In California, a newly developed system transforms human waste into a powerful tool for profitable and sustainable energy and agriculture in resource-limited regions. The prototype, outlined in a Stanford-led study published Aug. 19 in Nature Water, recovers a valuable fertilizer from urine, using solar energy that can also provide power for other uses. In the process, the system provides essential sanitation, making wastewater safer to discharge or reuse for irrigation.
Nitrogen is a key component of commercial fertilizers. Traditionally, it’s produced using a carbon-intensive process and distributed globally from large industrial facilities, many of which are located in wealthier nations resulting in higher prices in low- and middle-income countries. Globally, the nitrogen in human urine is equivalent to about 14% of annual fertilizer demand.
The prototype separates ammonia – a chemical compound made up of nitrogen and hydrogen – from urine through a series of chambers separated by membranes, using solar-generated electricity to drive ions across and eventually trap ammonia as ammonium sulfate, a common fertilizer. Warming the system—using waste heat collected from the back of photovoltaic solar panels via an attached copper tube cold plate—helps speed up the process by encouraging ammonia gas production, the final step in the separation process. Solar panels also produce more electricity at lower temperatures, so collecting waste heat helps keep them cool and efficient.
Tags: California, Stanford, urine
Category: Research
