Joakim Krook

Landfill mining: a critical review of two decades of research.

Landfills have historically been seen as the ultimate solution for storing waste at minimum cost. It is now a well-known fact that such deposits have related implications such as long-term methane emissions, local pollution concerns, settling issues and limitations on urban development. Landfill mining has been suggested as a strategy to address such problems, and in principle means the excavation, processing, treatment and/or recycling of deposited materials. This study involves a literature review on landfill mining covering a meta-analysis of the main trends, objectives, topics and findings in 39 research papers published during the period 1988-2008. The results show that, so far, landfill mining has primarily been seen as a way to solve traditional management issues related to landfills such as lack of landfill space and local pollution concerns. Although most initiatives have involved some recovery of deposited resources, mainly cover soil and in some cases waste fuel, recycling efforts have often been largely secondary. Typically, simple soil excavation and screening equipment have therefore been applied, often demonstrating moderate performance in obtaining marketable recyclables. Several worldwide changes and recent research findings indicate the emergence of a new perspective on landfills as reservoirs for resource extraction. Although the potential of this approach appears significant, it is argued that facilitating implementation involves a number of research challenges in terms of technology innovation, clarifying the conditions for realization and developing standardized frameworks for evaluating economic and environmental performance from a systems perspective. In order to address these challenges, a combination of applied and theoretical research is required.

Metal contamination in recovered waste wood used as energy source in Sweden.

Abstract Large amounts of recovered waste wood (RWW) originating from construction and demolition activities (C&DWW) and industrial activities (IWW) are annually generated in Sweden. RWW is also imported for use as an energy source at biofuel boilers. Increased use of biomass is one strategy to decrease environmental impact, in general, and the emissions of green house gases, in particular. This study addresses the environmental and resource implications of metal occurrence in RWW that is used as an energy source at biofuel boilers. RWW contains elevated concentrations of arsenic, chromium, copper, zinc, mercury, nickel, lead and possibly cadmium. The metal composition of Swedish and imported RWW differs in that Swedish RWW contains higher concentrations of arsenic, chromium, zinc, nickel and copper, while imported RWW contains higher concentrations of lead, mercury and cadmium. Ashes from combustion of RWW are nowadays generally disposed in landfills due to their elevated metal concentrations. This practice makes it impossible to use these ashes as filler material thereby replacing extraction of raw materials and decreasing the need for landfill space. Furthermore, landfilling leads to accumulation of hazardous heavy metals that poses a future environmental and health problem. If RWW from construction and demolition should contribute optimally to a sustainable energy system, cleaner waste wood flows are a prerequisite. The elementary measure is to track potential pollution sources in this waste stream and find out which are significant. Furthermore, since most of the RWW is untreated and unpolluted wood, there is a great environmental potential to separate this flow through the waste management system. Such an approach might lead to decreased environmental pollution of heavy metals and an improved resource management.

Integrating remediation and resource recovery: On the economic conditions of landfill mining

This article analyzes the economic potential of integrating material separation and resource recovery into a landfill remediation project, and discusses the result and the largest impact factors. The analysis is done using a direct costs/revenues approach and the stochastic uncertainties are handled using Monte Carlo simulation. Two remediation scenarios are applied to a hypothetical landfill. One scenario includes only remediation, while the second scenario adds resource recovery to the remediation project. Moreover, the second scenario is divided into two cases, case A and B. In case A, the landfill tax needs to be paid for re-deposited material and the landfill holder does not own a combined heat and power plant (CHP), which leads to disposal costs in the form of gate fees. In case B, the landfill tax is waived on the re-deposited material and the landfill holder owns its own CHP. Results show that the remediation project in the first scenario costs about €23/ton. Adding resource recovery as in case A worsens the result to -€36/ton, while for case B the result improves to -€14/ton. This shows the importance of landfill tax and the access to a CHP. Other important factors for the result are the material composition in the landfill, the efficiency of the separation technology used, and the price of the saleable material.

Resource and Climate Implications of Landfill Mining A Case Study of Sweden

This study analyzes the amount of material deposited in Swedish municipal solid waste landfills, how much is extractable and recyclable, and what the resource and climate implications are if landfill mining coupled with resource recovery were to be implemented in Sweden. The analysis is based on two scenarios with different conventional separation technologies, one scenario using a mobile separation plant and the other using a more advanced stationary separation plant. Further, the approach uses Monte Carlo simulation to address the uncertainties attached to each of the different processes in the scenarios. Results show that Swedens several thousand municipal landfills contain more than 350 million tonnes (t) of material. If landfill mining combined with resource recovery is implemented using a contemporary stationary separation plant, it would be possible to extract about 7 million t of ferrous metals and 2 million t of nonferrous metals, enough to meet the demand of Swedish industry for ferrous and nonferrous metals for three and eight years, respectively. This study further shows that landfill mining could potentially lead to the equivalent of a one‐time reduction of about 50 million t of greenhouse gas emissions (carbon‐dioxide equivalents), corresponding to 75% of Swedens annual emissions.

The strategic role of recycling centres for environmental performance of waste management systems

This paper analyses how different actors influence the sorting quality of waste at recycling centres. Users (i.e. citizens) play an essential role since they conduct the actual sorting. They have difficulties sorting many of their discarded products, leading to decreased performance of the entire waste management system of which recycling centres are a part. Several measures addressing this problem are identified such as product design, improved terminology for labelling waste and increased manning at recycling centres. A fundamental task for managers and employees is to further develop information and guidance for users, both at home and at recycling centres. Several obstacles for improvements are also discussed, including working conditions and the economy of recycling centres, as well as the routines for communication and quality assurance among actors in the recycling business.

