Landfill Mining: Goldmine or Minefield?

As societies move waste management practices up the hierarchy towards recovery, recycling and re-use, we are still left with the environmental legacy associated with the historic use of landfill. In parallel, as resources have become scarcer and we increasingly recognise the value in wastes, attention has focused on landfill mining.

As societies move waste management practices up the hierarchy towards recovery, recycling and re-use, we are still left with the environmental legacy associated with the historic use of landfill. In parallel, as resources have become scarcer and we increasingly recognise the value in wastes, attention has focused on what potential value could be recovered through landfill mining.

by Kathryn Warren & Adam Read

Interest in landfill mining is widespread around the globe. It is growing significantly in developed economies where the value of the materials in the sites is expected to be high, where the value of the land if it could be reused is high and where the engineering of landfill sites since the 1970s makes them most suited to mining activities.

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But, for those focussed on waste prevention, recycling and waste treatment technologies, the concept of landfill mining still seems a little strange, and dare we say, alien in terms of modern waste management solutions.

Landfill mining often conjures up images of people scavenging a living from open dumps in developing economy locations. This is far from the truth. Rather, it is an unusual twist on the waste hierarchy by trying to recycle materials that were previously disposed of. But, timing, and a wide-spread changing realisation that resources are becoming scarcer is making landfill mining a far more acceptable and palatable term in sustainable waste management circles.

For these reasons, Landfill Mining and Reclamation (LFMR) is now beginning to be considered more seriously in both Europe and the U.S., and we have seen a recent increase in the discussion of landfill mining in the press - both in mainstream newspapers and more importantly in the trade press and among those working in the waste management sector - and most noticeably at a series of international conferences.

Benefits and Challenges

In addition to the potential recovery of recyclable materials (key ones being soil, plastics and metals), mining and reclaiming materials from landfill can result in additional benefits such as the mitigation of environmental impacts (pollution of watercourses), landfill void space recovery, freeing-up land for redevelopment and the reduction or elimination of costs associated with landfill aftercare and monitoring.

Excavating landfills to recover resources may sound relatively straightforward, but how much would it cost? Is it safe? What would be the environmental impacts? And when will it take hold as a core waste management solution?

In the summer of 2012 the Scottish Government, via Zero Waste Scotland, commissioned Ricardo-AEA to undertake a Scoping Study on the Feasibility and Viability of Landfill Mining and Reclamation in Scotland. The project involved a high level scoping study to investigate the environmental, economic and technical aspects of landfill mining and reclamation (LFMR) with the aim of testing its feasibility for Scotland. The study also reviewed the feasibility of LFMR based on documented historic projects around the world and with assessment of key issues impacting on LFMR feasibility.

History and Drivers

The current literature on LFMR identifies in excess of 60 documented projects undertaken worldwide since the first recorded project in Israel in the 1950s. Ricardo-AEA found reference to 57 projects, six of which were in England and many of which were trial projects. For there to be such a small number of documented landfill mining projects, when there are millions of landfills around the world, reflects that landfill mining is far from straight forward and that there have been limited drivers for landfill mining globally to date.

The review identified historic landfill mining projects and the drivers behind them (Table 1). It was found that the most common drivers included void space recovery, redevelopment of the site, to improve landfill engineering (or avoid potential hazards), to mitigate pollution and for materials recovery and energy generation.

It is evident that whilst material sorting and recovery often feature as part of a landfill mining project, in particular soil recovery, it is rarely the main driver for the project. Of the three projects in Europe where sorting and recovery were a primary driver, two were for energy recovery and material recycling (but these were just research projects) and the remaining site is the Remo landfill project in Belgium which is yet to commence, several years after being proposed.

The project is a joint venture between Advanced Plasma Power, a private UK company with a range of advanced thermal technologies for the recovery of energy from waste and Group Machiels, a Belgian company with a range of land, energy and renewables projects in Belgium. The project plans to mine the Remo Milieubeheer NV landfill in Belgium, which received 16 million tonnes of municipal solid waste (MSW) and commercial and industrial (C&I) waste from the 1970's onwards.

The project aims to recover materials for recycling and to capture and generate 75 MW to 100 MW of electricity from the residual waste by with gasification technology. This is a key project concerning the viability of LFMR in Europe, and many academics, waste operators and technical specialists are waiting to see how this large-scale operation performs.

Key issues and Barriers

The study demonstrated that while extraction and separation of materials from landfilled waste is technically possible, it is little proven to date in terms of advanced separation on a large scale.

This is due to the fact that while LFMR operations have been undertaken in various parts of the world, including in the UK, material recovery does not feature highly as a driver or a theme of operation. However, provided that adequate controls are in place, including proper assessment of gas risk issues, landfill materials can be excavated using conventional excavators and associated plant. Material recovery operations associated with LFMR activities undertaken to-date have primarily comprised soil and metals removal, and, on occasion, the preparation of a refused derived fuel and the replacement and compaction of residual materials back in to the landfill.

It is expected that applying advanced waste separation technologies to landfilled waste will give rise to previously unseen challenges associated with separation efficiency, breakdown, blockage and high maintenance costs. Even with the rapid evolution of separation and sorting technologies in Materials Recycling Facilities, their application to underground, buried or excavated waste streams remains relatively new. This is considered by most as far from ideal with expected reductions in performance and the enhanced risk of equipment failure etc.

The choice of sorting technology employed, the operational procedures and health and safety and environmental protection measures used will be subject to the nature of the waste present in the landfill. One of the key barriers to LFMR is the difficulty in understanding the composition of the waste that has been landfilled. Records for many older landfills (pre 1970 in the UK for example) are non-existent or patchy at best. Where waste composition is not well understood, the project may be too risky (for fear of uncovering hazardous wastes) and costs cannot be scoped appropriately. For example, there may be little value excavated if the landfill is full of C&D wastes.

