Benchmarking the environmental impacts of representative heavy mineral concentrate (HMC) production in Australia: a life cycle assessment approach

Heavy Mineral Sands (HMS) extraction is energy-intensive and generates significant Greenhouse Gas (GHG) emissions, making it essential to identify key sources of Global Warming Potential (GWP) and energy use to develop sustainable reduction strategies. This study aims to characterize the main LCA indicators of Heavy Mineral Concentrate (HMC) production in two representative Australian wet and dry mining operations. The cradle-to-gate LCA was conducted for two operations to systematically evaluate their environmental impacts of production. The Life Cycle Inventory (LCI) was developed using real operational data, ensuring high data fidelity and compliance with standard framework. The environmental impacts were assessed using the ReCiPe midpoint impact assessment method, while the Cumulative Energy Demand (CED) method was applied to quantify the total amount of direct energy and embodied energy consumed. This structured methodology enables quantification of inputs/outputs, and associated environmental impacts, facilitating hotspot analysis and providing a mechanistic understanding of the processes with the most significant environmental burdens. It was found that LCA impact indicators for energy consumption, GWP, water consumption, and waste generation (ECWW footprints) indicators are significantly lower in the dry mining operation compared to the wet mining one per unit of HMC produced. The dry mining route consumes 2,068.24 MJ/t HMC primary energy, which is more than 3.5 times less than the wet mining route at 7,298.46 MJ/t HMC, and contributes 141.66 kg CO₂-e/t HMC to GWP, nearly 4 times less than the wet mining route at 537.82 kg CO₂-e/t HMC. The dry operation requires 3 times less water and generates more than 8 times less waste. The data also showed that regardless of the adopted mining technique, the energy demand and GHG emissions are highly dependent on the ore grade and the geological conditions of the ore reserve. It was also concluded that the environmental impact indicators are highly affected by the energy source, hence there is an imperative demand for green sources of energy for the operations going forward.