As a society we often equate the residuals of processes as “waste” whether it be tailings from mining and milling processes, leftover food scraps from our kitchens, or the end-results of our own bodily functions. It is also not uncommon to view these residuals as liabilities, or something that simply has to be managed in a way that minimizes impact to the bottom line of a balance sheet, to stakeholders or to the environment. As our world increasingly focuses on sustainability and developing a Circular Economy, the ability to reframe our thinking of materials from “wastes and liabilities” to “resources and opportunities” has the potential to transform aspects of mine closure and reclamation, providing environmental and economic benefits to a wide array of stakeholders.
Municipal biosolids are the residuals from municipal wastewater and sludge treatment. Solids are settled out and removed from wastewater processes, and subsequently treated to reduce pathogen and bacteria counts such that the materials meet jurisdictional regulatory requirements. Municipal biosolids are an organic material containing many vital nutrients for plant growth including nitrogen and phosphorous.
Cities worldwide grapple with the challenges of accommodating an expanding population: as the number of humans on Earth approaches 8 billion people, the challenges associated with managing natural resources and residuals continues to evolve as well.
Approaches to managing biosolids have historically included landfilling, incineration and sea-dumping incurring costs to the producing municipalities, and creating environmental risks. The use of composting and agricultural application to manage biosolids has allowed for these residuals to be beneficially re-used, providing valuable nutrients to crops and helping to alleviate burdens associated with disposing of a product formerly considered to be ‘waste’.
Revegetation of mine affected lands can require large volumes of organic soils and amendments; one traditional approach has been to source these materials from borrow areas (although borrowing erroneously implies that these materials will eventually be returned). With the contribution of millions of city-dwellers to biosolids production, there exists the potential to develop a consistent and high-quality supply of organic soils and amendments. Mine reclamation and revegetation could provide a year-round disposal option.
Application of municipal biosolids for mine reclamation is not a new concept, several studies have evaluated the use of biosolids for revegetating mine impacted areas and have examined the impact of biosolids on metal leaching and acid rock drainage. Despite encouraging findings, the use of biosolids in mine reclamation has not been widely adopted.
Our team of soil scientists, plant ecologist, geologists, engineers, agrologists, and geochemists are constantly working with clients to develop effective solutions to unique challenges. Our experience examining the physical and chemical characteristics of tailings and mine waste at the laboratory scale using tools like our advanced customizable leach columns, allows Okane to characterize site-specific materials and their suitability for reclamation. Our expertise in designing and overseeing the construction of cover systems allows Okane to efficiently scale-up from the lab to the field.
As practitioners who seek to develop mine closure solutions which provide our clients and stakeholders with achievable, effective, and holistic closure planning services, we endeavour to continue advancing the research and implementation of new technologies and solutions.