2019, Faitli-et-al-Avaliação de um aterro de resíduos sólidos urbanos residuais para prospectiva 'mineração de aterros'

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https://doi.org/10.1177/0734242X19881197
Waste Management & Research
2019, Vol. 37(12) 1229 –1239
© The Author(s) 2019
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DOI: 10.1177/0734242X19881197
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Introduction
Secondary raw materials are becoming more and more impor-
tant for the EU economy in the spotlight of a circular economy. 
Rational waste management practices could lead to a more effi-
cient use of raw materials and to the waste reduction. If consid-
ering that in Europe there are about 150,000–500,000 landfills, 
the EU secondary raw materials potential is very significant. 
The deposited wastes, especially many residual municipal solid 
waste (RMSW) landfills, represent a large amount of secondary 
raw materials for later utilisation, as well as environmental 
problems. The ‘landfill mining’ concept targets the extraction, 
processing and primary commodity materials recycling from 
the deposited wastes (Hernández Parrodi et al., 2018). 
Decomposition processes in municipal solid waste (MSW) 
landfills result in the formation of heat, leachate and landfill gas 
(Faitli et al., 2015a, 2015b). After a certain time period, the 
majority of the biologically degradable components will 
decompose, therefore the environmental hazard potential 
decreases and the landfilled useful materials could become 
more accessible. Secondary raw materials are getting a more 
and more important role in waste-to-material and waste-to-
energy production. Recently, recultivated landfills have con-
tained a large amount of non-degradable materials, which could 
be utilised as secondary raw materials or fuels (Krüse, 2015). 
There are many case studies in the literature reporting data of 
technical and economic considerations about possible landfill 
mining (Hermann et al., 2014; Hernández Parrodi et al., 2018; 
Krook et al., 2012; Tielmans and Laevers, 2010; Wolfsberger 
et al., 2015). It is obvious that lots of information about the 
materials and their conditions is necessary for being able to 
decide whether it would be worth mining a landfill and to 
design the mining and processing technologies. Furthermore, 
the analytical methods have to be developed and optimised for 
this task. Such sampling methods as reported by Aldrian et al. 
(2016) and Faitli et al. (2018) can be good starting points, but 
these methods have to be adapted for such a specific task. If 
sampling serves enough information, cost-benefit analysis can 
be performed (Krüse, 2015; Zhou et al., 2015) for economic 
considerations. The work of Zhou et al. (2015) applied a cost-
benefit analysis model for assessing the economic feasibility, 
which is important for promoting landfill mining. Their model 
includes eight indicators of costs and nine indicators of bene-
fits. Four landfill-mining scenarios were designed and analysed 
based on field data. The economic feasibility of landfill mining 
Assessment of a residual municipal 
solid waste landfill for prospective 
‘landfill mining’
J Faitli1 , S Nagy1, R Romenda1, I Gombkötő1, L Bokányi1 
and L Barna2
Abstract
Landfill mining is a prospective tool for the recycling of valuable materials (waste-to-material) and secondary fuel (waste-to-energy) 
from old, therefore more or less stabilised municipal solid waste landfills. The main target of Horizon 2020 ‘SMARTGROUND’ 
R&D was improving the availability and accessibility of data and information from both urban landfills and mining dumps through 
a set of activities to integrate all the data – from existing sources and new information retrieved with time progress – in a single EU 
database. Concerning urban landfills, a new sampling protocol was designed on the basis of the current Hungarian national municipal 
solid waste analysis standards, optimised for landfill mining. This protocol was then applied in a sampling campaign on a municipal 
solid waste landfill in Debrecen, Hungary. The composition and parameters of the landfilled materials were measured as a 12-year 
timescale. The total wet and dry mass of the valuable components possible for utilisation was estimated.
Keywords
Residual municipal solid wastes (RMSW), landfill mining, sampling, sieving, sorting
Received 21 August 2018, accepted 16 September 2019 by Associate Editor Dimitris Dermatas.
1 Institute of Raw Materials Preparation and Environmental 
Processing, University of Miskolc, Miskolc, Hungary
2A.K.S.D Ltd, Debrecen, Hungary
Corresponding author:
J Faitli, Institute of Raw Materials Preparation and Environmental 
Processing, University of Miskolc, Egyetemváros, Miskolc 3515, 
Hungary. 
