Yellow Is the New Green: Is Pee-Cycling Greener Than a Composting Toilet?

CC BY 2.0. Ajay Tallam on Flickr

Teddy Roosevelt noted that "civilized people ought to know how to dispose of the sewage in some other way than putting it into the drinking water." And indeed, at the time he said it, most of the civilized world did, the millions of Chinese and Japanese who collected sewage and used poop in the fields, and pee for many different purposes, from making gunpowder to whitening teeth. There was no need for public urinals; people put bowls out in the street for people to pee in because they wanted more than they could make themselves.

Over at BuildingGreen, Alex Wilson titles his post Urine Collection Beats Composting Toilets for Nutrient Recycling. (Behind a paywall? read it on Green Building Advisor.) He summarizes the problems with the existing sewage regime in North America, where we mix it all with potable water and then send it to treatment plants "where energy- and chemical-intensive processes use bacteria to break down organic wastes, separate out biosolids, kill pathogens, and release that water into rivers or aquifers."

This misses such a great opportunity: to collect the stuff before it is mixed with poop and flushed away. Alex writes:

When most people think of creating fertilizer from animal waste, they think of manure. Composted cow manure, for example, is widely sold in garden centers. But there are actually far more nutrients in urine than in fecal matter. In human waste, 88% of the nitrogen is contained in the urine, along with 66% of the phosphorous, according to Swedish research, while nearly all of the hazards—including bacterial pathogens—are contained in the fecal matter.

Urine is pretty easy to deal with; any bacteria in it (say from urinary tract infections)is usually is killed by the ammonia in it in a short time. So far so good. Then Alex asks:

Better than composting toilets?

Pee Separation For Recycling photo
Migrated Image

Photo of urine separating toilet instructions from Sweden

This is comparing apples and bicycles; they are two separate concepts. In places like cities and towns with central sewage systems, a water based separating system is better than the combined system. They do it in Sweden.


Hot Poop on Composting Toilets: Separett/Screen capture

In the composting toilet world, there are a number of urine separating units. All of them claim that you get better compost from the poop by separating it; Separett claims that " because the urine is removed, the volume is much smaller, and the mixture does not ferment, creating that familiar smell of overused outhouses."

Alex is right about the importance of urine separating toilets. But they are not better than composting toilets; they are two aspects of the system. In fact, we need both.

Here's a round-up of some of our stories about urine separation.

Blue diversion toilet

© Blue Diversion

Poop and pee are valuable stuff; that's why people used to collect it and even pay for it. That's why our current toilet system is so awful, just mixing them with lots of water and flushing them away.Blue Diversion develops a toilet that's a lot more than flush and forget


© Chris Toala Olivares

Plants need phosphorus, and we are running out of the stuff; some say we will reach peak phosphorus by 2030. That's we should recycling urine, to recover the phosphorus in it instead of flushing it away. More: Peecycling will fertilize the green roofs of Amsterdam

peak phosphorus
So how can we stop phosphate pollution, recycle it, and keep it in the food chain where we need it? Composting crop residues would be a good way of recycling this valued nutrient back into the soil, cutting the need for new applications of fertilizer -- so would capturing some of the 3 million tons of phosphorus that cycles through human bodies annually, after being consumed in our food. Cordell [of the Global Phosphorus Research Initiative] says we should give top priority to recycling our urine, which contains more than half of all the phosphorus that we excrete.

More: Fred Pearce On Peak Phosphorus: It's Time For Pee-Cycling

Scientists and Toilets

Prof Chang, Dr Giannis, Prof Wang, Dr Rajagopal, and Dr Chen with the No Mix Vacuum Toilet./Promo image

As one Swedish researcher noted, "Don't mix what God separates". Poop without a lot of water or urine makes for " richer sludge and produces more methane, which can be turned into gas or electricity". We are approaching Peak Phosphorus and will need all the fertilizer from pee that we can get. More: Singapore University Puts Together The Plumbing System That Everyone Should Be Using