November 19^th is World Toilet Day—a day organized by the United Nations to celebrate toilets and raise awareness of people living without access to safely managed sanitation. UN-Water leads the event, promoting sanitation and water services that are resilient, effective, accessible, and shieled from harm. 3.5 billion people live without safely managed sanitation, including 2.2 billion who lack access to safe drinking water and 2 billion who lack access to basic hygiene services.

Poorly managed sanitation, including unsafe drinking water and hygiene, are responsible for the deaths of around 1,000 children every day. Children who live in fragile contexts such as those under conflict, vulnerable to extreme weather events, neglect, and other disasters are four times more likely to lack basic sanitation. Human waste in the environment is a serious health concern with links to disease transmission, and proper toilet facilities are especially important for women and girls.

At the same time, human waste has historically been used as a fertilizer for agriculture in many countries. As of 2024, the EPA estimated that as much as 3.5 million dry metric tons of treated sewage waste is spread as fertilizer in the U.S. every year, despite some states restricting or banning biosolid fertilizer due to contamination concerns.

To recognize World Toilet Day, Renewable Agriculture and Food Systems is featuring a series of four articles reviewing the use of human waste in agriculture. These articles have been selected by Editor-in-Chief Katherine Dentzman. They investigate what drives growers to use human waste as a fertilizer supplement, particularly in sub-Saharan Africa, along with the potential benefits and risks of such use. One study also looks at US growers’ perceptions of recycled water and municipally treated wastewater, including how different understandings impact risk and willingness of use.

Below, we provide citations and a brief description of each article. We encourage you to pick at least one that interests you and read it in more depth in honor of World Toilet Day.

McOmber, C., Zhuang, Y., Raudales, R.E., Vadas, T.M., & Kirchhoff, C.J. (2021). What is recycled water, anyway? Investigating greenhouse grower definitions, perceptions, and willingness to use recycled water. Renewable Agriculture and Food Systems 36(5):491-500.

• This study investigates US greenhouse growers’ perceptions and definitions of recycled water for irrigation. Specifically, the assumption that growers understand recycled water as municipally treated wastewater is tested.
• Findings indicate that few growers defined wastewater as coming from municipally treated wastewater, instead describing it variously as captured water, treated water, recirculated water, and reused water. Definition type was significantly associated with respondents’ concerns that the recycled water may contain chemicals, bacteria, and viruses. Growers were less willing to use recycled water on or near edible food crops, suggesting concerns related to contamination.

Daadi, B.E., & Latacz-Lohmann, U. (2020). Organic fertilizer use by smallholder farmers: typology of management approaches in northern Ghana. Renewable Agriculture and Food Systems 36(2):192-206.

• Daadi and Latacz-Lohmann use an exploratory factor analysis to identify a set of organic fertilizer management approaches used by farmers in northern Ghana. Four major approaches were identified, including Augmentary Compost Use Approach, Urban Human Waste Organic Fertilizer Approach, Integrated Livestock Manure Approach, and Mineral Fertilizer Cost Constraint Organic Approach.
• The Urban Human Waste Organic Fertilizer Approach was dominated by variables indicated the farmers’ use of human excreta, particularly from urban sources. Farmers in this category were more often men farming near urban areas who raised cereal crops. They typically arranged for dump truck drivers to dispose of their contents on farmers’ cereal plots, with the intention of enhancing the soil’s water holding capacity and assist crops in resisting drought.

McCord, A.I., Stefanos, S.A., Tumwesige, V., et al. (2020). Anaerobic digestion in Uganda: risks and opportunities for integration of waste management and agricultural systems. Renewable Agriculture and Food Systems 35(6):678-687.

• This study analyzed the inputs and outputs of seven micro-scale anaerobic digesters in Kampala, Uganda to determine their safety and potential to meet fertilizer application needs.
• They found that digester effluent did not meet international safety standards for wastewater discharge or field application. However, the digestate did have potential as a suitable source of fertilizer given its nutrient profile. Increased performance of digesters in removing contaminants is suggested to make better use of this system’s potential.

Cofie, O.O., Kranjac-Berisavljevic, G., & Drechsel, P. (2005). The use of human waste for peri-urban agriculture in Northern Ghana. Renewable Agriculture and Food Systems 20(2):73-80. doi:10.1079/RAF200491

• The authors investigate the driving factors, constraints, and potentials for using human waste as agricultural fertilizer in northern Ghana. Field surveys and focus groups were carried out with 90 farmers as well as officials of the local Municipal Sanitation Unit.
• Over 60% of farmers used faecal sludge as a method of increasing soil fertility and yields in maize and sorghum. It was perceived to be low risk due to long periods of drying; however, 22% of farmers complained of itching feet and foot rot after working with faecal sludge without foot coverings. Foul smells, transportation issues, and public mockery were also identified as constraints; nonetheless, faecal sludge was in high demand and the market was competitive.
• The authors conclude with a call for further research into safety issues and outreach related to proper handling and hygiene practices.