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The potential of the ballistic separator type STT6000 as a first step for the recovery of RDF from old landfill material: A case study at Mont-Saint-Guibert landfill (Belgium)

This project has received funding from the European Union's EU Framework Programme for Research and Innovation Horizon 2020 under Grant Agreement No 721185
Rheinisch-Westfälische Technische Hochschule Aachen
Cristina Garcia Lopez, M.Sc. Contact: |
The potential of the ballistic separator type STT6000 as a first step
for the recovery of RDF from old landfill material: a case study at
Mont-Saint-Guibert landfill (Belgium)
Landfill mining has received a growing interest in recent years due to previous
investigations, which show that landfills could deliver a stream of secondary
materials and energy1.It is known that each landfill site has its own potential with
regard to landfill mining. Factors such as the age of the landfill, type of landfill and its
location have an impact on the type of materials stored. The uncertainties behind
landfills can complicate its mining activity and increase the risks and the costs of the
One of the possible revenues that can mitigate the economic costs of landfill mining
projects is the recovery of Refused-Derived-Fuels (RDFs) from old landfills and
additionally decrease the amount of material that has to be landfilled. The RDFs can
be used to reduce the use of fossil fuels in cement plants, conventional thermal
power plants, industrial plants, incineration in furnaces with energy recovery,
gasification and pyrolysis.
The RDFs can be obtained from landfills with Mixed Municipal Solid Waste (MMSW)
by an extensive, complex and costly process, since the composition of the material is
very heterogeneous and presents a high moisture content. Besides, these
heterogeneity make the mechanical processing more challenging. Therefore, new
technologies/strategies have to be employed in order to enhance the production of
RDFs from old landfills.
Excavation and mechanical processing
In September 2017, 200 m3of landfilled material were excavated from the Mont
Saint Guibert landfill, Belgium. The excavated area had dimensions of 5x6x8 m
(L*W*H), the top 4 m consisted of a clay cover layer, which was removed. The
excavated material was identified as mixed MMSW including some C&D waste
(ρt=0,80Mg/m3). Directly after the excavation, the material was transported to the
ballistic separator to separate it into different fractions (Fig. 2)
Figure 2. Ballistic Separator STT 6000 and its output flows with landfilled material
Ballistic Separator STT 6000
A ballistic separator (Fig. 1) is a processing unit designed to separate solid waste
depending on the characteristics size, density and shape. The inclination of the
equipment and the oscillating movement of the paddles allows the gravimetric
separation of the flow in three different fractions: 3D fraction (rolling and heavy, 2D
fraction (light and flat) and the sieved fraction (fines). The ballistic separator STT
6000 (Fig. 2), developed and built by STADLER®, is a robust and resistant separator to
process large waste streams from construction and demolition (C&D), as well as
MMSW and industrial waste.
Figure 1. Schematic diagram of a ballistic separator adopted from M. Hans3
C. García López1, J.C. Hernández Parrodi2, B. Küppers3, A. Clausen1, T. Pretz1
1 Department of Processing and Recycling, RWTH, Aachen, 52062, North Rhine Westphalia, Germany
B Renewi Belgium NV, Gerard Mercatorstraat 8,3920 Lommel, Belgium
3 Chair of Waste Processing Technology and Waste Management, Montanuniversitaet Leoben, Leoben, 8700, Austria
1. H. Särkkä, S. Hirvonen, J. Gråsten Characterization of municipal solid waste landfill
for secondary raw materials”, in Smart ground consortium (Dec 2016).
2. European Standard CEN TC 343 Solid Recovered Fuels
3. M. Hans, D. Goldmann, Recyclingtechnik : Fachbuch für Lehre und Praxis. 2. Aufl.
2016. Wiesbaden : Springer Fachmedien Wiesbaden, 2016.
This case study corresponds to the New-Mine Project and attempts to draw the
reader’s attention to recent advances in mechanical processing achieved through the
use of a Ballistic Separator, type STT6000,as a first step for the production of RDF
from excavated waste of an old landfill (1970s). The main objective of this test is to
study the efficiency of the Ballistic Separator as the first step of the mechanical
treatment without pre-shredder, keeping the original particle size of the material
throughout the pre-processing in order to avoid losing small valuable particles with
other treatments.