Email: ejtfaitj@uni-miskolc.hu
881197WMR0010.1177/0734242X19881197Waste Management & ResearchFaitli et al.
research-article2019
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1230 Waste Management & Research 37(12)
was then evaluated by the indicator of net present value. If sam-
pling serves enough information, the real challenge is the devel-
opment of the technology by which the exploited material can 
be processed and commodity materials can be produced for 
later utilisation. According to Krook et al. (2012), simple soil 
excavation and screening equipment have typically been 
applied, often demonstrating moderate performance in obtain-
ing marketable recyclables, but there are more advanced options 
too. Hernández Parrodi et al. (2018) summarised the state-of-
the-art of landfill mining in a recent article focusing on the 
results of many landfill analyses and especially focusing on the 
processing and utilisation options of the fine fraction.
This article focuses on the sampling and analyses of the MSW 
landfill in Debrecen as a case study on the basis of a newly devel-
oped sampling and sample preparation protocol. Material com-
position of the landfill and its variations, as well as the estimation 
of the total amount of various material categories is presented.
Area of case study, the RMSW landfill in 
Debrecen
The examined RMSW landfill is located in the south-western 
part of Debrecen (East-Hungary) over a total area of about 
230,000 m2 (GPS: North 47.491882; East 21.595435). 
A.K.S.D. Ltd, the operator of the Debrecen landfill, was 
established in 1991 (51% Austrian and 49% city municipality 
ownership). Its main activity is transportation, processing and 
disposal of MSW according to European standards arisen in 
Debrecen and its agglomeration. This company also collects 
and handles wastes from industrial sources to a lesser extent. 
The Regional Waste Management Facility of Debrecen was 
established in 1991 and a 20.1-ha area for waste disposal land-
fill (with combined insulation system) was built. Figure 1 
shows the schematic map of the Debrecen RMSW landfill. At 
the time of sampling, landfill sections III and IV were fully 
uploaded and more than 10m in depth of RMSW had been 
landfilled into landfill section V.
Active use of the first 3.3-ha area section of the landfill was 
started in 1993 and then it was followed by further sections 
(Table 1).
Approximately 2,423,970 m3 (3,746,090 t) of waste was land-
filled into sections I–V until the end of 2016. It means that the 
average annual landfilling waste amount was 162,800 t. The 
designed maximal height of this landfill is 25 m, measured from 
the insulation layer, so the capacity of sections I–VI together is 
totally near 4.2 million m3. Assuming the same annual amount of 
deposition, the landfill will be closed in 2028. The following 
types of wastes had been deposited in the landfill.
•• Residual MSWs, landfilled without sorting and preparation, 
originated from Debrecen and its agglomeration (annual 
amount: 60–70 kt y-1).
•• Non-hazardous industrial wastes (drilling sludge, scrap prod-
ucts, insulation materials, packaging, other production wastes 
(10–15 kty-1).
•• Inert wastes, their annual amount has decreased from 50–60 t 
to 20 t y-1 recently. Reasons of the decrease are the so-far built 
processing capacities and the introduced state landfilling fee. 
Separate collection of packaging materials (dry or non-con-
taminated by food wastes) was introduced in Debrecen only 
in 2014.
Materials and methods
Standard sampling protocols
The quality and quantity of the generated MSW changes all around 
the globe, so the applied sampling methods are different too. One 
of the first European standards was probably the French standard 
NF X30-413 (2006) derived from the MODECOM methodology. 
The MODECOM methodology was developed on the basis of 
Gy’s (1979) sampling theory. This method is based on collecting 
vehicles sampling. Another generally applied method is the so-
called SWA-Tool developed by a European project consortium 
(EU Project Report, 2004). Weichgrebe et al. (2017) carried out a 
detailed RMSW sampling campaign in West-Zone Bangalore, 
Figure 1. Schematic map of the Debrecen RMSW landfill.
Boreholes on the landfill sections III, IV and V are marked.
Source: Authors.
Table 1. Area and year of opening of different landfill 
sections.
