Landfill gas is produced through the anaerobic decomposition of organic waste in landfills. It consists primarily of methane and carbon dioxide. The production of landfill gas depends on factors like the type and moisture of waste, temperature, pH levels, and the exclusion of oxygen. Landfill gas can be harvested and used to generate electricity but must be treated to remove contaminants first. While a source of renewable energy, uncaptured landfill gas is a potent greenhouse gas, so its proper collection and use provides environmental benefits.

1. Production of LFG,
Conditions for gas
production,
Quality, Quantity,
Gas Yield
and Energy Value
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2. Source of Landfill Gas
Municipal Solid Waste (MSW) is
deposited in the Landfill, preferably
in a Sanitary Landfill, with bottom
lining, capping, leachate and LFG,
well-field management and highly
trained staff.
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3. Anaerobic decomposition of MSW
• MSW contains different carbon-compounds
• A part of it is degradable organic carbon DOC
• Every ton of MSW (household waste) may
contain 150 to 200kg of DOC
• Also it contains water as waste moisture and
rain water
• Bacteria degrades in a natural way the organic
carbon (nutrients) in combination with moisture
• Under anaerobic conditions Methane bacteria
produce LFG, mainly containing CH4 and CO2
LFG is produced by bacterial decomposition
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4. Anaerobic decomposition in Landfill
Transformation of organic
matter into LFG in steps:
1) Hydrolysis and
Fermentation
2) Acetogenesis
3) Methanogenesis
Strictly under anaerobic
conditions to LFG with
~60%CH4+ ~ 40%CO2
and H2O
Hydrolysis and Fermentation
Acetogenesis
Methanogenesis, pH 6.5 to 8.0
H2, CO2Acetate
Fatty Acids (VFAs),
Amino acids, Sugars
CH4 , CO2 , H2O
Organic material
Proteine, Carbohydrates, Fats
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5. Anaerobic decomposition of MSW
• Anaerobic conditions, means strictly under exclusion of
Air / Oxygen
• Methanisation is sensitive to pH-value of the leachate,
condition between pH6.5 and pH8 are necessary
• Temperature is a critical element, optimally 35 to 55°C
• Limitation of toxic substances such as heavy metals,
Chlorinated and Fluorinated compounds, detergents, etc.
• When conditions are not fulfilled, then the methane
production will slow down and may even stop
Conditions for successful methanisation are:
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6. The 5 phases of Landfills life
Generation of LFG
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7. Native Landfill Gas
When Gas produced in the Landfill is not extracted
by a pumping system, then we say it is Native
Landfill Gas.
 Methane CH4 up to 60 %
 Carbon dioxide CO2 up to 40 %
 Nitrogen N2 <2 %
 Oxygen O2 0 %
In “young” Landfills, temperature in the waste body
can be as high as 50..60°C
Typically composed of:
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8.  Methane CH4 40 - 50 %
 Carbon dioxide CO2 35 - 45 %
 Nitrogen N2 5 - 15 %
 Oxygen O2 0 - 3 %
 The gas is saturated with water vapour (moisture)
- at 40°C as much as 50gH2O/m3
LFG
- cooling to 10°C containing 10gH2O/m3
LFG
- condensation occurs of 40gH2O/m3
LFG
On the other hand when Landfill Gas is extracted
steadily by a degassing plant, then the
composition changes:
Characteristic of LFG
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9.  Hydrogen sulphide H2S 100 - 500 mg/m3
 Mercaptane (e.g CHnSH) << (very little)
 Chlorinated compounds HCI 20 - 100 mg/m3
 Fluorinated (e.g. Freons) FI 10 - 50 mg/m3
 Polyaromatic Hydrocarbons PAHs 0 - 50 mg/m3
(or BTEX: Benzene, Toluene, Xylene)
 Siloxane (Silicone compounds) 0 - 50 mg/m3
Trace substances in LFG
Landfill Gas usually trace substances which are
harmful to equipment and environment, like:
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10. Facts of O2 in LFG
When extracting gas from the Landfill O2 is
usually available in more or less quantities !
• When the gas extraction is done correctly, low
concentrations of O2 less then 2 % can be
considered as normal, safety is granted
• O2 concentrations of near 3% are indicator for a
malfunction of the gas extraction, the system is
still safe but corrective measures are to be done
• When O2 is reaching 6%, then a potential
danger of explosion is given. In such a case
safety of the system is not any more fulfilled!
This is a potentially dangerous situation!
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11. • Gas piping is damaged (mechanically)
• Gas wellhead is damaged or bent
• Bad sealing of wellhead, clay filling dried out
• Bad landfill cover, fissures washed out by rain
• Hydraulic seals of gas system are faulty
• Aspiration of air through leachate system
• Suction at the gas wells too strong, “overpull”
• Incorrect operation of the gas plant, wrong
regulation of flow/pressure at the gas wells
O2 is present in LFG because:
Reasons for having O2 in LFG
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12. Issues from Siloxane
In gas engines, siloxanes
are oxidised to silicon
dioxide forming solid, hard
and abrasive crystals.
SiO2 will deposit on cylinders,
pistons and valves. Engine
maintenance will rise abruptly and
often cause breakdown of the
engine. Many cases of destroyed
engines are known! 12

