Vecka 3

Question 1

Describe the principle of TSAAD and explain advantages compared to anaerobic degradation in a typical landfill containing organic waste.

Answer 1

TSAAD - Two-Step AnAerobic Degradation
The method is not used that much.
Step 1: food waste turns acid, high organic concentrations. Step 2: waste that is already in methanogenic state, are happy to have degradable material, produces gas. Metals are trapped in this step.
The leachate is strong and then goes to the second step and produce gas.
Advantages: The leachate will turn into gas instead of going into leachate treatment. Metals are trapped in the second step, and therefore it is not as much in the leachate going out.
Possible advantages of TSAAD over conventional landfilling were summarised by Lagerkvist as:
- No or minimal methane emission from the landfill to the atmosphere during acidogenic degradation.
- Formation of methane can be controlled – both with regard to where and when it should be formed. In addition, the production rate can be varied when desired.
- Many hazardous compounds are mobilised during the acidogenic conditions and are degraded or fixed during methanogenic conditions. This makes it possible to liberate large waste volume from a share of its most harmful constituents and to concentrate these in a smaller volume.
The waste is placed in a cell where intense acidogenic conditions are promoted, chiefly through moisture addition and the minimisation of air contact. The development of a methanogenic microflora is under these conditions suppressed by a low pH and high volatile acid concentration. In parallel, a volume stable methanogenic conditions is established. Because the main substrate of MSW cell is used as the second step, a reasonable volume may be about 1/!0 of the acidogenic cell. Another alternative is to use high-rate reactors for the methanogenic step, in which case further volume reduction is possible

Question 2

Briefly describe the different degradation phases occuring in a landfill containing biodegradable waste.

Answer 2

Acidogenic and methanogenic.
Aerobic and anaerobic degradation.
The biological degradation starts already before the waste is collected and it continues in the landfill. To begin with aerobic degradation processes will dominate, but when the oxygen brought into the landfill with the waste has been consumed, anaerobic degradation processes will dominate. Anaerobic degradation proceeds in several steps.
- Hydrolysis: Large organic molecules are converted into smaller, soluble molecules such as short chain fatty acids, simple sugars and amino acids.
- Acidogenesis: The hydrolysed compounds are converted by bacteria into organic acids and alcohols. These are further degraded to smaller compounds. As a result, the pH decreases. The gas formed in this stage contains mainly CO¬2 and little H2.
- Methanogenesis: Organic acids, formed in the acidogenic stage, are converted into CH4 and CO2. An important intermediate as acetate since methanogens can only consume 1- and 2-C-compounds. Methane generation may start within a few months but may also take several years. Methanogens are more sensitive to sudden changes in their environment than the acidogens, e.g., oxygen may poison methanogens.

Question 3

The aerobic, acidogenic and methanogenic degradation states are three characterstic degradation states of landfilled organic waste that are controlled by biological degradation processes. How do they affect leachate quantity and quality?

Answer 3

Leachate quantity and quality lecture, graphs with the different states and the composition of gas, leachate etc.
COD is higher in acid phase and than decreases in the transition phase to stable methane phase.
pH increases where the highest pH is in the end of acid phase and than decreases in the stable methane phase.
NH4+ increases and has a peak in the acid phase but then is quite stable in the transition phase with a slow decrease to the methane phase.
SO42- is high in the aerobic phase, than increases to the peak in the acid phase. It then “drastically” decreases in the transition phase, hitting “bottom” and then doesn’t really exist in the methane phase.
Cl has a steady decrease from the beginning to the end.
HCO3- increases from the acid phase to the methane phase were it is the highest.
Zn, Fe has it’s highest peaks in the acid phase to then decrease in the transition phase to be “non existent” in the methane phase.
From examination questions and example answers:
- Aerobic phase: high degradation rate leads to compaction and high temperatures lead to drought, thus some leachate will be pressed out of the material, but in small amounts with high concentrations.
- Acidogenic phase:  high organic content (BOD, COD, BOD/COD >0.4), low pH and alkalinity, high concentrations of most metals. Leachate volumes are reduced slightly by hydrolysis but are much higher than during aerobic degradation.
- Methanogenic phase:  low organic content (BOD, COD, BOD/COD <0.2), immobilization of metals in the waste matrix,… water loss in gas yields similar leachate volumes as during acidogenic degradation.

