compost can be kept completely oxygenated,
mixed, moist and warm.
Waste and peat moss enter through a port in the top of the Bio-drum.
The drum handle on the front of the unit is turned periodically
to rotate the Bio-drum. This tumbling action thoroughly oxygenates
and mixes every part of the compost, keeping it uniformly moist.
As the drum rotates, a door closes automatically to keep the waste
inside the drum. After turning, a lock automatically maintains the
Bio-drum in a top dead center position ready to receive new material.
To prevent the compost from getting saturated, a screen at the
rear of the drum filters any excess liquid directly into the evaporating
chamber. By protecting the compost from direct heat, the Bio-drum
also keeps the compost uniformly moist.
Lastly, the Bio-drum can hold the necessary mass of material to
retain the natural heat developed in the core of the compost. On
some units, insulation on the outside of the drum prevents heat
loss from the Bio-drum. When the drum gets full, some compost is
extracted into the finishing drawer. This is done simply by pulling
the drum locker, and rotating the drum backwards. Now, the drum
door remains open, and compost falls into the second chamber - the
compost finishing drawer.
Advantages of Composting
in a Bio-Drum
Tumbling implants oxygen throughout the compost for use by aerobic
Tumbling ensures that the bulking material is well mixed into
The screen at the rear ensures the compost does not get saturated
and drive out the oxygen
Tumbling distributes the moisture evenly throughout the compost
The compost is shielded from direct heat and so does not dry out.
The mass in the drum enables the compost to hold warmth in the
core of the compost.
The Compost Finishing
The compost finishing drawer, the second independent chamber, is
below the composting drum, and just above the evaporating chamber.
Compost in this drawer is totally isolated from material in the
Bio-drum, is surrounded by drying air, and is no longer subject
to contamination from fresh waste. It is here that the composting
and sanitation processes are completed, and the compost becomes
safe to handle. The pull-out finishing drawer is removed by hand
and the sanitized compost may be emptied whenever it is necessary
to extract more compost from the drum. To be doubly safe, compost
should not be used on edible vegetables.
Advantages of a Separate
Compost Finishing Drawer
Composting can be completed in the drawer without contamination
by fresh waste.
Compost in the drawer is gradually dried ready for removal
Finished compost can be simply and safely removed
The third chamber, the base of the toilet, is the evaporating surface
from where any excess liquids which cannot be absorbed by the compost
are evaporated or drained. Air is drawn in through intake holes
at the base of the toilet, over the evaporating surface, and up
the vent stack. On electric models, air is drawn in by a fan, while
non electric models use natural draft induced by the chimney effect
of a 4" vent stack. In both cases a partial vacuum is maintained
which ensures that no odors can escape. Evaporation is assisted
onelectric models by a thermostaticallycontrolledheating element
in a sealed compartment underneath the evaporating chamber. This
heater keeps the floor of the chamber warm.
Advantages of a Separate
The large surface area maximizes evaporation.
A large volume of air moves directly over the evaporating surface
to speed moisture removal.
A base heater directly warms the evaporate for optimum results.
(Electric units only!)