IMPROVING LANDFILL GAS RECOVERY Recent Evaluations, Results of Large Scale Tests in California, United States

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1 IMPROVING LANDFILL GAS RECOVERY Recent Evaluations, Results of Large Scale Tests in California, United States Don Augenstein (A) Ramin Yazdani (B), Jeff Kieffer (B) Paul Imhoff (C) Morton Barlaz (D) Harold Bentley (E) John Benemann (A) (speaker) A. Institute for Environmental Management, (IEM Inc), Palo Alto CA USA B. Yolo County Public Works and Planning, Woodland CA, USA C. University of Delaware, Newark, DE USA D. North Carolina State University, Raleigh, NC USA E. Hydro Geo Chem, Tucson, AZ Methane to Markets Expo, Beijing, China. Oct 30-Nov 1, Cosponsored by China National Development Commission and U.S. Environmental Protection Agency. US Copyright by IEM, Inc. May be used freely under Creative Commons Attribution- Share Alike 3.0 United States License rules of the United States. See web address

2 ISSUES -- FREQUENT LIMITATIONS WITH LANDFILL GAS RECOVERY: 1. Inefficiencies of collection, and problems with air entrainment, and maintaining constant methane content in extracted gas 2. Conventional landfills decompose very slowly over decades and may decompose incompletely (the infamous dry tomb ) 3. Fugitive methane emissions and losses in early stages of filling when extraction is often inconvenient, inefficient (or absent) 4. Tedious and slow iterations of monitoring/adjustment/control when basing such control on "typical" indicators like wellhead gas composition 5. Predicting most effective designs for gas recovery 6. Predicting and assessing methane recoverability at a given site, where misses in predictions lead to performance shortfalls relative to expectations THERE IS ROOM FOR IMPROVEMENT!!

3 Fig. 1 Simplified schematic section of conventional LFG well and gas flow Cover layers Cover layers More landfill extends on WASTE WASTE More landfill-- -extends on well Base layers Arrows and lengths denote gas flows or fluxes.. Note variable surface fluxes and emissions distant from well, entrainment near well, inefficient collection

4 PENROSE SURFACE FLUX ZISON, Getty Syntheic Fuels and Pacific Energy..

5 SHELDON ARLETA LANDFILL RELATIVE SURFACE FLUX

6 REPORTED RECOVERY EFFICIENCIES 1. SPOKAS et al THREE LANDFILLS < 10% methane emitted (excellent) 2. BORJESSON et al measurements summarized Emissions generally 30-60% of CH4 generated 3. USEPA Default 75% (estimate) BUT MEASUREMENTS ARE DIFFICULT AND: Point in time measurements do not cover (a) early emissions of methane during filling, or (b) at long terms. Long term generation can be significant at k = 0.04 year -1, over 30% of methane generated from waste 30 years or more after placement Capture of methane at long terms can be difficult inefficiencies increase due to diffusion and other factors. WHEN METHANE GENERATION FROM BEGINNING TO END OF FILLING IS CONSIDERED, COLLECTION AT MOST SITES LIKELY 60-85%. HOW MIGHT EFFICIENCY BE INCREASED?

7 IMPROVING CAPTURE WITH CONVENTIONAL APPROACHES: 1. THICKER COVER > 5ft clay (cost) 2. OVERPULL EXTRACT AT % GENERATION (air entrainment and energy use problems) 3. MORE AND CLOSER EXTRACTION WELLS 4. MORE INTENSIVE AND FREQUENT MONITORING 5. FIX COVER CRACKS Conventional approaches can give diminishing returns

8 Controlled Landfill-- minimize greenhouse emissions, maximize lfg energy FILL QUICKLY, MINIMIZE LFG LOSSES COVER WITH CONDUCTIVE GAS RECOVERY LAYER --- THEN POLYMER COVER (GEOMEMBRANE). LOW PERMEABILITY CLAY CAN ALSO BE USED. ONLY THEN ENHANCE METHANE GENERATION BY LIQUID: --COMPLETE LFG GENERATION SOONER --AVOID LONG TERM COLLECTION DIFFICULTIES, DIFFUSIONAL LOSSES, WITH LONG-TERM LOW- RATE LFG GENERATION. CONTROL AIR INTRUSION -- ALSO HELPS MAXIMIZE GENERATION AND RECOVERY

