Analysis of RMSW Deposited a Decade Ago for Later “Landfill Mining”

J. Faitli1, S. Nagy1, R. Romenda1, I. Gombkötő1, L. Bokányi1, L. Barna2

1Institute of Raw Materials Preparation and Environmental Processing, University of Miskolc, 3515, Hungary 2A.K.S.D Ltd., Debrecen, 4031, Hungary

Keywords: residual municipal solid wastes (RMSW), landfill mining, sampling, sieving, sorting Presenting author email: ejtfaitj@uni-miskolc.hu

ABSTRACT Landfill mining is a prospective tool for getting valuable waste-to-material and waste-to-energy raw materials from old, therefore more or less stabilised landfills. A new sampling and average sample preparation protocol was designed on the basis of the current Hungarian municipal solid waste (MSW) analysis standards, optimised for landfill mining. A case study and sampling campaign on the Debrecen, Hungary MSW landfill was carried out. The composition and features of the landfilled materials were measured on a 12 years’ timescale. The total wet and dry mass of the valuable components was estimated. INTRODUCTION Raw materials are becoming more important for the EU economy, thus considering the increasing scarcity and raising prices, the recycling and recovery of these materials is relevant. Rational waste management practices could lead to a more efficient use of raw materials and to waste reduction. If we consider that in Europe there are between 150,000 to 500,000 highly variable landfills, the EU secondary raw materials potential is significant. The so far deposited wastes, especially the many residual municipal solid waste (RMSW) landfills represent not only an environmental problem but large amount of secondary raw materials for later utilisation. This concept is called “landfill mining” targeting the exploitation, processing and primary commodity materials production from the deposited wastes. Decomposition processes in municipal solid waste (MSW) landfills result heat, leachate and landfill gas (Faitli et al. 2015a and 2015b). After an appropriate time period majority of the biologically degradable components will be decomposed, therefore the environmental hazard potential decreases and the landfilled structural materials become more accessible. Secondary raw materials are getting more and more important role in waste-to-material and waste-to-energy production. Recultivated landfills contain large amount of non-degradable materials which could be utilised as secondary raw materials or energy (Krüse 2015). There are many case studies in the literature reporting survey data of technical and economic considerations about possible landfill mining (Tielmans et al. 2010, Krook et al. 2012, Hermann et al. 2014, 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's worth the mining and to design the mining and processing technologies, therefore analytical methods have to be developed and optimised for this task. Such sampling methods reported by Aldrian et al. (2016) and Faitli et al. (2018) can be good starting points but these methods have to be adapted for this specific task. If sampling serves enough information cost-benefit analysis can be performed (Zhou et al. 2015, Krüse 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 benefits. Four landfill mining scenarios were designed and analysed based on field data. The economic feasibility of landfill mining was then evaluated by the indicator of net present value.” If sampling serves enough information the real challenge is the development of the technology by with the exploited material can be processed and commodity materials can be produced for later utilisation. According to Krook et al. (2012) “typically, simple soil excavation and screening equipment have therefore been applied, often demonstrating moderate performance in obtaining marketable recyclables” but there are out more advanced options too.

This paper is focusing on the sampling and analyses of the municipal solid waste landfill in Debrecen as a case study on the basis of a newly developed sampling and sample preparation protocol. Material composition of the landfill and its tendencies as well as the estimation of the total amount of various material categories is presented. Area of case study, the MSW Landfill of Debrecen The examined MSW landfill is located in the south-western part of Debrecen (East – Hungary) on a total area of about 230,000 m2 (GPS: North 47.491882; East 21.595435). The A.K.S.D. Ltd, the operator of the Debrecen Landfill was established in December 1991 (51% Austrian and 49 % city municipality ownership). Its main activity is transportation and disposal of municipal solid waste and industrial waste according to European standards in Debrecen and its agglomeration. The Regional Waste Management Facility of Debrecen was established in 1991 and 20.1 ha area for waste disposal landfill (with combined insulation system) was built. The google map image (Figure 1) was captured at 14th April 2017; however, the satellite image on google was made earlier. It can be well seen that landfill section no. V is under preparation. At the time of sampling, more than 10 m in depth of MSW had been landfilled into this section.

Figure 1. Google satellite image of the Debrecen MSW Landfill.

