In situ recovery of resources from waste repositories

Having historically disposed of vast quantities of industrial, municipal, metallurgical and mining waste into the ground, societies have put into geological storage an enormous amount of resources in a range of materials of value such as metals and energy (in the form of biomass and polymers). Therefore, instead of considering these waste repositories to be a legacy waste issue and a long-term liability, a paradigm shift is required to view these installations as "resource hubs" for future recovery. The proposed research aims to contribute towards the development of a new and exciting research field related to resource recovery from existing waste repositories and seeks to address the following central question:

Can resources, specifically elements of value (e.g. Au, Pd, Ag, Cu, Pb, Zn, Co, Ni, Sn and Cr), 'E-tech' elements used in clean energy and other environmental applications (e.g. neodymium and other rare earth elements) and energy (through enhanced methane generation) be recovered by leaching and other treatments whilst the material lies in situ, thus avoiding the need to actively mine the material and thereby minimising ecological and environmental impacts?

The fundamental geoscience research question that underpins this is:

How can we understand and manipulate the in situ biogeochemistry of the waste within the geological repository to recover resource?

The rationale behind the research is to examine new technologies for resource recovery with a lower environmental impact than active ('dig and process') mining of wastes, or of virgin ores.

The concept and technology of in situ leaching has been developed in the mining industry for recovery of uranium and copper, and is done by circulating solutions to extract the elements and/or stimulating and enhancing microbial leaching. The possibility of transferring this concept for application to recovery of resource from waste repositories has not been fully addressed previously. Wastes display diverse compositions, mineralogies and textures very different to that of ores and thus will require new science to understand and develop leaching methods to solubilise valuable components.

We will consider resource extraction from the full range of wastes currently in UK waste repositories including industrial and commercial waste (anticipated to be metal-rich), incinerator and fuel ash, mineral wastes and municipal wastes to examine the idea of in situ leaching. We are particularly keen to identify during the grant which types of landfilled waste streams might be relatively enriched in certain resources and focus the research on recovery from these wastes as a starting point. We envisage that in situ leaching could sidestep many of the problems that prevent realisation of the resource potential of waste repositories, with important impacts not only in the UK but internationally. Furthermore, our aim is to not only investigate means to recover resource through in situ leaching but to also investigate how we can appropriately benchmark such processes (which we anticipate may have substantially lower environmental and human health impacts) in terms of life-cycle, human health and ecosystems service costs as well as public opinion for comparison to retrieval of landfilled resources by 'conventional' dig-and-process landfill mining and against conventional mining of the same resources. This aims to provide evidence to demonstrate not only that the techniques are technically feasible but that they offer reduced impact compared to conventional technologies, are acceptable to stakeholders and thus are a feasible and appropriate approach to future management of wastes.

We feel strongly that this research has real potential to actually kick-start a truly new discipline - in situ recovery of resources from waste repositories. The project is likely to have numerous social, economic and environmental impacts affecting a range of players in the waste recovery sector, as well as on residential communities and wider society in the future. Based on the model of impact defined by the RCUK, our work will contribute to both academic, and economic and societal impact. As a measure of our Academic Impact, we anticipate developing a new branch of technology - in situ recovery of resource from waste repositories and delivering and training highly skilled researchers. As a measure of our economic and societal impact, we will i) contribute towards evidence-based policy-making and influencing public policies and legislation at a local and regional level through our project partners and ii) contribute towards resource recovery, environmental sustainability, protection and impact reduction. 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 in situ. In the medium and longer term the project could have significant and wide-reaching benefits for a number of stakeholders, and these are also being considered in the lifetime of the project. The potential beneficiaries, and the ways in which they will gain from the research, are as follows:

- Industry: which will gain, in the short term, from new knowledge on the contents of waste and a clearer picture of the UK's potential for in situ recovery from the typology of sites. Ultimately, it could gain economic advantage from turning waste into an asset by transforming them into viable ore deposits.

- Repository owners: who could gain economically from: new funding streams generated by recovered resources; more rapid reclamation (i.e. turnover) of sites; and reducing future liabilities (i.e. potential costs) (in the medium-long term) thereby allowing improved management of repositories all of which, as noted by a project partner, has the potential for 'substantial benefit both in terms of the long-term site stewardship and reduction in fugitive emissions'.

- Engineers and other professionals engaged with waste repositories: who will gain marketable knowledge, and advanced tools (e.g. the Resource Recovery model), to deal with waste (in the short-medium term).

- Regulators and policy makers: who will be able to develop more effective policies and regulations, by being equipped with better understandings (and evidence) of impacts of interventions in waste deposits, and new techniques to identify effective and socially acceptable recovery (in the short-medium term).

- Residents and communities (in proximity to sites and transportation routes), who, in the longer term, will avoid disruption because in situ techniques have less impact than ex situ extraction and other forms of repository mining, and who will benefit from the removal of hazardous components of waste deposits (in the medium-long term).

- Broader society: which will have more secure access to resources, reduced environmental and landscape impacts (because of reduced mining of virgin ores), more waste 'reuse' (rather than disposal), and hence enhanced recycling with the reduced need for geological disposal (in the medium-long term).