Metal and minerals industry prospects for sustainability

    Antoine Allanore forges sustainable path for the metals and minerals industry.


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    Following the recent COP21 climate change agreement in Paris, the metals and minerals industry is facing increasing pressure to reduce greenhouse gas (GHG) emissions. The mining, extraction, and manufacture of semi-finished raw materials is responsible for about 10 percent of global energy use and more than a third of global industrial GHG emissions. The industry is also a major source of sulfur dioxide (SO2) emissions, which contributes to air pollution and acid rain, and releases over 15 billion tons of tailings and waste rock per year, requiring expensive treatment and storage.

    While you could argue that the world would be better off if most of our oil and gas reserves remained underground, it’s more difficult to make the same argument about metals and minerals. Metals are essential to the development of the clean energy technologies required to achieve COP21 goals, and minerals are used for agricultural fertilizer. Consumption of metals and minerals has increased at a much faster rate than population growth, a trend that is expected to continue as we add another two billion people by 2050.

    The need to forge a more sustainable path has led MIT and Antoine Allanore, a professor in MIT’s Department of Material Science and Engineering, to establish the Metals & Minerals for the Environment (MME) program. Launched in 2015 under the umbrella of the MIT Environmental Solution Initiative, MME is bringing industry and academia together to develop practical solutions to the industry’s challenges.

    MME will host its first symposium at MIT in May 2017 to present novel ideas and approaches for sustainability. “The symposium will be an opportunity to bring the industry together with MIT faculty,” says Allanore, who has himself developed sustainable technologies for both metals and minerals extraction. “We are bringing in people from the various departments at MIT, including Chemistry and Civil Engineering who have developed solvents for other industries that could be relevant for metals extraction or minerals separation. There are also breakthroughs in Materials Science at MIT that we can apply, and we are working with the Sloan School to develop new ways to evaluate the impact of policy or strategic decisions on long-term sustainability.”

    A large share of the industry’s carbon footprint comes from transporting vast amounts of raw ore halfway around the world – typically to China – and then transporting semi-finished goods to other far corners. To greatly reduce energy consumption and emissions, MME proposes redesigning the supply chain to consolidate mining, extraction, and perhaps even the manufacture of semi-finished metals at the same or nearby locations.

    MME also wants to help the industry improve its social and environmental impact on nearby communities. For example, the group will provide guidance on how to avoid conflict minerals and improve relations with local stakeholders.

    Mining and Extraction: Using Novel Solvents and Electricity

    The metals and minerals supply chain starts with mining, followed by an initial “concentration” stage – usually in the same location – in which valuable minerals are separated from others. While there are some incremental efficiencies that can be introduced here, Allanore and the MME are focusing primarily on reducing and managing waste from the concentration stage. Waste can include silica and other toxic materials that can be spread by wind and water, which can lead to devastating impacts on agriculture, the environment, and human health.

    “We can develop new recovery methods in existing mines that reduce the amount of waste while increasing the cost value of the operations,” says Allanore. “There are new solvents being developed that absorb or bind to particular elements in the mineral, allowing for faster and more selective recovery.” The MME is also investigating how to improve the reliability of containing dams, and how to deploy sensor networks to more closely monitor for spills.

    The next stage is extraction, the conversion of concentrated minerals into metal. Eventually, one of the best ways to improve efficiency and environmental impact is to integrate extraction with the concentration phase by locating smelters in the same location (see below). Even without such integration, however, much can be done to improve this very energy and carbon intensive process.

    Beyond switching to cleaner energy sources, smelter operators can “tap into the knowledge of chemical engineers, physicists, and mechanical engineers who have developed new extraction technologies in other industries,” says Allanore. “This is a clear opportunity to rethink the chemical basis of extraction methods in order to reduce the amount of hydrocarbon, carbon, hydrogen, and other energy intensive chemicals.”

