Resource Recovery and Remediation of Alkaline Wastes

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Over half a billion tonnes of alkaline (i.e. bleach-like) wastes are produced globally each year by industries such as steel production, alumina refining and coal-fired power generation. These wastes are currently stored in piles or landfill and can pose serious environmental hazards. Water that filters through the waste is toxic to aquatic life and dust generated as it is moved and stored is a public health hazard. It can take decades for these risks to fade. On the other hand, alkaline wastes contain large quantities of materials we would like to recover for re-use, particularly metals important to the technologies of the future, such as vanadium, used in steel manufacture for offshore wind turbines, lithium and cobalt for vehicle fuel cells and rare earth elements crucial for next-generation solar power systems. The obvious solution: using the profits from recovering resources locked in the waste to pay for remediation of the pollution, is hampered by the environmental damage caused by digging up stored waste piles and the expense of extracting the metals from the waste using existing technology.Ground-breaking pilot research recently conducted by the team proposing this project shows that harnessing the power of low-cost, low-energy natural processes could solve the problem. We are developing a unique 'biomining' approach to increase the rate at which resources stored in the waste dissolve into water passing through it. Our pilot tests have shown that covering the waste pile with a layer of 'solid municipal waste' (compost) is very effective in driving this process. As water flows through waste treated with compost, metals like vanadium leach out to levels over twice those of untreated piles. The metal solution then flows out of the bottom of the waste pile under gravity. The high concentrations mean that extracting metals from this solution becomes viable using existing technology which we propose to implement as part of this project. In effect the valuable resources are extracted without digging up the waste.The resource recovery benefits are matched by benefits to the environment. The layer of compost reduces dust generation from the site, and allows more CO2 to penetrate into the pile where it is locked away in significant quantities by reacting to form solid carbonate minerals. As elements like vanadium are pollutants as well as resources, recovery will eliminate the pollution alkaline waste weathering causes. Furthermore, the weathered waste piles have ideal conditions for nationally-scarce, orchid-rich plant communities to become established, making them suitable for restoration to create habitat of high conservation value.In order to turn the extremely promising results of our pilot studies into optimised, industry-ready processes we must better understand the specific mechanisms which control the biomining and develop a road map for negotiating the economic, legislative, environmental and societal challenges to the implementation of a new technology in an established industry with strict requirements for environmental protection. Our proposed research will tackle both these aspects in parallel. The combined package: recovery of the metal resources while suppressing dust, increasing carbon sequestration and treating the pollution caused, would be hugely beneficial to partners in our project from both industry (Tata Steel, Rio Tinto and the Minerals Industry Research Organisation) and environmental protection (Environment Agency).The project will bring together key commercial partners with a multi-disciplinary team of environmental scientists, waste policy experts and specialists in systems analysis and stakeholder engagement to pave the way for transforming resource recovery and environmental remediation. This team will investigate the key obstacles to this transformation and identify potential remedies, such as lobbying for legislative change or making a clear business case for resource recovery.