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Every living organism consumes nutrients and creates waste. To transform waste back to nutrients and complete this cycle, nature uses the processes of decomposition and evaporation. As is often the case, nature seems to be doing business in the best way possible.

That’s why Sun-Mar™ toilets are designed not only to harness these natural processes but to optimize and accelerate them.


Toilet waste is over 90% water content. This can be evaporated and carried back to the atmosphere through the vent system. The small amount of remaining material is recycled into a useful fertilizing soil.

Wherever there is a poorly working septic system, a Sun-Mar™ can take care of the toilet waste; where there is an outhouse we offer the luxury of an indoor facility; and where there is no toilet at all, a Sun-Mar™ provides the right environmental choice. Sun-Mar™ units are economical, quick to install and easy to use.

621274Because no chemicals and no septic systems are used, fragile environments can be protected. A Sun-Mar™ composting unit is an environmentally healthy choice for recycling human waste. The Sun-Mar™ system produces no pollutants while collecting nutrients. With a Sun-Mar™, recycling is made easy!

As well as ensuring anaerobic breakdown in the Bio-drum, Sun-Mar™ ensures an odor free environment by engineering the air flow within the unit to maintain a partial vacuum at all times. Air is being drawn in either by a fan (or on non-electric units by the vent chimney) over the evaporating chamber and up the vent stack. Not only does this evaporate excess liquid, but by continuously pulling air in we ensure no smell escapes from the unit.

Evaporation is assisted on electric units by a thermostatically controlled heater in a sealed compartment underneath the evaporating chamber.

The Composting Chamber

Introduction to the Bio-Drum

The unique Sun-Mar™ Bio-Drum replicates the perfect environment for composting; combining moisture, warmth, organic material and oxygen. This design is patented.

The Bio-Drum allows aerobic microbes to flourish, which accelerates the break down of the waste.


There is a waste inlet port at the top of the drum that allows the waste, along with a bulking agent, to enter the drum. In order to aerate the composting matter, periodically turn the handle (on the front of the self-contained unit or on the side of the central units) to rotate the drum. The inlet door will automatically close during this process to ensure that no compost leaves the drum.

When it is time to empty the contents of the Bio-drum, you will need to release the drum locker and turn the drum backwards. This will force the inlet port to open, allowing the compost to drop into the finishing drawer.

After this process is complete, the bio-drum will lock itself back into place and the drum will be ready to receive new waste.

Advantages of the Bio-drum

Supplying Oxygen

The Bio-Drum system ensures the compost is thoroughly mixed and oxygenated. In fact, Bio-drum is the most effective and simplest way to achieve this kind of oxygenation.

Every time you rotate the drum, the entire pile of compost is imbued with oxygen. Oxygen is integral to the composting process. It allows aerobic bacteria to break down compost quickly and without any unpleasant odours.

Moisture control

Our patented Bio-Drum offers a moisture control benefit that is exclusive to the Bio-Drum design. Moisture control is integral to successful composting.

If the moisture content is below 40% the composting process will slow down and eventually stop. The Bio-Drum is designed so that direct heat is never applied to the compost, meaning it won’t dry out. The regular tumbling process also distributes the moisture evenly through the compost.

When moisture rises above 60%, oxygen begins to dissipate from a compost pile, leaving it to become increasingly anaerobic (similar to a septic system). The Bio-Drum system, however, works to avoid this by allowing excess fluid to drain through a screen at the base of the drum into an evaporation chamber. This optimizes the speed of the composting process.

Temperature Control

As the microbes work, they generate heat, which is largely retained in the compost pile by virtue of its mass. Ordinarily, this provides adequate heat to attain optimum composting conditions. However, in colder locations, where the ambient temperature is regularly below 13 degrees C, we generally supply a 240-volt unit, which includes a heater. The heat output is controlled by a thermostat to prevent the compost from drying out, which would otherwise slow down the processing.

The perfect environment for Aerobic Bacteria

The enemy of composting is anaerobic bacteria; an uneven distribution or lack of oxygen, and excess moisture harbour such bacteria. Anaerobic bacteria create nasty odours and inhibit waste from breaking down quickly. Aerobic bacteria transform waste into carbon dioxide and water, leaving behind simple salts, which are perfect for re-absorption by plants.

The exceptional oxygenation, moisture and temperature control created by the Sun-Mar™ Bio-Drum provides the ideal environment for aerobic bacteria to flourish and break down organic waste rapidly and without odour.

Evaporation Chamber

Compost needs to be kept moist. It should not, however, be saturated. To avoid this in a Sun-Mar™ composting toilet, excess liquid drains from the compost mass through a stainless steel mesh screen, where it collects in an evaporation chamber. The essential difference between the non-electric or 12 volt NE model and the 240-volt electric model is the provision of a heater under the evaporation tray in the electric unit. The difference between the two types of model is explained below.

The Finishing Drawer

The benefits of the separate Compost Finishing Drawer

The benefits of housing older compost in a separate finishing compartment are innumerable. Perhaps the most significant of these is the fact that this older processing compost can’t be contaminated by new waste. The humus that is processing in the finishing drawer can compost gradually without the addition of any new waste, and can then be safely removed via the easy to access drawer.

How the units work (aside from the Centrex 3000 series)

When the drum is rotated backwards, the humus drops into the finishing drawer, where it is isolated from any new waste.

The humus in the drawer continues to compost, aided by a flow of air. Once the composting is complete the small and lightweight drawer is removed by hand, without the need for any tools, and emptied in your garden.

The process is then repeated by rotating the drum to deposit another lot of humus into the drawer.

Centrex 3000 Range

The Centrex 3000 works on a continuous flow design to maximise its capacity and improve the composting process. As the composting drum fills, the rotation of the drum forces the compost along the length of the Centrex 3000 drum then automatically discharges finished compost into a separate collection box.

Unlike with the smaller Centrex 2000, the drum doesn’t have to be rotated backwards for emptying (except for seasonal use). For seasonal use, the drum can be emptied in the Spring by rotating the drum backwards and dropping compost into a collection drawer on the right-hand side of the unit.

CM LP recipient of 2020 Good Design Award Read more