Ask most people what a urine separator is for and they'll say "stopping the smell" — and they're right. Keep the wee away from the poo and the solids stay dry, so you never get that sharp, eye-watering ammonia stink. But there's a second half to the story that doesn't get told nearly enough: the liquid you're diverting isn't waste. It's one of the best free fertilisers you'll ever get your hands on. Gardeners have nicknamed it "liquid gold," and once you start using it, you'll see why.
Here's how to put it to work.
First, the easy way: a soakaway
If you want the no-brainer, zero-maintenance option, send your urine straight to a soakaway. Dig a good hole, fill it with rubble or stones so it drains well, and pipe the urine into it. That's it. You put the effort in once, digging it properly, and then you forget about it. The ground quietly soaks up the nutrients and any plants or trees nearby will thank you for it — you'll often notice the greenery around a soakaway growing noticeably better than everything else.
It's the perfect choice if you just want your toilet to work and you're not bothered about collecting anything.
The resource route: collect it in a container
If you'd rather treat your urine as the resource it is, divert it into a 25-litre container instead. A quick, honest word of warning: a full container gets heavy, and if urine sits in the bottle too long it goes a bit gloopy and starts to smell — though you'll only really notice that when you come to pour it out. Use it reasonably fresh and you'll have no trouble.
Once you've collected it, you've got two brilliant uses.
Feed it straight to your plants (diluted). Fresh urine is too strong to use neat — it'll scorch leaves and roots. Dilute it with water, roughly 1 part urine to 10 parts water for general use (go weaker, around 1:20, for young or delicate plants), and pour it onto the soil around the base of the plant rather than over the foliage. Urine is naturally rich in nitrogen, so it's especially good for leafy, nitrogen-hungry crops like cabbages, kale, spinach, chard and sweetcorn.
Pour it on your compost heap. Urine is a fantastic compost activator. It's loaded with nitrogen, which is exactly the fuel the microbes in your heap need to get going — they use it to multiply and break down all that carbon-rich material faster. If your compost has stalled or feels too "brown" and dry, a dose of urine wakes it up and speeds the whole thing along. It's the simplest way to turn a sluggish heap into rich compost.
Going further: the tree bog
If you've got a bit of land, you can take it a step further with what's sometimes called a tree bog: plant trees right next to your composting toilet and let them drink up the nutrients directly. The results can be remarkable — trees fed this way will often grow at double the rate of their neighbours. My brother in South Africa keeps it beautifully simple: a flexible pipe runs from his toilet into his forest garden, and every so often he just moves the pipe to feed a different patch. Free fertiliser, happy trees, no fuss.
None of this works without clean separation
Every one of these uses depends on one thing: keeping the urine clean and separate from the solids in the first place. That's the whole job of a good urine separator.
We make two, and both do the job well — it really comes down to your build. The Compact Separator is my go-to for wheelie-bin composting toilets, because it leaves more room at the back for the solids container. The Complete Separator has a smaller footprint, which makes it the better fit for tighter spaces like a house bathroom or a campervan.
Get the separation right and you don't just lose the smell — you gain a steady supply of liquid gold for your garden.