Landfill Section No. Area (ha) Start of operation
I. 3.3 1993
II. 3.5 1996
III. 3.3 2004
IV. 3.2 2007
V. 3.2 2014
VI. 3.5 2020
Faitli et al. 1231
India, on the basis of the SWA-Tool and the German Standard 
LAGA PN 98 (2001). AbdAlqader and Hamad (2012) carried out 
a RMSW campaign in the Gaza Strip based on the previous ver-
sion of the ASTM D5231-92 (2016) Standard. These standards 
give guidelines about the stratification of the examined population, 
the substance of sampling (e.g. collecting vehicles or collecting 
bins), the number and quantity of single and mixed (average) sam-
ples, the sorting and screening protocol, the sorted material catego-
ries and sub-categories, the taking and preparation of sub-samples 
for drying and chemical analysis and so on. The comparison of the 
results of the different methods is difficult, because of the different 
definitions of the methods and terms. For example, each men-
tioned protocol defines the so-called ‘fine’ material category, but 
the size differs (<20 mm in NF X30-413, <14 mm according to 
Weichgrebe et al. (2017), <10 mm in SWA-Tool, etc.). It is clear 
that everyone has to follow its own national requirements.
The current Hungarian Standards MSZ 21420 Parts: 28 and 29 
(2005) regarding the analysis of MSWs were introduced in 2005. 
The developed sampling protocol – applied here – optimised for 
analysing earlier landfilled waste is based on these standards; there-
fore it is appropriate to briefly describe them. The Hungarian 
Standards are based on Gy’s sampling theory and the MODECOM 
methodology (Gy, 1979), but details were tailored to the Hungarian 
situation in 2005. Waste collecting vehicles were selected for sam-
pling. The raw sample in a vehicle characterised the sector (lot or 
stratum), namely the area from where the waste had been collected. 
The total unloaded waste had to be put over by a ~250-L volume 
bucket loader. Randomly, 10 increments (single samples) were 
selected and mixed together forming the gross (averaged or simply 
the average) sample. In this way, the minimal mass of the average 
sample of MSW was 500 kg, comprising ten 50-kg single samples 
(MSZ 21420-28). The flowsheet of the standard average sample 
preparation is shown in Figure 2 (MSZ 21420-29).
The sample preparation consisted of two parts, namely the 
primary and the secondary sorting. During the primary sorting, a 
100-mm square opening sieve was positioned on top of a frame, 
below there was a 20-mm square opening sieve and underneath 
there was a tray. The total average sample was fed partially onto 
the 100-mm sieve. During simultaneous sorting and sieving 
the oversize fraction was sorted into 12 material categories. 
The standard material categories according to the MSZ 21420 
Parts: 28 and 29 Standards are: 1, Bio (biologically degradable 
materials, food residues, plants, etc.); 2, Paper; 3, Cardboard; 4, 
Composite (multi-components layered packing materials); 5, 
Textile; 6, Hygienic (diaper, tampon, tissue paper, etc.); 7, 
Plastics; 8, Combustible (other uncategorised combustibles, 
wood, leather, etc.); 9, Glass; 10, Metals; 11, Non-combustible 
(other uncategorised non-combustibles or inert, stone, brick, 
etc.); 12, Hazardous (medicine, batteries, etc.). The 13th mate-
rial category was the 20-mm square openings sieve undersize, 
called fines. According to the sample nomogram for MSW the 
minimal processed mass for the 20–100 mm size fraction was 
lower, therefore this fraction could be split, and only a 30–40 kg 
subsample should be fed onto the 20 mm square openings sieve 
for the secondary sorting. The dry substance composition had to 
be measured by drying of the given quantities of each category 
in a heated chamber at 105°C until mass equilibrium. The neces-
sary minimal masses for dry matter and chemical analyses were 
20 kg of the Bio; 4.5 kg of the Fine and 2 kg of all other material 
categories. If someone wanted to measure a mechanical, biologi-
cal or chemical property of the sampled MSW, the laboratory 
analytical samples would have to be prepared using the sorted 
material categories separately. The quantity and quality, namely 
the particle size of a given analytical sample was determined by 
the applied laboratory instrument. However, as a rule of thumb, 
the subsample of each examined material category has to be 
ground below 1 mm. The suitable comminution device depends 
on the material; cutting mills, planetary ball mills, crushing 
rolls, rotary shredders, etc. are generally used. After the sample 
preparation of each material category, only the prepared indi-
vidual powders could be mixed again according to their meas-
ured mass concentrations. This mixed powder was then supplied 
to the laboratory for the analysis. 