Boreholes on the landfill sections III, IV and V are marked. 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).

Table 1. Area and year of opening of 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

Approximately 2,423,970 m3 (3,746,090 tons) waste was landfilled into sections I-V until the end of 2016. It means that the average annual landfilling waste amount was 162,800 tons. 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 municipal solid wastes, landfilled without sorting and preparation originated from Debrecen and its agglomeration (annual amount: 60…70 ktons/year); - non-hazardous industrial wastes (drilling sludge, scrap products, insulation materials, packaging, disposed hazardous wastes, other production wastes (10…15 ktons/year); - inert wastes, it’s annual amount has been decreased from 50…60 tons to 20 tons/year lately. Reasons of the decrease are the so far built processing capacities and the so far introduced state landfilling contribution fee. Separate collection of packaging materials (so called dry or non-contaminated by food wastes) was introduced in Debrecen only in 2014. MATERIALS AND METHODS Development of the applied sampling protocol

The currently in force Hungarian Standards MSZ 21420 Parts: 28 and 29 regarding the analysis of municipal solid wastes were introduced in 2005. The developed sampling protocol - applied here - optimised for analysing earlier landfilled wastes is based on these standards; therefore it is appropriate to shortly describe them. The Hungarian Standards are based on Gy’s sampling theory (Gy, 1979). Waste collecting vehicles can be selected for sampling. The raw sample in a vehicle characterises the sector (lot), namely the area where from the waste had been collected. The total unloaded waste has to be put over by a ~250 litres volume bucket loader. Randomly 10 increments (single samples) have to be selected and mixed together forming the gross (averaged or simply the average) sample. By this way the minimal mass of the average sample of MSW is 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).

Figure 2. Sampling protocol, according to Hungarian Standards MSZ 21420 Parts: 28 and 29.

The sample preparation consists of two parts, namely the primary and the secondary sorting. During the primary sorting a 100 mm mesh sieve is positioned on top of a frame, below there is a 20 mm mesh sieve and underneath there is a tray. The total average sample is fed partially onto the 100 mm mesh sieve. During simultaneous sorting and sieving the oversize fraction is sorted into twelve 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 (two-component 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 material category is the 20 mm mesh sieve undersize, called Fine. According to the sample nomogram for MSW the minimal mass for the 20 – 100 mm size fraction is less, therefore this fraction can be splitted and only a 30 – 40 kg subsample should be fed onto the 20 mm mesh sieve for the secondary sorting. The dry material composition has to be measured by drying the given quantities of each category in a heated chamber at 105 °C until mass equilibrium. If someone wants to measure a mechanical, biological or chemical feature of the sampled MSW, the laboratory analytical samples have to be prepared using the sorted material components separately; only the prepared individual powders can be mixed again according to the measured mass concentrations. Before landfill mining the characterisation of the deposited material is crucial, however the so far described standard sampling protocol had to be modified, had to be optimised for the given task. The average sample cannot 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 technical 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.

Figure 3. Auger (left) and average sample III/M (right).

The 0.8 m diameter screw rotates into the material then it is - with the sample - teared out upward direction by the machine. By this way the landfill could be sampled as function of depth. In addition to the standard analysis, it was necessary to measure material composition as a function of some discrete size fractions too. This knowledge is necessary for the design of the waste processing technology for the exploitable material. 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 handsorting of it is difficult. For this reason the application of a drum sieve machine is beneficial because it loosens the material and the dirty fine fractions are removed as well. This way the safety of the sorting workers and the accuracy of sorting increase too. Figure 4 shows the designed flowsheet for the average sample preparation.

Figure 4. The developed sampling protocol for landfill mining.

Each average sample gained from drilling was sieved by a drum sieve machine equipped with a 40×40 mm square-shaped mesh drum sieve (Figure 5 left). The mass of the total drum sieve undersize (<40 mm) fraction was measured by an appropriate scale. A 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 simultaneously from coarser into finer particle sizes. Simple 1.2×1.2 m sieve frames were used; the applied square mesh sizes were 100, 50 and 20 mm. This is a “2” sieve series, where the width of size fractions practically doubles. The sorted material components and their numbering are shown in Table 2. Number of the standard material categories was considerably reduced, because the two most important aims of landfill mining are the waste-to-material and waste-to-energy.