3D > 200 mm
3D 200-90 mm 2D 200-90 mm
2D > 200 mm
< 200 mm
Sieve 200 mm / 90 mm
After the material was dried and sorted into categories, two promising flows were
detected as potential RDF recovery flows: 2D> 200 mm (referred as 2D < 275 mm”
in Fig. 3) and 2D 200-90 mm. These flows had a higher concentration of
combustibles (paper, textile, plastic 2D and rest) than the other four flows.
[% dm]
Ash content
[% dm]
Ash content
Wood 0%
15,2 -1% 16,9 11%
Paper 2%
15,9 -4% 15,2 12%
Textile 8%
22,5 -8% 22,7 20%
2D Plastics 30%
35,1 -38% 40,9 13%
3D Plastics 5%
32,4 -5% 30,6 12%
Fe metals 0%
0,0 -2% 0,0 100%
NFe metals 0%
0,0 -0% 0,0 100%
Inert 3%
0,1 -2% 0,1 100%
Glass 0%
0,0 -0% 0,0 100%
Rest 18%
18,5 -10% 23,3 17%
Fines 34%
1,9 -31% 1,9 88%
Total value 100% 19,5 -100%
22,6 40%
MSG, Belgium [2D <275 mm] (2018)
< 90 mm
It can be concluded from the results obtained that processing excavated landfill
material with ballistic separation, as a first step of the mechanical treatment, can
yield fractions with appealing calorific values, such as 19,5 MJ/kg and 22,6 MJ/kg.
This results in an enhance of landfill mining projects without the need of additional
sorting equipment and with high throughputs (ca. 75Mg/h). Further information
about the influence of the initial moisture on the GCV and the concentration of
chlorine, sulphur and mercury has to be obtained, in order to determine the quality
of the produced RDF.
Figure 3. Gross calorific value (GCV) of the 2D fraction output flows
Landfill owners, governmental institutions, technology providers, academia and local communities are important stakeholders involved in Enhanced Landfill Mining (ELFM). This concept of excavating and processing historical waste streams to higher added values can be seen as a continuation of traditional landfill mining (LFM) and seems to be an innovative and promising idea for potential environmental and societal benefits. However, ELFM’s profitability is still under debate, and environmental as well as societal impacts have to be further investigated. This study provides a first step towards an anticipatory approach, assessing ELFM through stakeholder integration. In the study, semi-structured interviews were conducted with various stakeholders, involved in a case study in Flanders, Belgium. Participants were selected across a quadruple helix (QH) framework, i.e. industrial, governmental, scientific, and local community actors. The research comprises 13 interviews conducted with an aim to elicit stakeholder needs for ELFM implementation using a general inductive approach. In total 18 different stakeholder needs were identified. The paper explains how the stakeholder needs refer to the different dimensions of sustainability, which groups of stakeholders they primarily affect, and what types of uncertainty could be influenced by their implementation. The stakeholder needs are structured into societal, environmental, regulatory and techno-economic needs. Results show additional economic, environmental, and societal aspects of ELFM to be integrated into ELFM research, as well as a need for the dynamic modeling of impacts.
Gråsten Characterization of municipal solid waste landfill for secondary raw materials
  • H Särkkä
  • S Hirvonen
H. Särkkä, S. Hirvonen, J. Gråsten Characterization of municipal solid waste landfill for secondary raw materials", in Smart ground consortium (Dec 2016).
Recyclingtechnik : Fachbuch für Lehre und Praxis. 2. Aufl
  • M Hans
  • D Goldmann
M. Hans, D. Goldmann, Recyclingtechnik : Fachbuch für Lehre und Praxis. 2. Aufl. 2016. Wiesbaden : Springer Fachmedien Wiesbaden, 2016.