R3AW: Resource Recovery and Remediation for Alkaline Wastes

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Highly alkaline (i.e. bleach-like) wastes are produced in large quantities by various globally important industrial processes. For example, up to 180 million tonnes of slags are produced each year by the steel industry, while up to 120 million tonnes of bauxite processing residue (from aluminium refining) are generated globally. Traditionally, these wastes have simply been dumped into landfill sites, and pose significant environmental risks. For example, water percolating through the landfill to form "leachate" is toxic to aquatic life, and dust generated from landfill activity can pose public health hazards. On the other hand, these wastes can also provide potential resources we would like to recover. Global mineral and metal prices are high, and there is renewed interest in recovery of metals from any available source. This is particularly the case for those metals important for technological applications, such as vanadium for high grade steel manufacture and rare earth elements for "hi-tech" applications such as visual displays, computer memory and green technologies such as wind turbines and hybrid cars. The potential of highly alkaline waste for metal recovery is enormous; not only is waste produced in large amounts every day, but there is up to 100 years of "legacy" stockpiles in some areas. Unfortunately, the concentration of metals within the leachate is low, and recovering metals from it would be expensive. Directly digging up legacy sites is feasible, but is also expensive and would cause a lot of environmental disturbance. Recent ground-breaking work by the project team has shown that we can accelerate natural weathering processes of steel industry residues by covering it with compost. This concentrates metals like nickel and vanadium to recoverable concentrations in the leachate with almost no physical disturbance. Covering the waste material in compost will also reduce - potentially prevent - dust generation. The compost used in these experiments is "municipal organic waste" that is mostly put into landfill today, so the treatment can be done at almost no financial cost and with a knock-on environmental benefit. If this were not enough, the compost allows more dissolved CO2 to penetrate into the waste material where it reacts with the metals to form carbonate minerals. This is an important means of carbon sequestration, which will offset some of the emissions from the industry. Further deposition of carbonate minerals can be encouraged within the leachate itself once it reaches surface, sequestering even more carbon and consuming some of the low value metals in the leachate it would be worthwhile to recover.As ever, there remain considerable economic, legislative, environmental and social issues that need to be addressed to ensure the responsible development of this kind of industry as well as a range of scientific challenges we still need to address. R3AW aims to address these challenges by bringing together key commercial partners (e.g. steel, cement and alumina industries) with a multi-disciplinary team of environmental scientists, waste policy experts and experts in systems analysis and stakeholder engagement to pave the way to transform resource recovery and environmental remediation in the steel and cement industries and elsewhere. Our objectives for the project are:1) Develop an interdisciplinary approach involving researchers and all other stakeholders to identify key scientific, economic and societal needs and questions surrounding resource recovery from caustic waste streams.2) Undertake preliminary assessment of the accelerated leaching approach we are pioneering under field conditions in the UK.3) Determine the critical scientific, industrial, societal and policy issues currently limiting application of this highly promising science in a manner that can be addressed in future government and industrially funded projects.4) Develop full research proposals to address these questions.