From spoil to soil: utilising waste materials to create soils for mine rehabilitation

Abstract

The Latrobe Valley in Victoria, southeast Australia, is home to three large open-cast brown coal mines. Due to the nature of the mining operations, there is a lack of topsoil to cover the whole area that is to be progressively rehabilitated. This has led to the development of technosols, employing the ideas of the circular economy by using waste products from three industries located in the Latrobe Valley: mining and energy production (overburden, subsoil, topsoil, waste brown coal and fly ash from the powerplant), paper milling and recycling (effluent sewage recovery and recycling waste) and municipal green waste collection (compost). These waste products have been mixed at different ratios and tested in laboratory, greenhouse and field conditions to establish the best type of technosol that is safe for the environment and can turn into a productive soil in the long-term. If proven suitable, this new concept will not only aid in rehabilitation of large post-mining areas but also help in waste reduction. In a greenhouse study, we tested plant germination and growth in seven different mixtures. Although grass germination was highest in natural topsoil, both grass and clover biomass and leaf length were generally higher in technosols than in topsoil. Also, the plant tissue nutrient levels were similar or higher in technosols than in topsoil. Four out of seven technosols were then transferred into a field trial. Preliminary results from the trial have shown that plant biomass in three out of four technosols is greater than in natural topsoil. Further monitoring of soil properties is being undertaken to assess long-term performance of these soils.

Technosols Derived from Mining, Urban, and Agro-Industrial Waste for the Remediation of Metal(loid)-Polluted Soils: A Microcosm Assay

“…Besides the general soil functions, Technosols have the capacity to create/stimulate several biogeochemical and edaphic processes (e.g., neutralise acid, decrease sulfide oxidation, immobilise metal(loid)s, increase soil fertility, and stimulate soil biological activity), leading to the sustainability of the rehabilitation process in the medium-and long-term [11,13,14]. The effectiveness of this ecotechnology for the rehabilitation of mining areas (soils, tailings, and leachates) was demonstrated in previous studies for a wide range of Technosols and climate regions both in microcosm studies under controlled conditions [14][15][16][17][18] and large-scale interventions [19][20][21][22][23][24]. However, there are few studies that analyse the changes produced in the physical, chemical, and biological properties at the same time, and this holistic approach is essential to understand the evolution of remediation techniques applied to polluted soils.…”

A Green Solution for the Rehabilitation of Marginal Lands: The Case of Lablab purpureus (L.) Sweet Grown in Technosols

“…In particular, Technosols, based on a pedo-engineering, sustainability, and circular economy approach, have been shown to be effective in mining land rehabilitation (soils, tailings, and leachates), both in microcosm studies under controlled conditions [ 24 , 25 , 26 , 27 ] and in the field [ 28 , 29 , 30 , 31 ]. These consist of human-made soils (called Technosol “a la carte” or tailor-made Technosol [ 18 ]) designed specifically for a particular environmental problem, whose properties and pedogenesis are characterised by their technical origin (containing ≥20% artefacts: wastes or materials from anthropic activities [ 32 ]).…”