To grow food in our modern civilization, we mine phosphate and potassium. We ship them across the world. We lose some, and use a lot of energy, in the process.
These minerals are essential for making artificial fertilizers – fertilizers that have changed the world!
Multiple times we have feared that our world faced mass starvation as populations grew. Instead, a combination of these fertilizers and the development of high-yielding crops mean we can still feed most of our bulging planet.
What’s more, the ability to produce more crops on less land helps us protect our remaining natural landscape – a landscape that would otherwise be torn up to produce more food.
But we face problems.
Not only is the current process of fertilizing land energy intense and wasteful, it also uses a scarce resource. At some point, some scientists believe, we will run out of phosphorus.
Other scientists believe we have many years of phosphate left. But still, large deposits of these are concentrated in a few countries, while phosphate is running out in nations like the USA.
As we’ll see, our current reliance on fertilizer is bad for the environment and compromises food security.
But imagine if there was a free resource we could use to improve our soil. A resource that existed in every country. A resource that was plentiful, but is currently mostly discarded.
There is – and it’s called humanure.
What is humanure?
Humanure is simply composted human excrement. It usually refers to excrement captured in a compost toilet and then composted. It is also occasionally used to refer to the sludge produced by waste sewage treatment.
History of humanure
Humanure is nothing new – in fact, it’s been used for thousands of years.
In Neolithic Scotland, early farmers ran their plows through middens before tilling the soil, while in China “night soil” was gathered from towns and cities and sold to farmers.
In the Middle Ages, human excrement was used in Europe to fertilize gardens. Farmers would also collect the waste from outhouses, cesspools, and public privies, and use it to fertilize their land. Meanwhile, in Japan, villages came to blows over who had the right to collect and use excrement on their land.
The use of humanure wasn’t always a hygienic process. In China, for example, night soil was often left to ferment in pools, a process which risked the spread of pathogens and disease (not to mention the smell!)
However, as we shall see, with modern composting techniques we can eliminate many of these pathogens.
Learn more: Composting History: The Fascinating Story of An Ancient Science
How does it all work?
The process starts with a compost or dry toilet. Close to the toilet, a container is placed. The container contains a material such as sawdust, which is scooped out and placed over the excrement to stop smells from escaping.
Periodically, the remains are collected and added to a composting system, which can be anything from a drum to a compost heap.
Joseph Jenkins of The Humanure Handbook places straw under and around the compost to provide insulation. If the process is done correctly, and thermophilic composting takes place, few odors are released.
For those interested, human feces have a C: N ratio of 10:1, which makes it one of the hotter manures.
What problems does humanure solve?
Food Security & Food Prices
2021 was not a good year for farmers buying fertilizer, with prices rocketing by 80%.
Any hopes of relief would soon be dashed when the Ukraine war started. Russia, a key fertilizer manufacturer, restricted exports and global shipping companies veered away from the country, leading to fertilizer prices reaching an all-time high.
These problems have helped contribute to sky-high food prices and a cost of living crisis for millions of people. Yet at the same time, on average each of us produces 145 kg a year of excrement.
(Total annual world poop has been valued at 9.5 billion dollars, albeit as an energy source rather than as fertilizer.)
Some countries do attempt to reclaim the nutrients while treating wastewater. Unfortunately, it’s an inefficient process, with around 90% of phosphorus lost in the process.
Turn that excrement into compost, and we could reduce our reliance on other, sometimes unstable, countries.
At the same time, and especially in the poorer areas of the world which are less able to afford fertilizer, humanure could help to improve the quality of poor agricultural land, improving soil structure and reducing the impact of drought.
Reduce water waste
What happens to all that food waste?
In those of us lucky enough to live in rich countries, it is flushed down the loo with water clean and pure enough to drink out of.
Each flush uses about 6 liters of water, and on average we go to the toilet 6-7 times a day. In total, we use about 36-42 liters of treated water to get rid of valuable organic waste.
Reduce water pollution
And what happens to that water once we have defecated? In rich countries and in poor, it can often end up in rivers and seas.
Water pollution doesn’t just come from our waste, either. The nutrients in artificial fertilizers are often readily available to plants, but that also means it is easily washed out by rain into our rivers and water courses.
That all means our water has huge amounts of nitrogen in it. This causes algae blooms which throw off toxins that can cause brain and liver damage.
As the algae bloom dies, they suck the oxygen out of the water creating dead zones where nothing can live.
In contrast, many of the nutrients in compost are fixed in organic materials and are not easily washed out by rain.
Instead, they are steadily taken up by microorganisms, some of which work in a symbiotic relationship with plants.
A lot of blame gets put on farting cows, but human waste also releases damaging greenhouse gasses – especially in our current waste management systems.
In fact, it’s estimated that human sanitation accounts for between 2 and 6% of methane emissions alone.
Proper composting has the potential to vastly reduce that number. In fact, one study in Haiti found that composted human waste released 0.5% methane – compared to between 20-80% for the pit latrines and lagoon methods often used in third-world countries.
And that’s even before we start to count the cost of shipping fertilizer around the world!
Solve sanitation problems in poor countries
3.6 billion people still don’t have access to proper sanitation – and 494 million people still have to defecate outside. That leads to diseases almost eliminated in the West – diseases which kill over 485,000 people every single year.
Yet the work of charities in these countries shows what can be achieved. In Haiti, for example, SOIL has provided sanitary toilets for 6000 people while turning 510 tons of excrement into agricultural-grade fertilizer.
What about human disease?
It is, of course, natural to worry about disease. After all, we have just been talking about the diseases caused by human excrement which has not been treated.
Science tells us, though, that if the right composting conditions are used there’s little risk to the process. As compost gets hot, thermophilic bacteria destroy many pathogens.
More get killed in the maturing process, aided by the ability of worms to destroy antibiotic-resistant genes.
While humanure is popular with permaculture fans, it’s unlikely to gain mass traction in the richer parts of the world.
Trained by convenience and ease, it’s hard to see how people will transition from flushing down poop with water in pristine toilets to collecting excrement and lumping it to a compost pile.
Even for those who are fans, its application is likely just not viable for the many people who live in high-rise apartments and dense city blocks with little or no gardens.
There is also the problem of our legacy sanitation systems.
These are designed to flush all down in one with water. Replacing every pipe and toilet with a system designed to collect waste and somehow funnel it to a compost facility is likely to be hugely expensive.
A more intriguing possibility lies in the poorer parts of the world. In stark contrast to the white porcelain that greets and graces our bottoms, a huge amount of people don’t have access to good sanitation.
With little to lose in terms of comfort and more to gain both in terms of sanitation, reduced disease and increased fertility for often poor soil, compost toilets have proved an easier ask in third-world countries.
Scaling current efforts, though, is another thing. Perhaps when countries do come to building infrastructure in their poorer regions, systems will be designed which capture the value of our waste, rather than flush it down expensive toilets and into our rivers and seas.