The benefits and advantages of dry toilets

What do composting toilets do?

Composting toilets treat human excrement using biological processes, turning it into organic compost material that can be used to fertilise the soil. They are small-scale, complete waste processing systems. The eastern world has been using composting toilets for hundreds of years, but it is only in recent years that they have become more popular in the west.

All composting toilets decompose waste by creating the aerobic conditions for bacteria and other macro and micro-organisms to thrive. The objective is to destroy harmful pathogens, eliminate the risk to human health and environment, and transform the waste nutrients into fertile soil. They typically break down waste material to a small percentage of its original volume.

Most toilet composting systems are low-temperature (mouldering) toilets. The waste material must be left for long enough for pathogens to break down naturally.

Our important difference

Compost that is too wet can become anaerobic and produce unpleasant smells. Because of this, our composting toilets separate urine from faeces. The collected urine goes through a process of nitrification, resulting in an odourless, bacteria-free liquid that can be used as a fertiliser or leached safely into the ground. The faeces and toilet paper are collected in a holding tank under the toilet seat with a composting medium using a screen to avoid any unpleasant sights and to keep out flies and other unwanted bugs. The tank either has a stirrer or rotation mechanism to distribute the material and allow even decomposition. When the tank is full it is removed and either stored until fully decomposed or added to a compost pile or rapid composter.

Other composting toilets either drain liquid from the waste tank (by which time it is polluted and unsafe) or require the addition of dry material regularly (increasing the volume substantially and therefore requiring a much larger installation) – separation at source is the best solution.

It is also important to ensure a good air flow over the solid matter. With our toilets this is achieved by using a small fan, powered by electricity to draw air down from the toilet compartment, over the solids and out through a small air vent. This ensures that there is never, ever, any smell in the room and virtually none outside. By using an fly-screen in this vent there is no chance of flies entering the toilet and causing unpleasantness.

Other toilets either require the regular addition of dry, absorbent material, or use sun-heated vents, or wind-drawn vents to generate the air-flow. All these methods are either incenvenient, or unreliable.

The advantages of Composting Toilets

All composting toilets require a little management to ensure that they remain clean, hygienic and odour free. All need to have compost material removed at regular intervals. But these are minor inconveniences compared to the advantages of composting toilets. They protect groundwater, surface water and soil from sewage pollution, prevent the accumulation of hazardous pathogenic waste, and solve the problem of disposing sewage sludge to landfill. They save huge quantities of water in a world where water is an increasingly scarce resource, and require very little infrastructure. They are low-impact, low-maintenance and can also adapt to any situation, even in places where it is difficult or inappropriate to establish a mains toilet system such as on board boats, in vehicles, on hard rocky soils, high water tables, near springs or in an environmentally sensitive area. They are also useful as temporary toilets on building sites or work sites, especially if they are then re-used in the final building.

Composting toilets are an excellent example of sustainable design. They provide a safe and effective way to save resources and prevent pollution, whilst saving money and energy for the owner and the community. At the same time they produce a valuable end-product that can be used to fertilise the soil. Once these remarkable benefits are understood such toilets are likely to become even more popular.