Developing a monitoring method facilitating continual improvements in the sorting of waste at recycling centres

Beneficial use of waste relies on efficient systems for collection and separation. In Sweden, a bring system involving recycling centres for collection of bulky, electr(on)ic and hazardous waste has been introduced. A significant share of this waste is incorrectly sorted, causing downstream environmental implications. At present, however, there is a lack of affordable and accurate monitoring methods for providing the recycling centres with the necessary facts for improving the sorting of waste. The aim of this study was therefore to evaluate the usability of a simplified and potentially more suitable waste monitoring method for recycling centres. This method is based on standardised observations where the occurrence of incorrect sorting is monitored by taking digital pictures of the waste which then are analysed according to certain guidelines. The results show that the developed monitoring method could offer a resource-efficient and useful tool for proactive quality work at recycling centres, involving continuous efforts in developing and evaluating measures for improved sorting of waste. More research is however needed in order to determine to what extent the obtained results from the monitoring method are reliable.

A Cable Laid Is a Cable Played: On the Hibernation Logic behind Urban Infrastructure Mines

Our societies are reliant on metals to such an extent that the total amounts of some of them in the built environment are comparable in size to the remaining amounts in known mountain ores. Because of concerns about mineral scarcity, the United Nations has assessed alternative sources for metal extraction and targeted urban areas in general and infrastructure systems in particular, since these are large, spatially concentrated and rich in metals. Referring to the possibility of recovering these metal stocks, infrastructure systems constitute what material flow researchers has conceptually termed “urban mines.” While most urban infrastructure is in use, significant amounts of cables and pipes have been disconnected and remain in their subsurface locations; they are “hibernating.” In this article, we analyze the occurrence of such hibernation in the Swedish city of Norrköpings urban infrastructure mine where, we know from a previous study, that every fourth kilo of infrastructure is discarded. Our applied perspective is different from the logic of system expansion as a way to meet increased demand often found in the field of infrastructure studies since we are interested in how systems are disconnected and left behind. This enables us to offer a refined understanding of the concepts of infrastructure “decline” and infrastructure “cold spots.” We argue that to prevent the increase of dormant infrastructures and to engage in the urban mining of already dormant infrastructures, we must develop a sensibility to the materiality of derelict infrastructure components and the underlying causes for why they form different kinds of spatial patterns.

Preservative-treated sawn timber in Sweden: waste beyond control

Wood preservatives contain hazardous substances that cause environmental implications during waste management. The objective of this study was to analyse the waste management of preservative-treated sawn timber in Sweden from a pollution perspective and in regard to the present waste policy. Firstly, the generation of waste was modelled and then the methods of disposal were analysed from direct inquiries to waste facilities and from mass balance considerations. The results show that the discarded amount of preservative-treated sawn timber has increased and today exceeds 150 000 tonnes per year. This waste generation will continue for many years and will contain several thousand tonnes of arsenic and chromium. According to the Swedish Waste Decree, preservative-treated sawn timber is to be separately handled as hazardous waste. At present, however, most of the waste unintentionally becomes dispersed in non-hazardous waste, making it difficult to control the outflows of hazardous substances from preservative-treated sawn timber.

Perspectives on recycling centres and future developments.

The overall aim of this paper is to draw combined, all-embracing conclusions based on a long-term multidisciplinary research programme on recycling centres in Sweden, focussing on working conditions, environment and system performance. A second aim is to give recommendations for their development of new and existing recycling centres and to discuss implications for the future design and organisation. Several opportunities for improvement of recycling centres were identified, such as design, layout, ease with which users could sort their waste, the work environment, conflicting needs and goals within the industry, and industrialisation. Combining all results from the research, which consisted of different disciplinary aspects, made it possible to analyse and elucidate their interrelations. Waste sorting quality was recognized as the most prominent improvement field in the recycling centre system. The research identified the importance of involving stakeholders with different perspectives when planning a recycling centre in order to get functionality and high performance. Practical proposals of how to plan and build recycling centres are given in a detailed checklist.

A new dawn for buried garbage? An investigation of the marketability of previously disposed shredder waste.

This paper examines the market potential of disposed shredder waste, a resource that is increasingly emphasized as a future mine. A framework with gate requirements of various outlets was developed and contrasted with a pilot project focusing on excavated waste from a shredder landfill, sorted in an advanced recycling facility. Only the smallest fraction by percentage had an outlet, the metals (8%), which were sold according to a lower quality class. The other fractions (92%) were not accepted for incineration, as construction materials or even for re-deposition. Previous studies have shown similar lack of marketability. This means that even if one fraction can be recovered, the outlet of the other material is often unpredictable, resulting in a waste disposal problem, which easily prevents a landfill mining project altogether. This calls for marketability and usability of deposited waste to become a central issue for landfill mining research. The paper concludes by discussing how concerned actors can enhance the marketability, for example by pre-treating the disposed waste to acclimatize it to existing sorting methods. However, for concerned actors to become interested in approaching unconventional resources such as deposited waste, greater regulatory flexibility is needed in which, for example, re-deposition could be allowed as long as the environmental benefits of the projects outweigh the disadvantages.