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Landfill Mining - A Comprehensive Literature Review

Authors:
1
LANDFILL MINING A COMPREHENSIVE REVIEW
A REPORT BY -
ARINDAM DHAR
ENHANCED GRADUATE TEACHING ASSISTANT
UNIVERSITY OF TEXAS AT ARLINGTON
EMAIL: arindamdhar2004@gmail.com
2
Contents
1. Introduction: ............................................................................................................................................. 7
2. History of landfill mining ........................................................................................................................... 7
3. Landfill Mining Initiatives in the US .......................................................................................................... 9
3.1 Naples Landfill, Collier County, Florida ............................................................................................. 16
3.2 Town of Thompson, Connecticut ...................................................................................................... 17
3.3 Edinburg, New York........................................................................................................................... 18
3.4 Other projects in New York ............................................................................................................... 18
3.5 LFM projects in Pennsylvania ............................................................................................................ 20
3.5.1 Frey Farm Landfill, Lancaster County ......................................................................................... 20
3.5.2 Hopewell Landfill, York County .................................................................................................. 21
3.5.3 Bethlehem Landfill ..................................................................................................................... 22
3.6 Barre and Newbury Landfill, Massachusetts .................................................................................... 22
3.7 Bethlehem Landfill, New Hampshire ................................................................................................ 22
3.8 Live Oak Landfill, Atlanta, Georgia .................................................................................................... 22
3.9 Wyandot County Environmental Sanitary Landfill, Ohio .................................................................. 23
3.10 Shawano County Landfill, Wisconsin .............................................................................................. 24
3.11 Central Disposal Systems Landfill, Iowa .......................................................................................... 24
3.12 Pike Sanitation Landfill. Ohio .......................................................................................................... 25
3.13 La Crosse County, Wisconsin .......................................................................................................... 26
3.14 Dean Forest Landfill, Georgia .......................................................................................................... 26
3.15 Clovis Landfill Reclamation Project, California ................................................................................ 27
3.16 Winnebago County, Wisconsin ....................................................................................................... 28
3.17 Phoenix Rio Salado Project, Arizona ............................................................................................... 28
3.18 A detailed case study Perdido Landfill, Escambia County, Florida............................................... 29
3.18.1 Overview: ................................................................................................................................. 29
3.18.2 Pilot scale project: .................................................................................................................... 31
3.18.3 Full scale project: ..................................................................................................................... 32
3.18.4 Project costs and benefits: ....................................................................................................... 34
3.18.5 Lessons Learnt: ......................................................................................................................... 35
4. Process of Landfill Mining ....................................................................................................................... 36
5. Equipment Involved ................................................................................................................................ 39
5.1 Equipment for Waste excavation or scraping ................................................................................... 40
3
5.2 Equipment for material handling and sorting ................................................................................... 40
5.3 Equipment for Screening .................................................................................................................. 40
5.4 Equipment for Transportation .......................................................................................................... 43
5.5 Air separation technologies: ......................................................................................................... 44
5.6 Metal separators ........................................................................................................................... 44
6. Planning for Landfill Mining .................................................................................................................... 45
6.1 Slope stability .................................................................................................................................... 46
6.2 Access road ....................................................................................................................................... 46
6.3 Worker Health and Safety Plan ......................................................................................................... 46
6.4 Storm water and Leachate Management ......................................................................................... 47
6.5 Accidental Fire control ...................................................................................................................... 47
6.6 Soil cover ........................................................................................................................................... 47
6.7 Waste reception area ........................................................................................................................ 48
6.8 Mechanical equipment ..................................................................................................................... 48
6.9 Staff training ...................................................................................................................................... 48
6.10 Management of Oversize Recovered Materials ............................................................................. 48
6.11 Management of Reclaimed Soil ...................................................................................................... 48
7. Economic Feasibility of Landfill Mining ................................................................................................... 49
8. Environmental Impacts of landfill mining ............................................................................................... 53
8.1 Literature review on environmental impacts of landfills:................................................................. 53
8.2 Positive Environmental Impacts of LFM: .......................................................................................... 56
8.2.1 Removal of potential source of pollution: ................................................................................. 56
8.2.2 Liner installation/retrofitting and removing hazardous material: ............................................. 56
8.2.3 Landfill Capacity Extension: ....................................................................................................... 56
8.2.4 Soil reclamation: ........................................................................................................................ 56
8.2.5 Energy production:..................................................................................................................... 56
8.2.6 Material Recycling ...................................................................................................................... 57
8.2.7 Freeing-up land for other uses: .................................................................................................. 57
8.3 Negative Environmental Impacts of Landfill ..................................................................................... 57
8.3.1 Hazardous waste management ................................................................................................. 57
8.3.2 Release of Landfill gas and odor ................................................................................................ 57
8.3.3 Release of leachate and management of surface runoff ........................................................... 58
8.3.4 Release of dust ........................................................................................................................... 58
4
8.3.5 Subsidence or collapse of cells................................................................................................... 58
9. Challenges of Landfill Mining .................................................................................................................. 59
9.1 Technical Challenges ......................................................................................................................... 59
9.2 Economic Challenges ........................................................................................................................ 60
9.3 Environmental Challenges ................................................................................................................ 60
10. Enhanced Landfill Mining (ELFM) .......................................................................................................... 61
10.1 Evolving Landfill Mining Concepts .................................................................................................. 61
10.1.1 Bioreactor Landfills ...................................................................................................................... 62
10.1.2 Evolution of ELFM ........................................................................................................................ 64
10.2 Closing the Circle (CtC) the first ELFM project ............................................................................. 65
10.4 Environmental and Economic Feasibility of ELFM .......................................................................... 67
10.4.1 Environmental feasibility of ELFM ........................................................................................... 69
10.4.2 Economic Feasibility of ELFM ................................................................................................... 73
10.5 Summary and Conclusions .............................................................................................................. 75
11. Conclusion ............................................................................................................................................. 76
12. Recommendations ................................................................................................................................ 77
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List of Tables
Table 1 Details of Landfill Mining Operations performed worldwide ........................................................ 10
Table 2 Soil to waste ratios of different landfill reclamation projects in New York (modified and
reproduced from Krogmann and Qu, 1997) ............................................................................................... 19
Table 3 Composition of reclaimed MSW (screen overs) by volume of landfills in Ney York State,
determined by visual inspection (Reis 1995, reproduced from Krogmann and Qu, 1997) ........................ 20
Table 4 Mining cost and benefit elements (Reproduced from IWCS 2009) ............................................... 34
Table 5 Summary of Excavation Volumes and Costs for Landfill Mining Projects in the US (Reproduced
from IWCS 2009) ......................................................................................................................................... 35
Table 6 Benefits and costs of reclamation of a landfill (Reproduced from Van der Zee et al., 2004) ........ 50
Table 7 Hazards which may be encountered during excavation of dumpsites (Kurian et al 2008 cited in
RenoSam 2009) ........................................................................................................................................... 61
Table 8 Mitigating measures in connection with dumpsite excavation (Kurian et al 2008 cited in
RenoSam 2009) ........................................................................................................................................... 62
Table 9 Distinct landfill mining/management concepts that are under development (Reproduced from
Jones et al., 2013) ....................................................................................................................................... 63
Table 10 Percentage changes in net impact of basic scenario, for the scenarios in the sensitivity analysis
(colored cells represent the IW valorisation) (Reproduced from Danthurebandara, 2015) ...................... 74
Table 11 Net Present Value sensitivity analysis using Monte Carlo simulations ........................................ 75
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List of Figures
Figure 1 Cumulative number of truckloads of different mined constituents (Reproduced from Jain et al.,
2013) ........................................................................................................................................................... 33
Figure 2 Distribution of various constituents of mined material (Reproduced from Jain et al., 2013) ...... 34
Figure 3 Generalized landfill mining process flow diagram (reproduced from Jain et al., 2014) ............... 38
Figure 4 Landfill mining process (reproduced from IWCS 2009) ................................................................ 39
Figure 5 Use of Loader for Waste Sorting and Handling (Reproduced from IWCS 2009) .......................... 41
Figure 6 A trammel screen in operation (Reproduced from IWCS, 2009) .................................................. 42
Figure 7 A shaker screen in operation (Reproduced from IWCS, 2009) ..................................................... 42
Figure 8 List of potential technologies for landfill mining operation (Reproduced from Ford et al., 2013)
.................................................................................................................................................................... 43
Figure 9 Expected value for (a) added and (b) avoided GHG emissions (in million tonnes CO2 equivalents)
for different types of processes in the stationary plant scenario. GHG =greenhouse gas; CO2 =carbon
dioxide. (Reproduced from Frandegard et al. (2013b) ............................................................................... 55
Figure 10 General ELFM process flow diagram for the Closing the Circle project (RDF= SRF= Solid
Recovered Fuel) (Reproduced from Jones et al., 2013) .............................................................................. 67
Figure 11 Overview of ELFM processes of REMO Landfill (Reproduced from Danthurebandara, 2015) ... 68
Figure 12 Illustration of the structure and data flow of ELFM model (Reproduced from Danthurebandara,
2015) ........................................................................................................................................................... 69
Figure 13 Normalised environmental profile of valorisation of 1 tonne of MSW/IW (basic scenario)
(Negative impact score signifies positive (or avoided) environmental impact) (Reproduced from
Danthurebandara, 2015) ............................................................................................................................ 70
Figure 14 Contribution of different ELFM processes- Normalised environmental profile of valorisation of
1 tonne of MSW/IW (basic scenario) (Negative impact score signifies positive (or avoided) environmental
impact) (Reproduced from Danthurebandara, 2015) ................................................................................. 71
Figure 15 Environmental profile of valorisation of total waste present in the landfill compared to Do
Nothing scenario with normalised data per impact category (top panel) and single score data (bottom
panel) (Negative impact score signifies positive (or avoided) environmental impact) (Reproduced from
Danthurebandara, 2015) ............................................................................................................................ 72
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1. Introduction:
A landfill is a large area of land or an excavated site that is specifically designed and built to receive
wastes. In many regions of the world, landfills have long been seen as a final way to store waste at
minimum cost (Krook et al., 2012). This dependence on landfilling has created a chain of long-term
economic, social and environmental impacts. Apart from material and energy wastage, landfill
deposits generate methane emissions due to organic degradation (Mor et al., 2006; Sormunen et al.,
2008) and contribute to local pollution due to leaching of hazardous substances if not properly
contained (Flyhammar, 1997). Also, space constraint is another challenge for landfill operation,
especially in densely populated areas (Zhao et al., 2007). Over the years, most regions have
accumulated a large number of old and/or still operational landfills containing vast amounts of
obsolete materials and products for a long time, some of them more valuable than others (Lifset et
al., 2002; Zhao et al., 2007). Present worldwide situations like rapidly growing competition for
resources, increasing raw material prices, diminishing natural reservoirs for valuable resources and
increasing environmental problems make resource extraction from alternative sources a viable
option (Kapur, 2006; Halada, 2009, Krook et al., 2012). Such possibilities challenge the current view
of landfills as a final destination for waste and indicate the emergence of a new perspective of
Landfill Mining, primarily as a valuable material extraction and energy resource recovery strategy
(Krook et al., 2012).
Landfill Mining (LFM) can be defined as
“the excavation and treatment of waste from an active
or inactive landfill for one or more of the following purposes: conservation of landfill space,
reduction in landfill area, elimination of a potential contamination source, mitigation of an
existing contamination source, energy recovery from excavated waste, reuse of recovered
materials, reduction in waste management system costs and site re-development”
(Cossu et
al., 1996). Krook et al. (2012) defined landfill mining as
“a process for extracting materials or
other solid natural resources from waste materials that previously have been disposed of by
burying them in the ground”
. This report attempts to summarize the available literature
published till date and analyze the trends, challenges and opportunities of landfill mining.
2. History of landfill mining
Savage et al. (1993) reports that landfill mining was introduced in Tel Aviv, Israel in 1953 as a way to
obtain fertilizers for orchards. This remained the only reported initiative for several decades (Krook
et al., 2012). Increased concerns for impending shortages of landfill space in the United States (US)
prepared the stage for further LFM projects as one strategy to regain storage capacities (Kruse,
2015). The first projects in the US were started in Naples, Florida (1986-1992) and Edinburgh, New
York (1988). Both were motivated by avoiding and reducing closure costs as well as the
environmental footprint of the landfills (US-EPA, 1997). The project in Naples was not only the
first one of a series that followed, but also the first one to incorporate a broad range of resource
recovery strategies into its design (Kruse, 2015):
i) recover landfill cover material,
ii) using combustible waste as fuel for a close by waste-to-energy facility and
iii) recover recyclable materials.
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However, the project proved successful only in recovering cover materials, as the plant for
producing additional fuel was never developed. By 1990, four LFM projects were already initiated.
The first European pilot project that aimed at reducing occupied landfill volume and to prove the
technical and economic feasibility of LFM was conducted in Germany (Burghof) in 1993
(Rettenberger et al., 1995 cited in Kruse, 2015). A series of other projects in Germany followed,
which were motivated by hazard prevention (Hölzle, 2010 cited in Kruse, 2015).
In 1994, the first LFM activities were launched both in Italy (Sardinia) and Sweden (Filbona). These
projects were a consequence of efforts to reduce impending local risks from poor installation and
space shortages due to expanding cities (Cossu et al., 1996 cited in Kruse, 2015).
Despite the fact that first projects in Europe and elsewhere have been pursued, LFM was until now
not commercialized on a large scale. Many pilot applications have been reported in the literature, but
full scale projects are fewer as the environmental legislation tends to be stricter, (Gaitanarou et al.,
2014). The pilot projects are located mainly in Germany (Hogland 2002), the Netherlands (Van der
Zee et al. 2004), Finland (Kaartinen et al. 2013). Some pilot scale projects in the United Kingdom
(Hayward-Higham 2008 cited in Gaitanarou et al., 2014 ) did not prosper and, although designed,
were finally abandoned (Gaitanarou et al., 2014). Not much information is available on landfill
mining projects that have been carried out on a worldwide basis. Numerous studies and LFM
projects have carried out in the rest of the world, mainly in Asia. Most of them are located in India
(Kurian et al. 2003; Hogland et al. 2005) and China (Zhao et al. 2007; Lou et al. 2009 cited in
Gaitanarou et al., 2014), as their vast population has created issues related to landfilling (Gaitanarou
et al., 2014). It has been reported that LFMR projects have been planned or implemented at the
Non Khaem Landfill in Bangkok, Thailand, and at the Nanjido Landfill serving metropolitan
Seoul, Korea (Strange 2008)
There are a number of reasons for adopting LFM, but nearly all of them were motivated by local
pollution problems or hazard prevention. Resource recovery was seldom the driver of LFM in the
past, but has recently gained more importance (Kruse, 2015). A law passed in Germany in 2005
forbids only relocation of an old landfill without recovering resources from the stored content. A
public support scheme in Bavaria subsidizes efforts to explore old landfills and the materials stored
therein. These policies and incentives have led to a boom in landfill mining activities in 2007 and
2008 (Bockreis and Knapp,2011 cited in Kruse, 2015).