Question 4

Discuss advantages of using ratios of variables e.g., BOD/COD, N/P, CH4/CO2 compared to using each variable separetly. When would you use what (ratio or single)?

Answer 4

BOD/COD, indicates the percentage of organic matter that is biologically degradable.
N/P, changes with degradation state since the mobilisation of P is much lower under methanogenic conditions than in acidogenic. E.g., in experiments where the biodegradable fraction of MSW was treated acidogenically and methanogenically, the ratios were 5 and 0.14 respectively.
CH4/CO2, expresses the methane content of the biogas. This indicates what types of substrate the gas is generated from, or may indicate the type of biological process in which the gas has been generated or converted (CH4/(CH4+CO2).
Single: if you want to know the concentration

Question 5

You are responsible for the operations of a landfill receiving large amounts of easilty degradable organic material. If you want to avoid the acidogenic degradation phase, what strategy can be used to achieve this?

Answer 5

Leachate quantity and quality, slide with the 0.5 compost layer
Pre-treated layer in the bottom takes care of the nasty leachate and produces gas instead.
Pre-treated, but no place or so. What can you do in the landfill? Fråga Amorina vad hon svarade. Put a compost in the bottom, it takes care of the leachate from the “new” waste on top and produces methane.

Question 6

Argue for separates treatment of municipal wastewater and landfill leachate.

Answer 6

Since the volumes of leachate from the landfill can vary throughout the year (seasonal changes etc) it is not always suitable for the leachate to go into the wastewater plant. There are also sometimes other elements in the leachate that the wastewater plant is not “used to” handle/treat, which means that some elements can go to the recipient when it shouldn’t. Also, one argument is that landfills are often not close to cities, which also wastewater plants are, but they are often not as close, which means that the leachate from the landfill must be pumped through pipes long distances.
From the lecture:
- Effects often poor
- Variation in flow and quality (seasonal, precipitations & irrigation events)  equalisation basins
- Differences in quality: higher contents of COD, AOX, N (NH4), metals (Fe, Mn) and salts; lower amounts of P and particles; dependency on degradation phases
From examination questions and example answers:
Basic considerations for the choice of leachate treatment:
- Flexibility with regard to leachate quantity and quality
- minimization of all rest products
- Avoid to add extra substances like flocculants, precipitants
- Compliance with current and future regulations (e.g. discharge limits)
- Conformance and compatibility with secondary or extensive treatment steps
- Technical and economical feasibility
Co-treatment with municipal wastewater:
- Effects often poor; treatment in the MWW plant is not designed for (methanogenic) landfill leachate
- Variation in flow and quality (seasonal, precipitations & irrigation events). Can be solved with equalisation basins
- Differences in quality
- Higher COD, AOX, N (NH4), metals (Fe, Mn), salts
- Lower P
- Less particles
- Dependency on degradation phases (pH, concentrations, …)

Question 7

Why is it important to make analyses immediately after sampling?

Answer 7

• Vissa bakterier Kanske trivs I miljön
• Saker kan oxidera
• Volatila substanser kan försvinna
  Leachate quantity and quality “changes in redox potential, pH, and suspended solids for leachate stored in closed bottles at 5oC.
  Conductivity may decrease as well as COD. The turbidity increases. The redox potential increases with time as well as the suspended solids (SS). The pH looks quite stable but with a slight increase after some time to then decrease

Question 8

In what ways can nitrogen be reduced in leachates?

