Composting toilets are less fuss, less of a fright, and less expensive to install than you might think. The ecological benefits are undeniable, but it’s important to note that no compost toilet system is as flush-and-forget as an old-fashioned flush toilet.

Outdoor toilets

Ventilation (read:smells!) is obviously a major concern when you use a compost toilet. After all, that’s why we invented the ‘water closet’ in the first place – to whisk the poo (and its smell) away to… well, somewhere else. Moving the whole deal outside is the least complicated approach to dealing with nasty niffs, but there are indoor options too.

a very attractive composting toilet from Free Range Designs, image

‘Gypsy Caravan’ composting toilet, Free Range Designs

If you’re prepared to toilet al fresco, you have plenty of options. In all of them, urine is collected using a diverter to keep the solids as dry as possible. This aids good composting, and helps avoid the ‘foul drain’ smell. The urine can be collected (for dilution and use as a fertilizer) or run to a soakaway.

After each use, the composting toilet is dosed with a layer of high-carbon ‘soak’ material, such as sawdust, shredded paper, hay or straw. With a properly designed system odours are minimal and are usually controlled by passive ventilation or a small fan.

Free Range Designs offer some very attractive options starting from around £1500, and also sell self-build plans. Waste is collected in standard wheelie bins. Once full (which takes quite a while) the bin is removed and left to finish composting for at least a year before use anywhere except in a vegetable garden. offer a no-frills but otherwise similar system, ready assembled for £1,125 plus postage. They also sell the ‘guts’ of the system (timber framed box with urine separating toilet seat with 2 x 60ltr containers, 2 urine containers, pipework for the urine separation and laminated instruction sheets) for £675.

Rotaloo supply a more sophisticated Australian design where the collecting chamber rotates on a carousel system, bringing a new empty container into position. This means that the waste spends its whole composting life in the chamber, and is fully composted by the time it has worked its way right round. The smallest rotaloo is suitable for a household of four people. The size of the unit can pose a design problem in retrofits, but Rotaloo say they are very happy to work with customers to find the best solution. Price on application.

Indoor toilets supply the simplest indoor composting toilet range, the Separett, from £389. These are slightly more sophisticated versions of the outdoor designs above, in that they feature a 12V or 220V fan that draws air from the room through the toilet and out through a ventilation pipe. This makes sure that there is no question of bad smells hanging about, but also helps the waste to dry out a bit which aids proper composting.

In Separett toilets, solid waste is collected in an integral bucket which takes four to six weeks to fill. This is then capped with ordinary soil and carried outside to sit with the lid slightly loose for six months, and then moved to a heap for maturation for at least another six months. Biodegradable bucket liners are also available if you have a particular fear of ‘contamination’ when handling humanure.

naturum compost toilet

Naturum compost toilet from Biolan

Biolan offer a more technical solution, the Naturum Dry Toilet from £1798. This has a pedal-operated rotating drum and some complicated looking seals which, the manufacturers claim, makes a fan unnecessary. It looks refreshingly similar to a flush WC, if a bit of an odd shape. Fresh waste is tumbled along with the composting mass and so breaks down very quickly. Rather than emptying a bucket, you remove a container full of low-odour finished product about once a month. This can be added straight to your compost heap and should be composted for a further six months before use.

Unlike simpler products, the Naturum uses the bowl design and seals to separate urine, so it can be used bidet-style with a shower head, and males can urinate standing up if they wish.

More expensive and technical products on the UK market include the Sun-Mar toilet system (available in the UK from Eastwood Services) and the catchily-titled Clivus Multrum system. Prices are – you guessed it – available on application.

Not ready for a compost toilet?

If you decide that a compost loo isn’t for you (at least, not yet) you can still reduce your existing loo’s water consumption. If it isn’t already dual-flush, change the flush mechanism – or if that doesn’t appeal use a hippo bag to reduce the flush volume. A couple of clean bricks can do the same job if the cistern has room for them, but watch the weight. More importantly, try to get out of the habit of flushing after you urinate if possible. This obviously requires the whole household to co-operate (or at least not object), but flushing urine away with clean water really isn’t necessary unless the toilet bowl starts to smell. Just put the lid down.


Prices correct at the time of writing.

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