So you installed a compost toilet. You’ve been using it for a while. You’ve been making compost and now, that compost is mature and ‘ready’ – what can you do with it?
That’s a great question and firstly, let’s say well done! If you’d been using a compost toilet as your primary toilet for 12 months, you’ve saved around 10,000* litres of pure, fresh drinking water.
What you can do with it, depends to an extent on who’s been using your toilet. If your toilet has been used by lots of different people (for example if you run courses or a camping/glamping site), then I’d take a precautionary approach to how you use the compost on the basis that you don’t know much about the health of the users and whether they might have been on any medications. The composting process (using heat and/or time) will deal with pathogens and medicines, but it’s wise to perhaps restrict the use of the humanure compost as a mulch around trees, or in flower beds.
If the toilet has been used by yourself and your family, and everyone is in reasonable health, then you can be more certain of the safety of the compost and use it accordingly. Personally, I’ve used my home-made humanure compost in and around my garden and allotment in the same manner as any other bought-in compost.
There is legislation from the Environment Agency (for England and Wales, although I suspect that Scotland and Northern Ireland have similar regulations in place too), that covers treating ‘sewage sludge’ (which is the term they use to cover, amongst other things, the solid output from compost toilets) on site – the main restriction is that you cannot sell food that has been grown in or with your humanure compost. Nothing stopping personal consumption.
You could use it to grow food commercially, but the process would need to be professionally examined and tested to ensure it is safe. Some of the output from commercial sewage treatment works is heat treated (to kill pathogens) and is sold to farmers as a soil amendment, although personally I have concerns about other pollutants (such as heavy metals) in commercial sewage treatment works that may end up present in the treated sewage sludge.
- I worked out the 10,000 litres per year, per person on the basis that on average a person will use and flush the toilet 5-8 times a day, and I assumed an average flush volume of 5 litres. Actual results may be higher or lower depending on your personal toilet habits and the type of flushing toilet used