19 Aug 2021

The Scoop on Poop

 by Anne Munier

The scoop on poop

We all do it, most of us don’t like to talk about it, but perhaps we should get over that, because poop is not only fascinating, it’s also powerful stuff that may be a solution to at least a couple world problems! Let’s start with the basics:

What is it? Poop is waste from our bodies. We eat, our bodies take in nutrients, and then pass out what’s not needed. So poo is basically undigested food, along with bile (more on that in a moment), bacteria, parasites, and dead cells. Other names include stool, faeces, human waste, excreta, bowel movements, and a few more that are somewhat less polite.

Why the brown colour? Poo is usually brown because that’s the colour that bile- a substance our liver produces to help digest fats- becomes as it passes through the digestive system. Fun fact: bile starts out yellow-green. When we have diarrhea (which tends to come out extra quickly), the bile doesn’t have time to change colour as it passes through the intestines, hence diarrhea is often more of a yellow or green colour.

Why are we grossed out by poo? Evolution, of course! We’ve evolved to be disgusted by poo to reduce our chances touching the stuff. This reduces the chances of being infected by disease-causing microbes or parasites that it could be harbouring. The smell, which comes from the bacteria that break down food in our digestive system, probably helps as well. 

A proud manure producer! Photo by Ian Barbour

Is poo useful? Oh, my yes! Agricultural manure is basically livestock poop (often it’s been composted first), which helps crops grow by providing nutrients and bacteria, and by making the soil more rich and fertile. It also improves soil’s ability to hold onto moisture, and can reduce erosion. Yay manure!

Anything else? You bet, now we’re getting to the really exciting part. Let’s talk alternative energy.

But first, let’s recognize that every year we produce hundreds of billions of kg of poo worldwide (yeah, take a moment to think about that. Or…. don’t). Either way, that can be a heaping sanitation problem, particularly in areas that don’t have good quality infrastructure for dealing with human waste. When people are in close contact with poo, they can get sick from the germs and parasites, which can cause diseases like cholera, dysentery, or typhoid.

So- billions of people on Earth producing billions of kg of potentially harmful waste- that’s a problem. Meanwhile we’re looking for ways to make our energy system more ecologically friendly to reduce the impacts of climate change- another problem. A response to both problems: Biogas!

Biogas is produced when organic matter (like food waste, wood, agricultural waste, and yes, human and animal poo) is digested in a sealed container without any oxygen. The gas is then captured and used for energy, like cooking gas, fuel for cars and trucks, electricity, or heat. It doesn’t even smell bad!

The solids that are left behind are a great, high quality fertilizer that can be used in landscaping or farming. Another benefit!


Biogas plan: Organic matter goes in, biogas bubbles out the top, and "digestate" (i.e. fertilizer) is left over

It’s a simple concept, but please don’t try it at home; it’s not *that* simple.

Let’s check out some examples: 

This Sumatran orangutan is contributing to clean energy!

  • The Toronto Zoo recently started putting the 2,000 tonnes of waste that their animals produce every year to good use. They combine it with thousands of tonnes of grocery store waste, and generate enough biogas to power 500 homes! In the process they’re reducing thousands of tonnes of greenhouse gas emissions, those heat-trapping gases that are causing climate change!

  • A primary school in Uganda is now able to cook student lunches thanks to human waste-derived biofuel.

  • Poop power will soon be heating about 600 homes in the Vancouver area!

  • England has “bio-buses” that run entirely on gas from human faeces and food.

Poo-powered buses in England!

And that’s just the start. The United Nations anticipates that human waste could power 138 million homes while improving human and environmental health. Companies investing in the technology to make it happen are popping up all over the world.

Suddenly, a waste problem becomes part of the solution to clean energy! And we certainly won’t be running out of the raw material (that is, human poop) anytime soon.