Landfill mining - analysis of possibilities and limitations

Project in Industrial Ecology
-
Landfill Mining
Analysis of possibilities and limitations
_________________________________________________________________________________
Author: Paolo Fornaseri
Supervisor: Monika Olsson
________________________________________________________________________________
Abstract
Starting from the actual problems related to landfilling, the possible remediation methods are briefly
listed and the landfill mining approach (LFM) is analysed in detail, talking about opportunities and
risks, process and procedures, quality of recovered materials and possible uses, outcomes, planning
aspects, and critical issues. The gathered information is then used to depict the typical decision-
making frame related to the remediation of landfills. Cost-Benefit Analysis (CBA) and Risk
Assessment are described as examples of useful tools in these situations, in order to meet the needs
of the municipalities and take into account the threat to the environment, constituted mainly by
contamination of groundwater. Taking into account the information needed by the decision-makers,
some useful techniques for monitoring landfills and to evaluate the landfill composition are then
described. Finally the LFM approach is introduced in a broader picture to support the need of deep
changes in the waste management system in order to avoid completely landfilling and further
problems.

2
Table of Contents
1. Aims and Objectives of the project..................................................................................................3
2. Introduction – Why should we care about wastes?..........................................................................3
Always throwing something away...................................................................................................3
Reducing the Resources and Threating the Environment................................................................3
3. A brief history of waste management: from ocean dumping to landfilling.....................................3
General Characteristics of Landfills ................................................................................................3
How Landfills should be – The Sustainability Dream.....................................................................4
How Landfills are – Far from the Dream.........................................................................................4
4. Reclamation of Landfills – Solutions for Critical Situations...........................................................4
Passive methods...............................................................................................................................4
Active methods ................................................................................................................................4
5. The Landfill Mining Approach........................................................................................................5
Opportunities....................................................................................................................................5
Risks.................................................................................................................................................5
Process .............................................................................................................................................6
Quality of Recovered Materials and Possible Uses .........................................................................7
Planning ...........................................................................................................................................8
Limitations and Barriers – How to convince the stakeholders?.......................................................8
6. Information needed for decision-making and available tools..........................................................9
Characterization of the Decision Frame...........................................................................................9
Most Important Environmental Aspects ........................................................................................10
Helpful Tools for Decision-Making...............................................................................................11
7. Techniques for analysing landfills .................................................................................................12
Techniques for Monitoring ............................................................................................................12
Techniques to evaluate the Landfill Composition .........................................................................12
8. Discussion......................................................................................................................................14
9. Conclusion .....................................................................................................................................14
10. References....................................................................................................................................15

3
1. Aim of the project
The main goal of this project is to evaluate the Landfill Mining approach as one of the possible
reclamation methods for critical landfills. Hence the problem of landfilling and of its consequences
is described. From this starting point, the landfill mining is discussed from the point of view of
results for the environment, economic convenience and feasibility.
2. Introduction – Why should we care about wastes?
Always throwing something away
Each day, each person, directly or indirectly, with consciousness or not, is producing wastes. It is
not just something about the things that we are actually throwing away in a precise moment in time,
the paper coffee cup, the plastic spoon, the packaging for the milk, the box for the washing machine
powder. Even considering a durable good, a mobile phone for instance, we know that, sooner or
later, we will get rid of it, again producing waste.
Reducing the Resources and Threating the Environment
The linear flow of materials, from extraction to disposal, without appropriate reuse or recycling, is
constantly depleting the available resources. The most common practices diffused worldwide to
manage wastes, that are landfilling and incineration, transform the materials in a nature that makes
them almost useless, and sometimes poisoning for the environment. Considering the waste-to-
energy alternative, the burning of this refuse-derived fuel RDF is polluting the air, and the residual
ashes must be stored properly because of their toxicity. On the other side landfilling is occupying
huge volumes of land, and the mixing of all the wastes in a close system can have unpredictable
consequences. For example the geomembrane used to contain wastes in landfills can be damaged or
lose its characteristics over time. This can eventually result in leaks of leachate that are
tremendously dangerous for the groundwater for the high concentration of contaminants present in
leachate.
3. A brief history of waste management: from ocean dumping to
landfilling
Until the beginning of the twentieth century wastes were still treated in a very rustic way, just trying
to hide them somehow in the earth or in the sea (Vesilind, et al., 2002). However nowadays waste
management is a very complex subject. Each country has its own policy and rules are becoming
always stricter.
At first this approach was necessary in order to find the “right” spaces to store all the wastes. One of
the first examples of landfilling can be found in California, where in 1935 a sort of big hole in the
ground was used as landfill. The fact that today this site is considered by the U.S. Environmental
Protection Agency (EPA) very dangerous for its content (highly hazardous materials) it is a sign
that there wasn’t a great regard for what was buried in these first landfills (Vesilind, et al., 2002).
Currently waste disposal directives take into account the high level of risk related to landfills, in
consequence of the awareness acquired in the past. However the waste management is still very far
from the “state of the art”.
General Characteristics of Landfills
In a landfill heterogeneous materials are put together. Usually there are almost no data about the
specific composition of a landfill, but considering the results of previous studies, an average