Figure 5. Drum sieve (left) and sorting on the 100 mm mesh sieve frame (right).

The developed sampling protocol is flexible because after each sieve the mass of the undersize fraction can be reduced by sample splitting. If the recommendation (500 kg sample mass for 100 mm) of Gy (1979) is accepted the following sampling nomogram can be applied:

mAS = C ∙ X953 (1) The constant in Equation 1 is C = 500 tons/m3 and X95 is the 95 % particle size. According to this sampling nomogram the minimal processed material is 63 kg on the 50 mm sieve and 4 kg on the 20 mm sieve.

Boring was carried out in Debrecen on 9th 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 9 discrete average samples were analysed. Roman numbers indicate the borehole and capital letters indicate the vertical position; 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 deposited between 2004 and 2016, therefore the obtained data represents a 12 years’ timescale. The applied analytical methods Moisture contents were measured by drying at 105 °C according to the standards. Many different subsamples were made afterwards to gain data characterizing different portions of the material (waste-to-material components, waste-to-energy components, < 20 mm fraction) and different parts of the landfill (time scale). The so called “waste-to-energy” subsamples were prepared by mixing of the following sorted material categories: plastic, paper, combustible and textile according to the measured dry composition of the analysis. In the case of the waste-to-energy components, calorific value measurements, elementary chemical analysis, elementary chemical analysis of the ash and critical element content analysis of the ash had been carried out. The < 20 mm fine fractions were analysed for the followings: TOC, DOC, elemental chemical analysis, dissolution and critical element content. TOC and DOC were measured by an ELEMENTAR Vario TOC device. Different units: namely a Perkin Elmer FIMS 400 Hg-analyser, a Perkin Elmer Optima 5300 DV ICP-OES device, an UNICAM UV2-200 UV/VIS spectrophotometer, a CEM Mars 5, a Perkin Elmer 2400 Series II CHNS/O Analyser and a VWR DL-53 drying cabinet were used for chemical analysis. An e2k Combustion Calorimeter (MSZ EN 15400:2011) was used to measure calorific values. RESULTS The wet mass composition of all of the nine average samples was measured. Only the results of sample III/M are shown in Table 2 as an example.

Table 2. The wet material composition by mass of the III/M sample. Wet mass ratio and component content of the size fractions

SIZE

FR

AC

TIO

N /

Mat

eria

l ca

tego

ry

1 Pa

per

2 T

extil

e

3 Pl

astic

4 C

ombu

stib

le

5a A

l

5b F

e

5c C

u

5d S

tain

less

st

eel

6 In

ert

7 B

io

8 <2

0 m

m

> 100 mm 0.57 1.0 7.45 2.77 0 0.21 0.03 0 1.25 0 - ∑ 13.28 % 50-100 mm 0.095 0.26 3.49 0.42 0 0.25 0 0 1.76 0 - ∑ 6.28 %

20-50 mm 0.95 0.08 1.97 0.53 0.12 0.08 0.02 0 4.06 0 - ∑ 7.82 % <20 mm - - - - - - - - - - 72.61 ∑ 72.61 % Total 1.63 1.35 12.91 3.71 0.12 0.54 0.05 0 7.08 0 72.61 ∑ 100 %

Distribution of material components in the size fractions > 100 mm 35.35 74.39 57.67 74.56 0 39.24 60.51 0 17.66 0 -

50-100 mm 5.84 19.7 27.03 11.24 0 45.93 0 0 24.93 0 -

20-50 mm 58.81 5.91 15.29 14.19 100 14.83 39.49 0 57.41 0 -

<20 mm - - - - - - - - - 0 100

∑ 100 100 100 100 100 100 100 0 100 0 100

As it was described earlier the number of the standard material categories was significantly reduced according to the landfill mining aim of sampling. The sorted material categories were as follows: 1 Paper (paper, carton, composite together); 2 Textile (textile, cloth); 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 Fine or < 20 mm. The metal category was sub-sorted into four sub-categories because these categories are potential raw materials for waste-to-material utilisation. Each drilling characterises the given landfill section and the three drillings characterise the total landfill, therefore the wet and dry average composition of the 9 samples were calculated and this data is shown in Table 3.

Table 3. Average material composition by mass of the 9 samplings.