Following are some of the beneficial reasons for adopting LFM (Reno Sam, 2009):
Expansion of landfill lifetime (conservation of landfill space or increase in storage capacity)
Pollution prevention and mitigation of existing sources of contamination
Material and energy recovery
Reduction of waste management system costs
Site redevelopment
Currently, LFM has been revolutionized, where resource recovery has become the primary goal of
mining. LFM has been redefined as Enhanced Landfill Mining (ELFM). According to Geysen et al.,
(2013),
In our novel ELFM vision, the goal is not to stabilise the materials but rather to
valorise the various waste streams either as material or as energy”.
ELFM has gained
9
popularity in Flanders, Belgium, where research and pilot studies have led to a series of publications
(Geysen et al., 2009;Jones et al. 2012;Bosmans et al., 2013; Quaghebeur, et al.,2013;Van Passel et
al.,2013). ELFM is discussed in details in the chapter 10 of this report.
Table 1 summarizes all the reported mining activities till date.
3. Landfill Mining Initiatives in the US
“In the U.S., one of the most important drivers for this revival of interest in landfill mining
during the 1990s was, either directly or indirectly, stricter environmental legislation. Such
regulations forced many landfills to close down and also involved tougher requirements on
final closure and post management, e.g. long-term monitoring of pollutants (Spencer, 1990;
Richard et al., 1996a; 1996b). This took place in a time when landfilling was still by far the
most commonly applied waste disposal method in the country and getting permission to
develop new landfills was becoming increasingly difficult, primarily due to strong public
opposition. Excavation, processing, treatment and recovery of landfilled materials then
emerged as a promising strategy to solve the increasing shortage of landfill void capacity
and to reduce or postpone costs related to final closure, retrofitting and post-monitoring of
the growing number of old landfills reaching end-of-life (Dickinson, 1995; Reeves and
Murray, 1996; 1997). At the same time, other benefits such as revenue from recovered
materials and reclaimed land potentially could be obtained. In Europe and Asia, the
situation was somewhat similar although in these regions the growing need for remediation
of old landfills and removal of deposits hampering urban development seems to have been
important drivers for the increased interest in landfill mining as well (Cossu et al., 1996;
Hogland et al., 1996; Hylands, 1998).
Around 2000, the research intensity on landfill mining suddenly decreased and since then
only sporadic initiatives have been reported in the scientific literature. There could certainly
be several reasons for this change in activity such as economic downturns or less demand
for landfill space in certain regions of the world due to introduction of more sophisticated
waste treatment and recycling programs. However, one important reason is probably the
fact that many feasibility studies from the 1990s found that it often was difficult to obtain
high-quality, marketable recyclables from the deposits (e.g. Savage et al., 1993; Krogmann
and Qu, 1997). This is critical as it decreases the capacity for creating new landfill space or
reducing the need for remediation and final closure. A “new” waste disposal problem might
be generated, as well as limiting possible benefits in terms of revenue from recovered
materials. Hull et al. (2005) argues that landfill mining is only economically viable under
certain conditions: as an alternative option for remediation preferably co-financed from
clean-up funds; for removal of deposits hampering urban development; for extraction of
supplementary waste fuel in order to secure full working load at waste incinerators; or for
creating new landfill space by using existing sites and infrastructure, thereby also
facilitating the permitting process.”
(Krook et al., 2012)
10
Table 1 Details of Landfill Mining Operations performed worldwide
Sl.
No.
Year
Country
Landfill
Reference
1
1953
Israel
Hiriya
Shual and Hillel
(1958) and Savage
et al. (1993) cited
in Kurian et al.
(2003b) and
Ortner et al. (2014)
2
1986-
1992
Florida,
USA
Naples
Lee and Jones
(1990) cited in
Kurian et al.
(2003b) and Ortner
et al. (2014).
3
1988
New York, USA
Edinburg
Strange (2010) cited
in Ortner et al.
(2014)
4
1989
India
Deonar
Scheu and
Bhattacharya (1997)
cited in Kurian et al.
(2003a) and Ortner
et al. (2014)
5
1989
Connecticut,
USA
Thompson
Guerriero (1996)
6
1989
New
Hampshire,
USA
Bethlehem
Strange (2010) cited
in Ortner et al.
(2014)
7
1990
Austria
Donaupark
Spillmann et al.
(1992) cited in
Mocker et al. (2009)
and Ortner et al.
(2014)
8
1990
Wisconsin, USA
Winnebago County
Landfill
IWCS (2009)
9
1990-
1995
New York, USA
Horicon
Guerriero (1996)
10
1990-
1995
New York, USA
Chester
Guerriero (1996)
11
1990-
1995
New York, USA
Coloni
Guerriero (1996)
12
1990-
1995
New York, USA
Tonawanda
Guerriero (1996)
13
1990-
1995
New York, USA
Moriah
Guerriero (1996)
11
Sl.
No.
Year
Country
Landfill
Reference
14
1990-
2012
Arizona, USA
Phoenix Rio Salado
Project
IWCS (2009)
15
1991-
1993
Pennsylvania,
USA
Frey Farm
Kurian et al.
(2003b) cited in
Ortner et al. (2014)
16
1991
Pennsylvania,
USA
Hopewell landfill
Guerriero (1996)
17
1993
Germany
Burgof
Rottenberger and
Göschl (1994) cited
in Hogland et al.
(2004) and Ortner
et al. (2014)
18
1993
Sweden
Landskrona
Bergstedt (2008)
cited in Hölzle
(2010), RenoSam
(2009) and Ortner
et al. (2014)
19
1993
Massachussets,
USA
Martone (Barre)
Landfill,
Strange (2010) cited
in Ortner et al.
(2014)
20
1993
Massachusetts,
USA
Newbury
Nelson (1995) cited
in RenoSam (2009)
and Ortner et al.
(2014)
21
1994
Canada
McDougall
Nelson (1995) cited
in RenoSam (2009)
and Ortner et al.
(2014)
22
1994
Germany
Sengenbühl
Hogland (2002)
cited in Kurian et al.
(2003a) and Ortner
et al. (2014)
23
1994
Italy
Cagliari
Cossu et al. (1995)
cited in Hogland et
al. (2004) and
Ortner et al. (2014)
24
1994
Sweden
Filbona
Hogland et al.
(1997) cited in
Mocker et al. (2009)
and Ortner et al.
(2014)
12
Sl.
No.
Year
Country
Landfill
Reference
25
1994
New York, USA
Hague
Nelson (1995) cited
in Kurian et al.
(2003b) and Ortner
et al. (2014)
26
1995
Germany
Schöneiche
Bockreis and Jager
(2009) cited in
Ortner et al. (2014)
27
1996-
2000
Austria
Helene Berger
Federal
Environmental
Agency Austria
(2010) cited in
Ortner et al. (2014)
28
1996-
2000
Ohio,USA
Pike Sanitation
Landfill
IWCS (2009)
29
1997-
1998
Georgia, USA
Live Oak
Kurian et al.
(2003b) cited in
Ortner et al. (2014)
30
1997-
2006
Georgia,USA
Dean Forest
Landfill
IWCS (2009)
31
1998-
2008
California, USA
Clovis Landfill
IWCS (2009)
32
1999
Ohio, USA
Wyandot County
landfill
IWCS (2009)
33
2000
Iowa, USA
Central Disposal
Systems Landfill
IWCS (2009)
34
2001
Austria
Kiener-Deponie
Federal
Environmental
Agency Austria
(2010) cited in
Ortner et al. (2014)
35
2001-
2002
Wisconsin, USA
Shawano County
Landfill
IWCS (2009)
36
2002
Austria
Fischer
Federal
Environmental
Agency Austria
(2010) cited in
Ortner et al. (2014)
37
2002
Germany
Längen moos
AWB (2010) cited
in Ortner et al.
(2014)
13
Sl.
No.
Year
Country
Landfill
Reference
38
2002-
2005
Sri Lanka
Guhagoda
Werellagama and
Samarakoon (2007)
cited in Ortner et al.
(2014)
39
2004
India
Kodungaiyur
Kurian et al. (2003a)
cited in Ortner et al.
(2014)
40
2004
India
Perungudi
Kurian et al. (2003a)
cited in Ortner et al.
(2014)
41
2005-
2008
Wisconsin, USA
La Crosse County
Landfill
IWCS (2009)
42
2006
Germany
Rennerod
Hölzle (2010) cited
in Ortner et al.
(2014)
43
Up
to
2007
United Arab
Emirates
Sharjah
Göschl (2006) cited
in Hölzle (2010) and
Ortner et al. (2014)
44
2007-
2015
Switzerland
Kölliken
SMDK (2009) cited
in Ortner et al.
(2014)
45
2008
Germany
Tiefenbach
GAB (2010) cited in
Ortner et al. (2010)
46
2008
Switzerland
Elbisgraben
BAFU (2009) cited
in Ortner et al.
(2014)
47
2009
Germany
Am Heckenweiner
GAB (2010) cited in
Ortner et al. (2014)
48
2009
Germany
Holzg’wandenweg
GAB (2010) cited in
Ortner et al. (2014)
49
2009
Germany
Jagerbergl
GAB (2010) cited in
Ortner et al. (2014)
50
2009
Germany
Pitztalsgrund
GAB (2010) cited in
Ortner et al. (2014)
51
2009
Germany
Scheffau
GAB (2010) cited in
Ortner et al. (2014)
14
Sl.
No.
Year
Country
Landfill
Reference
52
2009
Germany
Walkmühle
Hölzle (2010) cited
in Ortner et al.
(2014)
53
2009
Germany
Hechingen and
Reiskirchen
Gäth and Nispel
(2010) cited in
Ortner et al. (2014)
54
2009-
2011
Florida, USA
Perdido Landfill
IWCS (2009)
55
1994-
2020
South Korea
Nanjido
Strange (2010) cited
in Ortner et al.
(2014)
56
-------
South Korea
Ulsan
Cha et al. (1997)
cited in Hogland et
al. (2004) and
Ortner et al. (2014)
57
-------
Thailand
Nonthaburi
Prechthai et al.
(2006) cited in
Ortner et al. (2014)
58
-------
Thailand
Non Khaem
Strange (2010) cited
in Ortner et al.
(2014)
59
-------
China
San Lin
Kurian et al.
(2003b) cited in
Ortner et al. (2014)
60
-------
Germany
Baβlitz
Hogland (2002)
cited in Kurian et al.
(2003b) and Ortner
et al. (2014)
61
-------
Germany
Dobeln-Hohenlauft
Hogland (2002)
cited in Kurian et al.
(2003b) and Ortner
et al. (2014)
62
-------
Germany
Dresden
Hogland (2002)
cited in Kurian et al.
(2003b) and Ortner
et al. (2014)
63
-------
Netherlands
Arnhem
De Groot (2001)
cited in van der Zee
et al. (2004) and
Ortner et al. (2014)
15
Sl.
No.
Year
Country
Landfill
Reference
64
-------
Netherlands
Born
De Visser (2002)
cited in van der Zee
et al. (2004) and
Ortner et al. (2014)
65
-------
Netherlands
Apeldoorn
VAR (2000) cited in
Van der Zee et al.
(2004) and Ortner
et al. (2014)
66
-------
Netherlands
Heiloo
De Visser (2001)
cited in Van der Zee
et al. (2004) and
Ortner et al. (2014)
67
-------
Netherlands
Veenendaal
Geusebroek (2001)
cited in Kurian et al.
(2003b) and Ortner
et al. (2014)
68
-------
Sweden
Gladsax
Hogland et al.
(2004) cited in
Ortner et al. (2014)
69
------
Sweden
Måsalycke
Hogland et al.
(2004) cited in
Ortner et al. (2014)
70
-------
Pennsylvania,
USA
Bethlehem
Nelson (1995) cited
in
RenoSam (2009)
and Ortner et al.
(2014)
71
------
Delaware, USA
Sandtown
Hogland (2002)
cited in Kurian et
al.(2003b) and
Ortner et al. (2014)
72
Massachusetts,
USA
Barre (Same as
Martone)
Strange (1998)
73
Vermont, USA
Halifax
Reeve & Murray,
(1996) cited in
RenoSam (2009)
The success of a landfill reclamation project depends largely on site specific factors as well as project
goals. Several pilot and full scale studies were undertaken in numerous states of US including
Florida, New York, Pennsylvania, Massachusetts, New Hampshire and Delaware, as well as in
Ontario, Canada, with a specific objective for each project (Guerriero, 1996). Some of the
implemented and reported projects are discussed below:
16
3.1 Naples Landfill, Collier County, Florida
The Collier County, FL, project (Naples Landfill) was the first publicized effort in the US to reclaim
soil and recyclable materials from an existing sanitary landfill. Beginning in 1988, two cells of the
Naples Landfill, covering a total area of 26 acres (10.5 hectares) were reclaimed by open face mining
using a front-end loader as a demonstration project (Guerriero, 1996). The mined material was fed
into a vibrating screen plant (with a two and a half inch screen) at a rate of 90-100 tons per hour.
Eighty five percent of the material passed through the screen and was recycled as cover material.
The oversized residue consisted of glass, plastics, metals, wood and rocks (Spencer 1990). The
permit stated that the oversized residue could be "reburied or temporarily stored for recycling" in a
lined portion of the landfill. Also, the permit stated
“other uses for reclaimed earthen materials
will be determined pending future testing for hazardous constituents”
(Spencer 1990). Based
on success of the demonstration project, Collier County decided to continue landfill reclamation
activities (Collier County Solid Waste Department, 1991 cited in Guerriero, 1996)
According to Collier County Solid Waste Department (1991),
“Since the soil in Florida is
composed primarily of sand, the process is also separating approximately 15 percent of the
ferrous metal in the waste to a quality acceptable for recycling,that is, unhindered by soil
residue more typically found on landfilled ferrous metal. The project was originally initiated
to reclaim material for burning in a waste-to-energy plant as the supplementary fuel, in
place of wood chips. Even though the waste-to-energy was not implemented, the project is
still economically feasible based on reuse of the recovered soil as landfill cover”
(Collier
County Solid Waste Department, 1991 cited in Guerriero, 1996)
The County invested about $300,000 in the landfill mining equipment. It is estimated that the use of
the recovered soil material from the excavated landfill will reduce expenditures for cover dirt by $4
million, making the project economically viable by recovering soil material alone. Hence, Collier
County terminated its contract for the proposed waste-to-energy facility (Spencer, 1990).
