Keeping urine separate is usually the key to a successful composting toilet. Our toilets all come with a wee separator, which is used to divert the urine away from the solids into a separate container or soak away. This keeps the solid waste odour free and optimises the composting process. For the process to work aerobically, moisture levels need to be controlled: too dry, and the mass decomposes slowly or not at all; too wet and anaerobic organisms thrive, creating undesirable smells.

We developed the urine separator ourselves when we weren’t able to find a suitable product anywhere else. It is designed to fit standard piping and attachments and is made from recycled plastic. It slides in under the toilet seat platform and is easily removed for cleaning.

As urine is high in nitrogen, potassium and phosphorus, it can be used as a fertiliser (on nonfood plants) when mixed about 1:10 in water. Soak-aways divert the urine in a pipe, which can be run underground to feed fast growing trees like ash or willow.

Many of our ready-made composting toilets feature the ubiquitous wheelie bin – an innovative and hassle free system for composting human manure. Using a wheelie bin may at first sound strange, but if we were to hire a team of designers to come up with the perfect receptacle to hold humanure then after two years and a huge budget they would come back with the wheelie bin!

Wheelie bins are easy to move, watertight, rodent proof and cheap, which makes storage and emptying a doddle.

Once you have filled your first bin then you replace it with a second bin. When this is full, you empty the first bin (which should have started to compost nicely by now) into a standard garden 1m x 1m compost box that allows the air to circulate and aerobic composting to happen more rapidly. Here the final stage of the compost process happens for up to a year. Each subsequent bin is added on top. The waste is reduced from 100% solids to 6% in one - two years.

The advantage of the wheelie bin system is that you can rotate the bins as quickly as they fill up. More people means more bins. On average, using the composting toilet everyday, it takes one adult 150 days to fill up a bin. So a group of six people would fill a bin in about 25 days, and a group of 15 people would fill a bin in about two weeks. If the toilet is used only occasionally, it will take much longer to fill the bin.

This system uses a large rectangular box made from recycled plastic that is divided into two compartments: one for current use and one for resting and composting. There is a urine diverter inside that pipes the liquid into an external 25 litre container or soak away, depending on your situation.

There are two large hatches at the back of the box to empty from, and a vent pipe. Each chamber has a larger capacity than the wheelie bin, which has the advantage of needing to empty it less often, although it is not as easy to empty as the bin. However, by the time you come to empty a full chamber, the solids should have turned into odourless compost and not be unpleasant to handle.

All our composting toilet designs have been driven by requests from clients. Can you build a small, lightweight compost toilet that can be carried by two people? Can you design a compost toilet that meets disabled access regulations? Can you build a compost toilet with wheels?

We love building bespoke compost toilets - it gives us a chance to break the mould again and redesign the toilet. Some of the ideas we would like to pursue are :

Composting Toilets for Hire : We are waiting for an opportunity to design compost toilet blocks to be used at festivals and large scale events. We all know how terrible toilets can be at festivals and would love to change this by designing compost toilets that can be easily assembled and disassembled and moved from one festival to another. Let us know if you would be interested in hiring our compost toilets.

Tree Bogs : Tree bogs are the ultimate composting toilet solutions. Any of our designs can be modified to be tree bogs. We are looking for a client who would like this solution implemented on their site. Let us know if it might be you.

Compost Toilet and Shower Cubicle : There has been a lot of interest in a dual compost toilet and shower cubicle suitable for camp sites. So far, we have not actually had a commission for one, but we are waiting for the right client to come along and give us the go ahead. Could this be what you are looking for?