Urine diverting flush toilet in Stockholm
Image by ecosan via Flickr

I grew up in a city of about 5 million people, where just about every house had at least one toilet, (this was not North America, where the average is closer to 2.5 per household), and every one of those toilets was flushed an average of 6-10 times a day per person. The idea of if it’s yellow let it mellow was not particularly popular in Australia growing up, maybe it was because of the heat, I don’t know. I was surprised when I attended a meeting in Castlegar about two years ago and someone suggested that it might be appropriate to not flush once in a while and an older gentleman stood up and accused the speaker of “wishing for us to be like animals” – as though the only thing that separated us from the apes was the invention of the full flush toilet. Give me a break.

Despite digging latrines while in the Army, my appreciation for the no-fuss flush toilet was still strong until a couple of years ago when I was struck with just how much nutrient was being flushed away. Somehow all the mention of nitrogen in wastewater engineering classes didn’t seem to be the same nitrogen that is necessary to grow just about any type of plant, including the food we eat. Sometimes we are blinkered in our response to a problem. As a professional I was taught to dispose of the “waste”, to collect it in sewers and transport it to million dollar facilities, screen the solids, then clean the liquids to discharge back into the river, lake or ocean – often at great cost.

Mining for Natural Nutrients

We live on about 2/3 of an acre in a sprawling suburban part of a rural city. To us, it’s an urban farm, but we’re still trying to get the City to wrap it’s mind around that idea. Farms need nutrient and as a society we have been happy to purchase expensive fertilizers to green up the lawn, make our roses grow bigger, and especially increase the crops in the veggie patch. The image above shows a urine separating toilet – the part at the front catches the sterile urine, while the back part deals with the solids. Note that this in not a composting toilet, it’s primary function is to reduce the nutrient load on treatment plants and rivers and collect urine for alternate uses. There are many examples of systems around the world, (including in developed countries for you naysayers), where these systems provide excellent nutrients for crop fields.

If you are a healthy person, your urine will be sterile and harmless right from the source, but any urine to be used as fertilizer in food production settings should be composted or stored for 6 months to kill any pathogens. In our household, a sealed gallon jug is used to collect urine and this is applied to our leaf pile in the backyard to provide nitrogen to assist in breaking down the leafy material. I find that we have too many birch leaves to deal with in our standard compost system, but I refuse to treat them as “yard waste” – in my mind there is no such thing and municipalities shouldn’t be pressured into collecting compostable material from yards as though it were waste.¬† Equally, we need to start thinking of all of the byproducts of life as resource streams – firstly reducing them where possible, reusing if appropriate, then returning them to useful states, through composting or recycling.


Note that in many jurisdictions it is illegal to install plumbing systems such as composting or urine separating toilets where sanitary sewer service is provided. For your health and safety, if you were to use urine to fertilize food crops, be sure to follow precautions detailed in a book like Liquid Gold, which is a great little book on the various methods, that have been tested and implemented with success around the world. If your diet is high in salt, so will your urine, so consider that before you decide to apply it to plants that might not be tolerant.

Liquid Gold: The Lore and Logic of Using Urine to Grow Plants” can be bought on Amazon.com and is an interesting read for anyone considering their impact on the earth.

The Logic of Growing With the Flow

If you know that you and your family are healthy, there is no scientific reason to not use urine to fertilize plants. If you wanted to be cautious, time, (6 months) or heat, (composting) will kill off any pathogens in the liquid gold. Reliance on industrial fertilizers  has to stop, these are produced from fossil fuels, transported by fossil fuels, and in agricultural settings applied by fossil fuel driven equipment. Natural fertilizer sources such as urine need to be considered as useful rather than a problem.

Published by Mike Thomas

Mike Thomas P.Eng. ENV SP, is the author of UrbanWorkbench.com and Director of Engineering at the City of Revelstoke in the Interior of British Columbia, Canada.

3 replies on “Liquid Gold”

  1. This is really fascinating! I had no idea you could compost urine and use it as a fertilizer. I would have thought it would be too acidic or caustic or whatever to have much value in it (some native cultures would use urine to bleach animal hides, for instance).

    The urine collecting toilet is also a very interesting idea, especially since it’s been found that drinking water in a lot of places contains the hormones and medications that we consume and then pee out. Sounds like this could be an answer to that problem … I mean, what else can we do? For lots of people not taking birth control pills or medications isn’t an option.

    So, let me get this straight, if I may: you guys collect your urine (do I want to know how?) and seal it up for 6 months to kill pathogens. Then you pour it on your compost. There is no smell, no increase of insects buzzing around, etc.?

    1. Thanks for the comment, and great to catch up on the street in Rossland yesterday. Essentially, the composting action and heat is going to speed up the breaking down of any pathogens – so applying to a leaf compost pile and turning regularly should keep the biological activity high.

      This is just one way of using urine in the garden, it is easy and there is little risk of killing plants by applying too much concentrated fertilizer or contaminating crops with this method.

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