Waste Water into Wine: An Idea for Producing More Phosphorus

A few shortages on the planet pose fairly ominous threats to humanity. Clean water is becoming scarce in some regions, and energy that simply can’t meet future demands. Some endangered animals have too few remaining individuals. And the political will to solve these problems? We’ve heard that’s been in short supply for decades.

One shortage that gets comparably little attention is expected to come with serious consequences. Industrial agriculture around the world, especially in developed countries, has mined soils for phosphorus and nitrogen—two elements vital for growing our food. There’s lots of nitrogen in the atmosphere (it makes up about 78 percent of our air, in fact) but phosphorus is harder to come by.

A reactor adds chemicals and turbulence to turn waste water into pellets nutritious for plants.
A reactor adds chemicals and turbulence to turn waste water into pellets nutritious for plants.

Every plant and animal needs P (its nickname on the periodic table of the elements) to build healthy cells, Because of the way it absorbs into soils and bonds with other elements, it’s challenging to move around. Morocco has the biggest phosphate deposits in the world, but it’s being depleted alarmingly quickly. A column in Nature last year projected that we could reach peak phosphate by 2030, meaning we’ll need more than we have. After that, it simply won’t be possible, with current means, to feed the entire world.

Racing against that clock is a team of Canadian researchers. Rather than try to convince the world to use less phosphorus (humans are, after all, not great at conserving in times of plenty), they’re trying to produce more of it. One resource we do have is waste water, and lots of it. And fortunately, one chemical prevalent in the water and other stuff we flush down our sinks and toilets is phosphorus.

On Vancouver’s Annacis island, in a research facility that looks a little more like a garage, Don Mavinic showed us his team’s creation. Waste water carries a lot of what’s known as struvite, a chemical mixture of ammonium, magnesium and phosphate. As it builds up, struvite acts like cement and clogs pipes of treatment plants. Mavinic and his research partner Fred Koch figured they would intercept the pipe-clogging struvite and turn it into environmentally-friendly fertilizer. With some help from Laurie Fretz of the Vancouver city government, they secured a lab with prime real estate: adjacent to a waste water treatment plant.

The product—pellets made of magnesium, ammonium and phosphorous—can be used to enrich soils.
The product—pellets made of magnesium, ammonium and phosphorus—can be used to enrich soils.

The machine that does the dirty work is a reactor that adds magnesium and sodium hydroxide, which effectively alters the PH balance and allows the waste water chemicals to bond together into pellets. The day we visited, they’d turned it on for us, adding air and water turbulence to the waste water compounds to get them to form pellets. It looked a little like a beaker full of confetti, with air pushing the particles upward and the heavier ones settling toward the bottom. It can run all day and night, Mavenic told us, and it’ll have to—the turbulence process takes a few days to produce pellets that are usable on farms.

A working prototype exists that can turn out several tons of pellets a month. It’s an impressive amount, but not yet quite in position to save the future of agriculture. But it’s on its way. Since 2010, the technology has been incorporated into five waste water facilities in North America, and is headed next to Europe.

The process, which isn’t yet as cheap as the researchers would like it to be, still has room to advance. What struck me, however, was that there aren’t many giant leaps left to take. The main input is something we throw away every day and the process to transform it into something useful has already been tested. Unlike some of the big scientific questions of our day—slowing climate change, stopping disease, landing on other planets—the solution to this one seems to already exist. It just requires some scale.

Before we left, Mavinic gave me a package of the pellets. Use these on any plants back home, he said. Coincidentally enough, I told him, I’ve been trying to grow an avocado plant from a pit on my desk at National Geographic. “Oooh,” he said smiling and nodding, like a person who knew something great that I would soon find out. “Put some of these on.” Plant food with simple phosphorus is about as pure as it gets. Since I first buried the pellets in the soil, the plant has shot up a noticeable few inches.

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