Human waste for sustainability?

2021. szeptember 21.

There are not many things in the world that connect all people, but our bodily processes are one of them. We all eat, drink, sleep and yes, we also all go to the toilet. The hindquarters and their not-so-lofty behaviour is not exactly an elegant topic, but it is often dealt with in humour and science. The latter, moreover, raises the question of why we don’t use human faeces for fertilisation worldwide, thus making our environment even more sustainable.


More specifically, an American professor, environmental engineer at the University of Illinois, Jeremy Guest, asks this question in a recently-published study. Of course, he was not the first one; the use of human waste was researched in the past and was found to be suitable for use in large-scale farming as well. This time, Guest described human waste-derived nutrient supply and demand location relationships using a single mathematical equation.

The quality of sanitation infrastructure varies greatly across the globe, as do people’s diets and the availability of land suitable for agriculture. Having the means to characterise and quantitatively compare a location’s nutrient-recovery potential can go a long way to better inform decision-makers when it comes to future sanitation and agriculture policy.”, Guest said.

The team performed extensive numerical and geographic analyses of dietary, population, sanitation and agricultural data from 107 countries to accomplish this quantitative characterisation at the global scale. The investigation revealed three distinct supply-demand typologies: some countries get sufficient nutrients that they can also distribute; in other states this proportion is shared, i.e. some places have only demand, elsewhere there are only nutrients. Finally, in the third group, the overall picture is mixed, where both relationships occur.

Guest says the United States falls into the second group because, although there are huge, densely-populated cities and gigantic agricultural areas, the latter are often far from the largest cities, thus human waste must be delivered to them.

The research team also sees a general trend for developed countries to belong to the second topology - there is simply no strong rural presence, small farms are declining, everything is automated and made convenient and thus further from a close-to-nature lifestyle than, for example, India’s rural regions.

Research is therefore primarily concerned with how to channel human faeces into the natural cycle in the future. On a small scale, however, this is a long-standing phenomenon: in 2016, National Geographic filmed the production of manure from human waste in Haiti, which was supposed to boost local agriculture. As nearly half of the population does not have access to modern sewer systems, human waste ends up in the environment, which can have a detrimental effect on health, even though it could be recycled; the fertile soil, brought to life by human faeces, is regenerated in half a year.

Of course, it should be mentioned that the researchers also looked at health systems in the model, i.e., they also considered the fact that human waste-derived fertilisation can have harmful effects on health. The researchers also added that no matter how promising the results, such a global system could only be applied with appropriate technical preparation.


Cover: Getty Images