On the hunt for alternatives to potash


Participants from the U.S., Canada, Brazil, European Union, the United Kingdom, China, and Africa will gather on the MIT campus for three days, Nov. 10-12, for the first International Workshop on Alternative Potash.

Cost-effective solutions to providing potassium fertilizer (potash) to the Southern Hemisphere are needed as the world’s population continues to grow, says Antoine Allanore, the Thomas B. King assistant professor of metallurgy at MIT.

Across the globe, regions in the Southern Hemisphere lack potassium resources, and their soils differ from soils in the Northern Hemisphere. “As of today, they are importing potash from the northern hemisphere,” Allanore says. The problem is not so much one of supply as of distribution and cost.

Just as lower world oil prices have curtailed growth in fracking and other alternative fuel sources, a robust market for potash in the Northern Hemisphere has made it cost prohibitive for new potash salt mines to open in the Southern Hemisphere.

“This is where a new technology could change that relationship. This is what all the participants are trying to think about. Maybe we are not looking for the good resource and maybe we are not making the best product and maybe changing that will actually allow the Southern Hemisphere countries access to fertilizer,” Allanore explains.

Allanore’s lab at MIT has been working on a potash alternative from feldspar from Brazil and China, a potassium-bearing rock that can be ground to a fine powder to enhance soil interaction to release potassium.

A recent paper by Allanore group postdoc Davide Ciceri demonstrated through microfluidic experiments that feldspar interacting with a strong acid can release sufficient quantities of potassium for agriculture.

Separately, a potash alternative developed in Allanore’s lab has shown good results in greenhouse tests on maize by the Brazilian Agricultural Research Corp. (Embrapa) in Brazil, where field trials are underway. “They were extremely happy,” Allanore says.

“The results show that there is uptake of potassium, so the plant, with this new material, is able to catch what it needs to grow, and there are some additional benefits. … If you provide too much of a single nutrient, a plant will take a lot of this nutrient and then will forget to take the other ones.

Apparently, according to the greenhouse tests, if you provide potassium at a rate that is sufficient for the plant needs, then the plant is better at taking up other nutrients,” he says.

World population is expected to grow to more than 9 billion by 2050, according to United Nations estimates, giving urgency to the problem.

“What matters is how much potassium is up taken by the plant from the field, and which source is used to bring potassium to the field. This is a truly interdisciplinary challenge. This is why we are bringing here some people who are soil scientists, agronomists as well as geologists, and materials chemists. We need to bring together these different specialists for discussions with each other,” Allanore says.

The word potash comes from “pot ash,” which was named after the pre-industrial practice of obtaining potassium compounds for making glass and porcelain by treating wood ashes with water and concentrating the solution by boiling in a pot, according to supplementary material from a previous paper by Ciceri, Allanore, and David Manning.

The chemical symbol for the element potassium is K, and the metric for the fertilizer is the amount of contained K2O, despite the fact that this molecule is never present in the resources, e.g. KCl.

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