Mining Polyhalite – 4,000 Feet Below the Surface

Where does polyhalite (Polysulphate) come from? Explore the Boulby Mine with agronomist Jason Haegele

February 2, 2024
4 mins
Dr. Jason Haegele
North American Agronomy Lead, ICL Growing Solutions

As an agronomist, I focus on what happens in the soil below the surface. Recently, I had an incredible opportunity to go far below the surface – 4,000 feet, in fact – to explore where one unique fertilizer gets its start.

The Boulby Mine – The Polyhalite Origin Story

Polysulphate®’s remarkable story begins at ICL’s Bouby Mine, the world’s only commercial polyhalite mine. ICL issued an invitation for a tour of the facility to me, Dan Tollefson, North American Product Lead for PLUS Fertilizers at ICL Group, and three individuals from Cavendish Agri Services.

The journey took us to the United Kingdom and the village of Saltburn-by-the-Sea where we learned that minerals were first discovered in the area in 1939. The Boulby Mine was constructed about 30 years later to extract salt and potash, a primary source of potassium fertilizer, and the first potash production occurred in 1973. Most of the accessible potash had been excavated by the early 2000s, yet deposits of the mineral polyhalite were plentiful.

Instead of shutting down the facility, ICL began researching the potential of using polyhalite as a fertilizer because the mineral contains four essential plant nutrients – sulfur, potassium, magnesium and calcium. Initial field trials showed very encouraging results and a few years ago, ICL began mining polyhalite. It now markets this 100% natural fertilizer around the world as Polysulphate®.

It’s hard to believe that 10 years ago, this product didn’t even exist. Now, in 2023, the Boulby Mine produced 1 million tons of material. Where other companies might have walked away when potash was no longer available, ICL chose to innovate and repurpose an existing mine resource to develop a new and very effective fertilizer.

Polyhalite (Polysulphate®) Below the Surface

While for the majority of my career, I have worked with what lies beneath the surface, I had never been in an underground mine before. It was fascinating.

Even the process of getting into the mine was an adventure. We rode an elevator 4,000 feet into the earth. The seven-minute ride was very loud because the shaft is also used for ventilation with air continually pushed through and the only light was from the headlamps of those on the elevator. After this experience, I have tremendous respect for the miners who travel underground to work every day to put in 12-hour shifts.

At the bottom of the mine, we reached an open, brightly lit area where various vehicles were parked. We rode about five miles to the location where mining is currently taking place. Being deep inside the earth was an incredible experience as I observed strata of rocks and minerals, all the while aware that the North Sea floated above our heads.

The mine was very, very warm with a temperature around 90° F. I was surprised to see miners wearing shorts and tank tops. One thing that stood out to me is that while many people are involved in operating the mine – mechanics, engineers, safety specialists and more – the actual process of mining requires just two people. One operates the mining machine and another drives a truck to collect the material as it is extracted.

Polyhalite is extracted as chunks of very hard rock that are crushed on site to the consistency of coarse salt. After going through a screen so the particles are more or less uniform in size, the mineral is transported via train to a port a few miles away, and then shipped around the world.

Polyhalite (Polysulphate®) – A Sustainable Choice

One of the wonderful aspects of polyhalite (Polysulphate®) from an environmental impact perspective is that every chunk of rock that’s brought up is crushed and used. For example, potash production requires additional physical and chemical processing to separate the clay and salt contained in the raw ore to isolate the desired potassium chloride (potash). Polyhalite is unique in that it can be entirely transformed into a usable product, which is one reason why Polysulphate® is classified as organic and recognized as a low carbon fertilizer.

Another unusual factor is the Boulby Mine is located in the midst of a national park, placing limits on truck traffic and requiring the finished product to be shipped by rail.

Polyhalite (Polysulphate®) in the Field

After completing the tour of Boulby Mine, our group visited one of the UK’s largest potato farms, where the grower shared his experience using Polysulphate®. While Polysulphate® is a flexible product and can be used on a broad range of crops, it is especially effective on root crops like potatoes because of the calcium it contains.

The team from Cavendish Agri Services thoroughly enjoyed their farm visit. Given their expertise in potato cultivation and processing, along with their involvement in Polysulphate® field trials across Canada, the experience was particularly valuable for them. Even though agriculture is a regional practice, we can all learn so much through global collaboration and knowledge sharing.

For me, the entire experience is one that expanded my perspective about what it takes for Polysulphate® to reach a farmer’s field in North America and the impact it is making on the folks who are growing our food. ICL’s outside-the-box thinking has created a growing market – demonstrating that while Polysulphate® is mined below, it goes above and beyond to deliver for the world’s farmers.