Additionally, the permit issued for Naples Landfill mining also set forth standards and procedures
which were the first ones to be documented. The main concerns of the state was unearthing of
hazardous waste and asbestos during excavation. Test pits were excavated and toxicity testing was
conducted on the samples from the proposed areas of mining. In addition, the permit required the
following (Spencer 1990):
“All supervisors and operators directly involved in the mining operation shall pass a course
in asbestos removal. All personnel directly involved in the mining operation shall wear
clothing/masks adequate to protect them from any hazardous substance at all times.
Random tests for asbestos shall be run twice monthly.
Any time asbestos is suspected, the following procedure shall be followed:
Operations in the area shall cease immediately. The material should be removed.
The department should be contacted immediately.
Reclamation in the area shall be prohibited unless asbestos testing turns out
negative.
17
In conjunction with the Department, the asbestos material will be removed and
reburied in the lined portion of the landfill. The asbestos location shall be surveyed
and recorded. The record shall be kept at the Naples landfill.
The only exposed area of mining operation shall be the open face. The working face shall be
kept to a minimum sue and covered at the end of the working day on Saturday.
No fugitive dust shall be generated by the mining excavation.
Should the excavation operation uncover an area that is still “anaerobically active”, mining
operations in that area shall cease immediately in order to avoid noxious odors.
Should the landfill excavation project be temporarily halted or terminated, final cover shall
be applied within 180 days. Final cover shall reach natural grade.
Precautions shall be taken to assure landfill cells are free from potentially dangerous gas
levels before any excavation work is begun.”
3.2 Town of Thompson, Connecticut
The idea to excavate the Town of Thompson’s 30-year-old landfill originated from a newspaper
clipping about the Collier County project, according to Donald Williams, Selectman in Thompson,
Connecticut (Spencer, 1990). The Town of Thompson, CT started landfill reclamation in 1989 to
create their much needed disposal space in the existing landfill. The Town received permission from
the Connecticut Department of Environmental Protection to excavate approximately one acre of an
existing landfill containing ash from dump burning, as identified from the results of test pits across
the 10 acre landfill (Guerriero, 1996).
Another factor that influenced Thompson’s decision to excavate the particular area is that much of
the landfill was operated under management practices required since the early 1970s, which
prevented burning and required daily cover, finished grades to drain off water, and capping with
relatively impervious material. It is of interest to note that the test pits in the areas where waste was
buried following these management practices had not degraded significantly. According to Spencer
(1990),
“Since the Town was interested in gaining additional landfill space, it decided to
conduct the project in the burn area rather than the less degraded areas. This decision made
for a very cost effective project since the excavated material was more easily separated into
reusable dirt than less degraded waste. Working from the end of November 1988 into
January 1989, a local contractor excavated and screened approximately 16,000 yards of
material from the approximately one-acre area, at a cost of $117,000. With an unexpected
$50,000 grant from the state, the cost of the excavation to the Town was $67,000, excluding
engineering costs for the project. Williams provided an estimate of the economic benefits of
the project to the Town at over $1 million considering that the Town gained over 15,000 tons
of waste disposal capacity, which would cost between $75 and $82 per ton tipping fee for
disposal at distant incinerators, plus the costs of constructing a transfer station, as well as
hauling the waste to the incinerators.”
. The Town gained about 18 months of disposal capacity
and additional time for planning of their solid waste management program (Cobb, 1988 cited in
Guerriero, 1996).
18
3.3 Edinburg, New York
Based on the Collier County project and upcoming closure of numerous landfills, the New York
State Energy Research and Development Authority (NYSERDA) and the New York State
Department of Environmental Conservation (NYSDEC) undertook research and development
(R&D) projects to determine the feasibility and cost-effectiveness of landfill reclamation. Successful
landfill reclamation would decrease the area requiring closure, decrease long-term monitoring
requirements, and allow for upgrade of the facility to a lined landfill or utilization of the reclaimed
land for another purpose (Guerriero 1996). Moreover, NYSERDA was particularly interested in
capturing the potential energy in the combustible and recyclable materials in the landfill (New York
State Energy Research and Development Authority, 1992 cited in Guerriero 1996).
The first project to start was municipal solid waste (MSW) landfill in Edinburg, NY (Guerriero
1996). NYSERDA initiated excavation of approximately one acre of the Town of Edinburg landfill
in 1990. The state, town and U.S. EPA contributed $305,000, $15,000 and $20,000 respectively for
this research and demonstration project. NYSERDA eventually planned to mine the entire 6.5 acre
site, at an estimated cost of $1.3 million (Spencer 1990).
The MSW landfill at Edinburg was chosen as industrial waste was unlikely to occur in the landfill
based on its service area and disposal history (Guerriero 1996). According to Spencer (1990),
The
plan is to excavate fill material, reclaim soil and recyclable materials, and then either reclaim
the land for development purposes or possibly construct a landfill which meets state
requirements. The project will characterize the proportion of various waste types excavated,
determine the Btu value of the waste, and evaluate the soil fraction to determine potential
uses.
This project addressed the following issues of landfill reclamation (mining) (Guerriero 1996):
excavation and separation techniques
appropriate uses for reclaimed material
a test burn of reclaimed refuse at a resource recovery facility (RRF);
specifications for work plan, health and safety monitoring and contingency plans and
economic factors.
The results of the study indicated that reclamation was feasible at Edinburgh landfill and as planned,
the town continued reclamation activities beyond the one acre reclaimed area (Spencer 1990).
3.4 Other projects in New York
Successful implementation of Edinburg project prompted NYSERDA to sponsor additional R&D
studies at six landfill sites in the state of New York (Tonawanda, Hague, Chester, Horicon, Moriah
and Colonie) to evaluate the feasibility of landfill mining under different site conditions (Guerriero
1996).
Out of these landfills, Hague Landfill was the first effort in USA to dig up and entirely remove an
old landfill to return the site to its natural state. It began in 1994 after performing a feasibility study
(Nelson, 1995 cited in Joseph et al., 2004). The project aimed to remove a 2.7 ha landfill owned by
the rural township to use the land for recreational purposes and removed about 76,500 m3 of waste
19
for recovery of ferrous metal and the beneficial use of soil fraction. The project budget was $ 1.3
million (Joseph et al., 2004).
Table 2 and table 3 compares the different properties of the reclaimed wastes from these landfills in
New York.
Table 2 Soil to waste ratios of different landfill reclamation projects in New York (modified and reproduced
from Krogmann and Qu, 1997)
It is of interest to note the following points from these studies:
i) The soil to waste ratios by volume after excavation and screening varied widely between
landfills (20:80 in Chester landfill to 75:25 in Edinburg landfill) (Krogmann and Qu,
1997)
ii) For the Colonie landfill it was reported that sections with waste from times when a
recycling program was implemented did not contain appreciable amounts of recyclables
of a marketable quality (Reis 1995)
iii) By volume, paper and plastic accounted for more than 50% of the screened waste for
most landfills. Five to ten percent by volume was metals in most landfills. High
percentage of stones up to 50% in the Horicon, NY landfill prevented the combustion
20
of the reclaimed MSW at a waste-to-energy facility without additional processing
(Krogmann and Qu, 1997).
Results of these feasibility studies support the need to identify site specific conditions and
reclamation options before implementing a full scale mining project (New York State Energy
Research and Development Authority, 1994 cited in Guerriero, 1996).
Table 3 Composition of reclaimed MSW (screen overs) by volume of landfills in Ney York State, determined
by visual inspection (Reis 1995, reproduced from Krogmann and Qu, 1997)
3.5 LFM projects in Pennsylvania
3.5.1 Frey Farm Landfill, Lancaster County
The Frey Farm landfill was opened for waste disposal in September 1988. A mass burn facility with
a design capacity of 1,100 tons/day was completed in December, 1990 (Joseph 2004). Between 1991
and 1993, about 219,500 m3 of MSW were excavated from the landfill (USEPA, 1997 cited in Joseph
2004). The major goals of the mining operation were the following (Guerriero 1996):
i) Reclaim landfill space
ii) Increase energy production at the RRF
iii) Recover ferrous metals and cover soil.
Due to insufficient waste delivery to the landfill, waste from the first 7 ha. cell were excavated and
added to fresh MSW (1 part of mined waste to 3 parts of fresh waste by weight basis) as
supplementary fuel for the mass burn facility (Nelson, 1995 cited in Joseph 2004).However, when
the mined material was mixed with fresh MSW, the yield reduced from 660 kWh/ton to 500
kWh/ton due to relatively low heating value of mined wastes (Joseph et al., 2004). The Pennsylvania
Department of Environmental Resources (PADER) monitored the mining operation. Though the
combustion of mined MSW did not have a negative impact on the permits for either the source
recovery facility or the landfill, but concerns were expressed by PADER about potential for changes
to storm water runoff, extra leachate generation and gas releases from the mining operation.
However, none of the concerns became a problem except for the additional traffic generated by
delivery of mined material to the project. The energy value of the mined material was estimated to
be US $33/ton (Joseph 2004).
Through this mining operation, Lancaster County converted 56% of the reclaimed waste into fuel
and also recovered 41% of the reclaimed material as soil by trammel operations. The remaining 3%
21
proved noncombustible and was reburied in the landfill (USEPA, 1997 cited in Joseph 2004). In
1992, the Authority reclaimed approximately 1,000 cubic yards (765 cubic meters) of cover soil each
week and sent approximately 2,000 cubic yards (1530 cubic meters) of reclaimed refuse to the RRF
(Lancaster County Solid Waste Management Authority, cited in Guerriero 1996).
Benefits of the project (RenoSam 2009):
Reclaimed landfill space
supplemented energy production and
recovered soil and ferrous metals.
Drawbacks of the project (RenoSam 2009):
increased generation of ash caused by the high soil content found in reclaimed waste
increased odor and air emissions
increased traffic on roads between the MWC and the landfill, and
increased wear on both the landfill operation and MWC equipment (i.e., due to the abrasive
properties of the reclaimed waste)
Costs for the resource recovery portion of the project were relatively low for the following reasons
(RenoSam 2009):
The distance for transporting both the reclaimed waste and the ash was only 18 miles each
way.
The management authority avoided commercial hauling prices by using its own trucks and
employees to transport the reclaimed waste and the ash.
The landfill and MWC were operated by the same management authority, thus no tipping
fees were required. (Generally, a higher tipping fee can be charged at an MWC for reclaimed
waste because of its abrasiveness and higher density, which increases the wear and tear on
equipment.)
By 1996, the mass burn facility operators had enough fresh waste to run at full capacity and no
longer needed mined waste as supplemental feed materials from Frey Farm Landfill. Thus, landfill
officials concluded the reclamation project in July, 1996 (RenoSam, 2009).
3.5.2 Hopewell Landfill, York County
The York County Solid Waste Authority (YCSWA) conducted a feasibility study in 1991 to consider
environmental, technical and economic factors and to evaluate the potential for landfill reclamation.
The goals for the mining operations are (Guerriero 1996):
i) Reclaim landfill space
ii) Reduce the potential for groundwater contamination.
The waste was passed through a 1" vibrating screen to recover soil particles and the soil to waste
ratio was 35:65 (Krogmann and Qu, 1997). Utilizing site-specific information generated by a field
investigation, and considering existing solid waste disposal practices in the municipality and
reasonable assumptions regarding landfill reclamation, the study illustrated that landfill reclamation
22
was economically viable depending on project implementation (Malcolm 1991 cited in Guerriero
1996).
3.5.3 Bethlehem Landfill
The City of Bethlehem conducted a demonstration project for reclamation while constructing the
first cell of landfill expansion to illustrate the benefits of the project. The demonstration project was
successful in meeting Pennsylvania Department of Protection's (PADER) specific guidance criteria
for maximum slopes for expansion construction. The city reclaimed a portion of the existing landfill
and regarded the slope to adjust the final grades before closure. This operation maximized air space
utilization and provision for vertical expansion, while retrieving soil for daily cover. Also, the odor
and litter problems anticipated by PADER were not realized (Guerriero 1996). This reclamation
operation allowed for implementation of landfill reclamation during subsequent landfill expansion
realizing larger cost savings (Campman and Everett, 1995 cited in Guerriero 1996).
3.6 Barre and Newbury Landfill, Massachusetts
A private sanitary landfill in Barre, Massachusetts submitted a proposal to mine a section of the
property filled between mid-1950s and 1970 as a part of permit application (Joseph et al., 2004).
Tests pits excavated for material evaluation showed that some of the cells were constructed to be
almost completely impervious to the external water infiltration. The excavated contents showed little
degradation. The recovered soil fraction was used as a cover material (Strange 1998 cited in Joseph
et al., 2004).
A 3.6 ha landfill serving a community of 6,400 people was reclaimed in 1993 at Newbury,
Massachusetts, to construct a new lined landfill of 1.6 ha. Soil recovered (two third of the mined
materials) was stock piled for future use as cover material (Nelson, 1995 cited in Joseph et al., 2004).
3.7 Bethlehem Landfill, New Hampshire
The Bethlehem landfill site in New Hampshire received wastes from small towns and rural tourist
areas between 1979 and 1987. In 1989, a new enterprise took over the company that owned the
landfill and filed a permit for landfill expansion. The New Hampshire Department of
Environmental Services (NHDES) permitted the company to the mine the unlined landfill and
relocate approximately 160 tons of material from the old, unlined portion of the landfill to the newly
lined section (Joseph et al. 2004). The permit prohibited any mining or waste removal operations
during summer months (June, July and August) due to odor concerns and required that odor
masking agents be applied to the wastes being processed (Strange, 1998 cited in Joseph et al., 2004).
Air quality (concentrations of oxygen, hydrogen sulphide, and volatile organics in the air) and quality
of storm water runoff (changes in conductivity and pH) were monitored throughout the mining
process. Only slight increases in conductivity were noticed, with no changes in pH. The mining
equipment employed consisted of two excavators, one front-end loader, four dump trucks, two
bulldozers, one trommel screen, and one odor control sprayer (Joseph et al., 2004).
3.8 Live Oak Landfill, Atlanta, Georgia
In January 1997, a pilot-scale project was initiated at the Live Oak landfill at Atlanta, Georgia to
assess the feasibility of in situ aerobic bioreduction of municipal solid waste (Smith et al, 2000 cited
in Joseph et al., 2004). This pilot scale project was carried out in a 10 meter lined cell containing
23
approximately 53,522 m3 of MSW of age no more than three years. Since the materials in the cell
contained a significant portion of biosolids from wastewater treatment plants, air and water (recycled
leachate mixed with fresh water) were injected into the fill material through wells to simulate the
aerobic decomposition of MSW. Routine monitoring of the process included the following (Joseph
et al., 2004):
Temperature measurement
Landfill gas composition
Water volumes pumped and leachate generation and
Physical, chemical, and biological characterization of leachate.