Development of a new sampling protocol 
for landfill mining
In the spotlight of landfill mining, the so-far-described standard 
sampling protocol (MSZ 21420 Parts: 28 and 29) needed to be 
modified and optimised for the given task.
Figure 2. Sampling protocol according to Hungarian Standards MSZ 21420 Parts: 28 and 29.
1232 Waste Management & Research 37(12)
•• Tailoring the taking of the average sample into cases of old 
landfills instead of collecting vehicles.
•• Improving the average sample preparation protocol: Adopting 
it for the dirty state of material in old landfills.
•• Improving the average sample preparation protocol: 
Optimising screening, sorting and splitting, when only the 
minimum but statistically correct amount of subsamples are 
processed in all steps.
•• Tailoring the sorted material categories as a function of size 
fractions for the main aims of landfill mining, namely waste-
to-material and waste-to-energy.
The average sample could not be taken with the application of 
a bucket loader; the suitable tool might be an auger. Core drilling 
is widely applied for geological surveys, but there might be tech-
nical problems during drilling of the non-brittle MSW. Figure 3 
(left) shows a machine equipped with a screw auger applied for 
the construction of landfill gas wells.
The 0.8-m diameter screw rotates in the material. It is then – 
with the sample – torn out upward by the machine. In this way, 
the various depths of landfill could be sampled. In addition to the 
standard analysis, it was necessary to measure material composi-
tion as a function of some discrete size fractions too. This knowl-
edge is necessary for the design of the waste processing 
technology of valuable materials. Figure 3 (right) shows the 
III/M (borehole in landfill section III, middle part) sample as an 
example. This sample was wet and dirty; therefore, the handsort-
ing of it was rather difficult. For this reason, the application of a 
drum sieve was beneficial because it loosened the material andthe dirty fine fractions could be removed as well. This method 
increased the safety of the sorting workers and the accuracy of 
sorting too. Figure 4 shows the designed flowsheet for the aver-
age sample preparation.
Each average sample gained from the drilling was sieved by a 
drum sieve machine equipped with 40 × 40 mm square openings 
(Figure 5, left). The mass of the total drum sieve undersize (<40 mm) 
Figure 3. Auger (left) and average sample III/M (right).
Source: Authors.
Figure 4. The developed sampling protocol for landfill mining.
Faitli et al. 1233
fraction was measured by an appropriate scale. A minimum 5 kg sub-
sample was taken from this material stream at the drop-off end of the 
belt conveyor. This 5 kg <40 mm subsample was sieved at 20 mm 
and the 20–40 mm fraction was hand sorted. The total drum sieve 
oversize (>40 mm) fraction of the average sample was processed as 
follows. The sample was gradually sieved and hand sorted simulta-
neously from coarser into finer particle sizes. Simple 1.2 × 1.2 m 
sieve frames were used; the applied square opening sizes were 100, 
50 and 20 mm. This is a ‘2’ sieve series, where the width of size frac-
tions practically doubles. The most important advantage of the 
developed average-sample-preparation protocol shown in Figure 4 
is that only the minimal, but still statistically correct quantities, of 
subsamples were processed in every preparation step. The new pro-
tocol (Figure 4) is principally different from the standard one (Figure 
2). The mass of each sample portion was measured during its feed-
ing into the analysis according to the standard one (Figure 2). On the 
contrary, the mass of the analysed sample portions (sorted and split 
components as well) was measured after processing. Therefore, the 
evaluation of the new protocol was a little bit harder, because the 
split and thrown out coarser fractions contained finer particle size 
fractions too, but this could be solved during the build-up of the 
complete mass balance of the sample. The sorted material compo-
nents and their numbering are shown in Table 2. The number of the 
standard material categories (MSZ 21420 Parts: 28 and 29) was con-
siderably reduced, because the two most important aims of landfill 
mining are the waste-to-material and waste-to-energy. The sorted 
material categories were as follows: 1. Paper (paper, carton, compos-
ite together); 2. Textile (textile, clothes); 3. Plastic; 4. Combustible 
(wood, leather, sponge, rubber, bone); 5a. Al (aluminium); 5b. Fe 
(iron/steel); 5c. Cu (copper); 5d. Stainless steel; 6. Inert (stone, tile, 
brick, ceramic, concrete); 7. Bio (biologically degradable wastes) 
and 8. Fines or <20 mm. The metal category was sub-sorted into four 
sub-categories because these categories were potential raw materials 
for waste-to-material utilisation.
