Folium – The Plan to Battle Phosphorus Depletion

For millennia, humans have fantasized about all sorts of terrible calamities that would leave us on the brink of extinction. These scenarios generally involve widespread infection, zombies, or sometimes, they include a world where humanity is struggling to survive due to the effects of human-accelerated global warming or a nuclear winter.

After all, there’s a reason why some people believed that the COVID-19 pandemic could be the triggering event for an apocalypse.

But don’t fret! Humans havent fallen victim to an existential disaster…yet. Many of us know about how greenhouse gases are changing the climate, how drinking water is becoming increasingly scarce, and how plastic pollution and overfishing plagues our oceans.

But have you thought about phosphorus?

Although phosphorus depletion is an issue that isn’t well-known or talked about much, it’s no less significant. As we continue to mine more and more phosphorus, humanity will eventually run out, leaving us without food. Yes, if we truly run out of phosphorus, we would literally have a global famine, because phosphorus plays a huge role in industrial agriculture.

This is the problem that we, Folium, are working towards solving. We believe in growth without consequence.

What exactly is phosphorus depletion?

Phosphorus is an essential nutrient for all forms of life, a key element in our DNA. All living organisms require daily phosphorus intake to produce energy and currently there’s no synthetic substitute: without phosphorus, there is no life.

Earth’s phosphorus is limited, and is being depleted at an alarming rate. At current consumption levels, we will run out of known phosphorus reserves in around 80 years, but unfortunately, consumption will not continue at current levels, so it is predicted that we will actually run out of phosphorus in the next 25–30 years.

Nearly 90% of phosphorus is used in the global food supply chain, most of it in crop fertilizers. Fertilizer use has quadrupled over the past half century and will continue rising as the population expands.

The growing wealth of developing countries allows people to afford more meat which has a “phosphorus footprint” 50 times higher than most vegetables. This, together with the increasing usage of biofuels, is estimated to double the demand for phosphorus fertilisers by 2050.

There was a time when humans operated self-sufficient farms, tilling the same land for years by managing waste effectively, making sure that everything that came out of the land eventually went back into it. In this closed-loop scenario, phosphate would have the capacity to be reused approximately 46 times as food, fuel, fertilizer, and food again.

In fertilizing techniques used today, which involve the annual application of phosphate-enriched chemical mixtures on top of nutrient-starved soil, phosphorus is used exactly once, then swept out to sea, a highly unsustainable practice.

How do we solve the problem?

The main way phosphorus is reintroduced to the environment post-consumption is through animal waste. While manure is still used around the world as fertilizer, human waste that was once returned directly to the soil is now collected in municipal waste facilities and released to the ocean. While most of the recoverable nutrients are currently lost, centralized municipal collection facilities present an opportunity to recycle large quantities of phosphorus with relatively little effort.

Numerous phosphorus recovery technologies do exist, such as biological phosphorus removal, chemical precipitation, electrolysis, adsorption, and crystallization.

Biological phosphorus removal utilizes polyphosphate-accumulating organisms to capture phosphorus in their cells. However, this method is limited by the lack of carbon sources and the difficulty of culturing pure bacteria. Chemical precipitation may consume expensive chemicals and produce large amounts of chemical sludge. Electrolysis is restricted by the small capacity of handling wastewater and the frequent renewal of electrodes.

Struvite, or magnesium ammonium phosphate, is a hard, clear crystal that forms naturally when ammonium-producing bacteria break down the urea in urine. It’s the same substance that causes kidney stones, and for centuries it has been caused problems with sewage systems globally, by forming hard, rock-like crystal deposits on the inside of pipes that build up and block off flow.

However, struvite is a non-toxic substance that can be used as a rich, slow-release phosphate fertilizer. In fact, struvite outperforms diammonium phosphate (DAP), the most widely-used fertilizer today, in terms of dry matter production, phosphorus uptake, and extractable residual phosphorus.

Struvite crystallization poses a potential solution to phosphorus depletion. Wastewater would be redirected through crystallizers which would allow for the crystallization of the struvite, after which the crystals would be harvested and used for the production of dry powder fertilizer.

We would use a water agitation type crystallizer, which realizes uniform mixing by changing the solution flow direction or the flow rate by increasing the diameters of the equipment from the bottom to the top. Through cone-shape structures we would reduce unwanted crystal loss at each junction, and recycled finer particles through an external recycler.

Based on research on water agitation crystallizers, this process would be able to remove 92% phosphate, and the purity of struvite would reach 99%. Additionally, there would be a settling zone at the top, through which seed crystals would be added into the crystallizers, allowing the finer crystals to continue to grow up in the upper supersaturated solution. The struvite crystals would then be crushed to form dry powder fertilizers.

The fertilizers would also be accompanied by an app called “Folialife” which would calculate potential soil and phosphorus runoff losses on a field-by-field basis as well as the quantity of fertilizer that should be used, based on the extent of available land, the area being cultivated, the amount, distribution and reliability of rainfall, and the cropping pattern.

Impact and future steps

100 m3 wastewater can form 1 kg of struvite. If all the wastewater in the world is treated by struvite crystallization, 63,000 tons of P2O5 could be recovered, equivalent to 16% of the phosphate rock production of the world.

171 g struvite can be recovered from livestock wastewater per square meter at most and the purity would be as high as 95% without washing. In fact, the presence of Mg in struvite makes it more attractive as an alternative to contemporary fertilizers for a few crops, which require magnesium as well.

Struvite-based fertilizer would have a lasting positive function to roots because of its slow release characteristics. Compared with other highly soluble fertilizers, struvite is also more suitable to use in vast areas of forest. Since the area of forest is too large to fertilize frequently, the use of struvite can decrease the frequency of fertilization and reduce the loss of nutrients.

Additionally, the app will promote the sustainable use of fertilizers. As an example, northern Chinese farmers use about 92 kg of phosphorus fertilizer per acre, of which only 39 kg are removed as crops. This means 53 kg, fully 58% of phosphorus, is not utilized and ultimately lost into the environment.

As China is the largest phosphorus consumer in the world, with 5.2 Mt consumed in 2009 alone , reducing the country’s phosphorus waste by even half would save the world over 1.5 Mt of phosphorus (3.45 Mt phosphate) per year.

However, there are drawbacks that we must work towards solving. Since livestock wastewater is full of impurities, especially heavy metal ions, the struvite recovered from livestock wastewater still contains heavy metal ions. From livestock-based struvite, toxic substances may diffuse into the aquatic environment or accumulate in soils and have an adverse effect on the human health and environment.

If you want to learn more about Folium and our vision for the future, reach out here:

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