Material flow analysis and material flow cost accounting of the resource-energy-water nexus: A case study of a sedimentary phosphate mine

Abstract

Implementing sustainability in mining requires adequate tools able to quantify resource use, identify inefficiencies, and plan improvements. This study used Material Flow Analysis (MFA) and Material Flow Cost Accounting (MFCA) to evaluate the efficiency of the phosphate production chain, along with energy and water use, during the extraction and pre-beneficiation stages at a phosphate mine. These tools enable a systematic identification of environmental and economic hotspots within the production chain. The analyses show that a considerable portion (over 47% above the planned cut-off grade) is currently not recovered within the existing production system, mainly during the extraction phase. Based on the assumed conversion efficiencies of diesel and electrical equipment, the weighted energy-conversion efficiency of the site was estimated at 52%, with diesel representing the main contributor to energy consumption, emissions and costs. Water consumption is moderate and exclusively sourced from a nearby wastewater treatment plant, but its current evaporative and irrigation-limited uses constrain its recycling opportunities. The study highlights several opportunities for sustainability improvements, including recovery of phosphate from historical spoil piles, electrification of key machinery, and reduction or substitution of water in dust suppression. Despite being based on one year of data and a single lithological log, the study provides a transferable framework, and the findings underscore the importance of integrated flow analysis to support more sustainable phosphate mining.