The developed sampling protocol was flexible because after 
each sieve the mass of the undersize fraction could be reduced by 
sample splitting. If the recommendation (500 kg sample mass for 
100 mm grain size) of Gy (1979) is accepted the following sam-
pling nomogram can be applied:
mAS C X= ⋅ 95
3 (1)
The constant for RMSW in equation (1) is C = 500 t m-3, X95 
is the 95% particle size and mAS is the minimal mass of the aver-
age sample. According to Gy’s sampling theory, the necessary 
minimal mass of a single sample (increment) and the average 
sample (gross) primarily depend on the mass of the coarsest par-
ticle in the sampled granular population. The coarsest particle 
cannot be determined in practice, therefore the so-called ‘char-
acterising coarsest particle’, namely the 95% particle size, is 
used as the basis for the sampling nomogram. In many practical 
cases, the 95% particle size is determined by a preliminary on-
site sampling to be able to design the sampling protocol. The 
necessary minimal mass of the average sample depends on many 
factors according to Gy (1979): Namely the number of material 
components, the mass concentration distribution of the material 
components, the granular size distribution, the liberation and 
intergrown ratio of given materials and so on. Furthermore, the 
most important factor is the acceptable statistical error. The 
result of Gy’s calculations for residual MSWs is 500 kg average 
sample. This result had been applied in the Hungarian standard 
MSZ 21420-28 (2005). The given constant in equation (1) con-
tains all these mentioned factors. According to this sampling 
nomogram, the minimal processed material is 63 kg in the case 
of the 50 mm sieve and 4 kg in the case of the 20 mm sieve.
Drilling was carried out in Debrecen on 9 February 2017, in 
landfill sections III, IV and V. The average borehole depth was 
about 12 m. The lower, middle and upper parts of the exploited 
material of each borehole were processed separately, therefore 
nine discrete average samples were analysed. Roman numbers 
indicate the borehole and capital letters indicate the vertical posi-
tion; the III/M sampling was carried out in landfill section III from 
the middle part of the borehole from a depth of 5–7 m, for example. 
The materials of these samples were landfilled between 2004 and 
2016, therefore the obtained data represents a 12-year timescale.
Material characterisation
Moisture contents were measured by drying at 105°C according 
to the standards (Hungarian Standard MSZ 21420 Parts: 28 and 
29, 2005). Many different subsamples were made afterwards to 
gain data, characterizing different portions of the material 
(waste-to-material components, waste-to-energy components, 
Figure 5. Drum sieve (left) and sorting on the 100 mm sieve frame (right).
Source: Authors.
1234 Waste Management & Research 37(12)
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 <20 mm fraction) and different parts of the landfill (time scale). 
The so-called ‘waste-to-energy’ subsamples were prepared by 
mixing the following sorted material categories: plastics, paper, 
combustible and textile according to the measured dry composi-
tion of the analysis. In the case of the waste-to-energy compo-
nents, the calorific value measurements and elementary chemical 
analyses of the ash were carried out. Some of the examined ele-
ments are on the 2017 EU list of critical raw materials. The 
resources of these elements, called shortly ‘critical elements’, 
are limited; therefore, any secondary raw material source is ben-
eficial. The <20 mm fine fractions were analysed for the follow-
ings: total organic carbon (TOC), dissolved organic carbon 
(DOC), elemental chemical analysis and leaching behaviour 
(EN 14429). TOC and DOC were measured by an ELEMENTAR 
Vario TOC device. Different units, namely a PerkinElmer FIMS 
400 Hg-analyser, a Perkin Elmer Optima 5300 DV ICP-OES 
device, an UNICAM UV2-200 UV/VIS spectrophotometer, a 
CEM Mars 5 and a Perkin Elmer 2400 Series II CHNS/O 
Analyser, were used for chemical analysis. An e2k Combustion 
Calorimeter (MSZ EN 15400:2011) was used to measure calo-
rific values. A VWR DL-53 drying cabinet was used to measure 
moisture content.