4
composition can be presumed. About three fourth of these materials are organic, and the main part
of this organic matter is biodegradable (Vesilend, 2002).
After an initial phase of relative quietness, the conditions in this particular ecosystem change and
promote biochemical decomposition. This, in addition to precipitations percolating through waste,
results in production of leachate and gases.
How Landfills should be – The Sustainability Dream
In a sustainable landfill the waste materials are treated in a way that avoids the risk of pollution into
the surrounding environment. Converting this definition in more technical terms, it means that the
emissions and the accumulation of dangerous substances in the landfill must reach safe levels
within 20-30 years (Cossu, 2010). And in this period proper barriers must avoid the contamination
by these pollutants of the nearby territory, isolating this big and not easily controllable bioreactor.
How Landfills are – Far from the Dream
Unluckily landfills, above all old ones, cannot be defined sustainable. The highest values of
concentrations of pollutants are usually reached in the first 5 years after the landfilling. However,
the reactions are lasting much more, and averaging the information obtained from the available
literature, after 30 years the equilibrium with the environment is not reached yet. (Scharff, 2006)
The dynamic of the landfill depends on a lot of factors (surrounding environment, climate, landfill
management, waste nature, barriers) and even with a good design of landfills, even using good
barriers to isolate this peculiar environment from the surrounding, it is almost impossible to avoid
groundwater contamination by leachate. (Vesilind, et al., 2002)
In the recent past, relying on the properties of the materials employed in the barriers, some landfills
were sited in delicate points, where the geological barriers are not so strong or nearly absent (Cossu,
2010). However, these artificial barriers are not lasting forever, and after a few decades or even less,
they are not preventing pollution of groundwater by leachate anymore (Lee, 2009).
Hence, even with a good planning, a landfill will be for a long time a potential source of danger.
The situation must be always kept under control and big operations might be necessary, even
reclamation ones, in order to preserve the environment and the health of the inhabitants living close
to the landfills. (Cossu, 2010)
4. Reclamation of Landfills – Solutions for Critical Situations
There are different types of reclamation, with different specific objectives. However, the main goal
is to lower the environmental impact of landfills. These operations are very expensive and complex
but they are needed when the emissions of the landfills are over the permitted levels.
Passive methods
These techniques try to improve the isolation of the landfill ecosystem. They are called passive
because no intervention is done on the wastes. They are just confined in a better way, with surface
caps to limit gas emissions and infiltration of storm water, or lateral/fund barriers. Hence it is not a
definitive solution and the landfill must be monitored continuously.
Active methods
These techniques have the goal of stabilizing or eventually removing the source of pollution.
Stabilizing means fasten the reactions in the landfill injecting oxygen in it. This method is called
“Airflow” and it could be the phase prior to “Landfill Mining” (LFM) that consists in digging out
all the materials in the landfill and treat them in order to reduce their impact in the long term.
(Cossu, 2010)

