Picture: ISTOCK
Picture: ISTOCK

Toronto — Injecting an industrial metal back into the ground could prove a boon for farmers and miners alike. The metal is zinc. Used mostly to reduce corrosion in iron and steel, zinc also is needed in trace amounts to keep humans and plants healthy. Without it in their diets, people are prone to diarrhoea, pneumonia and malaria, and crops are stunted.

The trouble is that farmland in South Asia, sub-Saharan Africa and Latin America is increasingly zinc-deficient, leading to more than 450,000 deaths annually of children under age five, a 2008 study in The Lancet showed. While use in agriculture remains small, sales of zinc-infused fertilisers from companies such Mosaic are growing. Farmers are trying to boost yields by reviving soils deprived of nutrients by over-use and a changing climate.

Canada’s Teck Resources has a test project in China. Another company is developing a mine in Nevada that may process ore just for crops. Expanding the market for zinc beyond steel and chemical producers would eventually bolster demand for the metal at a time of low stockpiles and surging prices. "It’s slow growth, but it’s steady growth," said Sean Davis, the principal analyst for a Houston-based unit of IHS Markit, a global mineral industry researcher. He estimates farmers will increase zinc use by about 4% annually over the next five years.

Last year, only about 270,000 tonnes of zinc were used on crops globally, IHS Markit estimates. This compares with 12.1-million tonnes by all users, according to Bloomberg Intelligence. However, with almost two-thirds of the world’s farms deficient in zinc, demand in agriculture could triple to 900,000 tonnes if it is used everywhere it’s needed, Davis said.

Tight supplies

More zinc in fertiliser could compound already tight supplies. Global demand has exceeded mine output in two of the past three years, after producers cut back during a slump in prices. Now, stockpiles monitored by the London Metal Exchange (LME) are down 71% from a peak in 2012 and at the lowest in more than seven years. Prices on the LME touched a nine-year high of $2,985 a tonne in November, and are up almost 40% from a year earlier at $2,586.50 as of Tuesday.

Researchers have been studying the benefits of zinc in crops as more of the world’s soil becomes stressed and loses nutrients. Arid and semi-arid regions are the most vulnerable because plants only absorb zinc when it’s dissolved in water.

A 2012, study by Agrochimica, an agriculture journal at Pisa University in Italy, showed as much as 70% of farmland in India and Pakistan is zinc-deficient, as is more than half the soil in China. Adding zinc to fertiliser can help, though results vary by region and crop. In the US, the largest agricultural producer, grain yields have increased anywhere from 12% to 180% with the addition of zinc, the journal reported.

Farm sales

For more than four years, Vancouver-based zinc producer Teck has been running field trials on rice crops in China in partnership with that country’s Ministry of Agriculture and the International Zinc Association (IZA). The results have been dramatic — a 20% increase in yields and a 40% rise in the nutritional content of the rice. The government now recommends the use of zinc-based fertilisers.

China, the world’s most-populous country and one of the largest agricultural producers, is only using about 20,000 tonnes of zinc a year on its crops. If the government’s recommendations were fully implemented, demand in the country could rise to 300,000 tonnes, according to Teck. "Obviously, the potential for this in terms of market is quite impressive," said Marcia Smith, Teck’s senior vice-president of sustainability and external affairs. "It’s a win for industry, it’s a win for local farmers because they’re producing more on their plot of land, and it’s a win for kids and anyone who has a zinc deficiency."

Super high-grade

"We can see a time in a couple of years when it would be required to have super high-grade zinc, the primary zinc, going into the fertiliser market," rather than using recycled material and scrap, said Andrew Green, director of environment, health and sustainability at the IZA.

The most common crop applications are in the form of zinc oxide or zinc sulphate, which are derived from the metal using chemical or heat treatments. Zinc oxide is cheaper than zinc sulphate but isn’t absorbed as easily by plants unless the soil is acidic, according to Daniel Kaiser, a soil specialist at the University of Minnesota who is experimenting with both products in studies in the state.

Mosiac, based in Minnesota, forecasts strong growth for its MicroEssentials fertilisers, one of which includes zinc. For several years, Bayer has been touting the benefits of zinc to farmers using its Antracol fungicide for rice, tomatoes and fruit. The Germany-based company discovered that it not only prevented blight, but also created healthier plants and better yields.

One company, Nevada Zinc, is considering making zinc oxide or sulphate at its Lone Mountain mine project in Nevada. The type of ore at the site would be easy to process into fertiliser-grade products, which may generate profit margins two and a half times higher than selling metal to a smelter for industrial use, CEO Bruce Durham said: "The amount of zinc in a pound of zinc fertiliser is about 25%, and a pound of zinc fertiliser sells for about the same price as a pound of zinc."


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