Quarrying & Mining Magazine
Mining

Why we desperately need 
Chatham Rise phosphate 

Potential seabed mining in this country has come at a critical time. BY PETER OWENS.

THE FARMING INDUSTRY has been the backbone of this country for a very long time.
In the 19th century big stations around the country, which had farmed sheep for wool, were broken up, the small farmer came into his own, and just about every district had its local cooperative dairy and freezing works.
This country became a world leader in developing farming practices and we learnt that in most regions pasture health and growth could be sustained only by the generous application of artificial fertiliser and the most efficient and best value for money was superphosphate. Millions of tonnes of phosphate rock was mined in New Zealand and when that source failed, more and more was imported from Nauru and other Pacific Islands.
In both World Wars the pastoral economies flourished because Great Britain undertook to buy the entire primary production of this country. This saw massive exports of meat, wool and dairy products to the United Kingdom, but they could have been even more massive had the pastoral industries had access to the phosphorous rock of Nauru. This island was occupied by the Japanese in 1942.
Shipments to New Zealand resumed almost immediately after the end of World War 2 and there was a rapid increase in the quantity and quality of the primary production.
Nauru was eventually worked out after some years of intensive excavation and we needed a new source of fertiliser. A variety of products were tried, but none was as good as superphosphate.
We found other sources further afield in the likes of the Middle East, but other countries began to use superphosphate in large quantities and world supplies became significantly reduced.
There have also been more specific problems, as most of the rock phosphate we import comes from mines in the Western Sahara which has been under armed occupation by Morocco since 1975. A shipment of phosphate rock en route for New Zealand was once intercepted and detained by the Western Sahara Liberation Movement. More recently, Panamanian authorities detained a Moroccan phosphate shipment from the Western Sahara after the Polisario Independence Movement claimed the cargo had been transported illegally.
Future disruption to sourcing of phosphate rock for our primary industry threatens our economy. There’s also another problem. The phosphate rock we source contains the carcinogenic metal cadmium and, in recent years, there has been rising concern about the high rate of cancer in some regions where there has been a regular and concentrated use of superphosphate containing high levels of cadmium.
In 2019, the European Union plans to set a 60 mg/kg P2O5 cadmium limit on phosphate rock that will eliminate all rock sourced from some mines in Morocco, Egypt, Israel, Senegal, Togo, Tunisia, Nauru and Christmas Island.

Chatham Rise

These challenges make our own resources of low cadmium, non-political, phosphate rock on the Chatham Rise very attractive. Indeed Chris Castle, managing director of Chatham Rock Phosphate, noted there is a need for New Zealand to secure its own low-cadmium and ethical phosphate resource for use as fertiliser to grow crops.
The size of Chatham’s estimated 20-year Mining Permit area, granted in 2013, totals 820 square kilometres. The company also needs an environmental permit called a ‘Marine Consent’ and is re-applying for this permit next year, having already been knocked back once.
Chatham’s phosphate resource is estimated at 23.4 million tonnes P2O5 with a present projected value of $427 million. The phosphate nodules lie at a depth of 400 metres and were formed five to 10 million years ago.
The company says it does not need to buy or build dredging equipment as it proposed that the Royal Boskalis Group be the mining contractor and carry out the phosphate dredging. Boskalis, which has a fleet of over 900 vessels and 10,000 employees in 90 countries, has been working with Chatham since 2011 to develop conceptual mining designs.
Boskalis, which has a strong reputation for its operational integrity, has also participated in Chatham’s environmental permitting process.
Operating assumptions are for one dredging vessel with a load capacity of 50,000 tonnes to operate a 12-day cycle for 30 cycles per year that would target a production rate of 1.5 million tonnes per year. This would comprise: one day to the mining site, three days mining, one day to port, three days unloading and four days allowance for weather and maintenance.
The present contract price of 30 percent P2O5 ex-Morocco is $120/tonne. If sold to make what we call superphosphate, Chatham’s rock is worth $110/tonne. If sold as reactive phosphate rock (RPR), retail value in New Zealand is $255/tonne. If sold internationally as RPR, the estimated price is $150/tonne.

This article first appeared in Q&M‘s December- January issue.

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