As worldwide demand for minerals surges, mining companies have been doubling down on investment into brownfield development, expanding or intensifying extraction at existing mine sites. In a new paper, researchers from The University of Queensland provide a snapshot of the potential social and environmental costs of this growing trend and the implications for sustainable development.
Although brownfield sites have already had mines operating on them, the research team led by UQ’s Sustainable Minerals Institute (SMI), found that there is little information available about the scale of expanded mining activities as countries race to secure the minerals to build renewable energy systems, digital infrastructure, and defence assets.
The paper, published in the international journal One Earth, shows increasing investment in brownfield mining over greenfield or “new” mines, and provides a snapshot of 366 brownfield sites across 58 countries and16 minerals including critical minerals like cobalt, copper and platinum to understand their social and environmental contexts.
Expansion of brownfield mining
Lead author and director of SMI’s of Centre for Social Responsibility in Mining, Professor Deanna Kemp explained that 60% of major company exploration budgets in 2024 were at or near existing mines, more than double 2016 levels.
“Brownfield mining is an appealing option for mining companies because it maintains production, offers a stronger return on investment, with fewer financial and regulatory risks than establishing new ‘greenfield’ mines, while also deferring the significant costs of closure and rehabilitation, that is, restoring land and managing waste after mining ends,” she said.
The study found that Chile leads global brownfield development, with 25.2% of total worldwide capital investment, followed by the United States (11.4%) and Australia (10.1%).
“Once a mine has been approved and permitted, expansion is typically a business-as-usual part of developing a mine, even when that expansion changes the original risk of social and environmental impact,” Professor Kemp said.
“Brownfield expansion often unfolds incrementally over time, with less public scrutiny: the risk factors involved in each mine site are unique and no-one has really been looking at the scale of growth brownfield mining globally.”
The researchers found that more than half of their sample were in locations with multiple complex risk factors like social conflict, fragile ecosystems, and weak governance, making it harder for governments and affected communities to respond to the risks presented by these expansions.
The missing middle: regulation of mine expansion
The destruction of a 47,000-year-old Indigenous cultural heritage site at Juukan Gorge, Australia in 2020, as part of a legal expansion of an iron ore mine, illustrates that brownfield projects have real and significant costs for local people and that developers can sometimes lose sight of what is important.
Professor Kemp explained that mine approval and regulatory standards are usually heavily focused on the front-end (assessing risks and impacts before a mine opens). There has, more recently, been an increasing focus on responsible mine closure, when the mine is shut down and the focus is on land rehabilitation. Both aspects are important, but the research highlights that the way mines expand and extend is becoming more important.
“In the “’middle’” of a mine’s lifespan, when the mine is active there is often less oversight or public focus: changes tend to be regulated, step by step, but the impacts of these expanded operations add up over time,” she said, and added that more research is needed to quantify the sheer scale of this trend towards greater reliance on brownfield sites, and their cumulative, long-term social and environmental effects.
Dr Julia Loginova, Senior Research Fellow at CSRM and a co-author on the paper, explained that given that capital is flowing into brownfields, regulatory and academic scrutiny should be moving there as well.
“Brownfield sites may be the fastest and economically attractive way to meet rising mineral demand, but it is important to anticipate and manage pressures and long-term liabilities, that’s why further research in this space is very much needed, because there is still a fundamental knowledge gap,” Dr Loginova said.
“There is a significant opportunity for interdisciplinary research to better understand scale and impacts, to support improved practice in the sector.”
John Owen, a senior co-author on the paper and an adjunct professor at the University of the Free State in South Africa, explained that the study shows the massive scale of brownfield development in the global minerals industry.
“The scale and complexity of the challenges involved in brownfield development requires a deft multidisciplinary approach,” he said.
