How to meet the world’s fertiliser needs

While 2014 marked 100 years since the start of World War I, Germany launched an economic battle against U.S. potash consumers four years earlier by halting export of potassium salts, over which it held a global monopoly. The U.S. struggled for a decade to meet its fertilizer needs, turning to alternative methods of producing potash, such as from brines in California and Nebraska and kelp from California. By the late 1920s cheap potash was again imported from Germany, and all the plants in Nebraska shut down.

Those are just a few of the interesting twists and turns in the history of potassium resources revealed in a sweeping survey from 1700 to the present by researchers at MIT and Newcastle University in Newcastle-Upon-Tyne, UK. It is being published in the Jan. 1, 2015, issue of Science of the Total Environment, a multidisciplinary journal dedicated to the interaction between atmosphere, hydrosphere, biosphere, lithosphere, and anthroposphere.

Many of the lessons of the past are relevant to today’s global potash market, in which countries in the Southern Hemisphere — such as Brazil or various countries in Africa — depend on exports from countries in the Northern Hemisphere. “Contextualizing the technical development of potassium sources within their historical context has been a fascinating journey,” says first author Davide Ciceri, a postdoctoral researcher in the Allanore Group at MIT. Antoine Allanore, principal investigator and corresponding author, adds, “We clearly see an entanglement of political decisions that favor one technology over another. Our analysis of the literature reveals that various sources of potassium (K) fertilizers are technically possible, but their practical implementation rests in the hands of the policymakers.” The researchers also reviewed extensively the patent literature for the production of potash from K-feldspar that date as far back as the 1850s.

Finding new sources

Allanore, the Thomas B. King Assistant Professor of Metallurgy in the Department of Materials Science and Engineering at MIT, is leading a research effort to produce alternative potassium fertilizers from silicate sources such as feldspars, which are abundant minerals all over the globe, but whose slow release of potassium traditionally ruled out their use as fertilizers.

The motivation for this collaborative and multidisciplinary article with Professor David Manning, a geologist and soil scientist from Newcastle University, lies at the core of sustainable materials extraction, according to Allanore. “It is important for us, researchers seeking to provide sustainable solutions, to always acknowledge that there is a significant body of prior knowledge on issues relating to materials of global importance, for example fertilizers for crop production. Then, understanding the societal and political dynamics that lead to a technology falling into disuse or on the contrary becoming adopted, is essential knowledge for us to design and transform the possible techniques into technologies for the 21st century, with the best attributes for adoption. The world of innovation in materials extraction is not only about fascinating science and enhanced technical performances; it is also about understanding the interplay between resources, technology and society,” he says.

History of change

One of three essential fertilizers, potash has been rocked by wars, exhaustion of natural resources, and introduction of new methods of production over the past 300 years. Potash is readily available in wood ash and burnt kelp residues, and the report notes that 250 potash works operated in Massachusetts in 1788, when the primary source was wood ash. Then, potash was used mainly in the making of glass and soap. Today, the predominant method of extraction is mining of soluble ores.

“Mining of potash minerals remains economically advantageous because of the known chemical processing required on the raw material, the well-established technology for mining operations, and the high concentration of K+ (ionic potassium) readily dissolved and available for plant growth,” the report says. However, availability does not equal accessibility, particularly for small farmers in places such as Africa. The report suggests that adapting historical practices such as burning certain plants or algae to produce potash might benefit local agricultural communities. Alternative sources include potassium compounds captured from flue dust in the cement industry. Potash also is found in residues of alcohol distilleries and sugar beet factories. Animal and even human waste are considered as manure sources.

Feeding the world

Widespread use of potassium-rich silicates has been held back by the slow rate of potassium release from such materials and the high cost of processing with respect to potash mining. “The commercial failure of enterprises of the past can be overcome if ways to release [potassium] at controlled rates are found. In this new perspective the value of silicate minerals becomes evident,” the report states.

The researchers believe innovations are needed that lead to a variety of locally sourced, sustainable potash options. “The direct consequence of innovation in the potash sector will be the development of efficient and affordable agriculture in the Global South and ultimately the possibility to feed the world,” they write.

Published in collaboration with MIT News

Author: Denis Paiste joined the Materials Processing Center at MIT in August 2012 from the newspaper business. He produces research updates, faculty profiles, photos and video for MPC’s monthly newsletter.

Image: An employee checks an above ground store of processed potassium salts at a Uralkali potash mine near the city of Berezniki in the Perm region close to Russia’s Ural mountains August 26, 2013. REUTERS/Sergei Karpukhin.