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.

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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

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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

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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)

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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.

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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)

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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 SieveMagnetic Separator

Air Classifier

Iron

Manual Sorting of Not

Processable Fractions

Fine Fraction (Soil)

RDFLight

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)

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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.

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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.

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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)

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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.

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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.

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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

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