It has been estimated, based on average amounts of materials per landfill in the EU, that landfills could provide up to 5% of the total needs of Europe for non-energy, non-food materials and minerals for the next 25 years.
But these are only estimates, and that’s the issue.
Our research work for Cranford University shows that, rather than just being a useless hazard, landfill sites are a significant source of resources, with pockets and veins of valuable materials. Landfill mining can become a commercially viable option both in support of the sustainability agenda and in land reclamation.
Up to this point authorities have not had any idea as to the extent and potential of materials for mining. There has been no inventory available of secondary raw materials (SRM) or critical raw materials present in EU landfills, which is the all-important basis for decisions to be made on the viability of investment into the approach. In these early years of landfill mining, there has also been only very limited knowledge on best practice and how to manage the excavation and recovery of valuable materials.
Mining solely for metals is not expected to be financially viable given the extent of the recovery operations involved. Other opportunities exist that together form the concept of ‘enhanced landfill mining’, including refusederived fuels from excavated materials. The land itself can be reclaimed and the soil remediated, making it available again for agriculture or development.
There are challenges in enhanced landfill mining which mean further research and development are needed before the full potential is realised. We need to understand more about each of the stages involved: the exploration, separation, transformation and upcycling technologies, and how these can best be applied in dealing with the differing urban and industrial landfill sites.
For example, excavating material or ‘ex-situ’ landfill mining has issues of managing odours and gas and dust release, with implications for environmental and human health. These issues are amplified by limited understanding of the exact wastes disposed of in sites. Some materials, such as asbestos, need to be left undisturbed – technically they should only be in specific sites for hazardous materials, but there is no guarantee. Processing the excavated materials would be similar to that of mechanical processes used on non-landfilled wastes, but here we are dealing with a vast proportion of inert and soil-like material. This in itself can be heavily contaminated with metals and requires careful management and/or further processing.
It is the soil which needs proper analysis and treatment and, in our research, it was this material where we found the high quantities of metals for potential recovery.
In recovering recyclable materials such as metals and plastics, we also need to consider chemical degradation because it may make them unsuitable for conventional recycling.
There are policy challenges in terms of creating the legal frameworks that allow for enhanced landfill mining, working in close co-operation with local communities affected by the works. Concerted action is underway to overcome these challenges and to make landfill mining a significant part of the future of waste strategies. A consortium of research institutes, including Cranfield University, alongside public bodies and private companies has formed the European Enhanced Landfill Mining Consortium or Eurelco ( www.eurelco.org).
The aim of Eurelco is for enhanced landfill mining to be implemented EU-wide as a keycomponent of a resource-efficient, circular and low-carbon economy by 2020. The potential of enhanced landfill mining was presented to the European Parliament last year, and has received backing from the European Horizon 2020 fund for a new project, Smart Ground (www.smart-ground.eu).
This work will develop an extensive understanding of SRM available in landfills across Europe. Smart Ground will open up understanding and the opportunity for markets in SRM, providing a picture of the value of landfill contents and the barriers to recovery.
Taking enhanced landfill mining seriously will mean turning a current threat, in terms of the environment and in rising costs of scarce resources, into the opportunity for a new and sustainable industry. The extent of the success of enhanced landfill mining will be dependent on shifting the activity into the business sector and not relying solely on public subsidies.
Some of the innovative technologies involved have the potential for further commercialisation to produce high added-value products such as hydrogen and for upcycling waste into building material products.
Dr Stuart Wagland is lecturer in renewable energy from waste and Dr Diogo Martins Gomes is science and technology impact officer at Cranfield University