Accelerating soil aggregate formation: a review on microbial processes as the critical step in a post-mining rehabilitation context

One of the most difficult challenges facing the coal mining industry is rehabilitation of open cut mines in the absence of sufficient quality and quantity of topsoil. As a result, the growth medium for rehabilitation of open cut mines is often mine spoil that has poor chemical and structural properties. Microorganisms play a critical role in natural soil forming processes, nutrient cycling and soil aggregate stabilisation. However, soil microbiota and their impact on soil chemistry and structure has traditionally been overlooked in mine site remediation and mine spoil amelioration. Soil bioengineering, using microbial inoculants to modify soil chemistry and structure, is a novel approach that has the potential to positively alter the chemical and physical limitations prevented by mine spoil and improve mine site rehabilitation outcomes. This review focuses on the importance of microbiology in the spoil-to-soil transformation after open cut coal mining and discusses the ways that microbial inoculants could be used to accelerate the amelioration of coal mine spoil during rehabilitation. The work seeks to establish a platform for soil bioengineering approaches to be considered during rehabilitation of open cut coal mines. The review focuses on Australian open cut coal mines but has application for all mines with nutrient limited substrates and/ or saline or sodic spoil that is prone to erosion.