Small sections of the test cells were mined from October 1997 to 1998 to characterize the materials
recovered and assess the procedures and equipment needs for full scale mining. The results showed
that none of the wastes were stabilized at this time of sampling. Laboratory analysis of the trace
metals of the humus fraction showed that As, Cd, Cr, Cu, Pb, Mo, Ni, Se and Zn were well within
limits set by USEPA for high quality compost (Joseph et al.,2004).
3.9 Wyandot County Environmental Sanitary Landfill, Ohio
Wyandot County Environmental Sanitary Landfill is operated and owned by Central Disposal
Systems (Ohio), Inc. and is located in Carey, Ohio. The landfill contains a total permitted disposal
area of 188 acres, consisting of both unlined and lined cells. The Ohio Environmental Protection
Agency mandated the owners to relocate waste from unlined cells to lined cells as groundwater
contamination was found in the vicinity of the site (IWCS 2009). The details of the mining project
are as follows (IWCS 2009):
The waste relocation was started in 1999 and the waste relocation activities were conducted
mainly during the winter to minimize odor issues.
The mining process consisted of excavating the waste (using one CAT 750) and hauling the
material to the on-site lined unit via off-road trucks.
The excavation was conducted by a private contractor and included only waste relocation
(i.e., no processing).
Some odors were noted, but with minimal impact. No hazardous material was reported to be
encountered during the waste excavation process.
Standard personal protective gear (hard hats, steel-toe boots, long-sleeve shirts, and gloves)
were worn during the project. The health and safety plan was typical of regular construction
projects and no provisions specific to waste were included. Respirators were used by the
staff as needed, however, specifics about the type of respirator used were not provided.
Mining operations were resumed continuously to avoid daily cover application to the
excavated area. Waste was relocated at a rate of approximately 300,000 yd3 per year. Thirty
acres of land have been reclaimed till 2012, totaling approximately 1.4 million yd3of waste.
The overall cost of the waste relocation project was estimated at $4/yd3.
Berms were constructed to manage storm water runoff and the runoff that came in contact
with the waste was managed as leachate leading to an improvement in groundwater quality
after mining began.
24
3.10 Shawano County Landfill, Wisconsin
This landfill contains both unlined and lined cells. The leachate from the unlined cells were collected
from a perimeter toe drain to prevent migration and sent off-site for treatment. To reduce the cost
of leachate treatment, a waste relocation project was initiated to excavate the waste from unlined
cells and dispose them in the adjacent lined cell (IWCS 2009). The details of the project are as
follows (IWCS 2009):
The project was started late in 2001 and was completed in early 2002 and was conducted in
the winter to minimize odor issues.
The excavating operation was performed using two excavators and wastes were hauled to
the on-site lined cell. Efficient processing of waste was prevented as screening of the waste
was hampered due to frozen waste.
Bulk volumes of soil were stockpiled and categorized as “clean”, “mildly contaminated”, and
“contaminated” based on concentrations from samples collected from the stockpiled soil.
o “Clean” soil was used on site for berm construction, road construction, or other
related projects.
o “Mildly contaminated” soil was permitted to be used anywhere with at least 2 ft of
clean soil.
o “Contaminated” soil placement was limited to interior slopes and was used within
lined areas of the landfill as daily and intermediate cover.
The project was executed by a private contractor and training in hazardous waste and
emergency response operations was conducted for all full-time site excavation workers.
A minimal amount of hazardous material (freon tanks, propane tanks etc.) was encountered
during the waste excavation process and the recovered hazardous materials were temporarily
stored in a designated area.
As the mined area included excavation below grade, storm water run-on was collected and
treated as leachate.
Twelve acres were reclaimed by relocating 0.3 to 0.4 million yd3 of waste. About 2 feet of
soil below the waste was scraped and stockpiled on the clay lined area. The cost of the waste
relocation project was approximately $3/yd3.
3.11 Central Disposal Systems Landfill, Iowa
This landfill is located in Lake Mills, Iowa and is owned and operated by Central Disposal Systems,
Inc. It consisted of a 10-acre unlined cell and a lined cell. Mining of waste in the unlined cell was
initiated to recover airspace and to avoid future groundwater contamination liability. The waste
relocation involved excavating the waste from unlined cells and disposing them in the adjacent lined
cell (IWCS 2009). The details of the project are as follows (IWCS 2009):
o The mining project was initiated in 2000.
o The excavating operation was performed using one backhoe (a CAT 365 with a 5 yd3
bucket) and the excavated material was hauled to an on-site lined unit by four trucks.
o This project did not employ significant waste processing; only the well-decomposed mined
waste was used as a daily cover.
25
o The project has been executed by a private contractor. Operators wore an oxygen analyzer
and respirator as and when needed. Explosivity of landfill gas was an issue and Lower
Explosive Limits (LEL) of methane was approached on some occasions. Hence, an
extensive hazardous waste management plan was used in the project.
o The plan included a staging area for temporary storage of hazardous waste and provisions
for asbestos management, but no hazardous material was encountered in the waste
excavation process.
o The waste relocation activity was mainly conducted during the winter to minimize odor
issues. Minimal odor issues primarily confined to the working area were encountered, with
no odor complaints from nearby residents. Air quality (VOCs and other gases) were analyzed
at least once an hour during excavation.
o Berms were constructed to manage storm water runoff and the runoff that came in contact
with the waste was managed as leachate.
o Ten acres was reclaimed till 2012 with waste relocation at a rate of approximately 1,000 to
1,500 yd3 per day, corresponding to the relocation of 250,000 yd3 of waste.
3.12 Pike Sanitation Landfill. Ohio
This landfill is located in Waverly, Ohio and is owned and operated by Pike Sanitation, Inc. It started
operation in the mid-1980s and contains both unlined (40 acres) and lined (125-acre, permitted in
1996) cells. The 40-acre unlined cell was located in the middle of a permitted 125-acre lined area.
The state regulations required 1 foot of select waste on the drainage layer before MSW disposal in a
cell to protect the liner system. The waste from the unlined cell was mined to be used as "select
waste" for the lined units (IWCS 2009). The details of the project are as follows (IWCS 2009):
o The waste relocation project was started in 1996 and completed in 2000. Mining operations
were performed during the winter (November to March) to minimize odor issues.
o The waste was excavated using one or two CAT 345 backhoes with 6 to 10 yd3 buckets and
hauled to an on-site lined unit using four to six off-road trucks.
o No materials processing was performed during the project.
o The project was executed by a private contractor. The record of the waste maintained by the
landfill owner indicated presence of asbestos containing material. Respirators were provided
to the staff for use when needed.
o No hazardous material other than asbestos was encountered during waste excavation. The
asbestos-containing materials were disposed of in the lined cell. The permit (NESHAP)
required the presence of a water truck and sprayer at the lined area to minimize asbestos
movement in the air.
o Odor issues were minimal and only a few complaints were received regarding odors during
the project. Dusting issues were not reported.
o Waste excavation was performed from a lower elevation to a higher elevation to avoid
stormwater run-on to the exposed waste.
o Waste excavation during the week was performed for 12 to 16 hours per day. Daily cover
was applied when operations stopped for an extended period (usually on weekends).
o Forty acres of land were reclaimed with waste relocation at a rate of approximately 40,000
yd3 per month, corresponding to the relocation of 700,000 to 800,000 yd3 of waste.
26
3.13 La Crosse County, Wisconsin
The facility is owned and operated by the county. It consisted of an unlined cell (approximately 25
acres with 1.2 million yd3 of waste), which operated from 1976 to 1990/1991, and a lined cell.
Groundwater contamination was observed at the site despite the presence of vertical leachate and
gas extraction wells in the unlined cell. Expansion of the existing lined cell and reduction of
potential future liability were the motivations behind the waste relocation project. Expansion of the
lined cell was not feasible as it required land acquisition. Also, a permit for a new landfill would have
been expensive and difficult due to high property value in the vicinity. The County also operated a
refuse-derived-fuel waste-to-energy plant since 1988. The larger waste pieces such as furniture, etc.
are disposed of in the lined landfill, while ash from the WTE plant is disposed of in an ash monofill
(IWCS 2009). The details of the project are as follows (IWCS 2009):
o The waste relocation project started on November 2005 and was expected to be completed
over three winters (to minimize odor issues).
o The waste was excavated using two backhoes with 4-yd3 buckets and hauled to the lined cell
using about a dozen off-road trucks, each with a capacity to hold approximately 12 yd3 of
waste.
o The County planned to recover metals using a trommel screen but dropped the plans as only
a small amount of these materials were encountered. Soil (clay) from the cap and from other
spots was recovered and used for future landfill operations. The contaminated soil (in
contact with waste or leachate) was stockpiled on the lined landfill.
o The project was executed by a private contractor. A detailed health and safety plan was
implemented.
o An area suspected to contain hazardous waste was isolated and the suspected items were
characterized by an expert team specialized in hazardous material characterization. Only
limited amounts of hazardous waste were encountered and incentives were provided to the
contractor and supervisor for hazardous waste detection.
o The gas-extraction system was aggressively operated and monitored to minimize odor from
the working face. The residents around the site were informed about the importance of the
project and occasional odor issues and no odor complaints were received during the first
phase of the project. Two dust monitors were installed at the site, although no dust issues
were encountered.
o Berms were constructed to manage storm water runoff and the runoff coming in contact
with the waste was treated as leachate.
o Daily cover was not used, even on weekends.
o About 25 acres of were reclaimed in the first phase, totaling about 500,000 yd3 of waste.
3.14 Dean Forest Landfill, Georgia
This facility the located in the City of Savannah, Georgia and is owned and operated by the city since
1984. The site layout consisted of quadrants, with three unlined cells and one partially lined cell. The
City has incinerated its waste since 1987 and ash generated at the plant is disposed of at this site. The
city also accepted some MSW, construction and demolition (C&D) debris, and other waste materials
such as sludge. The primary motivations behind the waste relocation project was a need for
expansion and capping a 35 acre portion of the landfill, which would cost about $ 2 million. The site
was eligible for a state grant (Hazardous Waste Trust Fund) of up to $2 million to implement
27
corrective measures to prevent groundwater impacts from Cadmium. The city proposed relocation
of waste from unlined to a lined cell and received the state grant (IWCS 2009). The details of the
project are as follows (IWCS 2009):
o The waste relocation project started in 1997 and was completed in 2006.
o The waste was excavated using two CAT 345 and hauled to an on-site lined unit via six or
seven off-road trucks (CAT 740).
o The excavated material was not processed. Lack of space and time were the main factors for
deciding not to process the mined material.
o The project was executed by a private contractor. A detailed health and safety plan was
implemented.
o No hazardous waste was reported to be encountered during the mining operations.
Although state rules prohibited placement of tires in the landfill, the permit allowed for
disposal of tires that were encountered during mining to be disposed of in the lined cell.
o No dust and odor issues were encountered during mining.
o Berms were constructed to manage storm water.
o Daily cover was applied.
o A total of 130 acres of land was reclaimed. Waste was relocated at a rate of approximately
7,000 yd3 per day, totaling about 650,000 yd3 of waste.
3.15 Clovis Landfill Reclamation Project, California
The facility is an MSW Landfill located in the City of Clovis, California and is owned and operated
by the city since 1957. The landfill receives 200 tons of MSW per day and is open only to City
collection trucks. The landfill consists of units built before 1992 were unlined units (before 1992),
clay-lined units (built from 1992 through 1998) and new cells (with a synthetic composite liner
system since 1998). A permit to expand from 55 acre waste footprint to a 78-acre waste footprint on
a 210-acre property was issued in December 2006. The primary motivations behind the landfill
mining was to address groundwater contamination mitigation, airspace recovery, and soil recovery
(IWCS 2009). The details of the project are as follows (IWCS 2009):
o The mining project started in 1998 and is expected to be completed in 2008.
o The waste was excavated using Cat D9 pushing to a Link-Belt 4300 excavator and screened
using Re-Tech Olympian Portable Trommel with a 2-inch screen. The screened waste was
directly loaded into 40-yd3 open-top dumps and hauled to lined portion of the landfill (1,000
to 1,500 feet away). A series of conveyors transported dirt and material smaller than 2 inches
in diameter to a soil stockpile. A Komatsu 155 dozer was used to consolidate the soil
stockpile at the end of the conveyors. The soil (including waste material smaller than 2
inches) comprised approximately 60% of the material excavated.
o The project was executed jointly by a private contractor and the City staff.
o An isolated area was designated for temporary storage of hazardous materials encountered
during mining.
o Odor from the mining project was more prevalent than from the working face of the
landfill, but did not travel far off-site. Regular surface monitoring for methane and other
gases was carried out. Minimal dust was encountered during the mining process. Minimal
vector problem and slight increase in windblown litter was observed.
28
o Storm water from the mining area was collected and sprayed back over the composite lined
portion of the facility.
o No daily cover was applied to the exposed waste in this particular project, but current
regulations of the California Integrated Waste Management Board require cover on all
mining projects.
o A total of 2.1 million yd3 of waste had been mined and screened till 2012, with a typical
mining rate of 1,100 yd3 per day. Mining is carried out approximately 190 days a year (about
75% of the working days), as inclement weather and equipment maintenance have resulted
in some delays. The total cost of the process was estimated at $4.84 per yd3.
3.16 Winnebago County, Wisconsin
This facility is located in Winnebago County, Wisconsin and is owned and operated by the county.
The landfill consists of both unlined and lined cells which were closed in 1989-1990. Water ponding
on the top surface of the lined cells was noticed due to differential settlement. Waste from unlined
area was excavated and disposed of on the top of the lined area. The primary motivations behind the
landfill mining operation was reduced monitoring near the unlined cells and eliminating the
procurement of soil for filling depressions on the top of lined cells (2 feet of clay as final cover)
(IWCS 2009). The details of the project are as follows (IWCS 2009):
The project started in the winter (late 1990) to avoid odor problems.
The clay cover over the lined cell (waste relocation cell) was scraped. Excavated waste from
unlined cells was spread and applied with a dozer.
Only ferrous metals were recovered from the mined materials using an electromagnet and
the remaining mined materials were disposed on top of a lined cell. No other waste
processing techniques were adopted.
A designated area was used for storing hazardous waste until it could be managed. The
hazardous waste management team was outfitted with Tyvek suits. Principal hazardous
materials encountered were lead-acid batteries that were subsequently recycled.
About 3 to 4 acres of land were reclaimed.