Mat

eria

l co

mpo

nent

1 Pa

per

2 T

extil

e

3 Pl

astic

4 C

ombu

stib

le

5a A

l

5b F

e

5c C

u

5d S

tain

less

st

eel

6 In

ert

7 B

io

8 <2

0 m

m

Wet material composition 4.88 4.58 20.63 5.33 0.62 2.19 0.04 0.01 11.23 0.42 50.07 ∑ 100 %

Corrected sample standard deviation

of wet 5.65 1.61 0.76 2.31 0.46 1.44 0.00 0.01 4.81 0.72 6.12 %

Dry material composition 4.61 3.03 21.16 4.55 0.86 2.90 0.06 0.01 14.60 0.21 48.02 ∑ 100 %

The fine fraction of a sample from each drilling was extensively tested in the laboratory; the results of the chemical analysis are shown in Table 4.

Table 4. Result of chemical analysis (TOC, DOC, elemental analysis of the <20 mm fractions) Applied equipment’s: ELEMENTAR Vario TOC device, Perkin Elmer FIMS 400 Hg-analyser; Perkin Elmer

Optima 5300 DV ICP-OES device; UNICAM UV2-200 UV/VIS spectrophotometer. Sample III/U <20 mm IV/M <20 mm V/M <20 mm Average

Uni

t

Ele

men

t. co

mpo

s.

Dis

solu

tion

in

dist

illed

w.

Ele

men

t. co

mpo

s.

Dis

solu

tion

in

dist

illed

w.

Ele

men

t. co

mpo

s.

Dis

solu

tion

in

dist

illed

w.

Low

er

mea

suri

ng li

mit

Ele

men

t. co

mpo

s.

Dis

solu

tion

in

dist

illed

w.

TOC

% m

/m 10.4 - 8.13 - 14.6 - 0.01 11.04 -

DOC

mg/

kg (d

ry b

ased

)

- 411 - 698 - 6980 1 - 2696 Fluoride - <1.0 - <1.0 - <1.0 1 - <1.0 Sulphate - 1030 - 580 - 110 10 - 573 Chloride - 860 - 1600 - 2130 10 - 1530

Al 10800 - 11300 - 12100 - 1.0 11400 - As - <0.1 - <0.1 - <0.1 0.1 - <0.1 Ba - 0.5 - <0.2 - <0.2 0.2 - 0.2 Co 5.9 - 5.2 - 5.1 - 0.25 5.4 - Cr 424* 0.1 86.4 0.1 89.3 <0.1 1.0 199.9 0.1 Cu 96.2 0.1 357 0.4 166 0.1 0.5 206.4 0.2 Li 8.5 - 7.7 - 7.3 - 0.2 7.8 - Mg 3300 - 3510 - 2980 - 2.0 3263 -

Mo - 0.1 - 0.1 - 0.1 0.1 - 0.1 Cd - <0.01 - <0.01 - <0.01 0.01 - <0.01 Ni - 0.1 - 0.1 - 0.1 0.1 - 0.1 Pb - <0.1 - <0.1 - <0.1 0.1 - <0.1 Sb 9.19 <0.02 4.62 <0.02 5.36 <0.02 1.0 6.39 <0.02 Se - <0.05 - 0.13 - <0.05 0.05 - 0.04 Zn - 0.3 - 0.2 - 0.2 0.1 - 0.2 Hg - <0.01 - <0.01 - <0.01 0.01 - <0.01

The average TOC content of the <20 mm fractions is 11.03 %, DOC is 2696 mg/kg. The newest landfill section (V) has the highest DOC and chloride content and has the lowest sulphate content. The aluminium and magnesium contents are relevant: cAl=1.14 % and cMg=0.33% according to Table 4. There are many critical elements on the list of the EU containing materials of which resources are limited; therefore any secondary raw material source is beneficial. Table 5 shows the analytical results of chemical analysis targeting into critical elements in the fine fractions.

