The future is sh*t and we just need to come around to the idea, says Bryn Nelson, author of Flush; The Remarkable Science of an Unlikely Treasure.
Our own disgust has cut us off from the "versatile and very abundant natural resource" that is human waste, the award-winning science writer tells Jesse Mulligan.
Photo: Will Wright / Unsplash
Bryn Nelson Photo: malcolmphoto.com
Poo can and should be used as a natural fertiliser and source of sustainable power, Nelson says, yet we're putting it where it shouldn't go.
By removing ourselves from the cycle of organic waste recycling – particularly its phosphorus, nitrogen and water content – we are harming the planet.
"In many cases what we're doing is putting our poo in the worst possible place or letting it run off into streams and bodies of water unchecked … when nature has this very efficient system."
Humanity can "rejoin the rest of nature" and stop harming the planet, Nelson says, by making better use of our poo.
From it, we can extract biome solids that can be converted into the soil and also phosphorus, which can be reused as fertiliser.
The most significant potential use for our waste, though, is via the conversion of wastewater.
Around the world, wastewater treatment plants are reinventing themselves as "resource recovery facilities" that produce biogas.
These facilities "recreate the human gut on a very large scale", Nelson says, to convert wastewater into very large volumes of biogas.
"It can be used to generate electricity, it can be used to generate heat. It can even be used to power vehicles like buses."
It's not technology standing in the way of us converting wastewater into biofuel on a large scale, he says.
The hurdles are sometimes political but mostly psychological.
Disgust – a very powerful emotion that evolved partly to keep us safe – makes us averse to substances that can potentially make us sick, such as bodily fluids.
In the case of poo, Nelson thinks our "disgust dials" have been turned up too high and aren't serving our best interests.
"Nature has had this very efficient recycling system in place for millions of years - when we die, the nutrients return to the earth. Poo is another way for these nutrients to be returned."
Photo: supplied
Turning the public on to the idea of poo as a power source will require the expertise of human behaviour specialists, he says.
"What needs to happen is, along with the technology, we also need to include some of the social scientists, psychologists, sociologists [in the transition] to make sure that we're educating people, getting them comfortable and helping them understand that the benefits outweigh the risks, but being honest and transparent - this is what we know, this is what we don't know, this is how it may help you and your community."
Long-range planning and lots of funding will also be required to reconfigure wastewater facilities, Nelson says, as well as careful testing of the process to ensure it's safe.
With many parts of the world already running low on safe drinking water, climate change may speed up our adjustment to the idea.
"The current drought conditions in many parts of the world have created an opening for this message to come through."
One "interesting and disturbing" note Nelson adds is that thanks to modern life, many westerners now generate poo that isn't good-quality enough to become premium fuel.
Our high-fat, high-carb, low-fibre diets, as well as our high antibiotic intake and sedimentary lifestyle, mean the diversity of our gut microbes isn't what it should be, Nelson says.
The communities that have the most diversity in their gut microbiomes – including some in the Amazon rainforest and Africa – have very little exposure to antibiotics and diets that are very high in fibre.
The fact that they also produce the most useful poo raises a very important ethical question, he says.
"How will these communities benefit from this resource? How do we use it in a way that supports these communities that have suffered exploitation, have suffered violence, have had many of their natural resources stripped? I think that's a really important ethical question and the field very much needs to be addressing that as well as we move forward."
Although Bryn Nelson says he's not a nutritionist, for a healthier gut he recommends eating a diversity of vegetables and fermented foods like yoghurt, sauerkraut and kimchi.
