Mining and metals industries can help turn the tide of climate change
Precipitation patterns are changing. There are more heat waves and extreme heat. Permafrost is being depleted and there is less sea ice. Seas and oceans are getting warmer, acidic, and levels are rising. Our living environment—its biodiversity, the very features of our coastlines, and our own human lives—are at risk. Every sector of the economy needs to take action to stop global warming before irreversible damage is done. Starting now.
Easier said than done. Much of our modern life depends on the mining and metallurgy sector. Metals and minerals are the raw materials that become buildings, transportation and manufactured items. But from digging to delivery, getting mining products to market creates as much as 5% of all greenhouse gas emissions.
Mining has two immovable limitations. The first is geography. The search for new ores is pushing mine sites further and further into remote areas. These locations often can’t connect to national grids, so they rely heavily on fossil fuels for electricity production. Transporting fuel, materials, and even workers is energy intensive.
The second constraint is chemistry. Metal smelting and refining processes are designed for carbon-based chemical reactions. The carbon contained in coal, coke and other reducing materials is used at stoichiometry to remove oxygen molecules from the oxide forms of many ores, which inevitably produces carbon dioxide as a byproduct.
Still, there are some good, emission-reducing opportunities these industries can take advantage of.
There are lower-carbon energy sources that can power mining processes. We can cut emissions by switching to cleaner-burning fuels, electrifying operations and using renewable power. We need to hurry the development of new energy storage methods, too. They’re needed to help supplement intermittent wind and solar generation options.
In mining, open pit operations are generally fuel intensive while underground operations are generally electricity intensive. Automating vehicles and conveyances can cut fuel consumption at both kinds of sites. With the right control systems and variable-frequency-drive motors, underground ventilation can consume less electricity. These are low-hanging-fruit solutions, for which technologies are well developed and commercially available.
The chemical recipe for smelting and refining can be optimized to improve product quality and reduce emissions. Off-gas treatment can go a step further still. Carbon-monoxide recovery in the ferroalloy industry can reduce the electricity that furnaces need by as much as 10%. Recovering heat from slag, with techniques like slag atomization, can be a game-changer for metal smelting.
In complex facilities, the focus is often on finding opportunities for discrete, individual processes. But looking at operations as a whole can reveal ways to benefit the environment and reduce costs, too. One example is the blasting versus milling trade-off. By limiting the use of explosives in a mine, blasting can be more effective in terms of the energy-per-tonne extracted. But doing so increases the size of the extracted ore pieces. That means more energy is needed in milling. Fine-tuning this balance can result in the best energy-per-tonne across both processes.
Adapting smelting and refining processes to recycled materials is also a promising avenue. Emissions can be lowered and waste reduced by recovering materials that have already been through the initial ore reduction process.
Of course, it’s always important to strike the right balance between regulations and the systems applied to mining and metallurgy. We want to drive emission reductions and foster innovation, but not by unnecessarily harming an industry that feeds so many others. By considering and implementing low-carbon solutions on a site-by-site basis, mining and metallurgy can do their fair part to turn the tide of climate change and avoid causing any additional harm to our environment.
About the author
Julia Davourie
Engineer, Environmental Services Group
Julia is an environmental engineer with an academic training in energy systems and environmental engineering and management. Most recently, Julia was involved in developing Key Performance Indicators (KPIs) for gold mining operations, working closely with the Systems and Process Controls group to automate data collection and KPI calculation for a gold mining client, with the objective to manage and reduce energy consumption and greenhouse gas emissions at a Nevada facility and later extend this system to all of the client’s mine sites.