5
5.The Landfill Mining Approach
The Landfill Mining method consists in transforming a repository of materials, which is constantly
threatening the environment for the kind of substances released, in a mine, with the goal of both
removing all the sources of danger and exploiting it as source of materials.
Opportunities
The main advantages of the LFM technique are listed here.
Avoiding further risks of contamination of the environment
The passive reclamation methods are not definitive. For example a surface cap will just
delay the problem in time, slowing the reactions that are happening in the landfill. The risk
of leaks of gases and leachate is anyway present (Cossu, 2010).
With the LFM all the materials are removed and hence the threat is eliminated permanently.
Recover of materials than can be recycled
Usually raw materials are obtained from ores. This is a process that requires a lot of energy.
Hence the landfill mining can compete with the extraction from ores. Sometimes the
concentration of some metals is higher in a landfill than in the correspondent ores
(aluminium in bauxite). The recycling of some materials like iron is quite convenient
because of the low level of pre-processing needed. Moreover the separator plants are already
part of normal equipment of landfills (magnetic separator in the case of iron).
Recover of materials with a significant heat value
Materials as paper, plastic, wood, that can be used as combustible in waste-to-energy power
plants. This is because the recycling of these materials is usually not convenient (huge costs
for preparing these materials to be recycled).
Permanent solution, zeroing of post-closure and monitoring costs
Even considering that part of the wastes must be landfilled again (the portion that has no
other uses), these wastes will be stable and even with percolation there will be no risk of
water contamination. Therefore the costs related to the maintenance of the landfill are
almost eliminated.
Recover of land
If the landfill is completely remediated, the land can be used again for each kind of activity.
Otherwise, the recovered volume can be used to landfill other wastes following the
procedures for a sustainable landfilling.
Risks
The operations are quite complex, both for the heterogeneity of the materials contained and for the
reactions on-going in the landfill. In fact, digging in the landfill means removing the waste-cover
materials that are isolating the core of the landfills where the reactions are happening. The
consequent release of the gases produced in the environment in an uncontrolled way could result in
pollution and high levels of odour.
Mechanical Instability of Wastes
While a lot of materials (plastic, paper, textures and metals) are giving to the body of the
landfill a good structure, allowing quite deep excavations, the heterogeneity can hide weak
parts, empty zones filled by liquids and gases.

6
Presence of Biogas
In the anoxic landfill environment the wastes degrade anaerobically. These reactions end in
the production of methane and carbon dioxide. This represents a risk for workers because of
the risk of explosions, and on a larger scale, it can increase the level of pollution of the area
(odour, greenhouse gases).
Hazardous wastes
Old landfills, which were settled and filled before a stricter regulation was implemented,
could contain hazardous wastes. (Cossu, 2010)
In general these conditions create a quite dangerous environment both for the workers and for the
people living nearby the landfill. Hence this activity must be well planned and the site must have
specific characteristics to be treated in this way.
Process
Analysis prior to the Operations
Before starting an operation of this level, highly expensive and complex, it is necessary to
gather information to help the process of decision-making. This information will be useful
for example in a Cost-Benefit Analysis (CBA) that is comparing the landfill mining project
with other ones of the same relevance at the municipal, provincial or regional level (usually
the central government is setting general norms and goals but the procedures are decided at
local levels). Even if an intervention is urgent (e.g. for problems of water contamination),
the landfill and the surroundings must be analysed deeply in order to understand if the LFM
could be a good solution, and eventually plan the activity itself.
“Airflow” Pre-treatment
The stabilization of the wastes through in situ aeration (the Italian patent Airflow by Spinoff
company is one example) has been proven to work very well, resulting in levels of
emissions during the landfill mining operations five times lower than the ones during normal
landfill operations (Cossu, 2010).
Digging Operations
The excavations are executed as commonly. However it is very important to investigate in
advance the area to be dug, to individuate possible leachate deposits that could be dangerous
during the operations. Cone Penetration Tests (CPT) can be executed (McKnight, 2005)
even if their efficiency has been proved to be quite low in this field (Olayiwola, 2010).
Moreover some samples of waste must be analysed to check to level of stability achieved
after the “Airflow” pre-treatment. If, after these tests, areas with common characteristics are
identified, the digging operations could be organized in order to excavate sequentially the
similar areas, to facilitate then the management (easier if wastes are more homogeneous) of
the extracted wastes. The additional information is very useful also in the planning of the
next step that is the treatment of recovered materials, above all to choose the separation
methods.
Usually the landfill is subdivided in modules. This organization is helpful in planning the
excavation activities and in managing data. The size of the modules is chosen taking into
account the quantity of wastes that can be processed during one day of operations. After
having concluded the intervention on one module, the walls of the nearby modules must be
protected temporarily in order to preserve the integrity of the next modules to dig. (Cossu,
2010)