Answer 8

Three general possibilities:
1. Incorporation into the biomass (micro-organisms or higher plants)  area and time extensive, season dependent
2. Oxidation of NH4+ to NO3- with subsequent reduction to N2 (N/DEN)  demand of energy, reducing agent, time, area; sensitive micro-organisms (N)
3. Anammox = anaerobic ammonium oxidation, carried out by a group of planctomycete bacteria: NH4+ + NO2- -  N2 + H2O

Question 9

A natural treatment system consists of three active parts. Name them and briefly describe the function of each part.

Answer 9

Soil particles –> filtration, retention
Soil organisms –> biodegradation (C) and transformation (N)
Plants –> incorporation, filtration, carbon source, surfaces for bacteria, wind protection, O2 source below water surface due to photosynthesis etc.

Question 10

What are the main pathways for carbin during aerobic and anaerobic waste degradation?

Answer 10

Split the landfill in the possible phases.
In aerobic degradation- CO2 is produced and water. Quite strong leachate. Main part is the gas phase.
In anaerobic degradation- Acidogenic: leachate; Methanogenic: LFG
From examination questions and example answers:
Aerobic: CO2 and biomass
Acidogenic: leachate
Methanogenic: LFG

Question 11

Explain why landfills may emit material?

Answer 11

Not a closed system. Reactions, such as gas, dissolution (rainwater gets polluted), diffusion.
If it is not mechanically stable, landslides can happen.
From examination questions and example answers:
There are several drivers of landfill emissions, some of the more important are
- Concentration gradients between the landfill and its surroundings
- Reactivity if the waste – chemical energy within the material, which can power reactions and phase changes.
- Fluxes of liquid or gases in the environment that may pass the landfill or part of it.
- Gradients of potential energy ca cause slides.

Question 12

Why does the leaching of lead decrease when the degradation state of a landfill shift from acidogenic to methanogenic conditions?

Answer 12

In acidogenic conditions there is more Pb than in methanogenic conditions. This can be explained by in the acidogenic state, there is lower pH, which makes the Pb more mobile (?). If considering Pb to behave in the same way as Zn and Fe in a landfill, then there is more of the element in the acidogenic state than in the methanogenic state since there is an increase of pH when the landfill goes to methanogenic state.
From examination questions and example answers:
- The pH increases
- The pe decreases and sulphide complexes may be formed
- Organic complexing agents are degraded

Question 13

The BOD/COD ratio of a leachate is often used to characterize the degradation state of a landfill:
- What do the abbrevations stand for?
- What is the relevance of a quotient in the range of 0.05-0.1 regarding the degradation processes in landfills and the consequences regarding leachate treatment?

Answer 13

The BOD/COD ratio can describe if the landfill is in methanogenic or acidogenic state. If it is between 0.05-0.1 it means that the landfill is in methanogenic state, which means that there is methane is increasing. What that means is that there could be less amount of dissolved metals and more particles in the leachate. The pH is higher than in the acidogenic state.
From examination questions and example answers:
- Biological/chemical oxygen demand
- Methanogenic degradation
- Basically hardly degradable organic matter, moderate-low metal content, etc –> difficult with biological treatment, poor effects if co-treatment with municipal solid waste water, etc

Question 14

Name and briefly describe three decisive (important) factors for the amount of leachate that can be expected from a landfill. When in the lifetime of a landfill can you expect most leachate?

Answer 14

The most amount of leachate is expected in the middle of the lifetime of a landfill. This is because the waste in the water must be saturated before it could start to “leak”.
Important factors: L/S ratio, how much water comes in (leachate quality: decisive factors for leachate quantity), groundwater pressure. Technical measures, how is it covered, how is the cover designed. No liquid waste to landfills. When do have more leachate?

From examination questions and example answers:
- Climate
- Landfill geometry
- Cover materials and design
- Waste properties (humidity, permeability)
- Degradation state
- Bottom liner & collection systems
- Operation … leachate recirculation

Question 15

During aerobic degradation the share of the substrate that goes into new biomass is up to about 40%, yielding a BOD/COD of 0.6. If you see a BOD/COD of 0.1, what can that mean?

