Saving the nutrients we piddle away
Where there's pee, there's phosphorus - and that's not a resource we can afford to pour down the drain. Nor should we waste the ammonia our urine contains, say EU-funded researchers who are developing a recovery process. Large buildings could soon house their own treatment systems to extract these substances for reuse, notably as fertilisers.
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The ValueFromUrine project does exactly what the name implies: it is producing technology that enables operators to extract valuable substances from urine. More specifically, it is developing self-contained processing units designed to recover phosphorus-rich struvite and the nitrogen compound ammonia.
The project is devising the technology for these modules, which private sector partners in the consortium then intend to commercialise for large buildings such as apartment or office blocks, universities or concert halls.
The system fits into a 20-foot container, says project coordinator Martijn Bijmans of Wetsus European Centre of Excellence for Sustainable Water Technology, the Netherlands. With another year to go in the project, the team has already designed an operational unit that has been running successfully for several months, he adds.
Why flush resources?
Some 80% of the nitrogen and half the phosphorus in domestic wastewater comes from urine. “We want to recover these substances, which are usually lost in wastewater treatment,” Bijmans explains. Both are much-needed fertilisers, with many other uses.
Finding an effective way to retrieve phosphorus is crucial, as the world’s mineral deposits of phosphate rock are running out, and nothing will grow without it. As for ammonium, recycling would save both the energy used to produce it for its many applications, and that needed to break it down in wastewater.
So why not just use raw urine to feed our crops? Indeed, this remains common practice in many parts of the world. But even where it’s allowed, this is not an efficient approach, says project manager Philipp Kuntke, also of Wetsus. Urine is mostly water, so you have to secure large streams to obtain enough phosphorus for your field, he explains. Concentrated in a solid, this element is far easier to handle, to trade and to ship.
It is also difficult to control the exact amount of nutrients in urine, and so there is a risk of applying too much, Bijmans adds. Profligacy with fertiliser comes at a cost, both to the purse and to the environment.
A golden opportunity
ValueFromUrine is developing a two-step process based on separate urine collection, typically from waterless urinals that empty into a storage tank through a dedicated set of pipes. In the first step, magnesium is added to precipitate the struvite, Kuntke explains. The remaining liquid is then treated in a bioelectrochemical system to extract the ammonia. This step also generates a bit of electricity, which helps to power the process.
On average, people produce 1.5 litres of urine per day, Kuntke notes. In a large building, all these pennies spent quickly add up.
By the time the project ends in August 2016, the partners plan to deliver the complete blueprint for a module that can handle one cubic metre per day. This volume would deliver about 1 kg of phosphorus and 10 kg of ammonium.
ValueFromUrine isn’t the only project exploring the recovery of nutrients from urine. “But,” says Bijmans, “we think that we have the best combination of technologies.” One of the advantages of the partners’ system is that the urine is processed at source, as opposed to approaches where it would have to be shipped to a central facility.
The project’s technology will be scalable for the pressing needs of individual constructions, but when and how it will be made available to customers remains to be seen. Another 10 years may be needed for full commercial development and so the business model is still under consideration, Bijmans explains.
That’s plenty of time for Europe to get its head round urine recovery and the unfamiliar and potentially water-free plumbing it involves. “It’s so weird that we still flush toilets with drinking water,” Bijmans notes. Phosphorus isn’t the only resource we can’t afford to waste.
PiLot instalLation of the Value From Urine project in front of Wetsus buiLding.