9 Test cell oblique view

10 Cumulated methane generation, Yolo 9000 Ton Cummulative Methane demonstration cells, Per Pound of Wet Waste 1.4 Ft 3 methane per lb gate waste Enhanced Cell Normal Range Expected f or a Conventional Design Control Cell 0.0 6/1996 1/1997 1/1998 1/1999 1/2000 1/2001 1/2002 1/2003 1/2004 1/2005 Date

11 Comparing profiles--enhanced vs. control cell --Enhanced decomposition reduces volume quickly,can extend landfill life. Control Cell Enhanced Cell

12 Scaleup: Completed 3.5 Acre (Northeast) cell, 2001 Don A. walking

13 CONTROLLED LANDFILL --OFFERS A NUMBER OF ADVANTAGES OVER CONVENTIONAL LANDFILL GAS RECOVERY. HOWEVER CAN BE DEMANDING OF TECHNICAL EXPERTISE, OPERATIONAL CARE, AND INFRASTRUCTURE. ON TOP OF THAT, GEOMEMBRANE COVER IS EXPENSIVE.

14 IMPROVING LFG RECOVERY VIA PERMEABLE LAYERS SHRED TIRES AND/OR RUBBLE OR WOOD CHIPS CONDUCTIVITIES FOR LFG FROM 10 3 TO 10 6 (I.E. THOUSAND TO MILLION FOLD) GREATER THAN SURROUNDING WASTE OR SOIL. THESE WIDELY AND ECONOMICALLY AVAILABLE FOR INCORPORATION INTO LANDFILLS. PERMEABLE (HIGHLY GAS CONDUCTIVE) LAYERS OF SUCH MATERIAL CAN BE EMPLACED DURING FILLING SLIGHTLY BELOW THE LANDFILL SURFACE LFG CAN BE CAPTURED EFFICIENTLY AND GO WHERE WE (LFGTE OPERATORS) WANT

15 SIMPLIFIED SCHEMATIC OF PERMEABLE LAYER USE ARROWS AND LENGTHS DENOTE GAS FLOWS OR FLUXES. NOTE EFFICIENT CAPTURE AND RE-ENTRAINMENT OF LFG ENTERING PERMEABLE LAYER WITH CONSEQUENT RECOVERY EFFICIENCY INCREASE. Gas extraction to use More landfill extends on Gas composition sample line or sensor High conductivity (permeable) layer Low permeability surface layer and/or geomembrane LFG RE-ENTRAINMENT HERE High conductivity (permeable) layer WASTE WASTE More landfill--- extends on well Base layers

16 University of Delaware Modeling of Air intrusion without and then with permeable layer (Tire Layer) Oxygen intrusion Depth (m) Depth (m) Tire layer Width (m) Width (m) Pumping well U D U D U D U D Without permeable (tire) layer With permeable (shred tire) layer

17 Pumping rate Results U D CH 4 emission through top biocover (%) With tire layer-ch 4 emission at K st Without tire layer-ch 4 emission at K st With tire layer-ch 4 emission at K=K st /10 Without tire layer With tire layer Without tire layer-ch 4 emission at K=K st / Pumping rate based on the total LFG generation rate (%)

18 Anaerobic Bioreactor CH 4 Capture Simulated effect of cracks in biocover Permeable layer increases the efficiency of CH 4 capture Shredded tires trash Methane Emission (%) no crack Number of cracks With tire layer Without tire layer U D

N 300 Gas to extraction system Approximate permeable layer footprint ( covering as

19 Figure : Top view of plan permeable layer test area, showing (at lower left) conductive layer textured ) footprint and well. N 300 Gas to extraction system Approximate permeable layer footprint ( covering as much area as practical) Final dimensions and shape to be determined WELL EXTRACTION ZONE BENEATH CONDUCTIVE LAYER ft

20 VIEW OF MULTI- ACRE SHRED TIRE LAYER

21 SHRED TIRE PERMEABLE LAYER BEING PLACED WASTE LAYERS

22 40 Permeable layer methane 30 Cover methane (yellow and brown) Barometric pressure Barometric pressure blue, right hand axis Permeable layer methane dark blue -- left hand axis Cover layer methane (2) brown and yellow -- left axis

