Opinion: Can responsible tailings management advance us towards carbon neutrality?
I started my career in the late 90s to early 2000s out of Perth, Western Australia.
Back then, I was fortunate to work with a highly innovative group of people looking to transform the way large volumes of un-neutralised caustic red mud tailings were being managed in an urbanising part of southern Perth. At the time, we (or at least I) didn’t fully understand that the science being applied had potential to directly reduce carbon released into the atmosphere through sequestration.
For the uninitiated, red muds are highly alkaline, and hence methods of reducing the material pH via carbon dioxide addition has multiple benefits. These include improving densification (reducing footprint utilisation), improving strength and safety, and reducing the severity of any unintended leakage to the environment through neutralisation and sequestration of carbon.
At the time (circa 2001) the latter benefit was not even considered in the selection process. It has been intentionally included at the rear of the list to illustrate how our thinking has evolved in the last 20 years. I did research on this topic in university, but my thesis did not touch on the topic of carbon change, neutrality, or sequestration. In today’s current situation, I am more confident neutralising alkaline residue with carbon dioxide could provide broader benefits, but would still be unlikely to be presented as the primary benefit, which I believe it ought to be.
Twenty years on and looking back in retrospect, what was attempted in the early 2000s was pioneering work. Unfortunately, due to cost pressures and challenges in chemistry stable over the longer term, these trials were abandoned. Recently while flying over the Pacific, with many hours to think, I began wondering how our current carbon neutrality aspirations might have changed the outcome from these earlier trials and decisions. Could these earlier technologies impact real positive change?
To promote more broad decision making in tailings projects, at Hatch we have advanced our climate change expertise, managed by our Frank Porretta, to help better articulate and quantify the benefits when more than direct costs are part of the decision process. We are doing this on numerous large tailings projects for some of the world’s largest and most diverse mining houses. This is part of a multi-business initiative to improve better project decision making, which attempts to balance short term financial and longer-term corporate social responsibilities.
Coincidental with the more frequent and extreme weather events experience from our changing climate (see: Board on Atmospheric Sciences and Climate, Attribution of Extreme weather events in the Context of Climate Change, 2016), our industry has been through a period of unprecedented catastrophic tailings failures. In some instances, our criteria have been slower the adopt criteria to safely management these more extreme and frequent conditions. These failures within the industry has led to a doubling down to eliminate all preventable failures. The implementation of tailings management procedures and standards such as the Global Industry Standard on Tailings Management (GISTM) has been the current approach. Although one of the lower forms of control, it is a starting point.
However, are their better controls? Engineers and scientists have been given the aptitude and responsibility to help solve big challenges. It’s in our DNA to do so, no matter how insurmountable they may seem. The predicament is that our industry has caused the direct harm to people and the environment, which we’ve been entrusted to protect.
But implementing solutions to eliminate failures, our highest control, requires an increase in energy consumption and financial investment, which could deviate from our carbon neutrality goals. How do we develop a balanced approach to managing not only our immediate stability risks with tailings, but also take into consideration the longer-term objectives to help mitigate climate change and the impacts it has on our designs?
Maybe the technologies developed 20 years ago, when injected into those currently showing the greatest promise in eliminating future harm from tailings facilities, provide a solution. By dosing CO2 with un-neutralised residue upstream of the filtration process, we can improve filterability and sequester carbon, thereby offsetting the delta used in these more energy intensive dewatering processes. This may also reduce potential for pH reversion, reducing the consequences from longer term environmental seepage. The landform from these processes also requires less storage of entrained and surface runoff water and is inherently safer to close and rehabilitate.
Although we may not have the full solution yet, we do have parts. We also understand how to combine and optimise these to form holistic solutions. As engineers and resources professionals this is what we do, take great ideas, and make them better for our collective benefit. At Hatch, teams of geotechnical, process, environmental and mechanical engineers are working closely to solve this problem. We are continuing to invest significant time and energy to advance our industry towards safer, less land intensive and carbon neutral tailings management.