Answer 15

Aerobic biodegradability cannot be larger than 0.6, because aerobic degradation has a 40% cell yield.
Low ratio, hard to degrade substrate.
It could also be a nice degradation but there is something hindering the degradation process, it could be toxins and chemicals (affects on BOD). COD in the lab, strong oxidising agent, so even Fe and other stuff not organic that gets oxidised.

From examination questions and example answers:
- The organic material is not readily biologically degradable, but oxidizable
- There are non-organic components in the material, which consume chemical oxidant
- Something is affecting the BOD-assay, e.g. toxicity

Question 16

Why does aerobic pre-treatment before landfilling promote a faster establishment of methanogenesis?

Answer 16

Decomposing of org. matter releases acids. These acids later create the acidogenic conditions in the landfill. When starting the decomposing earlier with pre-treatment, there is not as many acids produced, leading to a faster establishment to methanogenic state in the landfill.

From examination questions and example answers:
- Because easily degradable material is degraded during pre-treatment which otherwise would have formed organic acids and alcohols, thus lowered the pH (acidogenic degradation) and prevented the development of archae (methanogens).
- There are anaerobic niches in the waste also during composting, and anaerobic biota can develop there and thus a higher concentration of anaerobic microorganisms will be available at the onset of anaerobe conditions.

Question 17

Why is it that gas permeability in a landfill is higher in the horizontal direction than in the vertical?

Answer 17

The waste is in layers. The layers overlap which makes the vertical permeability harder than going in the horizontal direction.

From examination questions and example answers:
Because compaction and intermediate covers area applied horizontal or at least more horizontal than vertical and settlements tends to bring objects such as plastic bags to a more horizontal orientation (settlements are not lateral but vertical).

Question 18

Name two different methods for dividing a sample into representative sub samples. Explain one of them.

Answer 18

Riffle splitter
Coning and quartering
Spinning table…

Question 19

What constituents/pollutants occur typically in landfill leachate and must be treated? Choose among:
- Nitrogen/ammonium
- Suspended solids
- Fe and Mn
- Salts
- P
- COD

Answer 19

Nitrogen/ammonium, Fe and Mn (compared to waste water), salts, COD
P, landfills are often poor in P.
Suspended solids are “filtered” away in the landfill, it works as a big filter.

Question 20

LFG is often assumed to contain 50% CH4 and 50% CO2
- Is this a reasonable assumption?
- Will it change over time?
Motivate your choice with respect to the waste composition, the degradation products of different organic compounds, and the landfill conditions at the time of collection.

Answer 20

Yes, it is a reasonable assumption, the methane varies between 30-60 volume % in LFG. The composition changes over time. The composition depends on what type of waste that has been landfilled.
According to Lale:
No, can’t assume it.
Biogas formation- degradation processes: Complex organic compounds (fat, protein, carbohydrates), Simpler compounds (amino acids, fatty acids, sugar), Intermediates (VFA, alcohols), Acetic acid, CO2 and H2, Biogas (CH4 and CO2).
Higher alcohols, waxes, and higher fats 65-75% CH4
Lower fatty acids, glycerine 55-70% CH4
Protein 50% CH4
Carbohydrates, lactic acid, acetic acid 50% CH4
Citric acid 35-40% CH4
Formic acid 25% CH4
From examination questions and example answers:
No. LFG is not the same as biogas. Landfill gas is a mixture of gases from three main sources:
1. Biogas from the degradation of biopolymers in landfilled wastes.
2. Atmospheric air that is landfilled with the waste or enters the landfill and/or the LFG collection system
3. Gases or vapours from landfilled materials, e.g. vinyl chloride from PVC (compare table 8.2 compendium) and water vapour (due to increases temperature)
Yes, it changes over time. The lFG composition depends on the waste composition and the type of organic matter. For example, waste that mainly contains of carbohydrates or proteins will generate a biogas containing about 50% CH4 and 50% CO2. But for waste containing more fat, fatty acids or higher alcohols, the gas contain as much as 70% CH4 and only 30% CO2.
The landfill conditions at the time of collection influence the LFG composition, since acidogenic and methanogenic degradation yield different gaseous products.
For example, at the beginning of the methanogeneous activity, there is a very low methane content and a high carbon dioxide content. Due to higher solubility of CO2 in water, methane content ca be higher in very wet landfills. The heterogeneity of waste is also a source of LFG composition variation (difference between two distant samples in one landfill). The composition if LFG in older landfills can vary considerably. Atmospheric air can enter in the landfill and with the oxygen from the air, methane can be oxidized, which results in a reduction of the ratio CH4/CO2.