Table 5. Result of chemical analysis (critical element content of the <20 mm fractions) Applied equipment’s: PE NexION 300D ICP-MS 01. EPA Method 6020A:2007

Element Sample/Unit III/U <20 mm IV/M <20 mm V/M <20 mm Average Ag mg/kg (d.b) 1 <1 2 1 Au mg/kg (d.b) <2 <2 <2 <2 Ce mg/kg (d.b) 59.6 49.3 44.7 51.2 Dy mg/kg (d.b) 2.0 1.7 1.3 1.7 Er mg/kg (d.b) 1.1 1.0 0.8 1.0 Eu mg/kg (d.b) 0.6 0.5 <0.5 0.4 Gd mg/kg (d.b) 2.4 2.0 1.7 2.0 Ho mg/kg (d.b) <0.5 <0.5 <0.5 <0.5 La mg/kg (d.b) 19.6 16.3 17.1 17.7 Lu mg/kg (d.b) <0.5 <0.5 <0.5 <0.5 Nd mg/kg (d.b) 16.0 12.4 11.0 13.1 Pd mg/kg (d.b) <0.5 <0.5 <0.5 <0.5 Pr mg/kg (d.b) 3.8 3.0 2.6 3.1 Pt mg/kg (d.b) <0.5 <0.5 <0.5 <0.5 Ru mg/kg (d.b) <0.5 <0.5 <0.5 <0.5 Sc mg/kg (d.b) 5 5 3 4.3 Sm mg/kg (d.b) 2.8 2.2 1.9 2.3 Tb mg/kg (d.b) <0.5 <0.5 <0.5 <0.5 Tm mg/kg (d.b) <0.5 <0.5 <0.5 <0.5 Y mg/kg (d.b) 9.8 9.3 7.2 8.8

Yb mg/kg (d.b) 1.0 0.9 0.7 0.9 In mg/kg (d.b) <0.5 <0.5 <0.5 <0.5

According to Table 5 three critical elements have larger concentration than 10 mg/kg; these are cerium,

lanthanum and neodymium. 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 results of these laboratory tests.

Table 6. Measured calorific values of waste-to-energy fractions Applied equipment’s: e2k Combustion Calorimeter. MSZ EN 15400:2011

Sample/Unit Lower

measuring limit

III/U Energy fraction

IV/M Energy fraction

V/M Energy fraction

Average

Heat of combustion

MJ/kg 0.1 25.2 21.7 21.1 22.7

Calorific value

MJ/kg (d.b) 0.1 24.3 20.6 19.7 21.5

Ash content

% m/m 0.1 34.1 48.3 24.6 35.7

The average values of the tests are: 22.7 MJ/kg heat of combustion, 21.5 MJ/kg calorific value and 35.7

% m/m ash content. The analysed samples in the lab were dried during 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.

Table 7. Result of chemical analysis (elemental analysis of energy fractions) Applied equipment’s: 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. Element Sample/Unit Lower

measuring limit

III/U Energy fraction

IV/M Energy fraction

V/M Energy fraction

Average

Co mg/kg (d.b) 0.25 16.4 10.8 22.4 16.5 Cu mg/kg (d.b) 0.5 139 186 301 209 Li mg/kg (d.b) 0.2 22.3 20.7 50.3 31.1 Sb mg/kg (d.b) 1.0 11.2 11.1 19.6 14.0 Cr mg/kg (d.b) 1.0 1340 163 300 601 Al mg/kg (d.b) 1.0 20300 19900 53400 31200 Mg mg/kg (d.b) 2.0 6530 4440 7460 6143

The aluminium and magnesium contents are significant in the energetic components: cAl=3.12 % and cMg=0.61 % according to Table 7. The Al and Mg contents in the energetic components are much higher than in the < 20 mm fine fraction. Reason of that might be the large composite packaging material content in the energetic components. DISCUSSION Tendencies in material categories On the basis of the gained information by the sampling campaign 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 development. Beyond these, interesting trends of the composition of the landfilled RMSW have been revealed; the point of the introduction of the selective waste collection system by the municipality of Debrecen (2014) can be well seen on the time function plots (Figure 7 and 8) of the different material categories. The wet material composition of each landfill section (drilling) was averaged on the basis of the results of the relevant three samplings (Figure 6).

Figure 6. Wet material composition of landfill sections III, IV and V.

As time progresses more components are degraded, therefore the fine fraction and the inert component of the older landfill sections are higher. There were almost no any 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.

Figure 7. Timescale variation of waste-to-energy components.

According to Figure 7 the concentration of paper, textile and combustible categories did not changed much between 2004 and 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 due to the introduction of the separate waste collection system for the dry materials.

