Scientists for Future Austria
by Martin Auer
Every solution creates new problems. In order to contain the climate crisis, we must stop burning coal, oil and gas as soon as possible. But oil and natural gas typically contain 1 to 3 percent sulfur. And this sulfur is needed. Namely in the production of phosphate fertilizers and in the extraction of metals needed for the new green technologies, from photovoltaic systems to batteries for electric vehicles.
The world currently uses 246 million tons of sulfuric acid annually. More than 80 percent of the sulfur used worldwide comes from fossil fuels. Sulfur is currently a waste product from the purification of fossil products to limit sulfur dioxide emissions that cause acid rain. Phasing out these fuels will drastically reduce the supply of sulphur, while demand will increase.
Mark Maslin is Professor of Earth System Science at University College London. A study conducted under his direction[1] has found that the fossil phase-out needed to reach the net-zero target will be missing up to 2040 million tons of sulfur by 320, more than we use annually today. This would lead to an increase in the price of sulfuric acid. These prices could be more easily absorbed by the highly profitable "green" industries than by the fertilizer producers. This in turn would make fertilizers more expensive and food more expensive. Small producers in poorer countries in particular could afford less fertilizer and their yields would decline.
Sulfur is found in many products, from car tires to paper and laundry detergent. But its most important application is in the chemical industry, where sulfuric acid is used to break down a wide range of materials.
The rapid growth of low-carbon technologies such as high-performance batteries, light vehicle engines or solar panels will lead to increased mining of minerals, especially ores containing cobalt and nickel. Demand for cobalt could increase by 2 percent by 2050, nickel by 460 percent and neodymium by 99 percent. All of these metals are nowadays extracted using large amounts of sulfuric acid.
The increase in world population and changing eating habits will also increase the demand for sulfuric acid from the fertilizer industry.
While there is a vast supply of sulphate minerals, iron sulphides and elemental sulphur, including in volcanic rocks, mining would have to be drastically expanded to extract them. Converting sulfates to sulfur requires a lot of energy and causes large amounts of CO2 emissions with current methods. The extraction and processing of sulfur and sulfide minerals can be a source of air, soil and water pollution, acidify surface and ground water, and release toxins such as arsenic, thallium and mercury. And intensive mining is always associated with human rights problems.
recycling and innovation
So new sources of sulfur that don't come from fossil fuels have to be found. In addition, the demand for sulfur must be reduced through recycling and through innovative industrial processes that use less sulfuric acid.
Recovering phosphates from wastewater and processing them into fertilizer would reduce the need to use sulfuric acid to process phosphate rocks. This would help, on the one hand, to conserve the limited supply of phosphate rock and, on the other hand, to reduce the over-fertilization of water bodies. Algal blooms caused by over-fertilization lead to a lack of oxygen, suffocating fish and plants.
Recycling more lithium batteries would also help solve the problem. Developing batteries and motors that use fewer of the rare metals would also reduce the need for sulfuric acid.
Storing renewable energy without the use of batteries, through technologies such as using compressed air or gravity or the kinetic energy of flywheels and other innovations, would reduce both sulfuric acid and fossil fuel needs and drive decarbonization. In the future, bacteria could also be used to extract sulfur from sulfates.
National and international policies must therefore also take future sulfur shortages into account when planning for decarbonisation, by promoting recycling and finding alternative sources that have the lowest possible social and environmental costs.
Cover photo: Prasanta Kr Dutta on Unsplash
Spotted: Fabian Schipfer
[1] Maslin, M., Van Heerde, L. & Day, S. (2022) Sulfur: A potential resource crisis that could stifle green technology and threaten food security as the world decarbonises. The Geographical Journal, 00, 1-8. Online: https://rgs-ibg.onlinelibrary.wiley.com/doi/10.1111/geoj.12475
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