1. Progress Meeting - Rennes - November 2001 1 LANDFILL MODEL SPECIFICATIONS Fifth Framework Program Progress meeting Rennes, November 27-29, 2001 Progress meeting Rennes, November 27-29, 2001

2. Progress Meeting - Rennes - November 2001 2 Landfill modelling Aim of work Methodology What is a landfill ? Models specifications Conclusions Aim of work Methodology What is a landfill ? Models specifications Conclusions

3. Progress Meeting - Rennes - November 2001 3 Aim of work DELIVRABLE: SPECIFICATIONS OF LANDFILL MODELS  Numbers of outputs  Parameters  Mathematical equation used AIM: To supply the necessary information according to AWAST objectives  Matter balance  Energetic balance  Economical balance  Environmental aspects To simulate all the system of waste treatment

4. Progress Meeting - Rennes - November 2001 4 Landfill modelling Aim of work Methodology What is a landfill ? Models specifications Conclusions

5. Progress Meeting - Rennes - November 2001 5 Methodology Several steps 1. How it works ? 2. Level 0 = a black box  inputs  outputs  performance according to AWAST objectives 3. To increase the level of prediction  fundamental parameters (calibration / sizing)  cost of used

6. Progress Meeting - Rennes - November 2001 6 Landfill modelling Aim of work Methodology What is a landfill ? Models specifications Conclusions

7. Progress Meeting - Rennes - November 2001 7 What is a landfill ? Leachate generation Waste  o Water inflow from rainfall Deposited Waste  t Deposited Waste  t+1  Biogas generation

8. Progress Meeting - Rennes - November 2001 8 Waste degradation phenomenon... Water (rainfall or waste)  waste component mobilisation Controlled by: chemical reactions (oxidation, …) physical aspects (adsorption, …) biological reactions = principal factor Authors agree to say reactions of organic matter biodegradation are the most accurate for leachate composition.

9. Progress Meeting - Rennes - November 2001 9 Waste degradation phenomenon... Principal reactions: hydrolyze, aerobic oxidation, anaerobic degradation, acidogenesis, acetogenesis and methanogenesis Final products of biodegradation: Sulphur which precipitate with metals, Hydrogen (consumed), Methane and carbon dioxygen.

10. Progress Meeting - Rennes - November 2001 10 I - Aerobic oxidation II - Transition III - Anaerobic degradation IV - Stable phase V - Stable leachate 10-20 years

11. Progress Meeting - Rennes - November 2001 11 Consequences for modelling tasks:  G° = f(waste composition)  Generation rate = f(time) Biogas generation Waste composition  Total gas potential generation G°  Somewhat the degradation rate But, the degradation rate is much more influenced by landfill operation condition as water content, compaction and so on. Measurement Database

12. Progress Meeting - Rennes - November 2001 12 Biogas generation/production GENERATION Theory Total gas potential generation (m 3 tons -1 ) Reality Total effective gas generation (m 3 tons -1 ) Only, a part biomethanized (40 - 50%) Common value: C=225 kg C tons -1  G=189 m 3 tons -1 COHERENT with literature PRODUCTION Total gas production (m 3 tons -1 ) r : recovery (%) Total anaerobic degradation of organic carbon

13. Progress Meeting - Rennes - November 2001 13 Leachate composition LEACHATE COMPOSITION linked to: Waste (composition, component solubility) Parameters controlling biological activity (water content, temperature, oxygen content, pH, …) VARIATION with time  Stabilisation Measurement LITTERATURE BDO 5, COD decrease = f(time) Stabilised waste  prediction Database = f(landfill age)

14. Progress Meeting - Rennes - November 2001 14 Hydrological balance Water inflow  Rainfall Evapo(transpi)ration Run-off Type of cover Water inflow  Leachate generated Waste stocks of water Leachate generated  Leachate collected Leachate remaining Leachate infiltrated

15. Progress Meeting - Rennes - November 2001 15 Leachate flowrate  min cc Water retention  max Water retention Water release KINETIC

16. Progress Meeting - Rennes - November 2001 16 Models & AWAST objectives Matter balance  mean rates (database)  Time consideration for more accurate prediction with measurements for case study and calibration Economical aspect  NO Energetic balance  Biogas recovered Environmental balance  Biogas emission  Leachate exfiltration

17. Progress Meeting - Rennes - November 2001 17 Landfill modelling Aim of work Methodology What is a landfill ? Models specifications Conclusions

18. Progress Meeting - Rennes - November 2001 18 Landfill models 2 inputs: Waste + Rainfall 4 outputs: Collected leachate Infiltration of leachate Biogas emission to the atmosphere Biogas recovered (Run-off – evapo-transpiration) 2 aspects: Biogas + Leachate

19. Progress Meeting - Rennes - November 2001 19 Biogas model(0) A fixed production rate 5.5 m 3 ton -1 year -1 for 75% recovery 55% CH 4 - 45% CO 2 - pollutants ? Calculation of mean production rate  History of landfilling  Lag time  Total gas production /ton

20. Progress Meeting - Rennes - November 2001 20 Leachate - Model (0) Calculation of water inflow = f (type of cover, total rainfall per year) Calculation of exfiltration 1- Passive: clay - K=10 -9 m/s 2- Passive and active =f(holes in geomembrane) NO calculation of generated leachate  collected Darcy law

21. Progress Meeting - Rennes - November 2001 21 Leachate - Model (0) Composition  Database

22. Progress Meeting - Rennes - November 2001 22 Parameters - Model(0) Filled section 1: Area (m²) 2: Useful Height (m) 3: Density (m 3 /ton) 4: Top cover type (Simple, Mid-permeable, Impermeable) 5: Bottom cover type (Passive, Passive and active) 6: Recovery of biogas (%) Active section 7: Area (m²) 8: Age of the landfill section (years) 9: Bottom cover type (Passive, Passive and active) 10: Total rainfall per year (mm) 11: % of biodegradation (hidden parameter)

23. Progress Meeting - Rennes - November 2001 23 Biogas model(1) t: time (from the landfilling) G: effective gas production (m 3 ton -1 ) g max : maximum gas production rate (m 3 ton -1 year -1 ) t max : time of maximum gas production rate (year) k* : biodegradation coefficient (year -1 )  According to waste composition Parameters - Adjustement parameters

24. Progress Meeting - Rennes - November 2001 24 Biogas model(1)

25. Progress Meeting - Rennes - November 2001 25 Leachate model(1) Hydrological balance P Rainfall Collected leachate Infiltration ETP Evapo-transpiration Run-off Water inflow Top cover Bottom cover Remaining leachate S: Stock of water contained in waste RU: Stock of water contained in soil layer ETR = k*ETP k (type of plant) RUmax (type of soil) k ’ Permeability Data Aim of calculation

26. Progress Meeting - Rennes - November 2001 26 Collected leachate Calculation of input water for waste water retention (C p ) Calculation of waste water content from water input and waste input Calculation of water release Leachate model(1) If WC > WC c, then  cd WC t     d d T 2ln  Where: TdTd : Time of midterm release (month) WC : waste water content WC c : critical water content Adjustement parameters

27. Progress Meeting - Rennes - November 2001 27 CONCLUSION REMAINING TO DO: Leachate composition - Model (1): Database? Biogas valorisation Economic aspect Finalisation

28. Progress Meeting - Rennes - November 2001 28