A Science Voice from New Zealand

The phosphate crisis?

By Bill Morris

In the mornings I often ride my bike along the 13 kilometre stretch of road from Port Chalmers into Dunedin city. Once I’ve survived the onslaught of massive logging trucks and buses along that road I’m able to duck off onto the cycle lane, a peaceful section that takes me alongside the railway track and the harbour, past the yacht club and yards of shipping containers to the Ravensbourne fertilizer plant and wharf. The sulphuric tang of super phosphate strikes my nostrils as I ride past the plant, its tangle of steel pipes and towers steaming away in the morning sun. A ship is pulled up alongside the wharf and cranes are hauling scoops of sulphur from its bowels. The Ravensbourne plant is one of only two in New Zealand that manufacture superphosphate by mixing imported phosphate rock with sulphuric acid. The end product, commonly known as “super” by New Zealand farmers, is the fertilizer that has fuelled New Zealand agriculture for 150 years.  It is essential to farming and thus to our economy, but a crisis looms – our hungry world is running out of phosphate.

Phosphorous is a mineral that occurs in all living things and is essential to life. Plants require phosphorous for photosynthesis and animals for cell growth and hormone activity.   New Zealand soils are naturally quite phosphorous-deficient. Farmers in the 19th Century discovered that the application of superphosphate, which in those days was manufactured in Australia, vastly improved productivity, to the degree of up to 75%. From that point on, agriculture in this country was built on superphosphate.

In the 20th century, large concentrations of phosphate (from bird guano) on the Pacific Island of Nauru were heavily exploited by Britain, New Zealand and Australia, to the point that the island’s reserves became depleted and its natural environment devastated.

Today most of the world’s phosphate comes from fossilized shell-bed deposits in Morocco and Western Sahara, a tiny desert country that Morocco invaded in 1975. Since the invasion Morocco has held Western Sahara in an iron grip, excluding the area’s original inhabitants, the Sahrawi, behind a 2,700 kilometre fortified sand wall that is the largest military installation on Earth. While the Sahrawi people live in refugee shanty-towns on the other side, the Moroccan government exports the wealth of Western Sahara, in the form of raw phosphate rock, to countries all around the world, including New Zealand.

Demand for phosphate has risen dramatically in the last decade, fuelled by the rapid agricultural development of China and India as well as the demands of crops for biofuel production. In 2007 the price of phosphate more than doubled, causing many New Zealand farmers to start questioning the future of this vital resource. The green pastures upon which we produce the tons of milk and meat that drive our economy, are, after all an artificially created environment, kept viable only by the heavy addition of phosphates.

There is no argument that the world’s phosphate resources are finite and rapidly diminishing. In 2008 the dramatic price spike caused some to argue that we had reached, or long-passed “peak P,” a concept analogous to the more widely known Peak Oil – the point at which supplies of phosphate fall behind demand and we begin sliding down a negative-sloping curve toward poverty and famine. However, others, such as grassland agronomist Peter Cornish, argue that the situation is not as dire as it seemed in 2008 – there are still substantial phosphate reserves to be exploited, but they are harder to get to or, as in the case of Western Sahara, fraught by political instability and uncertainty.

A potentially lucrative source of phosphate exists on the sea floor off New Zealand’s coast   – 100 million tons of phosphate nodules formed by the concretion of decaying organic matter over millions of years. Two companies are already exploring the Chatham Rise with a view to mining there in the next few years. However the environmental impacts of this activity are not well-understood. In Namibia there has been very vocal opposition to similar plans from fishermen who fear it will be highly destructive of benthic ecologies and could have major impacts on fish life off that coast.

Driving south from Dunedin along State Highway One, just before Milton, the abandoned Ewing’s phosphate works stands testament to an industry that sprang up in these South Otago hills in the early 1900’s. It’s ironic that these hills are now greened by imported phosphate, when a century ago, over a quarter of a million tons of phosphate were mined right here. The rising global price for the commodity has encouraged local farmer Tony McDonnell to re-open the quarry on his farm and now Ravensdown fertilizer sells his locally mined rock alongside imported phosphate.

Ewings phosphate works, Clarendon. Image: Freepik

When Ewing’s was in operation a century ago, phosphate was cheap and the effects of its regular application not so well understood as they are today. It made the grass grow and in huge quantities and so it became an established and accepted part of every farmer’s yearly budget. Today we know that only about half of the phosphate that is applied by farmers is taken up by plants in the first five years – the rest is stored in the soil – building up over the decades so that there is actually a huge amount of phosphate going to waste. Some of this is also washed into waterways where it damages freshwater and marine ecologies. There are also growing concerns about the build-up in our soils of cadmium, an element found in phosphates that in high levels can damage soil health and be toxic to humans.

If phosphate prices, along with shipping costs (in relation to rising oil prices,) continue to soar, more effective use of this mineral will become essential if farmers in New Zealand hope to survive this century. Substantial amounts of phosphate can be recovered from animal and human waste and processes for achieving this need to be more fully explored.

Seen in the light of dwindling phosphate reserves, New Zealand’s agricultural prosperity begins to look like a brief, artificial blooming of wealth based on a false economy. One farmer I talked to told me that without phosphate, New Zealand would be a third world country. The extent to which we are able to curb our dependence on phosphate or at least find ways to use it more efficiently may soon determine the validity of his words.




Comments (2)

2 thoughts on “The phosphate crisis?

  1. Great post! It certainly seems that the importance of phosphate is unknown to many. Although it didn’t sneak past the attention of Nazi Germany…

    The phosphate supply to Britain, New Zealand and Australia was deemed so crucial to the war effort that in 1940 two German ships attacked the port facilities at Nauru. These were the first shots fired on land in the Pacific War, a year before the Japanese attack on Pearl Harbour. That is a pretty good testimony of how vital phosphate is!

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