    Extraction will always require energy, but considerable efficiencies can be achieved by using novel methods that can reduce the overall environmental impact. For example, new technologies could increase the amount of metals extracted, and for many ores, reduce sulfur dioxide (SO2) emissions.

    Here again, solvents are used to “accommodate impurities that come with the minerals that have not been separated at the mine,” says Allanore. “Current solvents dissolve part of the metal’s value, which is accumulated and discarded. If we can capture those elements, we can reduce the overall cost and emissions. We need to rethink the technical principles behind these reactors to allow a faster, more effective recovery of the raw materials.”

    One promising solution for non-ferrous metals extraction comes from MIT’s Allanore Group. “Today, a lot of energy is used to produce the air for the reactor, and to handle the SO2 and the dust generated by the reactor,” says Allanore. “We propose using the energy in an intensive, single-step reactor, with less maintenance and operating cost. We can use less energy and water, and release fewer emissions.”

    To extract copper from copper sulfide, for example, smelters use oxygen to burn out the sulfur, resulting in SO2. The process not only creates air pollution, but also produces metallic copper, “which is not pure enough to directly go into consumer electronics,” says Allanore. “The copper ore contains other valuable elements like molybdenum, rhenium, selenium, or silver, which must be separated later in the supply chain.”

    Allanore’s extraction technology avoids SO2 and results in a purer form of copper. “The idea is to separate copper sulfide into elemental sulfur and elemental copper using electricity instead of combustion and air,” he says. “This not only creates higher purity, but enables us to be selective. We could adapt it to selectively recover critical elements like molybdenum.”

    The selective nature of Allanore’s electrolytic process should also make it easier to recycle waste material. “Wastes that have been accumulating for decades often contain valuable elements, but existing technologies cannot integrate much recycled material without decreasing productivity,” says Allanore. His electrolytic system would let operators feed waste streams back into the system and optimize for particular metals based on market changes. Eventually, similar technology could even be used to reclaim metals and minerals from urban landfills.

    Ore Transportation: A Heavy Load for Climate Change

    The global supply chain for iron, steel, and other metals may be a marvel of logistics, but it makes little economic sense, especially with the resulting impact on GHG emissions and air quality. “We are using fossil fuels to transport 1.6 billion tons per year of iron ore from places like South America and Africa all the way across the world to places like China where it is transformed into semi-finished product such as steel, releasing more CO2,” says Allanore. The steel is then shipped around the world, including back to the regions where the ore was mined.

    As the pressure to reduce emissions grows, there is an opportunity to rethink the supply chain by “transforming the mining operation into a metal extraction plant,” says Allanore. “Today, the industry separates mining and metal extraction. Yet, the mining companies could also create semi-finished products, or the metal producer could own the mine.”

    In addition to the substantial cost, energy, and emissions benefits from greatly reducing transportation, integrated regional facilities that combine mining, concentration, and extraction could reduce operating expenses, emissions, and energy on site as well. MME is looking into various technologies that could better integrate these processes.

    Integrated plants would make it easier for manufacturers to track the source of their ores and metals in order to meet consumer demands for conflict-free metals or minerals from environmentally sustainable operations. This is growing more important as more consumer products companies require tracking of raw materials origins, says Allanore.

    MME also proposes that the industry use new tools to track mineral sources and emissions. “The COP21 agreement has left it up to each country to decide how to reduce emissions, so companies will need to negotiate with each government, each of which has different agendas,” says Allanore. “We can provide industry with science-based GHG accounting tools in order to identify where new technologies could help the companies decrease environmental impact and satisfy local governments.”

    New monitoring tools and sensor networks will also enable stricter local monitoring of emissions, thereby diminishing misunderstandings with local communities. “Transparency may be the best tool for mining companies to allow local citizens to see what is happening with emissions or contaminated dust and water,” says Allanore. “This transparency could inform local government influence and reduce tensions with stakeholders in the region.”

    Article courtesy of the MIT Industrial Liaison Program.

    Eric Brown | MIT Industrial Liaison Program
    September 12, 2016

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