3.17 Phoenix Rio Salado Project, Arizona
Due to federal dam construction in the early 1900s in the upper Salt and Verde rivers, the lower Salt
River has experienced wetland and riparian vegetation degradation. The Water Resources
Development Act of 1999 authorized the environmental restoration of these areas. The construction
zone of restoration project included 13 regulated and a few unregulated landfills. The project covers
a total area of more than 600 acres. Only the waste encountered within the construction zone of the
project was excavated and hauled to a disposal site. The Phoenix North Central Landfill, Del Rio
Landfill, and various dumps along the low flow channel were all partially mined, but waste screening
was performed only at two sites. Waste from all the other sites were hauled directly to a landfill.
(IWCS 2009). The details of the project are as follows (IWCS 2009):
The project was started in mid-1990s and was last reported to be ongoing in 2012.
The Phoenix North Central Landfill, Del Rio Landfill, and various dumps along the low
flow channel were all partially mined.
29
The City of Phoenix and the US Army Corps of Engineers conducted numerous landfill-
mining projects all along Salt River as a part of this restoration project. The contractors were
required to submit a health and safety plan for approval by the US Army Corps and the City
of Phoenix.
The majority of the hauled waste was C&D debris and was recycled. Maricopa County
contracted with R. E. Monk Construction for removing and segregating approximately
150,000 tons of waste. Primarily very wet C&D debris was encountered in this site. Hence,
the excavated waste was dried before screening. A front-end loader was used to pick larger
pieces of waste from the excavated material. Approximately 100,000 tons were screened with
a trommel and Grizzly screen and re-used as clean soil. Overall, the project was reported to
separate 80% of the mined materials, while the remaining portion was landfilled.
HAZWOPER-trained personnel supervised the mining operation and an on-call hazardous
waste contractor was employed for removal and management of hazardous waste, if
encountered. Minimal hazardous waste and asbestos-containing waste materials were
encountered.
Soil testing, approved by the Arizona Department of Environmental Quality, was performed
to identify contaminated soil.
Gas and odor issues were not reported during the project.
As of 2005, more than 380,000 yd3 of C&D debris, 20,250 yd3 of municipal solid waste, and
600 tons of tires were recovered during waste mining operations.
3.18 A detailed case study Perdido Landfill, Escambia County, Florida
3.18.1 Overview:
The Perdido Landfill is located in western Escambia County, Florida and is owned and operated by
Division of Solid Waste Management (DSWM) of Escambia County. The site consists of a
combination of unlined and lined cells. It contains closed and active Class I landfill areas, an active
Class III waste area, and other related waste management operations and facilities. From 1981 to
1990, the site includes closed and active Class I and Class III waste area, and other related waste
management operations and facilities. Several lined cells are located beside the unlined landfill area.
The landfill reached their capacity well before the projected life due to increased disposal tonnage
from Hurricanes Ivan and Dennis in 2004 and 2005, respectively (IWCS 2009). A new cell (Section
4) was permitted and constructed and waste is currently deposited in section 4 (Jain et al., 2013).
This expansion increased the disposal capacity by approximately 1.6 million yd3 and lifetime by
about four years (IWCS 2009). Site-specific constraints limited consideration to expand the landfill
into adjacent areas for future landfill operations. Availability of substantial airspace above the
unlined cells (elevation of all cells were about 30 metre below permitted height) provided an option
of reclamation of the unlined cells and construction of lined cells on reclaimed land to accommodate
future waste disposal. Moreover, elevated levels of benzene and vinyl chloride have been
encountered outside the property boundary and the unlined cells were identified as the cause (Jain et
al., 2013).
The primary motivating factors to consider and implement landfill reclamation at this sites were
(Jain et al., 2013):
30
i) To address groundwater contamination problems in old, unlined cells
ii) Increased capacity for future landfilling activities; and
iii) Reduced closure costs due to reduced landfill footprint area.
Other benefits of landfill reclamation included recovery of recyclables, particularly metals for resale,
and the use of reclaimed soil as daily cover. If used as part of an integrated strategy for sustainable
landfilling, reclamation could also serve as a means of recovering stabilized solid waste in a
bioreactor landfill operation (Nelson, 1994; Reinhart and Townsend, 1997 cited in Jain et al. 2013).
To determine the nature and volume of the waste to be excavated from these cells and to estimate
the reclamation cost, DSWM took a phased approach to evaluate the technical and economic
feasibility of the reclamation project (Jain et al., 2013). The first phase involved a desktop economic
and technical feasibility analysis. In the second phase, field investigations were conducted by DSWM
to collect site specific waste composition data and verify the bottom of unlined cells (IWCS 2009).
The key lessons learned from the first and second phase evaluations in 2006 are reported below:
The data from thirty nine 12.7 cm diameter boreholes indicated that the historical
topographic maps available for the unlined cells were reasonably accurate representations of
the landfill bottom. Based on the available topographic maps for the top and the bottom of
unlined cells, approximately 1.15 million m3 (1.5 million yd3) of material (final cover and
waste) was estimated to be available for mining in the unlined cells without any substantial
reclamation of the C & D waste that is deposited over a portion of the unlined cells (Jain et
al. 2013).
The thickness of the final cover soil was between 0.15 m to 4 m (as estimated from the 39
bore holes) (Jain et al. 2013) and constituted approximately 30% (by volume) of the volume
of unlined cells (excluding the area of C&D disposal on a portion of unlined cells) (IWCS
2009).
The soil fraction of the waste (excluding the soil contained in the berms separating the
trenches of the waste) recovered by waste screening (reclaimed soil) constituted about 24%
(60% by weight) of the volume of waste deposited in unlined cells. The actual soil content of
waste was estimated to be greater (IWCS 2009). A waste screening evaluation suggested that
effective segregation of soil could be achieved with an opening size between 2.5 cm (1 in.)
and 7.6 cm (3 in.), provided sufficient contact time was allowed (Jain et al., 2013).
Either a shaker screen (with vibrating fingers) or a trommel screen was recommended for
waste screening. A mesh-type screen used in this project was found to clog over time (IWCS
2009).
Dust and odor issues were minimal during excavation and screening (IWCS 2009). Blowing
litter was encountered during windy days (Jain et al., 2013).
Leachate seepage from the working face could be an issue during mining as two out of eight
test pits showed signs of leachate seepage (IWCS 2009).
A preliminary quality evaluation suggested that reclaimed soil could be used for land
application in an industrial land-use setting (IWCS 2009).The mining cost (waste excavation,
screening, hauling and hazardous material management) was estimated to be $8.6/yd3.
31
Higher mining rate (yd3/hr) and soil content could significantly reduce mining costs (IWCS
2009).
Cost-benefit analyses indicated that net revenue (revenue from the value of airspace minus
construction cost) would be greater for the expansion scenarios (including mining) than
those without mining (IWCS 2009).
According to IWCS (2009),
Based on the results of the preliminary investigations, the DSWM
decided to pursue a pilot scale mining project to collect more information such as reclaimed
soil content, and identification of the nature and content of hazardous material in unlined
cells to further refine the economic feasibility analysis
.
3.18.2 Pilot scale project:
About 2.5 acres of the north end of unlined cell were mined as a pilot project between June-
November, 2008. The mined material during the pilot project was estimated to be 54,300 yd3 (using
AutoCAD Civil 3D) (IWCS 2009). The different mining activities (waste excavation, screening and
transportation) for the pilot project were performed by Aero Training & Rental, Inc. (Destin,
Florida) (Jain et al. 2013). The waste was excavated in 10-to-20-ft-wide and 5-to-10-ft deep trenches
aligned in the north-south direction (IWCS 2009).
The screening process produced two separate fractions: screened waste (fraction retained on the
screen) and reclaimed soil (fraction passing through the screen). Three waste processing techniques
were evaluated in the pilot scale study to maximize the reclaimed soil (Jain et al.,2013):
i) Shredding excavated waste (particle size <15-20 cm) and subsequent screening with a
shaker screen,
ii) Screening with shaker and finger screens, and
iii) Screening using trommel screen.
Following are the details and the observations during the pilot scale study:
Visual inspections of the screen waste suggested that shaker screen had substantial soil
content in the screened waste. The trommel screen was found to be more efficient than a
shaker screen in separating soil from waste materials (Jain et al.,2013).
Waste shredding before screening did not improve soil separation efficiency significantly.
Wetting of the waste from rainfall negatively impacted both screen performance and
movement of dump trucks in the working area (Jain et al.,2013).
In August 2008, ferrous metal recovery was attempted by mounting a magnet on the shaker
screen, but was discontinued as the recovered ferrous material was not of marketable quality
(Jain et al., 2013).
No hazardous waste or asbestos-containing material, except for tires,was encountered during
the pilot-scale project. The dust, odor, and blowing litter did not hamper operations
significantly. Disposal of whole tires in landfills was permitted in the past but has been
banned for a long time in Florida. Hence, excavated whole tires were separated from the
screened waste, stored or stockpiled, and eventually transported to the on-site tire
management area (Jain et al., 2013).
32
The truckload number of different materials (screened waste, final cover soil, and reclaimed
soil) was tracked and used to estimate the reclaimed soil fraction of the excavated waste (Jain
et al.,2013). Approximately 1,250 truckloads of the screened waste were transported to the
lined cell for the final disposal. The reclaimed soil was occasionally transported to the active
lined cell by articulated dump trucks to be used as daily cover soil (IWCS 2009).
Wet weather hampered about 15% working days. The decision whether to continue or stop
the pilot mining operation on an inclement weather day was at the site supervisor’s and the
crew members’ discretion (IWCS 2009).
The precipitation run-off from the landfill surfaces covered with a soil layer or
geomembrane was considered stormwater and precipitation in contact with solid waste was
treated as leachate. A 15-mil high-density polyethylene (HDPE) liner was used over the
exposed waste when major rain events were expected to minimize leachate generation.
Diversion berms were also constructed to prevent storm water mixing with leachate (IWCS
2009).
A hazardous waste and special waste management plan was prepared before the start of the
project. However, no hazardous waste or Asbestos Containing Material (ACM) was
encountered during the project. Site workers wore typical construction gear (wear steel-toed
boots, long pants, long-sleeve shirts, safety glasses, safety vests, and hard hats,
rubber/leather gloves)while handling waste. The site supervisor and the operator of the
excavator used for waste excavation were HAZWOPER trained. No major health and safety
issues were encountered during the project (IWCS 2009).
According to Jain et al., (2013),
The results of the pilot scale study confirmed that the value of
airspace that can be recovered by excavating, screening of the excavated waste to segregate
reclaimed soil, and using reclaimed soil as daily cover would be greater than the reclamation
cost. In addition, a need for specifying a maximum soil content of the screened waste was
realized to ensure that the contractor is making diligent effort to maximize recovery of
reclaimed soil from the screening process.
3.18.3 Full scale project:
The unlined cells were targeted to be reclaimed in two phases. The details of the first phase are
reported below (Jain et al., 2013):
Phase I of the reclamation project continued from November 2009 to November 2011 and
included excavation of approximately 371,000 in-place m3 of unlined landfill airspace
(including MSW and final cover soil) from approximately 6.8 ha of unlined cells.
The final cover was removed progressively during reclamation to minimize the exposed
waste surface area and was stockpiled near the reclamation area before starting waste
excavation. Final cover soil was transported to the stockpile using articulated off-road trucks.
Approximately 30 cm of final cover soil was left undisturbed to minimize the waste’s
exposure to rainfall and hence minimize leachate generation. This cover soil also facilitated
the movement of off-road trucks. Berms of soil embedded in the waste were occasionally
encountered and were excavated and stockpiled or used as a daily cover.
33
A single wheel-base trommel with 7.6-cm opening size wire mesh screen drum (Wildcat
Model 626 Cougar) was used for the first 3 months of the screening operation (January
2010March 2010). As waste screening was found to be the rate limiting step due to
frequent breakdown (similar to pilot study), an identical second screen was mobilized to
increase the screening rate. The trammel screen was located away from the mining area to
minimize screen movement and wastes were transported to the screen using 15-m3
articulated off-road trucks. To increase efficiency of the project, the wire mesh screens were
replaced with a different wheel-base trommel with punch-plate screen drum (Doppstadt SM
720) in September 2010 and was used for the remainder of the project. The reclaimed soil
quantity, temporarily stockpiled near the screen and then transported to the active cell,
proved to be adequate to meet site’s daily cover requirement.
A storm water control berm was constructed to divert the storm water runoff from the lined
cells away from the reclamation area. The storm water runoff was diverted to a storm water
channel by either pumping or gravity drainage using corrugated high density polyethylene
(HDPE) culverts. Storm water runoff coming in contact with waste was managed as leachate
and controlled using soil berms constructed around the reclamation area.
The excavated whole tires were separated and transported to the on-site tire management
area as outlined in the pilot study.
The composition of the mined materials was estimated by tracking the truck loads of different
mined constituents (Figure 1). Figure 2 shows the composition of the mined materials excavated
from Perdido Landfill.
Figure 1 Cumulative number of truckloads of different mined constituents (Reproduced from Jain et al.,
2013)
34
Figure 2 Distribution of various constituents of mined material (Reproduced from Jain et al., 2013)
3.18.4 Project costs and benefits:
Table 4 lists the cost and benefit elements of the Perdido Landfill Project (IWCS 2009).
Table 4 Mining cost and benefit elements (Reproduced from IWCS 2009)
The Perdido landfill mining project cost $3.09 million. The main benefits of the project arose from
airspace and soil recovery. Approximately 230,600 in place m3 of net airspace was recovered. Based
on Phase I volume mining (371,000 in-place m3), the reclamation cost was estimated to be $8.33 per
in-place m3 airspace. Containment system construction (liner and cap construction plus landfill gas
collection system construction and operation) and post-closure care are some additional costs to be
35
considered, since these are to be incurred irrespective of operation procedures. However, avoidance
of groundwater contamination risk from the unlined cells were an additional benefit (Jain et al.,
2013).
The use of the final cover soil and reclaimed soil as intermediate and daily cover soil
precluded the use of materials from outside the existing landfill footprint (such as virgin
soil) as daily and intermediate covers. Therefore, the recovery and beneficial use of the final
cover soil, bermed soil, and reclaimed soil resulted in a savings of approximately 230,600 m
3
of lined airspace. This airspace would be valued at over $9 million, since at the current
waste density and tipping fee, the value of airspace at the site is approximately $40 per m3.
The gross monetary benefit of the project is estimated to be approximately $6 million. The
net benefit will be lower than $6 million as a part of the tipping fee is used to cover the cost
of compacting waste in the reclaimed airspace. ”
(Jain et al., 2013)
The summary of excavation volumes and costs for some landfill mining projects in the US are
reported in table 5.