Question 21

Describe in principle how one can determine the methane oxidation potential of a material in the laboratory. What do you have to do and how do you express the result?

Answer 21

The methane oxidation potential can be determined in a laboratory using a setup consisting of closed glass bottles with a bit of waste in them, some water so that the waste us saturated and then oxygen and methane/carbon dioxide. The gas will be measured throughout the experiment until there is no more gas in the bottle.
The result is expressed in g/kg TS on the y-axis and then there is time in days on the x-axis.

From examination questions and example answers:
Methane oxidation ca be measured by the drop in pressure resulting of the reaction
CH4 + 2 O2  CO2 + 2 H2O
Methane oxidation consumes three molecules of gas, while only one molecule of gas is produced, and therefore a decrease in pressure occurs.
Apart from the oxidation, also the assimilation of methane into cell carbon results in a pressure drop, since two molecules of gas are consumed and none produced
CH4 + O2  CHOH(s) + H2O
Add material (soil, waste), water and oxygen in closed bottle. Note the weight of everything. Add known amount/volume of CH4. Measure (with a syringe) and record the decrease in pressure over time. Add more CH4 until the pressure keeps stable.
The consumed methane is then calculated and the potential is expressed in gram or litre CH4 per gram of dry solids or per gram of volatile solids of the input material.

Question 22

Why are clays suitable as liner materials in landfill construction?

Answer 22

Clays has very low permeability, which means that leakage of leachate through the liner takes a longer time than if the material had a high permeability.

From examination questions and example answers:
- Low hydraulic conductivity (permeability)
- Ability to sorb and retain chemical compounds

Question 23

What is CEC and why is it important for a contaminant transport in soil?

Answer 23

CEC- the amount of cations a soil can hold.
The soil can therefore hold cations, which contaminants often are, and therefore “store” the contaminants. If the CEC is high, there are more contaminants that can “settle” and therefore not pollute the leachate. If the CEC is low, it cannot store as much contaminants as a soil with high CEC and therefore pollute the leachate more.
Low pH, anions can be adsorbed
High pH, cations can be adsorbed.

From examination questions and example answers:
Cation exchange capacity – the amount of cations a soil can hold. Clay particles provide surface for adsorption of cations (positively charged ions, metals).

Question 24

Explain how the hydraulic gradient influences contaminant transport in soil. What happens to the contaminant spread when the hydraulic gradient is equal to 0?

Answer 24

Look at the sketch.
If the hydraulic gradient is high, water on/in the landfill will flow quicker than if the hydraulic gradient is lower.
If the hydraulic gradient is almost equal to 0, this means that there is not really a slope and the waterflow is low. In the landfill, water then has a longer time getting exposed to the waste and therefore can get more contaminated. On the landfill, the water also takes a longer time to run off which means that more water can infiltrate and maybe even affect the liner (which could break).
Contaminants in soil, flow, diffusion, if no hydraulic gradient diffusion is the driving force for contaminant spread.
When it’s zero there is no water transport.
If zero, than it’s dry, you don’t have a spread of contaminants.