7
Treatment of Recovered Materials
Using the information gathered from the previous analysis, the separation of wastes must be
carefully planned in order to reach the highest level of efficiency.
The fractions that can be obtained are:
 Light, with high heat value (plastic, fabric and paper);
 Heavy (glass, stones and wood);
 Metals;
 Fine fraction;
 Not recoverable.
The separation techniques are mainly based on screening with sieves with different mesh
sizes, followed by a magnetic separator for iron and a screening based on density to separate
heavy and light fraction.
The separation plant can be similar to the ones normally used for separation of new wastes
(figure 1).
Rough Sieve
Fine Sieve
Magnetic
Separator
Air Classifier
Iron
Manual Sorting
of Not
Processable
Fractions
Fine Fraction
(Soil)
RDF
Light
Fraction
Sub
Separator
Heavy Fraction
Inerts
MSW dug
Wood, Fabric
Figure 1 – Structure of a Separation Plant for Mined Wastes
Quality of Recovered Materials and Possible Uses
Metals
The ferrous fraction is easily recoverable. This is because the magnetic separators are quite
effective, and this facility is present nowadays in almost all the separation plants for waste.
For the non-ferrous fraction it is not possible to rely on the magnetic property. However
eddy current separators could be used with good results (Sunk, 2006).
Light and Coarse Fraction
Composed mainly by paper, cardboard, wood, fabric and plastic, is easily separable from the
rest with sieves with large opening. This fraction is characterized by a high heat value (in
average 8-10 MJ/kg) and hence it could be used as combustible (RDF, Refuse Derived Fuel)
in waste-to-energy plants. In some cases the heat value is even too high, and to lower it, part
of the plastic fraction can be removed, washed and recycled. However it is unlikely that this
last way of proceeding would be worthy considering the costs and the benefits. (Cossu,
2010)

8
Fine Fraction
It is the fraction that passes through small opening sieves (mesh size 20-60mm). If the
treatment facility of the landfill used a shredder, this fine fraction can be even the 65-70%
(Rettenberger, 2011) of the total weight (not of the total volume since the density of this
fraction is quite high). The reuse of this fraction is quite critical since the heat value is quite
low (2-4 MJ/kg) and the high content of heavy metals precludes its use as fertilizer, despite
this fraction is usually mainly organic. However this portion can be used as cover material
for further landfilling. Moreover, it could be added to the light fraction in waste-to-energy
application to reduce the heat value when too high (Cossu, 2010).
Inert Materials
Stones and glass are the main components of the heavy fraction. They can be separated with
techniques that select using the density difference. Then the glass can be broken to obtain a
finer fraction to be separated from the rest with sieves.
Residual Fraction
This fraction must be landfilled again. However it can be compacted to very high density,
requiring then less space than in the pre-treatment condition. In addition, even if landfilled,
this portion is not problematic in the long term because of the low content of contaminants.
Planning
It is evident now how a good planning is needed because of the complexity of the operations.
The following can be considered a “to do” list before proceeding with LFM:
 Recognize the possible environmental impacts of the operations;
 Organize the different compartments for the intervention;
 Define the time of the operations;
 Identify the machines needed for (i) excavations, (ii) transport, (iii) treatment of wastes and
the number of workers;
 Assess the possible risks for workers to set adequate safety procedures;
 Estimate the amount of materials belonging to the different categories previously defined;
 Make a Cost-Benefit Analysis (CBA) and a Full Costing Accounting (FCA) to be aware of
costs and forecast possible profit for the operations (information needed for the decision-
makers);
 Consider the legislation.
Limitations and Barriers – How to convince the stakeholders?
As always the market prices of resources are driving the behaviour of companies, and
municipalities will take in consideration this option just in case of an evidently problematic landfill
site.
The most problematic part is the one that regards the supply of information for the decision-making.
The landfill mining, for its complexity and its costs, cannot be executed for all the landfills, at least
not for the moment. Hence the most relevant sites should be identified. The main reasons for which
a site can be considered as relevant are:
 The landfill is a potential threat for environment;
 The landfill is an important source of materials.
But a common sense evaluation is not enough for the decision-makers. A lot of parameters must be
taken into account, and at this stage some Environmental System Analysis tools can be useful.