Table 5 Summary of Excavation Volumes and Costs for Landfill Mining Projects in the US (Reproduced
from IWCS 2009)
3.18.5 Lessons Learnt:
Following factors significantly impact the economic viability of a landfill mining project (Jain
et al., 2013):
o Nature and end use of excavated waste
o Unit reclamation cost ($ per in-place m3)
36
o Cost of implementing environmental controls
The project was economically viable as 60% of the excavated airspace contained soil and
were beneficially used as cover soil. Also, the recovered airspace was worth substantially
more than the project cost (Jain et al., 2013).
Evaluation of waste excavation and processing rates of employed equipment are crucial for
the success of mining operation (Jain et al., 2013).
The swelling of the excavated waste should be considered while estimating the reclamation
cost. The swelling factor for waste was much greater than soil (1.5 in this project) (Jain et al.,
2013).
Knowledge of waste characteristics can reduce operational costs (no hazardous waste or
asbestos-containing materials were encountered in this project, which resulted in lower
reclamation costs than expected) (Jain et al., 2013).
Following are the conclusions drawn from the pilot study (IWCS 2009) :
o Soil (the final cover soil and the reclaimed soil) constituted more than 70% (by
volume) of the excavated material.
o The trommel screen was more efficient in separating soil and achieved better
material screening rate from the waste than the shaker screen. The same conclusion
was also reported in the Edinburg Landfill Mining Project in New York
(NYSERDA, 1992). The trommel also reduced the necessity of two loaders, as it was
capable of feeding the dump truck directly from its conveyor belt.
o Waste screening was determined to be the rate-limiting step of the project.
o Waste shredding before screening did not significantly increase soil separation
efficiency.
4. Process of Landfill Mining
Although the first landfill mining operation was reported back in 1953 in Tel Aviv, it remains a
relatively new approach to expand municipal solid waste (MSW) landfill capacity and avoid the high
cost of acquiring additional land or other environmental purposes. Mining projects are typically not
done just from the economic point of view (RenoSam 2009).
Typically, landfill mining consists of three basic operations (IWCS 2009):
Excavating waste,
Processing the excavated material, and
Managing the excavated or processed material.
The first operation involves waste excavation using common equipment in surface mining and
landfill operations like a backhoe or a hydraulic excavator. The excavated waste is subsequently
processed to meet objectives of the specific projects like separating bulky materials, sorting
hazardous material and other unidentified waste, screening soils from waste, and sorting materials
for recycling or use as fuel. Additional processing (magnets for ferrous metal separation etc.) and
management of the waste primarily depends on the project objectives, composition and condition of
the retrieved materials, and processing cost and time (IWCS 2009).
37
According to Joseph et al. (2004), the landfill mining process involves a set of conveyers and screens
that sort the solid waste into three separable fractions: oversized material, intermediate-sized waste
and dirt/humus. The oversized materials consist of recyclable metallic goods, white goods, plastics
and rubber. The intermediate-sized materials consist of partly decomposed organics, combustibles,
recyclables and the fine fraction will mostly be stabilized soil. The main part of the process is the
screening where the main separation is done for the oversized and the soil elements. Ferrous metals
are generated from the main stream by employing a magnetic separator and the non-ferrous parts
using an air classifier, which leaves behind the residue that could be combusted. Figure 3 outlines a
generalized landfill mining process flow diagram.
A general mining process can be described as follows (Joseph et al., 2004):
In landfill mining operations, an excavator removes the contents of the landfill cell. A
frontend loader then organizes the excavated materials into manageable stockpiles and
separates out bulky material. A trommel (a revolving cylindrical sieve) or vibrating screen
separates soil (including the cover material) and solid wastes from the reclaimed waste. The
size and type of screen used depends on the end use of the recovered material. For example,
if the reclaimed soil were to be used as landfill cover, a 6.25 mm screen is used for
separation. A smaller mesh screen (2.5 mm) may be used to remove smaller pieces of metal,
plastic, glass, and paper, if the reclaimed soil were meant for construction fill, or for another
end use requiring fill material with a high fraction of soil content. The separation of dirt/
humus material from the intermediate-sized waste is made using a screen grid with 6.25
mm openings.
Composition of waste and efficiency of mining technology dictates the success of the material
recovery (Cossu et al, 1996 cited in Joseph et al., 2004). The success of a project also depends on the
composition of the excavated waste, as non-recyclable part of the intermediate-sized and oversized
materials is typically reburied and affects airspace gain (Cossu et al, 1995, Hogland et al, 1995 cited
in Joseph et al., 2004). Facility operators must weigh the several benefits and drawbacks associated
with landfill mining before starting the project (Joseph et al., 2004). Also, a landfill needs to be 15
years older for a mining project to be successful (Strange 1998 cited in Joseph et al., 2004).
The following are the primary factors to be considered while deciding on the processing
methodology of landfill mining (IWCS 2009):
Objective of the mining operation, which also affects the selection of waste processing
equipment.
Condition and properties of excavated waste: Condition of the excavated waste is crucial for
the success of material separation. Soil lumps can prevent efficient soil separation in the
screen. Frozen waste (as encountered in Shawano County Landfill, Wisconsin) can also
cause difficulty in soil separation.
Potential end markets for recovered materials: In many instances (e.g Naples landfill mining
project in Collier County, Florida), the recovered material (ferrous metals, aluminum cans
etc.) must meet certain qualities in order to be sold in the market. The additional processing
costs in order to meet these requirements can play an important role in project’s feasibility.
38
Cost and time of processing: Separating and recycling glass recovered glass was discontinued
at the Naples Landfill mining project because of poor marketability and high transportation
costs.
A general outline of the landfill mining process is shown in Figure 4.
Figure 3 Generalized landfill mining process flow diagram (reproduced from Jain et al., 2014)
39
Figure 4 Landfill mining process (reproduced from IWCS 2009)
5. Equipment Involved
Mining of a landfill involves the use of equipment used both for surface mining and landfill
operations (IWCS 2009). Depending on the complexity of particular mining project, number of
machinery used may vary (RenoSam 2009). The following is a list of machines used in landfill
mining in increasing order of mining complexity (Wikipedia 2008 cited in RenoSam 2009):
Excavators and dump trucks
Moving floor and elevator conveyor belts
A coarse rotating trommel screen
A fine rotating trommel screen
A magnet and/or Eddy current separator
Front end loader
Odor control sprayer
An excavator or a front end loader is used to uncover the landfill materials. If a moving floor
conveyor belt is used, the excavator or front end loader places the excavated materials on the belt to
be carried to the sorting machine. A coarse trammel screen separates materials like appliances and
fabrics, whereas the smaller trammel separates the passing biodegraded soil fractions from retained
non-biodegradable, recyclable materials. An electromagnet and an eddy current separator mounted
along the conveyor belt removes ferrous metals and aluminum cans respectively from the waste
masses. Odor control sprayers are wheeled tractors with a cab, consisting of a movable spray arm
40
and a mounted reservoir, is used to reduce smell of exposed waste by spraying neutralizing agent
(RenoSam 2009).
The equipment involved can broadly be classified into three categories for further discussion:
Equipment for Waste excavation or scraping
Equipment for Material Handling and Sorting
Equipment for Screening
Equipment for Transportation
5.1 Equipment for Waste excavation or scraping
Two different approaches were adopted for waste excavation during landfill mining projects in the
US. The first approach involves using an excavator or a backhoe for waste excavation and loading
the excavated waste onto the screen or dump truck, depending on objective of the project. The
majority of mining projects in the US have adopted the first approach, using one or two excavators
depending on the desired excavation rate (IWCS 2009). In the second approach, a dozer was used to
scrape the waste along the slope (top to bottom) for collection by an excavator, which eventually
feeds the waste to a screen. Two of the landfill mining projects (City of Clovis and Frey Farm
Landfill) attempted waste scraping using a dozer after trying waste excavation using excavators
(IWCS 2009).
5.2 Equipment for material handling and sorting
Identifying and separating bulky items (furniture, electronics etc.) and hazardous wastes from the
mined materials forms an integral step in waste mining process. In some cases, large sized pieces
needs to be sorted out before placing excavated materials on the mechanical screen. A front-end
loader working with the excavator can be used for this purpose. Figure 5 shows a small loader used
at the City of Clovis mining project for handling bulkier items (IWCS 2009)
5.3 Equipment for Screening
Equipment for screening is generally a necessity in most of the projects, since soil fraction recovery
is attempted in nearly all the projects to make the project economically feasible. The main purpose
of screening, as the name itself suggests, is to separate the soil or fine fractions from the remaining
larger components. The separated fine fraction is generally used as daily or intermediate cover and
contains degraded organic materials and other small pieces of waste (e.g. glass) (IWCS 2009).
41
Figure 5 Use of Loader for Waste Sorting and Handling (Reproduced from IWCS 2009)
Generally two types of mechanical screens, trammel and shaker or vibratory screen, are used in
landfill mining operations. Performance evaluation of these two types of screens during Naples
landfill mining project show that trammel screen performed better and had fewer operational issues.
However, the opening sizes of trammel screen (3/4 ‘‘) and shaker screen (3’’) was different (Murphy
and Stessel, 1991 cited in IWCS, 2009). The performance evaluation between two types of vibratory
(shaker) screen (“Screen all” and “Waste manager”) and a trammel screen in the Edinburg mining
project in New York reported the trommel screen to be more efficient. Additionally, the trommel
was also capable of feeding the dump truck directly from its conveyor belt, reducing the need for
two loaders. (NYSERDA, 1992 cited in IWCS, 2009). Figure 6 and 7 shows the two types of screens
under operation at two different mining projects.
The screen opening size should be decided based on the required quality and final use of the
recovered soil. A larger sized screen produces lower quality and vice versa. However, larger screens
(3’’) can be used if the recovered soil is to be used as a final cover. For off-site applications of the
recovered soil, a smaller screen is recommended (IWCS 2009). According to (IWCS 2009),
“A 1-
inch screen was used at the Town of Edinburg project to separate the soil fraction from the
excavated waste. The majority of soil reclaimed from this project was used for off-site
applications. A 2-inch screen is being used at the City of Clovis landfill-mining project for
waste screening. A 1-inch and a 3-inch screen were used for waste screening for conducting
the landfill mining feasibility evaluation at the Perdido landfill. Material passing through 1-
42
inch screen was mainly composed of soil, glass shards, and decomposed organic matter.
The material passing through the 3-inch screen was mainly composed of soil, pieces of
paper, and film plastic.”
Figure 6 A trammel screen in operation (Reproduced from IWCS, 2009)
Figure 7 A shaker screen in operation (Reproduced from IWCS, 2009)
If metal recovery is attempted, the retained material on the screens are removed and put on a second
conveyor belt where an electromagnet removes any ferrous metal debris. An eddy current separator
can also be employed to recover aluminum cans. Depending on the level of resource recovery
attempted, an additional air classifier can be used for separating light organic material from heavy
organic material. These separated streams are then loaded onto trucks by front end loaders for
further processing or sale. On site manual processing can be justified to reduce transportation costs
(RenoSam 2009).
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5.4 Equipment for Transportation
Screened materials, both retained waste and screened soil, must be transported to their designated
disposal area. Depending on the distance from the working face to the location of final disposal and
the condition of the service roads, dump truck or off-road trucks can be used for hauling the
materials. Even a conveyor belt can be used for soil transport, as in the case of City of Clovis mining
project (IWCS 2009).
List of a range of technologies that can be potentially be used in a landfill mining (LFM) operation is
shown in Figure 8.
Figure 8 List of potential technologies for landfill mining operation (Reproduced from Ford et al., 2013)
In this section two technologies, Air technologies and metal separation technologies, are discussed
in some detail. Although these technologies are not frequently adopted, they may be crucial to
increase material recovery rates and contribute positively to the economic feasibility of the landfill
mining project provided suitable local market exists for the recovered materials.
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5.5 Air separation technologies:
Air technologies can take many forms, including windshifters, separation drums, air classifiers and
air knives. All air technologies are used for separation of light, low density fractions of waste from
heavy, high density fractions in a stream of air.
5.5.1 Windshifters:
A windshifter either sucks or blows the light material from the flow of waste exiting the conveyor
and is generally set up at the head of a conveyor. Additional processing includes gravity settling of
air removed fractions by decreasing the velocity in an expansion chamber (Ford et al., 2013).
5.5.2 Separation drums:
A separation drum is a contained unit which separates various grades of waste by varying air flow
using expansion chambers.
5.5.3 Air Classifier:
Air classifiers work on cyclone principle and use vortex flows and centrifugal forces to separate out
materials. These systems work best for fine or granular material and is typically used for composting
operations.
5.5.4 Air Knives:
Air knives are curtains of high velocity air operating either vertically or sideways to strip off light
materials from a conveyor belt or remove moisture from the materials.
However, the limitations of air technologies must be considered before assessing their suitability for
a particular project. According to Ford et al., (2013),
“Air separation technologies work best
where the waste is uniform in composition, loose and contains similarly sized particles of
materials of different density. Separation is hampered by waste which is highly variable,
clumped together, wet, entwined and of varying sizes. Balancing the flow of air to suit the
waste can be a challenge and can result in all or nothing being removed from the waste
stream. Trying to extract only one material out of plastic film, textiles and paper can prove
difficult since they are all low density materials. Inclusion of air technologies within the
design of a LFMR operation should be undertaken with great care, a detailed understanding
of the waste to be treated and following suitable trials” .
5.6 Metal separators
5.6.1 Ferrous metal separators
Ferrous metals are usually separated by employing overband magnets or drum magnets.
The overband magnet is a permanent or electromagnetic magnet with a running conveyor belt fitted
with it and the belt is placed perpendicularly over the flow of the waste. The magnet lifts off ferrous
metal and the conveyor belt fitted with the magnet moves the metals away from the magnet and
drops them in a container located away from the flow of waste. The main advantage of overband
magnets is that they are portable and relatively easier to maintain and operate. However, overband
magnets are not suitable for separating large metal objects, since the impact of heavy metals can
damage conveyor fabric and hamper free movement of the conveyor (Ford et al., 2013).
45
Drum magnets are more suitable for separating heavy ferrous metal objects. Drum magnets involve
a large diameter metal drum rotating around a magnet that acts upon a limited area of the drum and
placed in proximity of the waste stream. The separated ferrous metal objects stick to the drum and
are dropped into a chute or container beyond the influence of the magnet. Since a conveyor belt is
not used, high strength of magnet or impact of ferrous metals are not an issue and these
arrangements are more robust (Ford et al., 2013).
