Can you imagine a world where your food was grown in (composted) human waste?
A recent study conducted by Hafner et al has confirmed just that human excrement can be used in compost to safely grow vegetables.
The researchers tested three different waste-based fertiliser: two made from human urine, and one called “faecal compost” made entirely out of excrement. The effects were then compared to a commercial organic fertiliser.
The urine fertiliser produced similar or higher yields than the commercial one, while faecal compost produced on average 20-30% lower yields. However, the faecal compost also bolstered soil carbon and could maintain soil fertility for the long term.
In contrast, the exclusive use of artificial fertilisers can destroy soil structure over the long term, downgrading the ability of the soil to grow future crops.
The most sustainable option, the researchers concluded, seems to be combining urine fertiliser and faecal compost together – which can produce yields that are 5-10% lower than those of commercial fertilisers.
From soil tests and chemical analysis of harvested crops, the scientists also concluded that consumers don’t need to worry about health hazards when consuming food (or at least cabbages!) grown with human-waste based compost.
This is not a new idea! Human waste has been used for centuries, as people have long known that it contains essential nutrients needed by plants to grow strong and healthy. However, it has not always been composted – a process which is known to remove many diseases from compost.
Concerns about potential diseases led many countries to abandon the system of collecting night soil in favour of mass sewage collection and processing – sewage which is eventually pumped out to sea.
Artificial fertilisers took their place. These have enabled the world to feed a growing world with better yields – and without them we would likely have to destroy much of our remaining natural environments to do so.
However, all that comes with a cost. Artificial fertilisers are harmful to the environment. They also use mined phosphate, a scarce resource which some scientists think could be exhausted by 2040.
Fortunately, the study showed no health hazards when consuming food grown with this type of compost, making it a safe and viable option for farmers looking to increase their sustainability efforts.
For readers interested in learning more about Humanure, including its history, science and how to make it, I recommend checking out the excellent Humanure Handbook by Joseph Jenkins.