From examination questions and example answers:
The hydraulic gradient is a loss in pressure head per distance unit in the direction of the flow. The higher the hydraulic gradient, the higher the water and contaminant movement through the soil. If the hydraulic gradient equals to zero, the velocity of the water is zero. At i=0, contaminant spread is diffusion driven.

Question 25

Explain why landfill top covers are often made of material with very low permeability.
- How does it affect the waste degradation in the landfill?
- Discuss the sustainability of such covers for landfill management in a long-term perspective.

Answer 25

Covers are often impermeable because the amount of water going into the landfill decreases the amount of leachate. The main functions of a landfill cover are to:
- Isolation of the waste and protection of the environment
- Reduce water infiltration and store water
- Reduce gas emission and support gas collection
- Recultivation of the landfill area (restoration/remediation)
Sustainability: If the top cover is completely sealed, then there might be so that the degradation processes stop due to lack of air and water. When the liner breaks, all of the processes can start again, and this could happen when we don’t have monitoring of the landfill any longer so we can have emissions and so

Question 26

Why do you need a highly permeable drainage layer?

Answer 26

The drainage layer drains the cover layer and facilitates lateral run-off, it prevents from desiccation of the liner and reduces the leachate generation up to 75%. It is also needed so that the barrier layer is protected from the hydraulic pressure if there was no drainage. The drainage layer also takes away the water so that the soil on top doesn’t get to saturated and there is a landslide.
You don’t want to have air in the drainage layer, you don’t want to add oxygen, it will be attractive for the plant roots if there is oxygen in the layers. And you don’t want roots.
Not so much load on the liner. If the pipes are close, they help draining. If more slap and same distance, less water will be drained.

From examination questions and example answers:
- To create a capillary break so that the liner will not dry and crack
- Remove/minimize the water table (head) on top of the liner in order to support the function of the liner
- Avoid over-saturation of the protection layer above including e.g., a risk for slope slide
- Decrease the motivation for plant root intrusion

Question 27

Name three different barrier materials that can be used for sealing of bottom and/or the surface of a landfill. Describe advantages and disadvantages of the chosen materials.

Answer 27

Natural: clay minerals, ex. bentonite, silty soil
Synthetic: geomembranes, bentonite/textile
Secondary: fly ash, bottom ash, steel slag, waste from pulp and paper industry, sewage sludge

Question 28

How would you design a cover constrution for a municipal landfill? Describe the different layers and their function.

Answer 28

From the bottom:
Gas drainage and foundation layer- collects the gas that is produced in the landfill and makes the surface more even. “Foundation for the cover system, allow gas drainage, gives final shape of the landfill.”
Barrier layer, liner- a nearly impermeable layer that prevents gas from leaking out and from water getting in. “Prevention of water infiltration and gas leakage.”
Drainage layer- collects the water that goes through the vegetation and protection layer and prevents the barrier layer to break due to hydraulic pressure. “Drains the cover layer and facilitates lateral run-off, prevention of desiccation of the liner, reduction in leachate generation of up to 75%.”
Protection layer- protects the barrier layer from getting injured by roots, freezing, drying and so on. “Water storage, protection of the liner from penetration by plant roots and burrowing animals, protection of the underlying layers from desiccation and freezing as well as excessive wetting-drying cycles.”
Vegetation layer- a layer that hopefully does not have trees (roots!) but has other vegetation to prevent the whole cover from eroding. The vegetation layer also helps with the water since it functions as a storage for it and “increases” the evaporation. “Revegetation goals: visual improvement, allow plant growth, erosion control, increase evaporation.”
From examination questions and example answers:
0.3 m vegetation layer- plant colonization, water magazine, protection against erosion
> 1.5 m protection layer- water magazine, protection against desiccation, freezing, root penetration, erosion of the layers below
0.5-5 mm geomembrane- layer separation
0.4 m drainage layer- collection and discharge of percolation water, prevent water standing on liner
0.5-5 mm geomembrane
> 1 m barrier layer, liner- minimize gas and water transport
0.5-5 mm geomembrane
> 0.5 m gas drainage, foundation layer- surface adjustment, load distribution, gas transport

Question 29

How would you design a bottom construction for a municipal landfill? Describe the different layers and their function.

