Phosphate: Chatham Rise, New Zealand

Provinces and Case Studies

C D Castle

Chatham Rock Phosphate Ltd

Phosphate nodules averaging about 21% P2O5 are present on the seabed of the Chatham Rise. The nodules are within a silt/sand layer, generally less than 50cm thick, overlying an ooze/chalk layer. Economic concentrations of nodules are present over a 380 km2 area within which the average concentration is about 65,000 tonnes per km2.

It was extensively studied in the late 1970s and early 1980s but not developed. Chatham Rock Phosphate Ltd (CRP) was granted MP 55549 covering 820 square kilometres of the most prospective seabed in December 2013.

The Chatham Rise phospate material is highly reactive, is highly effective as a direct application fertilizer and also be processed into single super phosphate. Current imports of rock phosphate are 800,000t/yr, the majority from North Africa. For that, freight costs make up 1/3 of the landed cost and freight contributes 68% of the carbon footprint from mine to farm. The Chatham Rise material has Cd contents less than 2 ppm, amongst the lowest in the world. It therefore has strong economic, agronomic and environmental advantages over currently used material.

Recent studies have also established that both the seabed and the phosphate nodules contain rare earths and other potentially valuable minerals. The feasibility of economically viable extraction of these by products is presently being researched.

Chatham Rock Phosphate Ltd’s current timetable is to re-apply for an environmental permit in 2020 with full production targeted for 2023.

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