Results
The wet mass composition of all the nine average samples was 
measured. Only the results of sample III/M are shown in Table 2 
as an example.
Each drilling characterises the given landfill section and the 
three drillings characterise the total landfill, therefore the wet and 
dry average composition of the nine samples were calculated and 
this data is shown in Table 3.
Van Vossen and Prent (2011) summarised composition data of 
60 landfill mining projects. Data in Table 3 agrees well with the 
data of Van Vossen and Prent. Just one example, they defined the 
‘fine’ material category as <24 mm and reported 54.8% wet mass 
concentration for this material stream. The fine fraction of a sam-
ple from each drilling was extensively tested in the laboratory; 
the results of the chemical analyses are shown in Table 4.
The average TOC content of the <20 mm fractions is 11.03%, 
DOC is 2696 mg kg-1. The newest landfill section (V) has the 
highest DOC and chloride content and the lowest sulphate con-
tent. The aluminium and magnesium contents are high: 
cAl = 1.14% and cMg = 0.33% according to Table 4. Table 5 shows 
the analytical results of chemical analysis targeting into critical 
elements in the fine fractions.
According to Table 5, three critical elements have a greater con-
centration than 10 mg kg-1; they are cerium, lanthanum and neo-
dymium. The measured concentrations of these critical elements 
can be compared with their Clarke values for evaluating the critical 
raw material potential of the examined MSW landfill. The Clarke 
value is the average concentration of an element in the earth crust 
(Zepf, 2013). The Clarke value of Cerium is 43 mg kg-1, 20 mg kg-1 
for lanthanum and also 20 mg kg-1 for neodymium. The measured 
concentration value of cerium in the Debrecen MSW landfill fine 
Faitli et al. 1235
fraction exceeds its Clarke value, indicating a potential source. The 
concentrations of lanthanum and neodymium are also close for 
their Clarke values, respectively.
The other important utilisation of the landfill mined materials 
might be the waste-to-energy utilisation, therefore the sorted and 
dried energetic components of a sample of each drilling were 
mixed together and analytical samples were prepared. Table 6 
shows the calorific value results of these laboratory tests.
The average values of the tests are: 22.7 MJ kg-1 heat of com-
bustion, 21.5 MJ kg-1 calorific value and 35.7% m m-1 ash content. 
The analysed samples in the lab were dried during a period of 
previous determination of the moisture content. The deviation of 
ash content values is high. The heavy metal contents of the mixed 
energetic material components for each drilling were measured; 
results are shown in Table 7.
The aluminium and magnesium contents are significant in the 
energetic components: cAl = 3.12% and cMg = 0.61% according to 
Table 7. The aluminium and magnesium contents in the energetic 
components are much higher than in the <20 mm fine fraction. 
The reason might be the large composite packaging material con-
tent in the energetic components. Skutan and Brunner (2012) 
studied metal contents of different RDFs (refuse-derived fuels 
processed from MSW). They pointed out the difficulties of sam-
pling and producing of the analytical samples for metal chemical 
analysis. According to their data, the RDF aluminium concentra-
tion generally does not exceed 26 g kg-1. The high aluminium 
content of the waste-to-energy components in the Debrecen land-
fill will have to be taken into account during the design of the 
preparation technology.
Discussion
Tendencies in material categories
On the basis of the information obtained by the sampling cam-
paign, the total quantities of the landfilled materials in the 
Debrecen RMSW Landfill were estimated. These data can be 
used for economical calculations and for technology design. 
Beyond these, interesting trends of the composition of the 
landfilled RMSW have been revealed; the point of the intro-
duction of the selective waste collection system by the munic-
ipality of Debrecen in 2014 can be well detected on the time 
function plots of the different material categories. The wet 
substance composition of each landfill section (drilling) was 
averaged on the basis of the results of the relevant three sam-
plings (Figure 6).
As time progresses, more components are degraded, therefore 
the fine fraction and the inert component of the older landfill sec-
tions are higher. There were almost no sortable biologically 
decomposable categories on the samples; however, the fresh 
RMSW – at landfilling – generally contains significant amount of 
biomaterials. Probably the decomposed biomaterials had become 
part of the fine fraction.
