ASPIRE - Accelerated Supergene Processes in Repository Engineering

The UK faces serious strategic challenges with the future supply of aggregates, critical minerals and elements. At the same time, the UK must sustainably manage multimillion tonne annual arisings of industrial, mining and mineral wastes (IMMWs). The amount of these wastes generated is projected to increase over the coming years, particularly (i) ash from the combustion of biomass and municipal solid waste, and (ii) contaminated dredgings. These wastes will continue to be landfilled despite often containing valuable resources such as high concentrations of critical metals, soil macronutrients and useful mineral components, some of which actively drawdown atmospheric CO2.

The fundamental aim of the ASPIRE (Accelerated Supergene Processes In Repository Engineering) research project is to develop a sustainable method by which ashes, contaminated dredgings and other IMMWs can be stripped of any valuable elements. These stripped elements would then be concentrated in an ore zone for later retrieval and the cleaned residues also returned to use, for example as aggregates, cement additives, or agricultural amendments (including those for carbon sequestration through enhanced mineral weathering). It is a very challenging problem to devise a truly sustainable method to achieve this is an economically viable way, and almost all processes suggested so far in the literature for leaching wastes are themselves carbon and chemical intensive and thus non-sustainable.

We are proposing research that comprises the first steps in developing the "ASPIRE waste repository" concept with accelerated analogues of ore-forming "supergene" processes engineered in, such that the dormant waste undergoes processes to (i) concentrate valuable components (e.g. critical metals, phosphate) as an anthropogenic ore to facilitate their future recovery, and (ii) concurrently decontaminate residual mineral material so as to make it available as a bank of material to drawdown for "soft" uses in agriculture, silviculture, greenspace, landscaping in new developments, habitat creation and/or as a cement/concrete additive or replacement aggregate.

The processes investigated rely on rainwater passing through a vegetated surface layer which releases naturally occurring compounds from the plant roots and/or other natural organic matter which then pass through and strip valuable elements from the IMMW. The mobilised elements will then pass into a capture zone where they will be stripped from solution and concentrated to form an artificial ore. The research project will seek to engineer the internal processes of the temporary storage waste repository to optimise this. At the same time the upper vegetated surface of the waste repository will serve as greenspace with commensurate ecological and amenity value for local populations.

Among the key research challenges is in how to engineer the internal ASPIRE waste repository processes which rely on complex biogeochemical interactions and flow behaviour. Another critical research challenge is to develop an understanding of stakeholder and wider acceptability of this concept which does not fit with current legislation on waste management. With this project we seek to provide a circular technology solution for how we can sustainably manage the future multimillion tonne arisings of IMMW at a critical time as the UK government develops strategies and supporting regulation for the transition to a circular economy.

The proposed research works towards repositories which are engineered not to "store and contain" but to "store, contain, clean and concentrate" resources and enable future mining of the clean residues and anthropogenic ores within. The ASPIRE concept represents a novel overarching paradigm shift in waste management and circular economy (CE) for industrial, mineral and mining wastes (IMMWs). This research will take the first critical steps towards this genuine and fundamental change in the way that high-volume (IMMWs) are managed. As such, the project is likely to have numerous social, economic and environmental impacts affecting a range of stakeholder industries which produce large amounts of IMMWs as well as on local communities and wider society. Based on the model of impact defined by UKRI, our work will contribute to both academic, and economic and societal impact.

As a measure of our Academic Impact, we anticipate developing this new waste management concept, and in so doing deliver the first highly skilled researchers in this area. As a measure of our economic and societal impact, we will (i) contribute towards evidence-based policymaking by influencing public policies and legislation at a local and regional level through our project partners and (ii) contribute towards resource recovery, environmental sustainability and protection. The project's immediate impacts will be felt mainly through the generation and dissemination of new knowledge on the potential to recover resources from a range of wastes through temporary storage in ASPIRE repositories.

In the medium and longer term the project could have significant and wide-reaching benefits for multiple stakeholders (as follows), and these will be elucidated through the work of our impact team:
[1] Industries that generate IMMW will gain a way to convert both their long-term and ongoing liability from their waste generation into a long-term asset through recovering value from IMMW and releasing the land-value when the cleaned material/anthropogenic ore is returned to the CE.
[2] The ASPIRE concept could contribute to the UK's climate targets by providing a technology solution to support both "enhanced terrestrial weathering" which requires a source of clean silicate-based material to apply to agricultural fields and "Bio-Energy with Carbon Capture and Storage" which requires a large-scale solution to manage the ash arisings.
[3] Engineers and other professionals engaged with IMMW repositories design will gain marketable knowledge on management of future and legacy IMMWs.
[4] National and local government who deal with legacy sites of contaminated IMMW will have a new low-cost technology option.
[5] Regulators and policy makers, who will be able, at this critical juncture in the transition to a CE, to develop more effective policies and regulations regarding the management of IMMWs.
[6] Residents and communities, who may benefit from the amenity value provided by new greenspaces as well as other ecosystem services provided by the vegetated surface layer of ASPIRE repositories.
[7] Broader society: which will have more secure access to resources including critical minerals and elements, and aggregates, reduced environmental and landscape impacts (because of reduced mining of virgin ores), waste reuse rather than disposal, and reduced CO2 emissions for the UK.
[8] Future generations: current landfilling continues for many IMMW because of lack of a market at the time of generation, and/or because the materials are too contaminated for reuse. As such the wastes are landfilled, and it is falsely assumed that these wastes will stay safely contained within the repository and not imperil human health or environment. To prevent this the ASPIRE repository concept will ensure that waste is stored and treated in situ until the clean residue and anthropogenic ore are ready for return to the economy.