Landfill Wellfield and Project Components

1. Landfill Wellfield and Project Components

2. Outline • Objectives of LFG Collection/Control • Elements of a LFG collection System • LFG Destruction/ Utilization Options

3. Objectives • Recover and utilize LFG • Minimize potential environmental impacts • Control off-site migration • Control odors • Comply with regulatory requirements

4. Elements of an LFG Collection System • Network of interconnecting piping • LFG collection points • Vertical extraction wells • Horizontal collectors/trenches • Connection to existing vents, wells, etc.

5. Elements of an LFG Collection System (continued) • Elements of condensate management • Flow control • LFG blower/combustion device (flare, engine, etc.)

6. Landfill Gas Collection and Control System • Gas collection wells and blower – pull gas from landfill • Flares – greater than 95% destruction of landfill biogas • Monitoring equipment – used to balance well field and ensure proper operation

7. Vertical Extraction Wells • Most common approach for recovering LFG • Install in existing or operational disposal areas • Waste depth preferable >10 meters

8. Vertical Extraction Wells • Install approx 2.5 wells per hectare(~ 1 well per 0.4 hectare) • May lose efficiency or not work in landfills with elevated leachate levels

9. Landfill Gas Collection & Control Gas well and collection pipe.

10. Gas Monitoring Wells • Wells located on perimeter of landfill to monitor for off-site migration. • Placed in natural soil conditions. • Routine testing at same locations. • More reliable (uniform) results. • Verification through repetition. • Serves as a guide for system effectiveness.

11. Gas Monitoring Well

12. Testing for Gas Quality and Pressure • Performed on site at each well location • Portable equipment analyzes gas and measures pressure and flow. • Immediate results for maximizing balancing efforts.

13. Methane Sample Instrument

14. Vertical Extraction Wells Design Features • In-refuse wells: 75% of the refuse depth • Depth of in-soil wells varies • Groundwater level • Bottom of refuse • Depth of gas migration

15. Vertical Extraction Wells - Design Features (continued) • Boreholes typically 60 cm to 90 cm in diameter • Casing is generally PVC or HDPE • Bottom perforated - start 6 meters below ground surface • Spacing depends upon “radius of influence” (typical 60 m - 122 m)

16. Typical Vertical Extraction Well • Bentonite seal prevents air infiltration • Wellhead incorporates: • Flow control valve • Pressure monitoring port • Flow monitoring device (optional) • Thermometer (optional)

17. Auckland, New Zealand Vertical Extraction Wells - Examples • Los Angeles, California

18. Vertical Extraction Wells - Examples Los Colorados Landfill near Santiago, Chile Basural Landfill, Peru

19. Theoretical Radius of Influence of a Landfill Gas Well • Radius of influence 2 to 2.5 times well depth • Increase vacuum to increase the radius of influence • Variations in vacuum are the operator’s only control tool

20. Actual Radius of Influence of a Landfill Gas Well • A well’s radius of influence is unlikely to be ideal: • Variations in waste characteristics • Interim cover and cell configuration • Presence of leachate

21. Horizontal Collectors • Alternative approach for LFG recovery • Install in shallow areas • Install in existing or operational disposal areas

22. Horizontal Collectors (continued) • Install at a spacing of approx. 30 to 100 meters • Can be used in landfills with elevated leachate levels

23. Horizontal Collectors - Design Features • Install in trenches or place on grade and cover with gravel and waste

24. Horizontal Collectors - Design Features (continued) • Construct out of approx 100 mm slotted PVC or HDPE pipe • Alternatively construct out of “nested” 100 mm an 150 mm pipes

25. Typical Horizontal Collector Arrangement

26. Examples • Bangkok, Thailand • Los Angeles, California

27. Laterals and Headers • Pathway for LFG from wellheads to blowers • Can be above-grade or underground • Generally HDPE - PVC sometimes used above-grade • Sized on flow rate and pressure drop

28. Laterals and Headers (continued) • Pipe configuration often “looped” to provide alternative flow paths • Pipe sloped to promote condensate drainage • Unusual drops in vacuum normally due to condensate blockages

29. Condensate System • Condensate volume depends on LFG temperature and flow • LFG is assumed to be 100% saturated with water • LFG temperature is typically 32° to 54° C

30. LFG cools in the LFG collection piping and the moisture condenses out into the piping Piping designed to allow condensate to drain Traps allow for drainage by gravity Sumps collect condensate Condensate Removal - Design Features

31. Landfill Gas Flaring • Flaring • Open flares (candle-stick flares) • Enclosed flares (ground flares)

32. Combusts methane gas Open or enclosed flame Blower/Flare Station

33. Blower/Flare Station (continued) • May be used in combination with beneficial use system • Needed during utilization system startup and downtime

34. Location should be central to collection system, close to potential end user or utility service, away from trees Design with flexibility to handle future gas flows Blower/Flare Station - Design Features

35. Blower/Flare Station – Typical Elements • Moisture separator • Blowers • Flare (open or enclosed) • LFG piping and flame arrestor • Flow meter • Pilot fuel supply • Control panel (controls both blower and flare) • Auto shutoff valve

36. Landfill Gas Flares

37. Example

38. Landfill Gas Blowers

39. Enclosed Ground Flares • Flare body usually circular: 9 to 12 meters high • LFG combusted close to ground • Flame not visible from outside • Air louvers near stack base

40. Enclosed Ground Flares (continued) • Typical operating temperature range: 760 C to 870 C • Typical destruction of 98 to 99 percent (or greater) • More expensive than candlestick flares

41. Open (Candlestick) Flare Components • Vertical pipe • Flare tip at top of pipe - flame visible • Smaller than enclosed flare

42. Landfill Gas Beneficial Use • Methane is a valuable energy source. • Can be used to generate electricity in an internal combustion engine or turbine. • Can be used as a fuel in boilers or thermal kilns or dryers. • Can be used in infrared heaters.

43. Landfill Gas Beneficial Use • Dual benefit  destroys methane and other organic compounds in LFG • Offsets use of nonrenewable resources (coal, oil, gas) reducing emissions of • SO2, NOX, PM, CO2 • Landfill gas is generated 24 hours a day, seven days a week. • LFG can act as a long-term price and volatility hedge against fossil fuels

44. Landfill Gas Electricity Generation Internal Combustion Engine (range from 100 kW to 3 MW) Gas Turbine (range from 800 kW to 10.5 MW) Microturbine (range from 30 kW to 250 kW)

45. Pottery Studio Sugar Grove, NC LFG-fired Boiler Ft. Wayne, IN Diversity of Project TypesDirect Use of LFG • Direct-use projects are growing! • Boiler applications – replace natural gas, coal, fuel oil • Combined heat & power (CHP) • Direct thermal (dryers, kilns) • Natural gas pipeline injection • Medium & high Btu • Greenhouse • Leachate evaporation • Vehicle fuel (LNG, CNG) • Artist studio • Hydroponics • Aquaculture (fish farming) Greenhouse Burlington, NJ

46. Carbon Credit Benefits • Carbon Credit Markets • Through the Kyoto CDM/JI Mechanism • Tons of CO2 offsets are sold on an exchange market

47. LFG collection system design - site specific Basic Concept Provide path for LFG collection Manage condensate Burn or utilize the gas Always consider your operating goals Summary