According to Figure 7, the concentration of paper, textile and 
combustible categories did not changed much between 2004 and Ta
bl
e 
3.
 A
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1236 Waste Management & Research 37(12)
Ta
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Faitli et al. 1237
2008, and then it increased until 2010. Since 2014 there is a 
clearly visible decreasing trend for these material categories. 
Regarding the plastic category, its concentration first decreased, 
then from 2005 increased until 2014, then significantly decreased 
owing to the introduction of the separate waste collection system 
for the dry materials.
According to Figure 8, the mass concentration of the inert 
category increased as function of the deposition time. The 
Table 5. Result of chemical analysis (critical element content of the <20 mm fractions).
Element Sample/unit III/U <20 mm IV/M <20 mm V/M <20 mm Average
Ag mg kg-1 (d.b) 1 <1 2 1
Au mg kg-1 (d.b) <2 <2 <2 <2
Ce mg kg-1 (d.b) 59.6 49.3 44.7 51.2
Dy mg kg-1 (d.b) 2.0 1.7 1.3 1.7
Er mg kg-1 (d.b) 1.1 1.0 0.8 1.0
Eu mg kg-1 (d.b) 0.6 0.5 <0.5 0.4
Gd mg kg-1 (d.b) 2.4 2.0 1.7 2.0
Ho mg kg-1 (d.b) <0.5 <0.5 <0.5 <0.5
La mg kg-1 (d.b) 19.6 16.3 17.1 17.7
Lu mg kg-1 (d.b) <0.5 <0.5 <0.5 <0.5
Nd mg kg-1 (d.b) 16.0 12.4 11.0 13.1
Pd mg kg-1 (d.b) <0.5 <0.5 <0.5 <0.5
Pr mg kg-1 (d.b) 3.8 3.0 2.6 3.1
Pt mg kg-1 (d.b) <0.5 <0.5 <0.5 <0.5
Ru mg kg-1 (d.b) <0.5 <0.5 <0.5 <0.5
Sc mg kg-1 (d.b) 5 5 3 4.3
Sm mg kg-1 (d.b) 2.8 2.2 1.9 2.3
Tb mg kg-1 (d.b) <0.5 <0.5 <0.5 <0.5
Tm mg kg-1 (d.b) <0.5 <0.5 <0.5 <0.5
Y mg kg-1 (d.b) 9.8 9.3 7.2 8.8
Yb mg kg-1 (d.b) 1.0 0.9 0.7 0.9
In mg kg-1 (d.b) <0.5 <0.5 <0.5 <0.5
Applied equipment: PE NexION 300D ICP-MS 01. EPA Method 6020A:2007.
Table 6. Measured calorific values of waste-to-energy fractions.
Sample/unit Lower 
measuring limit
III/U
Energy fraction
IV/M
Energy fraction
V/M
Energy fraction
Average
Heat of combustion MJ kg-1 0.1 25.2 21.7 21.1 22.7
Calorific value MJ kg-1 (d.b) 0.1 24.3 20.6 19.7 21.5
Ash content % m m-1 0.1 34.1 48.3 24.6 35.7
Applied equipment: e2k Combustion Calorimeter. MSZ EN 15400:2011.
Table 7. Result of chemical analyses (elemental analyses of energy fractions).
Element Sample/unit Lower 
measuring limit
III/U
Energy fraction
IV/M
Energy fraction
V/M
Energy fraction
Average
Co mg kg-1 (d.b) 0.25 16.4 10.8 22.4 16.5
Cu mg kg-1 (d.b) 0.5 139 186 301 209
Li mg kg-1 (d.b) 0.2 22.3 20.7 50.3 31.1
Sb mg kg-1 (d.b) 1.0 11.2 11.1 19.6 14.0
Cr mg kg-1 (d.b) 1.0 1340 163 300 601
Al mg kg-1 (d.b) 1.0 20,300 19,900 53,400 31,200
Mg mg kg-1 (d.b) 2.0 6530 4440 7460 6143
Applied equipment: CEM Mars 5, Perkin Elmer 2400 Series II CHNS/O Analyser, Perkin Elmer FIMS 400, Perkin Elmer Optima 5300 DV ICP-
OES device, VWR DL-53 drying cabinet.
