Waste flushed down toilets could be a valuable resource and source of profit, and better for the environment, according to research by engineers at West Virginia University.
Kevin Orner, an assistant professor in the Benjamin A. Statler School of Engineering and Mineral Resources, is developing a technology that could treat urine on-site rather than in a remote centralized wastewater treatment facility. The technology, which can be installed under a toilet, enables rapid urine disposal and facilitates the recovery of nitrogen, a nutrient that can be sold as fertilizer.
Orner’s findings, published in the journal Environmental Technology, make urine recycling more feasible to integrate into existing infrastructure and could reduce the amount of nutrients entering lakes and rivers. Excessive nutrient discharge can promote the growth of algae that deplete dissolved oxygen in the water, putting aquatic ecosystems at risk.
The goal is to transform waste collection and disposal from an environmentally harmful service that costs money to one that is beneficial to the environment and makes money.
“You have a toilet and a sewer in your house that takes the waste to a treatment plant miles away,” Ona explained. “Building sewers connected to your home and treating waste from plants creates greenhouse gas emissions. To prevent nutrients from being discharged into local rivers, sewage treatment plants often use energy-intensive electric blowers to convert ammonium in wastewater into nitrates , and convert nitrate to nitrogen gas.”
So the nitrogen goes back into the environment without producing any useful products.
Waste recycling is not a new concept. Farmers have long used manure to enrich the soil and urine to repel pests. The process of turning manure into fertilizer is already being implemented on an industrial scale, and infrastructure and programs to recycle human urine are already underway in places like Nairobi, Kenya, and Brattleboro, Vermont.
For Ona, he envisions toilets that separate urine from feces, allowing each of these wastes to be collected, processed, and turned into useful commercial products—most often as agricultural fertilizer.
Orner believes the most viable approach doesn’t require a power source to operate. Urine-separating toilets are designed to separate solids from liquids and then deliver the urine to a nutrient recovery unit located in or connected to the toilet itself or which may be located in a residential or commercial basement.
But speed is critical for large-scale implementation. Since toilets typically receive urine several times a day, it must be processed quickly so it can be released into another unit to make room for the next dose – especially in a system small enough to attach to the toilet middle.
Orner’s work is significant because by inoculating soil with beneficial microbes in collection and treatment reservoirs, adding carbon particles to provide a growth surface for bacteria critical to the treatment process, and using a fill-and-draw procedure by removing small amounts of treated urine and By gradually adding fresh urine, his team was able to significantly speed up the treatment — reducing a process that could take weeks to one day in one phase of the study.
“Circular sanitation” has not yet become the cusp of the new normal. High-end urine-separating toilets look almost identical to existing toilets, but are more expensive. Cheaper versions may smell or require new behaviors from the user.
Poor policies surrounding urine fertilizer products are another hurdle. Orner noted that building codes in most communities do not consider such technologies in their permitting guidelines, although he has worked with the Gold Ribbon Commission to draft regulations for adoption by state or local governments.
However, these toilets are not only found in Kenya and Vermont, but also from Oregon to Paris and the Netherlands. Orner has a collaborator in Costa Rica who is “interested in taking the lessons learned from Brattleboro and applying them to Monteverde, an ecotourism community in the cloud forest,” Orner said.
“Of course, there’s an ‘ew’ factor when it comes to disposing of urine,” he added, “but the truth is, urine isn’t waste. It has value.”