Tailings, a by-product from the processing and extraction of raw minerals and metals from mined ore, are being re-examined as a potentially commercially viable resource for products like batteries and other electronics. We take a look at the evolution of the tailings industry and how EnviroGold Global is employing an innovative new process called the NVRO Process to support profitable, sustainable and responsible mining practices.
Historically, many mines were abandoned without proper reclamation, leaving a host of environmental issues in their wake, tailings among them.1 Today, billions of tonnes of tailings are produced globally each year.2 Reprocessing tailings represents a potential maturing of the industry, as it not only recovers valuable minerals but also reduces environmental harm. With growing pressure from stakeholders for responsible environmental practices, mining companies are increasingly prioritising tailings reprocessing as part of their ESG strategies.
There has been no agreed best approach to handling tailings. In the past, tailings were simply discharged into nearby water sources, a practice which continues in areas with steep, unstable terrain, like the Ok Tedi and Grasberg mines.3 By the 1900s, the negative impacts of uncontrolled tailings disposal including irrigation ditch blockages and downstream contamination became evident, causing greater conflicts with agricultural land use.4 Even tailings dams, purpose-built storage dams, were prone to chemical leakages, structural instability and high operating costs.
Barriers to reprocessing tailings
Reprocessing tailings in the past was not commercially appealing or viable. Extraction methods were inefficient, and the high variance in material concentrations and presence of chemical additives made it difficult to recover valuable materials.5
However, growing ESG pressures taking the focus off pure profit, and technological advancements like flotation, advanced gravity separation, high-intensity magnetic separation, leaching, roasting, and sensor-based sorting are changing how the sector views tailings.6
Case study: how EnviroGold Global is tackling environmental challenges with innovative solutions
Chemical leaching involves treating mined ore using a chemical agent (like nitric acid). The chemical agent converts the valuable minerals to a soluble form which can be extracted, while the undesired residual materials remain insoluble.
EnviroGold Global is a company targeting the treatment of sulphidic tailings, which are the cause of acid mine drainage and related environmental risks, by employing its proprietary NVRO Process. The NVRO Process uses a weak acid catalyst at atmospheric pressure and low exothermically generated temperatures to generate a self-sustaining chain reaction which chemically alters the sulphide bonds liberating the metal and making the acid generating sulphur available for neutralisation.
This process is more efficient than other common methods for tailings retreatment with lower capital and operating costs due to the fact that it does not require high pressure, high temperature or specialised equipment. Its residence time is shorter than other technologies which means that the size of the equipment can be scaled down compared to other technologies.
The NVRO Process is metal agnostic and can be used to reprocess sulphidic tailings and smelter byproducts to recover contained metals including precious and non-precious metals, strategic metals and rare earth metals.7 The exothermic reaction chemically alters the sulphides allowing the metals to be released for recovery by conventional methods, with a highly successful recovery rate of over 90% for targeted metals.8 As the water and leach solution is recycled through the system at very low temperatures to regenerate the catalysts in the reaction, the process is highly sustainable.9
In May 2024, EnviroGold Global announced that it had entered into an agreement to purchase an integrated metal processing plant developed at the CSIRO Australian Minerals Research Centre. As part of its customer engagement process, NVRO customer tailings are transported to the demonstration facility and processed using the NVRO Process. This demonstration plant accelerates the feasibility process and aids in the controlling of study costs.
After extraction of the metal, the tailings have a reduced environmental risk profile which can be further neutralised according to client specifications. The goal of the process will be to produce inert, dry stackable tailings (filtered sand like material) which can be laid down, compacted and planted with native soils and vegetation as part of environmental rehabilitation. Adopting this practice will mean a decrease in the need for tailings dams which require extensive maintenance due to the chemical and metal content in conventional tailings. This is poised to benefit developing mining countries facing water scarcity issues.10
EnviroGold Global’s pilot test of its technology in 2021 for the Hellyer Gold Mine successfully processed 500 kg of tailings.11 Following demand from multiple mines to trial the technology EnviroGold Global has developed a pipeline of interested customers.
The NVRO Process offers a commercially viable solution due to its low capital and operating costs, as well as its scalable, modular design.12 In January 2025, EnviroGold Global signed an MOU with Fraser Alexander, a global leader in mine tailings management and processing, to collaborate on deploying the technology across three tailings storage facilities.13 This is a significant step towards proving the potential of its clean leach process.
EnviroGold Global CEO, David Cam states, “EnviroGold’s continued momentum underscores its commitment to responsible growth and operational excellence. The company is accelerating the development of its Strategic Relationships and customer engagement, further reinforcing its first mover advantage and leadership position in the green mining and resource recovery sector.”
Next steps
As metal reserves decrease, the need for innovative solutions to remediate tailings becomes more pronounced. Amongst growing resource scarcity, EnviroGold Global’s technology highlights the ability to view tailings as a valuable source for both the metals and agricultural industry.
The NVRO Clean Leach process also contributes to mining companies satisfying their ESG obligations by preventing leaching into waterways, causing environmental harm. The anticipated commercialisation of the technology shows significant and promising advancement towards sustainable mining. Further innovation in other stages of the mining process will help to reduce the environmental footprint of the mining industry.14
The Hamilton Locke team advises across the energy project life cycle – from project development, grid connection, financing, and construction, including the buying and selling of development and operating projects. For more information, please contact Matt Baumgurtel.
1E Martin et al, ‘Stewardship of Tailings Facilities’ (Report No.20, International Institute for Environment and Development, April 2002) 4 (‘Stewardship of Tailings Facilities’).
2PIIA Suvio, ‘How to Reshape the Future of Tailings’, Minings and Metals Blog (Blog Post, 11 January 2024) < https://www.metso.com/insights/blog/mining-and-metals/how-to-reshape-the-future-of-tailings/> (‘The Future of Tailings’).
3Alex Jakubick et al, ‘Stabilisation of Tailings Deposits: International Experience’ (Article,2003), <https://www.researchgate.net/publication/242492520_STABILISATION_OF_TAILINGS_DEPOSITS_INTERNATIONAL_EXPERIENCE>.
4Stewardship of Tailings Facilities (n 1).
5Jason Palmer, ‘How to manage tailings efficiently and economically’, Metso, (Web Page) <https://www.metso.com/insights/blog/mining-and-metals/efficient-tailings-management/>.
6Hyunjin Na et al, ‘A review on the reprocessing of sulfide tailings for resource recovery and AMD prevention using mineral processing methods’ (2024) 218 Minerals Engineering.
7EnviroGold, ‘EnviroGold Global Acquires NVRO Clean Leach Process Demonstration Plant’ (Press Release, 2024) (‘EnviroGold Acquires Demonstration Plant’).
8EnviroGold, ‘NVRO Q4 2024 Corporate Presentation’ (Investor Presentation, 2024) <https://envirogoldglobal.com/wp-content/uploads/2024/11/NVRO-Q4-Corporate-Presentation.pdf> (Investor Presentation’).
9See ibid.
10The Future of Tailings (n 2).
11EnviroGold, ‘EnviroGold Announces Positive Pilot Plant Results Confirming Efficacy of Metals Recovery Technology’ (Press Release, 2023).
12Investor Presentation (n 9).
13EnviroGold, ‘EnviroGold Global Announces Strategic Alliance with Global Leader Fraser Alexander to Collaborate on Sustainable Mining Projects’ (Press Release, 2025).
14The Future of Tailings (n 2).
