The Compost Toilet Composition

What is a compost toilet?

Composting toilets, which are sometimes also called waterless toilets, dry toilets or biological toilets, work by collecting waste and through aerobic decomposition. These toilets are very useful for outside use, as they don’t require any water or electricity, allowing them to be used in remote locations or simply to save water and energy. Further environmental benefits include the fact that waste is recycled into nutrient rich compost for plants.


How do they work?

A compost toilet works by slowly decomposing human waste through thermophilic decomposition. This means that the enzymes in the waste produce energy, making the temperatures between 40-60 °C. This allows bacteria to thrive, and, as they oxidise, they kill the dangerous pathogens and also evaporate any excess moisture. The correct balance between oxygen, moisture, heat and organic material is needed to ensure a rich environment for the aerobic bacteria, as this transforms the waste into fertilizing soil.


It is really important that the urine is separated from the solid waste in the decomposition process, or else the waste will be too wet and contain an imbalance of nutrients. If urine is mixed into the waste it allows anaerobic organisms to thrive, producing ammonia, methane and hydrogen sulphide; which is what causes unpleasant smells. This is why Free Range Designs’ toilets are fitted with a urine separator, which is used to divert the urine away from the solids into a separate container.


Once you have used the toilet, it is essential that a handful of ‘soak’ is thrown into the composting container after the waste. The soak is made of straw or sawdust, and provides carbon and nitrogen; which is essential to create a balanced diet for the bacteria creating the compost. Soak works by adding a balance of nutrients including oxygen into the mix, and also absorbs excess moisture. The bacteria can then decompose waste aerobically, and produce nitrates, phosphates and sulphates; which are a healthy composition for soil.


What do compost toilets  consist of?

At Free Range Designs, we produce a range of high quality compost toilets made from composting-toilet-box_10reclaimed and sustainably sourced wood. From the simple, portable composting toilet to the state-of-the-art timber arc toilet, we can provide them all. The main feature of a composting toilet is the wooden cabin which provides privacy. Some designs, like the bog standard toilet, are elevated structures with steps, to allow room for the composting chamber underneath, and others use an elevated seat with a bucket underneath.


Inside the cabin is the toilet itself which is made of a raised pedestal and has a comfortable, liftable seat like normal toilets. We always fit our toilets with a urine separator and piping that either leads to a collection container, which can then be detached for emptying, or to a soakaway. There is plenty of space inside the cabins for a soak supply, and we can fit railings, hooks and storage space so you can provide sanitary supplies.


Compost toilets are the ideal environmentally friendly solution for outside or public bathrooms. Not only do they save energy, water and provide high quality plant compost, but they are also created using sustainable materials. Composting toilets can be used in campsites, parks, gardens, farms, allotments and even churches that don’t have bathroom facilities.