1238 Waste Management & Research 37(12)
measured concentration of the sortable biologically degradable 
category was almost zero. Processes taking place inside of the 
landfill have not been examined here, but this observation 
indicates that biodegradation must have happened, because 
most of the high bio content of the deposited RMSW had dis-
appeared or degraded into the fine (<20 mm) fraction. Landfill 
gas generation is a consequence of the biodegradation and this 
observation is consistent with landfill gas prognosis models in 
the literature (Faitli et al., 2017; Tabasaran and Rettenberger, 
1987; Tintner et al., 2011). The introduction of the separate 
collection of green wastes further decreased the quantity of 
bio-materials in the landfill. Concentration of the fine fraction 
significantly varies with time, but the landfill section average 
of it decreased, as shown in Figure 6.
Amount of different material categories
Based on the results of sampling, the total dry and wet mass of 
the examined material components was calculated for landfill 
sections I–V (Table 8). The total volume of landfill sections I–V 
was VT = 2,423,970 m3 and bulk density of the landfilled MSW–
RMSW was approximately ρ = 1000 kg m-3. These data were 
served by A.K.S.D. Ltd, the operator of the Debrecen Landfill. 
Table 8 shows that the estimated amount of plastic is the highest 
(regardless of the <20 mm fraction) 500,000 t. Mass of stored 
metals in landfill sections I–V is 69,300 t and the estimated total 
mass of the ‘energetic fraction’ is 858,600 t.
Conclusions
Our case study on the Debrecen Municipal Solid Waste Landfill, 
on landfill sections III–V containing RMSW deposited from 
2004 up to 2016, showed that the concentration of plastics in the 
stored waste is the highest (regardless of the <20 mm fraction): 
20.63 % m m-1 dry. The average concentration of the waste-to-
energy components is 35.42% m m-1 dry, while that of metals 
content is only 2.86% m m-1 dry.
Regarding the time of landfilling – namely the age of the land-
filled waste – different tendencies can be observed. The mass 
concentration of paper, textile and combustible did not changed 
much between 2004 and 2008, and afterwards they increased 
until 2010. Since 2014 there is a clearly visible decreasing trend 
for these material categories. Regarding the plastic category, its 
content first decreased, then from 2005 increased until 2014, then 
significantly decreased owing to the introduction of the separate 
waste collection system for the dry materials.
According to the results of samplings, the estimated wet 
amount of the fine fraction (<20 mm) was 1,213,700 t, plastics 
was 500,000 t, metals was 69,300 t and 858,600 t energetic frac-
tion (paper, textile, plastic and combustible) were landfilled in 
Table 8. The calculated total mass of each material component.
Material component 1 Paper 2 Textile 3 Plastic 4 Combustible 5a Al 5b Fe 5c Cu 5d Stainless 
steel
6 Inert 7 Bio 8 <20 mm
Total wet mass (kt) 118.3 111.0 500.1 129.2 15.0 53.1 1.0 0.2 272.2 10.2 1213.7
Total dry mass (kt) 75.0 49.3 344.5 74.1 14.0 47.2 1.0 0.2 237.7 3.4 781.7
Figure 8. Timescale variation of the residual components.
Figure 6. Wet substance composition of landfill sections III, 
IV and V.
Figure 7. Timescale variation of waste-to-energy 
components.
Faitli et al. 1239
sections I–V. These results provid a good basis for later cost-ben-
efit analysis and process technology design.
A new sampling and average sample preparation protocol was 
designed for landfill mining analysis. The carried measurements 
have proven that the protocol is well suited and flexible for the 
practical application.
Declaration of conflicting interests 
The authors declared no potential conflicts of interest with respect to 
the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for 
the research, authorship, and/or publication of this article: The 
SMARTGROUND R&D Project was funded by the European 
Union’s Horizon 2020 Research and Innovation Programme under 
Grant Agreement No 641988. The described work/article was carried 
out as a part of the ‘Sustainable Raw Material Management Thematic 
Network – RING 2017’, EFOP-3.6.2-16-2017-00010 project in the 
framework of the Széchenyi 2020 Program. The realisation of this 
project is supported by the European Union, co-financed by the 
European Social Fund.
ORCID iD
J Faitli https://orcid.org/0000-0002-4037-5208
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https://orcid.org/0000-0002-4037-5208
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