A new University of Illinois Urbana-Champaign study helps to define the global relationship between sustainable farming and sanitation technology. Credit: L. Brian Stauffer
It is becoming increasingly clear that human waste, sanitation technology, and sustainable agriculture will be interconnected in the future. According to Jeremy Guest, a professor at the University of Illinois Urbana-Champaign in civil and environmental engineering, countries may be closer to using human waste to fertilize, which could close the loop to more circular, sustainable economics.
New research identifies the spatial distributions of nutrients from human urine, including potassium, phosphorus, and nitrogen, and determines where they are found. This will help to identify supply-demand typologies and their prevalence around the world. It also has implications for resource recovery. These findings were published in Environmental Science and Technology.
Guest, who is also the U. of I's acting associate director for research, stated that "the total amount of nitrogen,phosphorus, and potassium in our bodies largely remains constant once we stop growing." "Whatever is in food or drink must be eliminated through our urine, feces, and sweat. If we know the diet of a person, we can calculate how many of each of these nutrients are in their bodily waste.
Guest and others have done previous studies to assess the possibility of recovering nutrients from human waste around the world and identified areas with an excess of human waste-derived nutrients relative the demand for fertilizers.
Guest stated that the new study was the first to use a single mathematical equation to analyze human waste-derived nutrients supply-demand relationships. Guest said that the quality of sanitation infrastructure and people's diets vary widely around the world. It is possible to quantitatively and qualitatively compare the nutrient-recovery potential of a particular location, which can help inform future agriculture and sanitation policy decisions.
To achieve this quantitative analysis at the global level, the team conducted extensive geographic and numerical analyses of data on dietary, population and sanitation from 107 countries. The investigation revealed three types of supply-demand typologies. These were countries with a colocated supply demand, countries with dislocated supply demand, and countries with different supply-demand proximities.
For example, Australia and the United States fall under the dislocated demand typology. Guest stated that they have intensive agriculture in places far from big cities. This means that the human waste-derived nutrients supply is far from where it is required. Even with modern sanitation infrastructure, nutrients will need to travel long distances as either heavy fluids or concentrated crystalline products. Guest stated that it would be economically sensible to use a concentrated product for the implementation of a human-waste-derived fertilizer in these areas.
According to the study, people in countries with colocated supply-demand typologies such as India, Nigeria, and Uganda are more likely to live near agricultural areas. This makes local reuse possible. However, many communities that have co-located supply-demand need to improve their sanitation infrastructure. Guest stated that a program utilizing human waste as fertilizer could make a significant difference in the areas' sanitation and agricultural conditions.
Brazil, Mexico and China all have a continuum between co-location and dislocation in nutrient supply. According to the study, policymakers should consider human waste-derived nutrients using more regionalized strategies as well as a variety of local reuse and transportation approaches. Guest stated that countries with higher incomes may have the infrastructure and financial support to pursue different technologies. However, those with less resources would need to prioritize resource-recovery technology for certain areas.
Surprised to discover that the typologies were very similar to the United Nations Human Development Index, the team decided to investigate.
"Higher HDI-scoring nations like Australia, Western Europe, and the U.S. tend to be in the dislocated demand typology while lower HDI countries tend to fit into the co-located supplier-demand typology. Guest acknowledged that there may be exceptions but the strong correlation was not expected.
Guest stated that the team hopes that this research will clarify the economic, sanitation, and agricultural characteristics of countries around the world so that decision-makers can prioritize investment, policies, and technologies that will promote a circular economy, and provide sanitation for all.
