Femi Alao, a researcher at the University of Benin’s Department of Agricultural Engineering, has uncovered a way to turn a household byproduct into a boon for farmers—and possibly a new revenue stream for the energy sector. His three-year study, published in *Discover Environment* (formerly *Discover Water*), shows that treated greywater from dormitory buildings can double the yield of irrigated pepper crops in Akure, Nigeria, while also improving soil fertility.
The experiment was straightforward but methodical. Alao and his team sourced greywater from the Federal University of Technology, Akure (FUTA) dormitories and fresh water from the university’s reservoir. Over three growing seasons—2016, 2017, and 2018—they irrigated pepper plants using both water sources in a controlled field setup. What they found was striking: treated greywater not only matched the performance of fresh water but significantly outperformed it. In 2016, pepper yield jumped from 0.19 kg/m² with fresh water to 0.405 kg/m² with treated greywater. Similar gains were recorded in the following years.
“At 5% probability value, TG significantly improved the growth and yield of pepper,” Alao notes. The treated greywater boosted soil macronutrients and fertility, suggesting a sustainable way to close the loop between wastewater and agriculture. “This isn’t just about saving water,” he adds. “It’s about transforming what was once waste into a resource that can enhance food production and reduce pressure on freshwater supplies.”
The implications extend beyond the farm gate. For the energy sector, this research points to a potential shift in how water utilities and agricultural operations interact. Treated greywater could reduce the demand for freshwater in irrigation, freeing up potable water for other uses. It also opens the door for decentralized water treatment systems—like constructed wetlands—near urban and peri-urban farms, cutting transport costs and energy use associated with large-scale irrigation infrastructure.
Greywater treatment is not new, but its integration into agricultural systems has often been overlooked. Alao’s work suggests that with proper treatment, greywater could become a reliable input for high-value crops, particularly in water-scarce regions. The energy sector, in particular, might see opportunities in developing modular treatment units that can be deployed close to irrigation sites, reducing both water and energy footprints.
As cities grow and freshwater becomes more constrained, innovations like this could redefine sustainable water management. For Alao, the next step is clear: scaling up the model. “Effective wastewater management will enhance irrigated agriculture and freshwater conservation,” he says. If the energy sector takes notice, we may soon see greywater treatment plants co-located with urban farms, turning a once-overlooked resource into a driver of both agricultural productivity and environmental resilience.