9
6. Information needed for decision-making and available tools
Characterization of the Decision Frame
Societal level
Usually the waste management is a subject in which the local governments have to make
their own decisions in order to fulfil national or international legislation. In Europe the
European Union decides a policy with specific goals, but the local governments have to
decide how to reach the proposed targets (e.g. Directive 2008/98/EC of the European
Parliament). The companies are nearly neglected, while a better cooperation could be
helpful.
Type of Problem
As outlined before, the problem is multifaceted, and requires a trade-off among
environmental effectiveness, cost efficiency and social acceptance.
Spatial Extension
The spatial extension depends on the degree of broadness that you want to introduce in the
study. Considering a certain landfill, the boundaries could be set just around it. However,
considering the possible water contamination, the boundaries must be extended until where
the polluted stream arrives. In addition, landfills are known for odour problems, and the
daily operations produce also noise and dust. Hence the borders should be set considering
this aspect too. Going further, in case of LFM, a lot of other facilities would be affected, for
instance the separation plants and likely also other landfills for the storage of the not
recoverable fractions.
Besides this, considering the life cycle of a landfill and not just its remediation, the whole
area served by this landfill should be considered, since the waste production, collection and
treatment influence deeply the characteristics of the landfill. And this, in addition to the
structure of the landfill itself, will affect the need in the future of remediation actions.
Time Boundaries
Landfills, once set up, are designed to be there forever, and they need constant monitoring.
The effects of a bad design can last for a long time and even rise after a very long time. And
even more when you are talking about sustainability, the time spans are always very large.
Therefore the time boundaries are in the order of magnitude of decades. This will however
increase the uncertainties and the reliability of the study. Eventually the depicted picture
suggests remaining on the conservative side for all the operations in order to lower the risks.
Participants in the Decision Procedure
Since the key decision-makers are the local governments, usually for this kind of activities
the public opinion is very important, above all the one of the people living close to these
facilities.
Concerns and Priorities
The need of intervention is driven mainly by environmental issues. When the environmental
problem is impending, the decision must be fast in order to avoid further worsening.
However, with the increasing prices of raw materials, landfills could become more and more
attractive as source of materials.
Moreover, the problems that are arising could suggest a change in the planning of future
waste management activities. The concern here is about the whole process, starting from the
production of products that then will become partly or completely wastes to be disposed.

10
Criteria for the Evaluation of the Environmental Decision
When the issue is urgent, the effectiveness on the environmental side is the main driver, and
even short term solutions can be preferred to long term ones if faster in the application. In
other cases all the other aspects mentioned before must be taken into account.
Most Important Environmental Aspects
Energy use
To each type of intervention (actually even for the non-intervention) an energy use is
correlated. In the case of LFM, energy use by the machines involved in the operations, from
stabilizing, digging and transporting to separating and treating wastes must be considered.
And if the machines used are in addition to the ones used for normal landfill operations, also
the energy use for building these machines should be added to the total.
On the other side some energy could be also recovered from the extraction of biogas (if the
landfill is treated as bioreactor) or from the combustion in e-waste plants of the high heat
value fraction recovered from landfills.
Resource use
Here the account of all resources should lead to a negative balance, thanks to the recovering
of materials during the intervention.
Land use
Landfills are reducing the availability of land and are compromising its use in a huge
timescale. The different intervention options impact the land use in different ways, both for
quantity and quality of land. In fact not just the volume used should be considered, but also
the level of terrestrial eco-toxicity.
Water Quality
In function of the risk of leakages of leachate, water quality is one of the most important
environmental aspects (Rong, 2009). The parameters that must be considered are numerous
(and almost all of them are affected by landfill leachate), starting from the more evident
ones, like taste and odour, to the ones for which a physical or chemical assessment is
needed:
 Biological oxygen demand (BOD);
 Chemical oxygen demand (COD);
 Total organic carbon (TOC);
 Total suspended solids (TSS) and total dissolved solids (TDS);
 Heavy metals;
 pH.
These are just some of the parameters that are affecting the water quality and aquatic eco-
toxicity. For example for water streams influenced by landfills, one of the most important is
the BOD that is a measure of the quantity of oxygen required by microorganisms to
decompose organic waste. If this value is too high, the oxygen dissolved in water decreases,
affecting all the organisms living in aquatic environments (Boguski, 2009).
Air Quality
The air quality is affected both by landfill in normal conditions and by remediation
operations. The anaerobic digestion leads to the production of methane and carbon dioxide.
These are the so called greenhouse gases that affect the global warming. On the other side
the LFM, with the digging operations is increasing consistently the level of dusts. (Cossu,
2010)

