ELFM step by step

Step 1: Inventory or mapping

The identification refers to the small-scale local level of the inventory. Here the individual dumping location is investigated and described in more detail.

Traditional soil remediation focuses on the adverse environmental impact of the dump material. Its crucial elements are the leachate and landfill gas diffusion.

However, the investigation of the ELFM potential requires a more detailed knowledge of the dump material. The first field tests were carried out on behalf of OVAM and compare the opportunities for application of 5 different geophysical techniques. These first tests also gave important information about the further development of the research programme. The further validation of these methods is necessary.

Step 2: Identifying / surveying

Inventory

Preparing an inventory involves mapping all landfill sites in Flanders and collecting and exchanging information about ELFM. To contribute to an optimal information flow, OVAM participates in the Flemish ELFM consortium. This multidisciplinary research consortium of actors with a broad diversity of expertise was set up in Flanders (Belgium) in 2008. The aim is to develop an approach to Enhanced Landfill Mining (ELFM) and thereby integrate landfilling in a more sustainable waste treatment. Today the upscaling of this consortium to EU level is being prepared.

The information gathering is not only limited to a literature study or field tests. Such an innovative topic also involves stakeholder management.

Inventory of landfill sites

In this context the existing OVAM databases are completed and linked with a view to opening up the available data (figure). A first major step was taken in 2012, but the quality control of the data shows that this is a continuous process for the coming planning period. A large-scale base map and associated database were prepared in 2013.

Prioritising landfill sites

A methodology was developed to prioritise landfill sites, both by their need for remediation and ELFM potential. This decision supporting model has been applied to a test series of 72 landfill sites. In 2013 this model was further refined and documented as Flaminco (Flanders Landfill Mining Challenges and Opportunities). An extension to the full landfill site inventory was made in 2013, together with a simple adjustment of the indicators and weighting factors. In the next years this method will be refined and tested in the field (depending on available budgets).

Step 3: Flaminco / DST

Enhanced Landfill Mining (ELFM) is the safe conditioning, excavation and integrated valorisation of landfilled waste streams as both materials and energy, using innovative transformation technologies and respecting the most stringent social and ecological criteria (Jones et al. 2013).

Flanders has about 2,000 landfill sites. Because of the economic situation and the prices of parent materials, the valorisation of the flows in a landfill site is currently not yet profitable for the large-scale exploitation of Flemish landfill sites. As a result, OVAM manages the stock of raw materials that is stored in landfill sites. This involves the development of a policy for the short, medium and long term.

The first step in such stock management is determining how large the stock is and where the different stocks are situated.

The various OVAM databases are the ideal starting point. The information that is stored in the land information register (register with all relevant information about land plots and soil contamination that is provided to OVAM) was brought together with the information from the database of taxes (licensed landfill sites) and the so-called POT archive. The POT archive is an inventory of land plots where potentially past activities have taken place that contaminated the soil, including landfill sites. Our database is updated continuously. After the listing of the various landfill sites in a database the first phase of mining happens, i.e. data mining.

This data mining consists of ranking the landfill sites by their ELFM potential. This estimate of potential was translated to the Flaminco model. Flaminco is a decision support model that helps determine the ELFM potential and the environmental prioritisation of landfill sites. To this goal a score system was developed per target and per criterion. Flaminco is the acronym for Flanders Landfill Mining, Challenges and Opportunities. The version Flaminco 1.0 became operational at OVAM in 2013.

The following seven criteria are taken into account:

  • the type of landfill site;
  • the time of dumping;
  • the volume of dump material;
  • the location of the landfill site, i.e. the land use;
  • the distance of the landfill site to processing sites;
  • the closeness of other landfill sites;
  • the necessity of soil remediation.

For the last criterion, the necessity of soil remediation, an additional elaboration was prepared.

The various landfill sites are ranked on the basis of certain weighting factors by the various aspects of ELFM: waste to materials (WtM), waste to energy (WtE), waste to land (WtL) and Resource Management – intermediate storage (RM).

In this way priorities are determined and further research is conducted.
In a next step that database is completed for the priority landfill sites and further soil investigation is carried out to further refine the potential for ELFM. In a later phase we investigate the landfill sites with a high potential for ELFM in more detail before we approach the exploitation. 
But first we carry out the necessary test projects.

Step 4: Exploiting landfill sites

Enhanced Landfill Mining (ELFM) is a concept that performs the valorisation of materials and energy from a landfill site as sustainably as possible with both a maximisation of material recycling and an optimal energy production. Through a thorough separation of the waste the best possible choice can be made. Already since 2012 OVAM has been testing various techniques and combinations of techniques on a pilot scale.

Landfill sites in Hasselt, Evergem and Zuienkerke have already been investigated. Within the concept of Enhanced Landfill Mining, OVAM commissioned an innovative separation of landfilled waste whereby it is indicated what flows have been released and what opportunities for valorisation exist. Five contractors responded and formulated a technical and financial proposal.

In parallel, OVAM launched a study assignment for the technical and economic monitoring and evaluation of the used separation tests.

Different questions were addressed here:

  • What fractions are obtained after separation and in what quantities?
  • How pure are the various fractions?
  • What are the opportunities for valorisation?
  • What is the degree of mobility of the used separation technologies?
  • What is the profitability?

Each contractor received around 100 tons of mixed urban waste from an official soil remediation of a landfill site in Zuienkerke. The waste was mostly dumped there in the 60s and is mainly household waste. These waste flows were separated by the contractors in partial flows with a view to a maximal materials and/or energy recovery. A combination of various separation techniques was tested: sieving, band magnets, hydrocyclones, belt filter press, windshifting, form separators, eddy currents, optical separation, aqua engine and ballistic separation. This test has shown that a separation is possible that allows the recovery of a larger portion of dump material as Waste to Materials and a limited proportion as Waste to Energy. Also on site a test was conducted to remove the plastic from the landfilled materials through a combination of various sieve techniques and wind shifter.

On the basis of the results of the separation tests and the findings of the contractors a number of proposals were formulated for conducting further innovative research on waste separation.