Another barrier is the quality of materials that are recovered. The quality of materials from a landfill is likely to be poor when compared to wastes being processed from 'new' or 'fresh' waste and materials are likely to be contaminated with soils, leachate and other materials, resulting in increased difficulties in obtaining quality recyclable materials. As such, market values for recovered plastics, metals etc. may be lower, and this could undermine the business case for landfill mining operations.

Next are environmental and social issues. LFMR has the potential to create significant localised environmental impacts, health and safety risks and nuisance concerns, bringing potentially dangerous materials to the surface such as asbestos. While mitigation measures can be put in place, the cost of doing so could be prohibitive for some potential projects. These issues will need to be considered on a project-by-project basis, and understanding the content of the target landfill site or cell is critical.

However, positive benefits may also result, in particular from the removal of potential sources of pollution, with obvious benefits to the local environment and potential improvements in local stakeholder perception. Furthermore, a LFMR project will create short term green jobs.

The quality of the materials recovered from excavated landfill sites is likely to be poor compared to fresh waste streams, with high levels of contamination leading to lower market prices Economics of Mining

As highlighted in Table 1, a number of historic landfill mining projects, including all projects in the UK, have been restricted to projects where waste has needed to be moved to undertake repairs to the landfill liner or to relocate the waste to make way for a road or other new infrastructure development.

The costs of these projects were thus 'less of a concern' comparative to the overall costs of the infrastructure delivery, and were in many cases seen as inevitable or unavoidable.

Where LFMR is being considered for the purposes of resource recovery and/or reclaiming land or void space, the economic viability becomes fundamental to deciding if a project should be undertaken.

The economic factors associated with landfill mining are complex and numerous and will vary significantly between different landfills and from one country to another. Some costs may be straightforward to estimate, while other costs will be more difficult to quantify. So getting the right people in to help, and early on in the evaluation process is key.

Besides the value of future land sale or new void space, revenues from recyclables and energy generation are acknowledged to be a main source of revenue in a LFMR project, but they are highly sensitive and need careful consideration in any proposed business plan.

The Capex and Opex will vary significantly between projects, and overall expenditure will be subject to a lot of variables.

Depth of landfill, waste composition, presence of hazardous waste, leachate level and waste moisture content, environmental mitigation measures required, level of reprocessing undertaken and choice of technology are some of the key factors influencing Capex and Opex.

A high level review of economic issues was undertaken to inform the Zero Waste Scotland scoping study. The study was not focused on a specific landfill, but set out to review feasibility and viability at a national level. In order to assess economic viability, a number of assumptions had to be made to determine a fictitious 'typical' landfill to consider in the assessment. A series of simple economic models were developed to examine this issue further:

Option 1a – RDF exported for use off site, landfill void space free for reuse; Option 1b – RDF exported for use off site, landfill site sold for residential development; Option 2a – Energy recovery on site, landfill void space free for reuse; and Option 2b – Energy recovery on site, landfill site sold for residential development.

All models included metal recovery for off-site sale. The models assumed the soil fraction, construction and demolition waste and glass is reused on site. Soil and rubble fractions recovered are likely to be limited to use onsite as end of waste criteria and the quality of these materials are likely to prevent off-site reuse.

The opportunity for recovery of plastics for recycling is considered to be limited by high processing costs, poor anticipated quality and lack of markets. It is considered that inclusion within RDF is currently the most probable route for this material. If this material was put back in the landfill, it would occupy a lot of void space owing to its low density.

The models were based on consideration of a fictitious landfill and were high level and simple. Nonetheless they were considered suitable to allow comparative assessment and were considered appropriate for a high level scoping study. The modelling considered a range of best, middle and worst case inputs. The key finding was that in most of the scenarios and model input situations considered, the model generated a loss. The exceptions were with the use of 'best outcome' model inputs for the two scenarios that involved energy recovery on site, e.g. Options 2a and 2b.

Financial viability of LFMR in Scotland is, at best, considered to be borderline given current circumstances, markets and costs. The modelling exercise indicated onsite energy recovery as a key influencing factor in LFMR economics, and is a theme that sites around the world will need to consider if they want to make LFMR a success.

Conclusions

Overall, the findings of the study indicate that LFMR operations could potentially be feasible in Scotland but viability is likely to be dependent on very specific circumstances.

Extending the life of a landfill by voidspace recovery or by placement of an engineered liner, increasing the real estate value of the land or the remediation or prevention of contamination are all factors that, coupled with resource and energy recovery potential, will increase the viability of a LFMR project in Scotland. The study also identified the potential to mitigate long-term emissions of landfill gas, a potent greenhouse gas, to atmosphere and to create green jobs.

Looking to the future, LFMR feasibility is likely to improve as separation technologies progress and the costs of mining decrease. As resources become scarcer and demands on land for development increase, so the pull factors for landfill mining will strengthen.

The tipping point for landfill mining in the UK may still be some 15-20 years away, when resource value, land value and processing costs align. In the shorter term LFMR could be an appropriate option in specific locations or circumstances – so we should watch this space.

Like everything else it is a numbers game, and landfill mining just doesn't add up financially right now. It is clearly feasible, but will remain a fantasy for the foreseeable future.

Kathryn Warren is a senior consultant at Ricardo-AEA.

Adam Read is global practice director for Ricardo-AEA's Resource Efficiency and Waste Management Practice.

The ZWS report can be downloaded from www.tinyurl.com/13389mz