11
Aesthetic
As already highlighted, landfills represent a big aesthetic problem, from the point of view of
odour, noise, and landscape.
All these environmental impacts affect directly the health of humans and of ecosystems.
Concentrating the attention on LFM, while reducing the effects on health in the short and long term
on the population, the operations could affect negatively the health of the workers engaged.
Helpful Tools for Decision-Making
One of the methods that is widely used in this field is the Cost-Benefit Analysis (CBA). In fact,
correlated to the environmental issue, limited budgets are available. Hence a cost-effective solution
in the short term could be preferred to the optimal one for the environment. This analysis could be
carried out for the different remediation options. Since the “to do nothing” option is taken in
account too, a Risk Assessment should be realized in order to know also the risks of just monitoring
passively the potential threats.
Example of CBA for LFM
In table 1 the most valuable elements for a LFM action are listed
Costs Benefits
 Preparation Work
 Construction of Plants (if needed)
 Landfill area for not recoverable
materials
 Environmental Permit
 Excavation
 Transport on-site
 Transport off-site
 Separation
 Re-use freed landfill capacity
 Re-use landfill area for urban development
 Selling of recovered materials
 Energy recovery from incineration
 Avoided aftercare costs
 Definitive solving of environmental issue
Table 1 (Van Vossen, 2011) – Costs and Benefits for a LFM intervention
The evaluation of all these aspects from an economic point of view is rather not easy. The
degree of uncertainty is very high, above all for the benefits part. The revenues that come
from use of recovered materials cannot be foreseen adequately before. In fact the actual
landfill content will be known just after the digging. This affects also the planning of the
activities, and the required equipment for separation.
Risk Assessment (probabilistic assessment of landfill remediation costs)
Since the landfill management involves many uncertainties, a Risk Assessment can be
useful to be aware of potential losses. To these potential losses, a magnitude and a
probability must be assigned in order to carry out the analysis. In the case of landfills, the
potential losses are the ones related to possible failures in the system and remediation
actions that are required after. In this way it is possible to forecast at a certain level of
confidence (usually 95%) the cost that are related to these remediation activities (Boone,
2011). And the result of these analyses can be used again in a CBA for the landfill mining
case, since with the LFM approach, these future risks are avoided.

12
7. Techniques for analysing landfills
As we have seen, costs and complexity are not the only obstacles. Uncertainty of information is a
tremendous issue that brings the risk of this operation to very high level. The only way to improve
the performances of actions is trying to improve the quality of information.
Techniques for Monitoring
The biggest threat for the environment caused by landfills is underground, that is water
contamination by leachate. This could be consequence of a failure of the membrane used to isolate
the landfill environment from the surroundings. Some methods for monitoring this danger are here
presented.
Analysis of Water Quality
A good practice is to analyse constantly the water quality of the streams that could be
affected by the landfill. If anomalous values are registered, with a statistical consistency, at
least the population can be alerted (Kenyon, 1997). However the happening of this event
means that the pollutants are already spread in a wide zone. A good design of landfills
would suggest siting these facilities as far as possible from water streams. If the water has
already been contaminated, this means that the soil is contaminated too because the
contaminants have to travel through this soil. The analyses of water are hence a necessary
check, but it would be preferable to have techniques to detect these failures in advance.
Environmental Modelling
Knowing the characteristics of the soil that encircles the landfill, it could be interesting to
model the effect of any leak in the surroundings, above all to have some clues about the
possible time spans. The information acquired in this way could be useful for a risk
assessment.
Geoelectrical Monitoring System (GMS)
In some recent landfills a particular system has been installed to check constantly the
integrity of the geomembrane. A grid of electrodes is able to measure constantly the
resistivity in the different areas of the liner. The geomembrane has a very high resistivity if
compared with soil and waste. Hence an increase in potential indicates the presence of a
failure in the liner. (RMC, 2007)
This technique seems to be very effective. However it does not work on existent landfills.
Ground Penetrating Radar (GPR)
This technique itself cannot be so powerful for the study of landfills because of the
randomness in the composition. However, implementing this method with other ones based
on acoustical, electrical, magnetic principles could be a cost-effective solution to detect
contaminant plumes beneath the body of the landfill (Pipan, 2000). The very good point of
this method is that it can be applied on each landfill.
Techniques to evaluate the Landfill Composition
In addition to the monitoring of the landfills that could evidence the need of a remediation activity,
information about landfill content must be supplied to the decision-makers in order to be able to do
a reliable CBA. Measuring of waste composition is a big issue even in everyday waste management
operations.