Another approach uses drum magnets in conjunction with conveyor, where drum magnets are used
as head pulleys of conveyor system. As the waste flow passes over the conveyor, non-ferrous wastes
drop from the end of the conveyor and the ferrous metal objects rotate around the head of the
pulley and drops into a chute or container after passing the influence of the magnet. Since there is
no impact of metal objects with the conveyor belt, the damage of conveyor belt is prevented (Ford
et al., 2013).
5.6.2 Non-ferrous metal separation
Eddy current separators are used to separate the remaining metals from the waste stream after
separation of ferrous metals. A rapidly spinning rotor creates an alternating polarity magnetic field in
the conveyor belt or pulley carrying waste, and the metals are repelled from the pulley/drum and
thrown over a splitter arrangement. However, the major disadvantage of this process is that the
efficiency of this operation is largely dependent on the pre-processing of the waste before this step.
Any loose plastic or other material adhering to the aluminum plastic can prevent it from being
efficiently separated. Hence, the efficiency of this separation procedure is largely unproven in the
LFM application due to possible high contamination (Ford et al., 2013).
6. Planning for Landfill Mining
The first step in planning a landfill mining and rehabilitation project should be a site survey to gather
site-specific information such as such as geological features, stability of the surrounding area, and
proximity of ground water, and should determine the fractions of usable soil, recyclable material,
combustible waste, and hazardous waste at the site (USEPA 1997 cited in RenoSam 2009).
A detailed site investigation is vital for the success of a landfill mining project. After collection of
site-specific information from the desktop study, which includes composition of the waste initially
put in place in the landfill, historic operating procedures, extent of degradation of the waste and
types of available markets, and uses for the recovered materials will determine the feasibility of LFM
at a particular location (RenoSam 2009).
The next step of site investigation involves planning for preliminary excavation and obtaining the
necessary regulatory approvals. The regulatory requirements for landfill mining vary from state to
state and are discussed in the next section. The plan should provide the specifications and details for
every activity that should be conducted during site investigation. The preliminary work plan must
include (Joseph et al., 2004):
The number of pits and/or trenches to be dug;
Equipment and material handling procedure;
46
Labor requirements and their safety;
Creation of a work zone with clearly marked boundaries; and
Necessary analytical testing, measurements and data collection.
A trench can provide a better idea about material characteristics (volumes, soil to waste ratio, waste
composition and state of decomposition) than a pit, but exposes a larger area and may create an
odor problem (Salerni, 1995 cited in Joseph et al., 2004). The site investigation information should
be analyzed to determine whether the proposed goals could be met within the project cost
framework (Joseph et al., 2004). The project costs should also be assessed based on the preceding
steps. The project costs and benefits are discussed in details in the next section, Economic feasibility
of landfill mining.
The issues to be considered while planning for landfill mining are discussed in detail below.
6.1 Slope stability
Existing steep waste slopes (if available) should be regarded. Unless compelled by proven
geotechnical reasons, waste side slopes must not be steeper than 1 in 3 (33% gradient) and top
slopes should not be more than 1 in 20 (5% gradient). Redistribution of waste due to slope
stabilization activities must not extend into the buffer zone of the landfill (Rushbrook, 2001 cited in
Joseph et al., 2004).
6.2 Access road
The disposal site should have easy access from the highway. The access road should permit the
passing of two trucks travelling in either direction (Joseph et al., 2004). Durability of access road is
crucial for efficient landfill mining operations and a durable (preferably asphalt) surface should be
prepared.
6.3 Worker Health and Safety Plan
Once a preliminary framework of the landfill mining is established, the health and safety risks posed
to the facility workers due to various planned mining operations must be identified. Methods of
eliminating or mitigating these identified risks should be developed and published as a part of the
comprehensive health and safety program. Additionally, all workers employed in the mining project
must be informed about these risks and trained in emergency response procedures (USEPA 1997,
cited in RenoSam 2009).
Although the health and safety program largely depends on site specific conditions, waste types,
project goals and can be particularly challenging, a typical health and safety program might call for
the following (RenoSam 2009):
Hazard communication (i.e., a Right to Know" component) to inform personnel of
potential risks.
Respiratory protection measures, including hazardous material identification and
assessment; engineering controls; written standard operating procedures; training in
equipment use, respirator selection, and fit testing; proper storage of materials; and periodic
reevaluation of safeguards.
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Confined workspace safety procedures, including air quality testing for explosive
concentrations, oxygen deficiency, and hydrogen sulfide levels, before any worker enters a
confined space (e.g., an excavation vault or a ditch deeper than 3 feet).
Dust and noise control.
Medical surveillance stipulations which are mandatory in certain circumstances and optional
in others.
Safety training that includes accident prevention and response procedures regarding
hazardous materials.
Recordkeeping.
The program should also list the equipment to be used by workers. The three categories of safety
equipment used in landfill mining projects are (RenoSam 2009):
Standard safety equipment (e.g., hard hats, steel-toed shoes, safety glasses and/or face
shields, protective gloves, and hearing protection).
Specialized safety equipment (e.g., chemically protective overalls, respiratory protection, and
self-contained breathing apparatus).
Monitoring equipment (e.g., a combustible gas meter, a hydrogen sulfide chemical reagent
diffusion tube indicator, and an oxygen analyzer).
6.4 Storm water and Leachate Management
Since mining of existing landfilled waste will result in a change of grade at the site, accumulation of
storm water becomes a possibility. A storm water management plan must be implemented to
prevent or at least minimize storm water contact with solid waste to prevent excessive leachate
management. Typically storm water was controlled by using diversion berms, grading the surface
adjacent to the waste to have storm water flow away from the working face (Joseph et al., 2004).
Leachate emanating from wet solid waste must be accounted for and accommodated in the existing
leachate management framework of the landfill.
6.5 Accidental Fire control
An emergency plan should be prepared to extinguish fire caused from accidental burning of solid
waste. The equipment and method to be used for extinguishing fires should be presented in the
plan. Isolation and rapid natural burnout or smothering with soil is preferred for extinguishing fire
(Joseph et al., 2004). The plan should also include procedures for notification of local fire protection
agencies for assistance in emergencies.
6.6 Soil cover
Soil cover is expensive compared to the benefits achieved by using it. Some mining projects
continued mining operations in shifts to work for about 16 hours a day to avoid soil cover.
However, it becomes a necessity during long breaks (e.g weekends). Soil cover can be avoided by
continuing mining operations throughout the day (24 hours), as done for Wyandot County
Environmental Sanitary Landfill, Ohio or may be minimized by keeping the excavation area to the
minimum. In case daily cover soil becomes unavoidable, the daily quantity of cover material (at least
5 cm depth of daily cover, 25 cm intermediate cover and 50 cm final cover) , preferably clay soils,
required should be estimated (Joseph et al., 2004).
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6.7 Waste reception area
A reception area, with an entrance gate and a gatehouse, should be built to regulate vehicle flow,
store waste records and provide shelter to the landfill staff (Joseph et al., 2004).
6.8 Mechanical equipment
The preparations for landfill mining should include a list of equipment to be used. The number and
type of equipment required will vary depending on the quantity of waste received each day and the
resources available to maintain and operate the equipment (Joseph et al., 2004).
6.9 Staff training
Training of staff is crucial to the success of landfill mining as they are directly responsible for
carrying out the operations.
“It is also for site personnel to understand that with training and
defined job descriptions comes the responsibility to perform properly the tasks they are
given. Status, pay, employment contracts and working conditions also influence the ability
and willingness of individual staff members to accept and carry out the responsibilities
placed up on them. These personnel issues must also be addressed during the planning
stage.”
(Joseph et al., 2004)
6.10 Management of Oversize Recovered Materials
The fate of oversized recovered material should be decided in the planning stage. The composition
of waste materials and their quality, as estimated from the site investigation, should help to decide
the fate of these materials. The management of these materials is primarily dependent on the
composition, processing level and available markets. Although several components of these
recovered materials seem to have value (glass, plastic etc.), metals are the most typical components
recovered from the landfill mining operations. The oversized material has been used as fuel in waste-
to-energy facilities for some cases and disposed of in lined cells of the landfill if end markets were non-
existent (IWCS 2009).
6.11 Management of Reclaimed Soil
Typically, the reclaimed soil from the landfill mining is used as daily and/or intermediate cover
during landfilling operations and constitutes more than 50% of the material recovered from MSW
landfills (on a weight basis) (US EPA, 1997; Jain et al., 2005 cited in IWCS, 2009). Only in some
cases, owing to higher quality of reclaimed soil due to adoption of a intricate screening system, the
reclaimed soil was used outside the landfill (construction fill) (US EPA, 1997 cited in IWCS, 2009).
Other end uses will be dictated by available markets, the quality of the material, and the regulatory
framework for reuse. According to IWCS (2009),
The issue that would most likely limit the
reuse of mined landfill fines for use outside of the landfill environment would be the
presence of trace chemicals. Given that a large variety of household, commercial, and
industrial waste containing chemicals are disposed of in MSW landfills, the potential impact
of these chemicals on the environment if the mined residues were reused must be
considered. When evaluating the likely chemicals of concern, it should be noted that most
organic chemicals should eventually be biodegraded in the biogeochemical environment of
a landfill (Field et al., 1995; Reinhart and Townsend, 1997; Atuanya et al., 2000; Cohen and
Speitel, 2001). Non-degradable chemicals such as heavy metals, however, will remain in the
waste unless leached out. Several investigations indicate that heavy metals would be
49
retained in the landfill (Belevi and Baccini, 1989; Gould et al., 1990; Finnveden, 1996;
Bozkurt et al., 1999). The concentrations of these chemicals in the mined material would
likely dictate the degree mined residue can be reused outside of the landfill environment.
Once the project plan is prepared, it should be presented to the relevant technical and regulatory
authorities. If the project is deemed feasible, an expanded work plan must be created to address the
material, movement, manpower and machine requirements. The main issues to be addressed in the
expanded work plan are listed below (Salerni, 1995 cited in Joseph et al., 2004):
How much material has to be moved in a day to reach the project goals without exceeding the
budget?
Where in the site will the equipment be placed?
• How will the materials be moved and stockpiled on site?
• How many workers will be needed to accomplish the tasks?
• What training do the workers require?
• What should be done with the wastes/recovered components after digging them up?
• What are the sampling and analysis protocols to determine the quality of excavated material?
7. Economic Feasibility of Landfill Mining
Although a considerable number of studies discuss about economic aspects of landfill mining (e.g.
Cobb and Ruckstuhl, 1988; Savage et al.,1993; Krogmann and Qu, 1997; Bryden, 2000 cited in
Krook et al., 2012), only a few studies (Fisher and Findlay, 1995; Van der Zee et al., 2004; Van
Vossen and Prent, 2011; Van Passel et al., 2013) discuss economics of landfill mining in detail.
Since no mining project is identical to one another due to unique set of site specific conditions and
objectives of each project, a common framework for evaluation of economic feasibility of landfill
mining project is unfounded. Nevertheless, the important findings of different studies reported in
the literature are discussed below:
Van der Zee et al. (2004) proposed an efficient 4 step approach to compare costs and benefits of
landfill mining on one (typically monetary) or on multiple dimensions. First, generally available
information such as region, proximity to highly populated areas, general characteristics (age, type of
landfill) is used as a proxy for the project potential and landfills are either classified as ‘qualified’ or
‘unqualified’ for further analysis. In the next step, site-specific information with the help of experts
is obtained. For the final set of options, a more extensive Multi-Criteria Analysis (MCA) involving
experts as well as stakeholders serve as basis for decision-making. They applied their evaluation
approach to a selected sample of 147 landfills in the Netherlands. By an investment of about
€7,000, they were able to shortlist the number of promising mining projects to two. This approach
made an important contribution to landfill mining economics by identifying costs and incorporating
the economic dimensions. However, a potential shortfall of their study is its reliability on a big
sample of data. Also, due to ownership characteristics, it is also not realistic to assume that a mining
50
company could buy off potential landfills for mining easily (Kruse, 2015). Additionally, Hogland
et al. (2011) pointed out that landfills from mid- 1950s to mid-1990s only would qualify
based on recycling potential as the later landfills would have much smaller recycling
potential due to the initiation of recycling programs. Table 6 lists the costs and benefits of the
landfill project as outlined by Van der Zee et al., (2004).
Van Passel et al. (2013) includes a societal dimension along with the private dimensions, as they
emphasize that landfill mining involves some beneficial societal effects like lower environmental
pollution, restoration of nature and biodiversity or reduced import dependency, all of which can
attract government incentives in favour of landfill mining. All these external societal causes were
incorporated in their Cost-Benefit Analysis (CBA) model into a single monetary dimension.
The comprehensive model generated by Van Passel et al. (2013) includes both Waste-to-Energy
(WtE) and Waste-to-Material (WtM) for maximum valorization of the resource potential. They
evaluated several economic key indicators for economic feasibility of a Landfill Mining project like
the Net Present Value (NPV), the payback time, the Internal Rate of Return (IRR) and
recommended the use of IRR, as it does not involve assumptions about discount rates. The model
inputs were derived from peer-reviewed sources ad Monte-Carlo Simulation is used for determining
the impact of key input factors. They also presented different monetary valuation approaches for the
land regained by conducting LFM project. The analysis showed that efficiency of WtE installations,
the price of CO2-certificates, electricity prices, investment costs of WtE installations,
operational costs of energy production and the support schemes have an important impact on
the economic performance and given adequate support mechanisms, LFM (specifically in Flanders,
Belgium) holds an incentive for private investors.
Table 6 Benefits and costs of reclamation of a landfill (Reproduced from Van der Zee et al., 2004)
Rettenberger (2010) assumes that metals are the only type of material that can be profitably
extracted from landfill mining operations. From this assumption, he concludes that landfill mining is
yet to become a profitable operation, as landfill mining costs amount to at least 30 EUR/m3
51
(including ferrous metals and combustibles sale) whereas the landfill after care costs vary within 5-25
Euro/m3. Hence, costs need to decrease further (e.g reduced gate fee for combustibles) before
landfill mining can become profitable.
Byrden (2000) developed a phase model to evaluate the feasibility of LFM projects, but specifically
for mining wood products from old landfills. He assessed market potential for recyclables, along
with associated transportation and land costs and the potential gains from selling the recovered land
and compared them with the traditional closure costs. The model was applied to two landfills in
Oregon and only one of them was found to be economically viable mainly due to lesser
transportation costs and presence of local market for the favourable one. Bryden (2000) also
recommends to consider the costs incurred by preventing future developments in the occupied land
space while forecasting closure costs.
Fisher and Findlay (1995) suggest landfill mining as an alternative way to reduce or eliminate landfill
after care costs and limit environmental impact. They recommend feasibility assessment to be
conducted in the overall context of solid waste management since landfills differ greatly in their
associated properties. Also, additional benefits such as the reduced landfill footprint and costs of re-
siting the landfill should be contrasted against conventional closure costs (Kruse, 2015).