Answer 29

Geological barrier- should be for hazardous waste > 5 m, and K < 110-9 m/s; and for non-hazardous waste > 1 m, and K < 110-9 m/s; and for inert waste > 1 m, K < 1*10-7 m/s. It could also be an artificial established geological barrier and that should be no less than 0.5 m thick.
Bottom liner- additionally to the geological barrier, landfills must be equipped with an artificial liner and a drainage system for the collection of leachates during operation and aftercare.

Question 30

What is landfill aftercare?

Answer 30

Recultivation
Gas- and leachate collection and treatment
Reduction of the emission potential by several technologies
Afteruse of the landfill site
“… as longs as the competent authority considers that a landfill is likely to cause a hazard to the environment…, the operator of the site shall be responsible for monitoring and analysing landfill gas and leachate… and groundwater regime in the vicinity of the site…” EU Landfill Directive (CEC, 1999) Art. 13 (d).

Question 31

What is meant by performance-based aftercare?

Answer 31

I början är den aktiv man renar lakvatten och tar hand om gas och har koll på deponin.
Med tiden gör man mindre, typ kollar så att saker är stabila
I slutet ska den kunna sköta sig själv, ska räcka med att man är där någon gång per år för att säkerställa att allt ser bra ut

Question 32

Discuss sustainability with regards to landfill aftercare.

Answer 32

• Applied to landfilling this would mean that each generation must take care of its own waste. Assuming that one generation corresponds to a period of 30-50 years, this implies that no active environmental measures should be necessary at a landfill after that. At that point in time, the impact of the unattended landfill on the environment should be acceptable, i.e., the waste should have reached “final storage quality” (FSQ).
• The definition of an “acceptable” impact on the environment is still subject to discussion.
• Setting aside funds for future generations to manage the waste landfilled today alone does not qualify as sustainable landfilling. The waste of the landfill must be treated and operated by the generation that has produced the waste in a manner that ensures an acceptable environmental impact within an appropriate timeframe.
• Sustainability of landfilling involves not only the landfill itself, but the whole waste management system: Landfilling should be viewed in a lifecycle analysis perspective, taking all impacts of pre-treatment, operation, and aftercare into consideration, and all the resources spent to achieve a certain future impact level at a landfill should be evaluated.
• A too rigid and general interpretation of sustainability may lead to excessive environmental burdens in meeting the criteria, and the decision to pass from active to passive environmental protection measures should be based on site-specific impact assessments and on actual monitoring of the site.

Question 33

Name two landfill post-closure activities.

Answer 33

• Gas production, quality, and emissions (above and below ground, on top of the landfill and in the surrounding areas)
• Leachate amount and quality
• Surface water amount and quality
• Ground water levels and quality up- and downstream
• Settlements
• Weather – temperature, precipitation, wind, …
• Instruments
  Conclusions regarding:
• Degradation state (degree of stabilisation) of the waste and remaining potential
• Functionality of the collection systems and barriers
• Need for action

Question 34

How may landfills affect the global warming?

Answer 34

Landfills may emit methane. Methane is a worse greenhouse gas than CO2. The LFG often gets burned and releases CO2, which also is a greenhouse gas.
You remove organic matter in the ground instead of burning it, so it won’t get released into the air.
If you have a very good methane oxidation potential, the leakage of methane can get reduced. If the conditions are very good, then the bacteria also can take some from the air.

From Examination questions and example answers:
Landfills may increase or decrease global warming in different ways, such as:
- Methane emissions may increase it
- Methane oxidation occurring in the top layer may decrease global warming
- Landfills are carbon sinks since some of the landfilled carbon stays in the landfill
- Landfilling is a waste disposal option with fairly low energy demand