13
Input Method
For national average waste composition, the input method represents an efficient and quite
effective technique. It relies on data from published industry production statistics. In fact,
above all for particular subsets of production with a short life-cycle, most of the things
produced will become sooner or later waste. (Vesilend, 2002)
However the outcome of this technique, as stated at the beginning, is a national average that
does not truly represent the average waste composition at all the local levels. And even at
the national level the result of this analysis must be valued critically because of import and
export activities. Moreover it is very likely that for the past years the availability of data is
not matching the requirements for this kind of analysis.
Manual Sampling
Before starting the mining activity, some small portions of the landfill can be dug, and the
recovered wastes can be examined manually, and the different identified fractions can be
weighed. However it is very difficult to have from a few samples a statistical significance.
The content of the landfill is not homogeneous, and in each area, at each depth, the quality
of the wastes could have a great degree of variability. In addition to this aspect, also the
necessity of manually sampling these wastes can be a threat for the health of the operators.
(Vesilend, 2002)
Photogrammetry
To avoid health problems, the analysis of photographs of waste disposed on a flat surface
can substitute the manual sampling (Vesilend, 2002). However this technique is time
consuming, and its results, already not very good for “fresh” wastes, could be not consistent
for mined wastes, for the difficulty in recognizing the type of waste just from a photograph.
In table 2 the fractions mined during a LFM operation in Austria are shown. In the left part of the
table there is the forecasted composition while on the right part the measured composition after the
mining.
Prior Investigation
(according to invitation to bid)
Clearing
(according to ARGE clearing)
Actual
cleared mass
Waste fraction Volume
(1000 m3
)
Mass
(1000 t)
Waste fraction Mass
(1000 t)
(% of prior
investigation)
Composting
material 185 167
Composting material
Pure fraction
Mixed fraction
414
190
360
Aluminium dross
28 40
Aluminium dross
Pure fraction
Mixed fraction
29
34
160
Light fraction
Plastic + textiles 187 + 26 192
Light fraction
Plastic + textiles
Household waste
109
51
80
Mineral
Rubble,
gravel,
covering material
47
100
32
311
Mineral
Rubble,
gravel,
covering material
52 15
No category 32 0 -
Sum 641 750 Sum 880 120
Toxic waste, barrels 400 pcs. Toxic waste, barrels 5059 pcs. 1265
Table 2 (Sarsby, 2001) – Comparison between forecasted and actual quantities of wastes during a LFM operation

14
Eventually it is evident the unreliability of all these methods. At the moment it seems that there is
no easy and cost-efficient way to know the composition of landfills a posteriori.
Nevertheless, a more refined “input method” with a complex management of data, based not only
on the production but also on the distribution of produced goods, could lead to interesting results. A
model can be built and then calibrated using data from already mined landfills. Further research is
needed in this field.
8. Discussion
The degree of uncertainty and complexity depict a challenging situation, in which it is very difficult
to provide good information for the decision-makers. It is even hard to understand if this solution is
good from an environmental point of view. The threat for the environment is removed, but a lot of
energy must be used for the whole process. Then, if we take into account the risks for the workers,
the need of setting new plants, to build new machines, the situation becomes even worse.
On the other side, the landfills must be monitored continuously and the level of experience is not
high enough to be sure that they will not give problems in the very long term since we are
landfilling from a relatively short period. For sure the main outcome of this study is that landfilling
is not the long term solution for the management of wastes. Or at least, not the kind of landfilling
that still nowadays is going on in a lot of countries. The mixing of materials makes future
interventions very problematic, from the point of view of planning and realization.
Hence, from the last point discussed, comes up the topic of cooperation among all the stakeholders,
in order to try to avoid the necessity of remediation actions in the future. The costs of waste
management are already very high at the moment of landfilling. Additional costs for monitoring or
even for remediation are not welcome by the municipalities. However, to solve these problems,
acting on the waste management side is not enough. The challenges in this subject are consequence
of stochastic inputs and rather not well-organized process. For example, the lack of a strict policy
on the production side regarding packaging lead to confusion for the consumers. The situation is
then worsened by the absence of a standardized system for the collection. The rules change among
the different municipalities and even in function of the delegated waste collection company. The
outcomes of this situation are unpredictable and always variable wastes, for which an efficient
separation system is difficult to organize or is not even possible. It is appreciable the effort of
certain local governments to treat this randomness, but each system eventually represents a big
sophistication compared with the initial issue. In a lot of countries for example the incineration
nowadays represents one of the biggest slices of this undesirable cake. It is questionable though the
goodness of this choice in the long term. A renovation of the whole process, trying to change
completely the actual perspective (couldn’t be avoided a big amount of wastes just with a small
effort?) could lead to a global reduction of energy and materials, besides the reduction of pollution.
This reasoning is not supported by explicit data (even if the actual degree of complexity suggests
that there should be something wrong), but this is the direction that the next studies should take.
9. Conclusion
After having analysed the LFM approach, it is hard to judge precisely the value of this method. This
is mainly because there are not effective methods to determine the content of a landfill before the
operations. Hence a CBA is seldom useful for the decision-making. In addition there is a list of
issues to deal with:
 High energy use during the operations;
 New plants might be needed for sorting and recycling;
 The need of landfill areas is not eliminated completely;