Van Vossen and Prent (2011) considered a multi-staged model with sequential material separation
steps to investigate the technical and financial feasibility of landfill mining. A hypothetical waste
composition with about 50% soil-to-waste ratio was considered based on composition data of 60
landfill investigation studies. Costs were assigned to every separation step. Cost-Benefit Analysis
(CBA) of both basic scenarios considered (partial separation and full separation, involving separation
of all 14 materials) for a standard landfill (500,000 tons of waste) yields a deficit. Costs for the
partial separation scenario are limited to EUR 17 per ton of waste, while full separation
costs are estimated to be around EUR 45 per ton of waste. Metal sales are able to reduce costs by
8.2% for the full separation scenario and 18% for partial recovery. Van Vossen and Prent (2011)
concluded that prospects for the profitability of landfill mining projects could increase if additional
benefits such as from the re-use of freed landfill space or recycling of plastic can be generated.
Bernhard et al. (2011) conducted a CBA of a landfill mining with an average composition based on
literature data. They assumed the following conditions:
Metal fractions are recovered and recycled
35% of combustible fraction is used as Refuse Derived Fuel (RDF) and 65% disposed off at
an incineration plant.
No on site treatment facility, hence both RDF and waste incineration impose costs.
Remaining materials are re-landfilled onsite.
The net costs generated from the analysis amounted to EUR 16.85 per m3, which varied
considerably from the estimate made by Rettenberger (2010) (EUR 30/m3). Bernhard et al. (2011)
also varied the input parameters to investigate the impact of specific parameters on cost. It is of
interest to note the findings (Bernhard et al., cited in Kruse, 2015):
Even in the case that no combustibles would be present in the landfill, LFM would still be
associated with net costs.
52
LFM would be profitable if the copper content would be 0.4% of the overall landfill (w/w)
or in case the aluminium concentration would be at 1.75%.
Prices for non-ferrous scrap would have to rise by the factor of five compared to
the assumed scenario.
The copper price would need to increase threefold for a LFM project to break even.
Changes in the aluminium price, given the assumptions made, almost have no effect on
overall profitability.
Winterstetter et al. (2015) devised an approach to identify critical factors for the economic feasibility
of the LFM project and assess the profitability of landfill mining. Their approach was distinct as it
included site-specific composition data, the modelling of sorting efficiencies based on data from
state-of-the-art technologies, taking into account the time value of money and the application of
techniques to represent uncertainty regarding input variables within the course of the assessment. By
the use of material flow analysis they aim to identify the recoverable fraction given current
technical possibilities. They also assessed the CO2-balance and associated cashflows, aiming to
represent the societal dimension of the project. They further calculate the NPV of the mining
project (four different scenarios) by using Monte-Carlo simulations to assess the impact of uncertain
input variables on the profitability. However, all investigated scenarios proved to be unprofitable
based on their assumptions (Winterstetter et al.,2015 cited in Kruse, 2015).
According to Krook et al., (2012),
“An overall conclusion in many of the reviewed papers is
that projects solely focusing on recovery of deposited resources from landfills are seldom
economically justified. An exception is an Italian study, presenting a positive cost-benefit
analysis for the recovery of foundry sand and iron fractions from an industrial landfill
(Zanetti and Godio, 2006)”.
The following information stated in RenoSam (2009) provides an insight into the costs of landfill
mining operations:
While the rate of mining with a single piece of processing equipment may be as high as 180
tons/h, typical operation is at a rate of 50 to 150 tons/h. Based on the information developed
by Landfill Mining, Inc. from its operation in the Collier County at 1995 prices, the cost of
landfill mining is expected to be less than about US $10/ton of waste mined. A large amount
of that cost is associated with rental of the processing equipment. The rental fee is typically
between US$16,000 to 19,000/month. For a large scale operating plant in Europe, a cost of $
75-100 per cubic meter was reported (Cossu et al, 1996). The cost of landfill mining at the
Filborna landfill in Sweden in 1994 was US $6.7/ton.
The results of an analysis of the weekly production data, project costs and assets realized
during 1992 and 1993 at the Frey Farm Landfill of Lancaster County show that 33% of the
project costs was associated with excavation and trommeling operations at the landfill.
Transportation of reclaimed waste to the resource recovery facility (RRF) and hauling ash
residue back to the landfill incurred 30% of the cost. The balance of the project costs was
associated with processing fees paid to the landfill mining operator, RRF and landfill host
53
communities. Revenues obtained from the sale of electricity from the RRF and recovered
ferrous metal offset these operating costs and resulted in net revenues of US$ 3.94 for every
ton of reclaimed material delivered to RRF. Additional assets recovered included cover soil
and landfill volume making the overall profit to US$ 13.30 for every ton of material
excavated.
In general, the economics of landfill mining depend on the depth of the waste material and
the ratio of wastes to soil. The deeper the waste is buried, the more expensive it is to reclaim
a landfill, per unit area (Salerni, 1995). In most cases, the presence of hazardous materials
will also affect the economic feasibility. Thus, this step in project planning of analyzing the
economics of landfill mining calls for investigating the following areas:
Current landfill capacity and projected demand
• Projected costs for landfill closure or expansion of the site
Current and projected costs of future liabilities
Projected markets for recycled and recovered materials
Projected value of land reclaimed for other uses.
8. Environmental Impacts of landfill mining
8.1 Literature review on environmental impacts of landfills:
Frandegard et al (2013a) proposed an environmental evaluation method for landfill mining using
Life Cycle Assessment (LCA) and Monte Carlo Simulation (MCS). The method included
considerations around the energy use of the involved processes, the efficiency of material and energy
recovery, and the net emissions. The developed method was used to evaluate three probable
scenarios of landfill mining (remediation only, landfill mining using a mobile plant and landfill
mining using stationery plant with state-of-the art technologies) for four environmental impact
factors: global warming potential, acidification, eutrophication and photochemical exudation. They
used their model to evaluate environmental potential of a landfill site with hypothetical composition.
However, their model can be used to in practice for the following decision areas:
Evaluating strategy potential (e.g. what is the overall potential of landfill mining in a region
or country)
Evaluating multiple landfill mining initiatives (e.g. which of several landfills has the best
environmental potential)
Evaluating a landfill mining initiative with regards to scenario differences (e.g. what should
be done)
Evaluating parameters (e.g. how should it be done) and
Evaluating an already finished project (e.g. what could have been done differently or how
did the outcome correspond to the initial evaluation).
54
However, Frandegard et al (2013a) suggests that even though the model is quite complex with over
330 input parameters, the model can be further improved by validating and analyzing possible
dependencies between different parameters and including more data based on real cases instead of
idealized data from an LCA database.
Additionally, Frandegard et al. (2013b) applies the developed approach as discussed above to
evaluate the resource and climate implications of landfill mining in Sweden. Their study concludes
that Energy recovery of combustibles, along with avoided electricity generation, is a large factor
when establishing the environmental potential of landfill mining and a more fossil-fuelintensive
energy mix tend to increase the avoided GHG emissions. Also, failure to recycle deposited plastic
would increase added emissions significantly as the avoided emissions from replacing virgin plastic
production would simply not occur. In summary, they concluded that based upon scenario, up to 75
million tonnes and 45 million tonnes of GHGs could be avoided using a stationery plant and a
mobile plant respectively and landfill mining may lead to a significant amount of avoided GHGs.
Figure 9 shows the expected value for GHG emissions for different types of processes in the
stationary plant scenario as determined by Frandegard et al. (2013b).
Jain et al.,(2014) identified major environmental impact categories for three scenarios (no mining,
waste relocation (no processing) to lined landfill, and landfill mining with material recovery and
energy production) and performed LCA with operational data from practical landfill mining cases
and Life Cycle Inventory (LCI). The study concluded the following:
The environmental impact of emissions associated with mining (diesel production, use of
mining equipment) was minor relative to environmental emissions associated with the “do
nothing” scenario (no mining).
The global warming potential (GWP) reduction realized by relocating waste was found to be
significant, even when it was assumed that the waste was mined after decomposing in the
landfill for 30 years.
The greatest environmental benefit from the landfill mining process was found to be the
recovery of metal components, which showed a benefit in nearly all impact categories
analyzed. Energy recovery through combustion of mined materials in Waste-to-Energy
(WtE) plants was found to be beneficial, however, in a smaller scale than metal recovery with
recycling.
The conservative assumptions used in the materials transport and reuse cases suggests that
transport distances less than those assumed in this analysis (500 km from the project site)
would provide an even greater environmental benefit.
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Figure 9 Expected value for (a) added and (b) avoided GHG emissions (in million tonnes CO2 equivalents)
for different types of processes in the stationary plant scenario. GHG =greenhouse gas; CO2 =carbon
dioxide. (Reproduced from Frandegard et al. (2013b)
Another LCA study by Hauschild et al.(2008) addressed the long-term impacts from metals and
persistent organic compounds from landfills (Hauschild et al., 2008 cited in Ortner et al.,2014). The
study introduced two new impact categories - the stored ecotoxicity and stored human toxicity of
contaminants remaining in the landfill after a ‘foreseeable’ time period of 100 years. The study
suggested to value long-term emissions of landfill differently from current emissions due to
changing background concentrations in the environment.
It is very important to demonstrate the environmental performance of landfill mining, at least for
the permitting process (Krook et al., 2013). On one hand, landfill mining, if performed optimally,
may lead to significant positive environmental impact. For example, according to Cohen-Rosenthal
(2004),
‘‘a 50 acre(20.3 hectares)landfill might contain as much as 240,000 tons (217,680
metric tons) of steel and 20,000 tons (18,140 metric tons)of aluminium’’
. Recycling such
amounts of metal and subsequently avoiding virgin production, will lead to large energy savings and
avoidance of many kinds of environmental pollution (Ayres, 1997 cited in Krook et al., 2012).
Furthermore, if the combustibles in landfills are used for energy recovery, the benefit is typically
several orders of magnitude larger. However, on the other hand, the extraction, processing,
transportation and recycling of deposited materials during landfill mining will require both material
and energy resources, which might generate significant negative impacts (Krook et al., 2013).
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Feasibility of landfill mining depends significantly on many factors like location, composition and
other site-specific considerations of a particular landfill.
“Some, for example, might contain large
amounts of valuable materials such as metals, almost no hazardous waste and be located
close to waste treatment and recycling plants, while for others the conditions for mining
may not be as favourable. Thus, in order to address the environmental performance of this
new perspective on landfill mining, there is a need for research applying a systems approach
(e.g. Life Cycle Assessment), enabling the balancing of positive and negative impacts taking
place on the local, regional and global scales (cf. Udo de Haes et al., 2000; Finnveden and
Moberg, 2005). Therefore, developing standardized frameworks for evaluating critical
factors for performance of different kinds of landfill mining initiatives is an essential
research challenge for facilitating implementation of this promising, but so far largely
theoretical strategy”
(Krook et al., 2012).
The positive and negative impacts of landfill are discussed in details in the next sections.
8.2 Positive Environmental Impacts of LFM:
8.2.1 Removal of potential source of pollution:
Landfill Mining prevents the possibility of leachate migration to groundwater/ surface water and
fugitive greenhouse gas emission to the atmosphere. Lateral gas migration may induce vegetation
stress, odour and risk to the human health, although landfill mining is expected to be conducted
after waste stabilization (Ford et al.,2013).
8.2.2 Liner installation/retrofitting and removing hazardous material:
Liner and leachate collection system can be installed in the old cells where not previously installed.
Already installed systems can be repaired. Also, since the definition of hazardous and special wastes
(e.g tyre in MSW landfill is banned in some states) have changed over time, hazardous wastes can be
relocated and effectively managed to reduce risk of contamination (Ford et al.,2013).
8.2.3 Landfill Capacity Extension:
Landfill mining extends the life of a landfill not only through re-use of the recovered space, but also
by recovering void spaces developed within the compacted waste due to degradation and uneven
settlement. Apart from commercial benefit discussed above, the environmental benefits include
avoiding impacts associated with the development of a new landfill such as material consumption,
material transportation, energy required in construction and potential impact of a new development
upon the local environment.
8.2.4 Soil reclamation:
Data from previous studies show that about half of the excavated material from the landfill is soil.
This reclaimed soil can be used as daily cover material (avoided cost and transportation impacts) or
off-site uses (earning revenue and offsetting virgin material use), depending on the quality of
reclaimed soil and existence of local market.
8.2.5 Energy production:
Combustible wastes can be thermally processed (WtE), reducing reliance on fossil fuels.
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8.2.6 Material Recycling
Recycling of valuable components like steel, aluminium, plastics etc. can reduce impact on the raw
materials for virgin material production.
8.2.7 Freeing-up land for other uses:
Landfill mining will lead to financial savings in long term management and the owners of the landfill
can be benefitted from easier permit surrender. From the environmental point of view, re-use of the
landfill will remove the burden of development elsewhere (Ford et al.,2013).
8.3 Negative Environmental Impacts of Landfill
8.3.1 Hazardous waste management
Hazardous wastes may be uncovered during landfill mining. The historical disposal data, if available,
could help predict the amount and location of these wastes and can help greatly during the planning
of landfill mining. A hazardous waste management plan should be in place before implementing
landfill mining operations. Management may include (Ford et al.,2013):
Development of appropriate human health and environmental risk assessments.
Development of management plans, including planning for the unknown, e.g. exposure of a
waste that was not anticipated.
Training of staff.
Provision of appropriate personal protective equipment (PPE) for site workers.
Provision of appropriate set-aside areas and appropriate containers for storage of waste.
Provision of migration barriers for dust and potentially windblown material, which could
include measures such as water mists/sprays, screens and netting.
Provision for re-interment of certain wastes elsewhere on the landfill where their exposure
presents an immediate risk, e.g. provision for the rapid re-interment of asbestos containing
wastes.
Nature and extent of hazardous wastes may substantially affect the cost and efficiency of landfill
mining and in extreme cases, may also prevent the landfill mining operation to take place (Ford et
al.,2013).
8.3.2 Release of Landfill gas and odor
Methane and other gases (hydrogen sulphide etc.), generated as a result of decomposition, are
trapped into the waste and may cause explosion, fires, odour and fatal health risks to human health.
To minimize such risks, landfill mining projects are generally undertaken on stabilized waste,
typically over 25 years old (Ford et al.,2013). However, the explosive limits of methane is generally
between 5 to 15%, whereas landfill gas is generally 50-60% methane, varying on the age and
composition of deposited waste (Ford et al.,2013). The gas released from the old waste is rapidly
diluted in the open air, but the risk of gas build up and subsequent explosion in <