13. Other harmful matter in LFG
 Condensate water
 Dust
 Solid particles like
sand, stones, plastic
chips, etc.
Furthermore Landfill Gas will carry along other
matter hindering and damaging components, like:
A degassing plant need to be outfitted with
Pre-Dewatering unit
Gas Filter Unit
at the entry of the gas station! 13

14. Gas pre-dewatering and filtering
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15. Favourable to gas production
Household waste (MSW), with much moisture 15

16. Favourable to gas production
Plastic bags must be tear open! 16

17. Favourable to gas production
Spreading and compacting the waste 17

18. Favourable to gas production
After smashing with compactor 18

19. Favourable to gas production
Garden and park waste, decomposable 19

20. Favourable to gas production
Food waste 20

21. Favourable to gas production
Overripe fruits, a full load of melons (unusual) 21

22. Inhibitors to LFG production
Wood is organic matter but will not produce gas! 22

23. Inhibitors to LFG production
Industrial waste, plastics, metals, no gas at all! 23

24. Inhibitors to LFG production
Building rubble, concrete blocks 24

25. Harmful and toxic waste
All this kind of waste is toxic and harmful to
humans and environment and should never be
deposited in a Landfill!
 Pressurised cans containing residual propellant
 Freon, i.e. from disposed fridges
 Batteries of any kind
 Chemical stuff or components containing them
 Hospital and medical waste
 Waste containing radioactive traces (?)
Can be for example:
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26. Duties of Landfill Owners
• LFG is continuously generated in a Landfill
• Gas escapes into the atmosphere when landfill
is under pressure, polluting the environment
• CH4 contributes 21 times more to the
greenhouse effect than CO2, is therefore harmful
to the environment
• LFG contains traces of hazardous components
• Can create potentially explosive mix with air
• LFG must therefore be collected and disposed
safely with thermal treatment
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27. Benefits for Landfill Owners
LFG also provide advantages and benefits:
• LFG has a energetical value of 4..5kWh/m3
• Electricity can be generated and supplied into grid
• Can be fired into boilers for production of hot
water, steam, hot air, etc.
• Make CNG / LNG as vehicle fuel
• Excess gas will be safely disposed HT Flares, for
the safeguard of our environment
• Every Landfill should therefore be outfitted with
a good functioning gas extraction plant
and with gas utilisation facilities! 27

28. Depending largely from conditions on site:
How much LFG from MSW?
 Type of waste disposal: waste dump or sanitary
landfill (engineered landfill)?
 Composition of waste: mainly household waste
with 150..220 kg/to DOC, or inert matter?
 Age of waste and disposing time?
 Wet waste or dry waste?
 Water table / water pockets in the landfill?
 Well field management, maintenance, measuring,
and regulation of the gas wells done?
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29.  Landfill with: 1’000’000 tons MSW
 Filling period: 10 years
 Peak gas extraction: 1’000 m3/h
 Long term gas yield: 400 m3/h
(over 10 years)
 Energy content of 400m3/h: ~2’000 kWh
 Electricity production: ~750 kWel
(during a period of 10 years)
“Rule of thumb”
 1 Mio tons of waste to produce 0,75 MW or
 1.3 Mio tons waste to produce 1 MW 29

30. LFG forecasting (calculation)
LFG production can be calculated with the help of
a tool basing on a mathematical FOD model:
 Is the first step to get knowledge of the gas yield
 Input data need to be collected accurately and
reality-close in order to make a gas calculation
 Wrong input data will end in wrong results!
 An on-site survey by an experienced person
capable to gather all relevant data and
information is necessary
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31. Example of LFG forecasting
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32. We recommend to consolidate the forecasting by
doing a Gas Pumping Trial in an advanced stage
• The GPT is used to validate the gas forecasting for the
particular year of the Gas Pumping Trial (GPT)
• By mean of a mobile degassing plant with flare, LFG will be
extracted according to a site tailored methodology
• Dynamic gas quality and quantity are regularly measured
for a period in order to determine the steady state gas yield
• The results of the GPT will be compared to the gas
calculation for the particular year of the pumping trial, to
constrain the future forecast
• The gas yield can be better predicted for the future, relying
on calculations and on field exploration
Consolidation of gas forecasting
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33. Thanks for your attention!
Feel free to ask questions and add
comments.
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35. Annoyances of LFG
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