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Energy efficiency: The first step in decarbonizing a mine

August 25, 2022

By Debra Johnson

Mining companies with ambitious net zero goals need urgency to make changes now. An energy audit is a good place to start.

Was it your mom or your dad who would always remind you to: “Close the door! You’re letting the (heat/air conditioning) out!”? Did they ever warn you that accelerating quickly while driving would waste gas?

If this sounds familiar, you already get the gist of an energy auditor. The mining, minerals, and metals industry can utilize energy auditors to improve energy efficiency and streamline operations. In examples from your home, energy savings exist on a small scale. They are usually simple. In the world of mining, the scales are much larger, as is the level of complexity. But the reality is the same: saving energy saves money.

Fuel and supplies often must be transported for many miles through rough terrain to reach remote mining locations.

How does an energy audit relate to achieving net zero and reducing greenhouse gases? 

It’s important to remember that energy includes both electricity and fuel. Energy efficiency in both areas can also lead to large reduction of greenhouse gases (GHG). This goal for mining is real. All major mining companies who belong to the International Council on Mining and Metals are committed to achieving net zero carbon by 2050 or sooner. Most of them also have progress goals, such as 30% by 2030.   

With current technology, we can know how much energy is being used in various mining and processing functions. In the past, mining companies could dismiss energy as “uncontrollable” in relation to other costs. That’s simply not the case today. Even across different power supplies, we can assess how much energy is used. A mine might run off diesel generators because it has no connection to the grid. Or, it may have clean hydro power supplied by a local utility. In either case, there is a cost involved. 

Understanding a mine’s energy should kickstart efficiency discussions to reduce energy usage, GHG emissions, and overall cost. The energy audit is the catalyst to start these discussions. The resulting energy reductions will reduce our industry’s GHG emissions.

Why conduct an energy audit? 

Reducing energy use and/or the cost of operating the mine is typically the key objective of an energy audit. It is important, however, to fully understand the goals of the organization and its stakeholders beyond general objectives. Mine managers and owners should determine their own “why” for conducting the audit because that will shape the scope of the work. For example, a mine owner considering major expenses for energy-saving measures will need a higher confidence level than one who is only focused on reducing costs.

Other potential benefits of an energy audit may include: 

  • Building a world-class mining operation
  • Improving processes, systems, and behaviors 
  • Instilling efficient and effective mining practices
  • Identifying ways to digitize, improve safety, and reduce GHG emissions
  • Gaining a competitive advantage
  • Creating a culture that builds awareness around ways to improve  

An electrical system in an underground mine.

How does it work?

The idea of an energy audit is nothing new. We have seen it on a small scale in our own homes, but it’s also existed for decades in commercial buildings. The tools that auditors use for formal building audits provide a basis for understanding mining energy audits. However, there are distinct differences. Audits for buildings are well-defined with standards. The American Society of Heating, Refrigerating and Air Conditioning Engineers is a primary one. Typically, energy use across buildings is predictable and measurable. The standards and consistency allow auditors to use benchmarks.

In contrast, mining energy audits have no formal guidelines. Mining operations have far more variables. Key variables may include the mine’s commodity, size or depth, location, age, and methods. An additional variable that can also make comparative benchmarking difficult in mining is mineral deposit quality. Lower grades with more waste rock will take more energy to mine and process. Auditors also must consider the energy demand of mining haul trucks. These trucks can be the size of a house! They can burn as much as 80 gallons (300 liters) of fuel per hour. Fuel use creates an immense carbon footprint. The truck’s footprint is intensified by the materials used to build the truck and the supplies used to maintain it. This is not an issue for building audits.

Mining trucks can burn as much as 80 gallons (300 liters) of fuel per hour, creating an immense carbon footprint.

Given the complexity of most operations, a mine energy audit team should understand the inner workings of mining and processing operations. The team should also have knowledge about the broad spectrum of equipment in use as well as alternatives to them. A strong energy audit team includes specialists in mining, processing, electrical engineering, fleets, and sustainability. Why? Because having this depth of experience on the team creates a greater understanding of the mine complex, which leads to better outcomes. This helps to ensure a thorough analysis of the energy-using systems. An energy audit includes these steps:  

  1. Collect and analyze historical energy use to create an energy balance.
  2. Study the mine site and its operations. This includes identifying the largest energy-consuming processes and equipment. 
  3. Identify and examine potential energy conservation measures (ECMs) that might reduce energy use and/or cost.
  4. Perform engineering and economic analyses of potential ECMs.
  5. Compute carbon emissions to profile a baseline carbon footprint and future impact from the ECMs. 
  6. Prepare a prioritized list of suitable ECMs.  
  7. Prepare a report of the analysis process and results.  

The energy balance estimates major energy users, then balances them against utility and fuel bills. It should include all energy sources such as electricity, diesel, natural gas, and renewables.

Site visits and interviews build on this analysis. Auditors gather more detailed information about large energy uses, discrepancies, suggestions for improvement, and more. On-site observations, measurements, and engineering estimates include basics such as lighting, HVAC, and motors. Mining energy audits expand on this to include haulage, pumping, crushing, processing, ventilation, conveying systems, and other systems.

Based on this work, energy auditors then prepare a report outlining the ECMs they identified. This report presents the estimated costs and benefits of the ECM projects. Results should provide information that managers need to decide if the site should apply the ECMs.  

Understanding a mine’s energy should kickstart efficiency discussions to reduce energy usage, greenhouse gas emissions, and overall cost.

Not a perfect process

As with any tool, limits exist. Most energy-audit approaches do not consider decisions made in mine design, planning, and purchasing activities. Such factors may add more complexity than the scope of the audit permits. In addition, audits typically don’t capture the energy impact from the dynamic nature of a mine site.

For example, auditors generally can’t account for changing ore quality, modified production schedules, or staff turnover. These changing conditions could mean new opportunities to improve energy efficiency. Or they may offset previous gains. Therefore, energy audits should be conducted regularly or when major workflows change.

Investing in renewable energy infrastructure can be an attractive option to reduce emissions on mine sites.

Energy audit as part one

An energy audit is a great first step on the path to net zero. It can identify “low-hanging fruit” that has a low cost relative to its potential savings. A proactive mine operator who implements ECMs from the audit is setting the mine up for success. The mine can both improve its bottom line and reduce its carbon footprint. 

As mines look 10 or 20 years into the future to achieve their net zero commitments, they must act now on financially viable ECMs. Management needs a sense of urgency—and this urgency is increasingly important. Pressure from consumers and governments is rising as they reward or punish mining operations based on carbon emissions.

When mine owners can improve energy efficiency with quick paybacks and without disrupting production, both the mine and our environment win. Much like at home when mom or dad said: “Close the door! Keep the cool air inside!” 

  • Debra Johnson

    Debra works with mining companies to achieve and exceed their ESG, carbon neutrality and net zero goals. Based in Phoenix, she is committed to solving sustainability issues in the mining industry.

    Contact Debra
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