This theme encompasses many different facets of research across STEMM, the social sciences and humanities, including the sustainability of natural and modified ecosystems in the face of societal development and climate change, climate change science, adaptation and mitigation, mining and its corresponding global environmental challenges, sustainability and the circular economy.

Available PhD projects

5. Environmentally sustainable closure of tailings storage facilities informed by life cycle analysis

UQ academic leads

Dr Talitha Santini, School of Earth and Environmental Sciences

Associate Professor Glen Corder, Sustainable Minerals Institute

Exeter academic leads

Professor Karen Hudson-Edwards, Environment and Sustainability Institute and Camborne School of Mines

Project description

Tailings (7 GT/yr produced worldwide) and other byproducts (56 GT/yr) of mineral extraction and processing activities pose a major challenge for closure of mine sites and refineries. These figures will increase as demand for resources increases and as ore grades decline, creating an urgent need for effective, rapid strategies to remediate and close tailings storage areas.
The main environmental challenges to closure lie in their chemical, physical, and biological properties: extreme pH (pH<4 or pH>9); high salinity and metal(loid) concentrations; and fine particle size favouring waterlogging and dust production. Most closure plans aim to establish a vegetation cover over the surface of tailings storage areas to improve stability, suppress dust export, and support a productive land use after closure. However, given the harsh properties above, direct revegetation into unremediated tailings is not usually a viable option. Instead, one of two strategies is employed:

  1. ‘Cap and store’: importation of high quality topsoil (stripped from another productive area offsite) as a plant growth medium, underlain by an impermeable/capillary break layer to limit interaction of tailings with rainfall, air, and biota
  2. ‘In situ remediation’: importation of chemical, physical, and biological amendments designed to remediate the tailings to form a viable plant growth medium by correcting its unfavourable properties.

A third, emerging option is ‘blended waste caps’, using a combination of imported materials and wastes onsite (e.g. vegetation mulch, sewage sludge) to create both a plant growth medium ‘cap’ and an impermeable/capillary break layer to separate this cap from the underlying unremediated tailings.

The three options each come with different timeframes for implementation, financial costs (installation earthworks, materials, freight to site), flexibility in technical feasibility across sites (desired end land use, climate, environmental setting, initial tailings properties), and environmental costs (materials extraction) and benefits (stored liabilities in tailings), summarised in the table below.

Option Implementation timeframe Financial costs Technical flexibility Environmental costs Environmental benefits
Cap and store Rapid High High High Low
In situ remediation Slow Low Low Moderate High
Blended waste caps Moderate Low Moderate Low Low

Although much effort has been focussed on developing the technical feasibility of these options, the question of which option provides the most sustainable overall environmental outcomes for a given site still remains unanswered.

This project will answer this question by undertaking a life cycle evaluation of each option applied to different major tailings types across environmental settings; considering how the outcomes for each of these options may be influenced by site-specific factors such as material availability, climate, and tailings properties; and constructing a decision-making framework for use in identifying the most environmentally sustainable option for a given site.

Apply

Submit UQ expression of interest form by 26 May 2018