Figure 8. Timescale variation of the residual components.

According to Figure 8 the ratio of the inert category is increasing as function of the deposition time. Concentration of the biologically degradable category is almost zero due to the spontaneous biodegradation taking place in the landfill, and due to the separate collection of green wastes. Concentration of the fine fraction is significantly varying with time, but the landfill section average of it is decreasing according to 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/m3. These data was served by the 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 tons. Mass of stored metals in landfill sections I ..V is 69,300 tons and the estimated total mass of the “energetic fraction” is 858,600 tons.

Table 8. The calculated total mass of each material component.

Mat

eria

l co

mpo

nent

1 Pa

per

2 T

extil

e

3 Pl

astic

4 C

ombu

stib

le

5a A

l

5b F

e

5c C

u

5d S

tain

less

st

eel

6 In

ert

7 B

io

8 <2

0 m

m

Total wet mass [ktons] 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 [ktons] 75.0 49.3 344.5 74.1 14.0 47.2 1.0 0.2 237.7 3.4 781.7 CONCLUSION

Our case study on the Debrecen Municipal Solid Waste Landfill, on the landfill sections III – V containing MSW deposited from 2004 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 dry. The average concentration of the waste-to-energy components is 35.42 % m/m dry, while that of metals content is only 2.86 % m/m dry.

Regarding the time of landfilling, - namely the age of the landfilled 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 concentration first decreased, then from 2005 increased until 2014, then significantly decreased due to the introduction of the separate waste collection system for the dry materials.

According to results of samplings the estimated wet amount of the fine fraction (<20 mm) was 1,213,700 tons, plastics was 500,000 tons, metals was 69,300 tons and 858,600 tons energetic fraction (paper, textile, plastic and combustible) were landfilled in sections I … V. These results are providing a good basis for later cost-benefit 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 practice. ACKNOWLEDGEMENT

The SMART GROUND project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No 641988. The described work/article was carried out as 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 realization of this project is supported by the European Union, co-financed by the European Social Fund. REFERENCES Aldrian, A., Sarc, R., Pomberger, R., Lorber, K. E. and Sipple, E.M.: Solid recovered fuels in the cement industry – semi-automated sample preparation unit as a means for facilitated practical application. WASTE MANAGEMENT & RESEARCH (2016) doi: 10.1177/0734242X15622816 Faitli, J., Csőke, B., Romenda, R., Nagy, Z. and Németh, S.: Developing the combined magnetic, electric and air flow (KLME) separator for RMSW processing. WASTE MANAGEMENT & RESEARCH (2018) doi: 10.1177/0734242X18770251 Faitli, J., Magyar, T., Romenda, R., Erdélyi, A. and Boldizsár, Cs.: Chapter 9. Laying the Foundation for Engineering Heat Management of Waste Landfills. In: Norma Chandler (ed.), Landfills: Environmental Impacts, Assessment and Management. 269 p. Hauppauge (NY): Nova Science Publishers, pp. 215-244. (2017) Faitli, J., Magyar, T., Erdélyi, A and Murányi, A.: Characterization of thermal properties of municipal solid waste landfills. WASTE MANAGEMENT 36:(1) pp. 213-221. (2015) Faitli, J., Erdélyi, A., Kontra, J., Magyar, T., Várfalvi, J. and Murányi, A.: Pilot Scale Decomposition Heat Extraction and Utilization System Built into the "Gyál Municipal Solid Waste Landfill". In: Cossu, R., He, P., Kjeldsen, P., Matsufuji, Y., Reinhart, D. and Stegmann, R., (eds.) 15th International Waste Management and Landfill Symposium: G13. Workshop: Heat utilization from landfills. S. Margherita di Pula, Italy, Paper 262. p. 12 (2015) Gy, P. M.: Sampling of Particulate Materials – Theory and Practice. Elsevier Scientific Publishing Company, New York (1979) Hermann, R., Baumgartner, R. and Sarc, R.: Landfill mining in Austria: Foundations for an integrated ecological and economic assessment. WASTE MANAGEMENT & RESEARCH 32: 48–58. (2014) Hungarian standard: MSZ 21420-28, 2005, Characterization of wastes. Part 28: Investigation of municipal wastes. Sampling.

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