15
 Dangerous conditions for workers.
Therefore it is very unlikely that a municipality would attempt to solve the problems of its landfills
with the considered approach since the risk, above all on the economic side, would be definitely too
high. Moreover, the difficulties for the reclamation of landfills suggest avoiding completely the
landfilling in the future.
10. References
Boguski, T. (2009). Landfills and Biochemical Oxygen Demand. Manhattan: Kansas State
University.
Boone, S. (2011). Probabilistic Assessment of Landfill Remediation Costs. CSVA 2011 Conference.
Toronto, Ontario.
Cossu, R. S. (2010). Sviluppo di un progetto di Landfill Mining - Rapporto Intermedio. Padova:
Regione Lombardia.
Kenyon, T. (1997, November 1). Landfills: Statistical Analysis Saves Landfills Compliance
Headaches. Accessed the 10th
december 2011 from Waste360:
http://waste360.com/mag/waste_landfills_statistical_analysis
Lee, G. (2009). Assessment of Engineered Waste Containment Barriers. Washington DC: National
Research Council of the National Academies.
McKnight, T. (2005). Engineering Properties and Cone Penetration Testing of MSW to predict
Landfill settlement. Gainesville: University of Florida.
Olayiwola, A. (2010). Ground Investigation into the Hydro-Geotechnical Characteristics of a
Municipal Waste Fill using static Cone Penetration Tests. Research Journal of Applied
Sciences, Engineering and Technology 2 (5), 466-475.
Pipan, M. F. (2000). Metodi Geofisici Integrati per la Caratterizzazione non invasiva di discariche
e siti contaminati. Trieste: Exploration Geophysics Group.
Rettenberger, G. (2011). Landfill Mining - New Developments in Waste Management. Nanyang
Technological University, Singapore: Ingenieurgruppe RUK.
RMC. (2007). Geoelectrical Monitoring System - GMS. Accessed the 15th
november 2011 from
RMC srl: http://www.rmcsrl.it/english/gms_ing.pdf
Rong, L. (2009). Management of Landfill Leachate. Tampere: University of Applied Sciences.
Sarsby, R. M. (2001). The exploitation of natural resources and the consequences. Green 3 : the 3rd
International Symposium on Geotechnics Related to the European Environment (p. 201).
Berlin: Heron Quay, London.
Scharff, H. (2006). Ideas and Intensions of the Dutch sustainable landfill programme. 1566 ZG
Assendelft, The Netherlands: NV Afvalzorg Holding.
Sunk, W. (2006). Increasing the Quantity and Quality of Metals Recovered at Waste-to-Energy
Facilities. Tampa, FL: Earth Engineering Center, Columbia University.
Van Vossen, W. P. (2011). Feasibility Study Sustainable Material and Energy Recovery from
Landfills in Europe. Thirteenth International Waste Management and Landfill Symposium.
Sardinia: Royal Hasknoning, The Netherlands.
Vesilend, P. W. (2002). Solid Waste Engineering. USA: Brooks/Cole.
Wikipedia. (2010). Accessed the 16th
october 2011: http://en.wikipedia.org/wiki/Landfill_mining

Landfill mining - analysis of possibilities and limitations

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Landfill mining - analysis of possibilities and limitations

Similar to Landfill mining - analysis of possibilities and limitations (20)

Recently uploaded

Recently uploaded (20)

Landfill mining - analysis of possibilities and limitations