Human waste, sanitation technology, and sustainable agriculture are becoming increasingly intertwined in the future. Countries may be growing closer to using human waste as fertilizer, according to research led by University of Illinois Urbana-Champaign civil and environmental engineering professor Jeremy Guest, completing the loop to more circular, sustainable economies.
What Does The Study Say?
A new study defines supply-demand location typologies, their frequency around the world, and the consequences for resource recovery by characterizing the spatial distribution of human urine-derived nutrients – nitrogen, phosphorous, and potassium – and agricultural fertilizer demand. “Environmental Science and Technology” is the journal that reported the findings.
“The total amount of nitrogen, phosphorus and potassium largely remains constant in our bodies, once we stop growing. Whatever comes in through food and drink must come out in our urine, feces and sweat. Knowing that, we can estimate how much of each of these nutrients is in a population’s bodily waste if we know their diet.”– Jeremy Guest, Acting Associate Director for Research, Institute for Sustainability, Energy, and Environment, University of Illinois Urbana-Champaign
One Of A Kind
Guest and others have already analyzed the possibility for recovering nutrients from human waste around the world and identified areas where there is a surplus of human waste-derived nutrients compared to local demand for agricultural fertilizers.
“This is the first study to use a single mathematical equation to characterize human waste-derived nutrient supply-demand location interactions,” Guest added. “The quality of sanitation infrastructure, as well as people’s diets and the quantity of land suited for agriculture, differs widely around the world.” Having the ability to describe and analyze a location’s nutrient-recovery capacity can help decision-makers make better decisions about future sanitation and agriculture policy.
To achieve this quantitative characterization at the global scale, the team conducted rigorous numerical and geographic assessments of nutritional, population, sanitation, and agricultural data from 107 nations. The research identified three unique supply-demand typologies: co-located supply-demand, dislocated supply-demand, and countries with heterogeneous supply-demand proximities.
The dislocated supply-demand typology, for example, applies to the United States and Australia. They practice intense agriculture in places remote from major cities, thus the nutrient supply obtained from human excrement is far from where it is needed, according to Guest. This means that nutrients would have to be delivered over long distances, either as heavy fluids or transformed into concentrated crystalline products, even with superior sanitary infrastructure in place. In terms of economics, Guest believes that working with a concentrated product to adopt a human waste-derived fertilizer in these nations makes sense.
Human populations are more substantively in the neighbourhood of agricultural areas in nations with co-located supply-demand typologies like India, Nigeria, and Uganda, according to the study, allowing for local reuse. There is, nevertheless, a need for enhanced sanitation infrastructure in many localities where supply and demand are co-located. According to Guest, developing a human waste-derived fertilizer program in these areas might be extremely useful to sanitation and agriculture.
Countries such as Brazil, Mexico, China, and Russia show a continuum of nutrient supply and demand co-location to displacement. Policymakers would need to address human waste-derived nutrient utilization with more regionalized plans and a variety of local reuse and transportation alternatives, according to the study. “Higher-income countries in this group may have the infrastructure and economic backing for multiple technologies,” Guest explained, “but those with fewer financial resources would have to prioritize resource-recovery technology in particular areas.”
The researchers hope that their findings will help to clarify the key economic, sanitation, and agricultural characteristics of countries around the world, allowing decision-makers to prioritize investment, policies, and technologies that will help them achieve their goals of a circular economy and universal sanitation.