23 SUBSURFACE COMPOSITION PROBES CAN ALLOW CONTROL, INDICATE (a) TOO LOW EXTRACTION (b) TOO HIGH EXTRACTION RATE Example landfill cross section showing approximate interface location between entrained air and LFG. Sensors/tubes detect subsurface gas composition Arrows ( ) denote LFG or gas flow interfacial location: ( Extraction too slow ) ( ext. too fast) LFG to blower and use or disposal Air in Landfill cover layers LFG emissions from surface here Air in Typical subsurface gas probes More landfillextends on Underpull LFG interface ENTRAINED AIR ZONE More landfill-- -extends on tes) Overpull LFG interface MSW LFG well extraction zone LFG ZONE Base layers of landfill MSW LFG well extraction zone

24 Simplified illustration: Subsurface probes to track and control LFG recovery (permeable layer used). Air/LFG interface location SAMPLING TUBES to conducting layer and cover SURFACE SOIL COVER More low permeability layers membrane and/or landfill--waste (thickness ca.1-2 meters) extends on Permeable layer LFG shred tires, chips etc Extraction line LFG to use SURFACE SOIL COVER Low permeability layers (Ca. 1 ft) lfg lfg lfg lfg WASTE LFG entrainment area here Deep well ca, feet deep WASTE lfg lfg lfg lfg 100 ft (30M) from surface to base layers More landfill--- extends on

25 RAPID MOISTURE PERMEATION NO LIQUID BUILDUP (1-3 cm/day with greenwaste/compost daily cover) ENHANCED CELL MOISTURE SENSOR READINGS-1995 TO Supplemental Liquid Added Between October 23, 1996 and April 15, 1997 Supplemental Liquid Added Between August 8, 2000 and October 30, 2000 Supplemental Liquid Added Between October 29, 2001 and November 30, Moisture Reading Apr-95 Jul-95 Nov-95 Feb-96 Jun-96 Oct-96 Jan-97 May-97 Aug-97 Dec-97 Apr-98 Jul-98 Nov-98 Mar-99 Jun-99 Oct-99 Jan-00 May-00 Sep-00 Dec-00 Apr-01 Jul-01 Nov-01 Mar-02 Jun-02 Oct-02 Jan-03 RAPID UNIMPEDED MOISTURE PERMEATION WITHOUT ADVERSE LFG COLLECTOR WATERLOGGING Date

26 Leachate Head Over the Liner (inches) COVER SOIL (REMNANT) CREATES LIQUID MANAGEMENT PROBLEMS GAS WELL WATERLOGGING, SLOWER MOISTURE INFILTRATION SIDE SEEPS, PERCHED LIQUIDS AND BLOCKED GAS WELLS Discovered Leachate Seeps 7/8/03 y = x R 2 = y = x Leachate Addition Rate = 1 17,016 Gallons per Day per R 2 = Leachate Recirculation Rate = y = x 210 Gallons per Day per Acre 0.5 R 2 = /9/03 7/8/03 9/6/03 11/5/03 1/4/04 3/4/04 5/3/04 7/2/04 8/31/04 10/30/04 Date Maximum Head Over the Liner Supplemental Liquid Added Linear (Supplemental Liquid Added) Overall Leachate Addition Rate = 888 Gallons per Day per Acre Leachate Recirculated Total Supplemental Liquid and Leachate Recirculated Linear (Leachate Recirculated) Liquid Added or Recirculated (Million Gallons)

27 0 100% 200% 300% Experienced recovery as fraction of modeled recovery

28 OTHER AVENUES TO IMPROVE LFG RECOVERY EARLY STAGE MEASURES PROJECTING GAS AVAILABILITY MODELING GENERATION PNEUMATIC GENERATION ASSESSMENT PEAKING ELECTRICITY IN-LANDFILL POLLUTANT BIOFILTRATION ADVANCED FINITE ELEMENT FLOW MODELING

29 SUMMARY PROMISING NEWER AVENUES AND APPROACHES AVAILABLE TO IMPROVE LFG CAPTURE. APPROACHES GIVING VERY ENCOURAGING RESULTS AT YOLO COUNTY IEM, INC., WITH PROJECT MEMBERS WOULD LIKE TO APPLY WIDELY, INCLUDING PARTICIPATING IN CHINA PROJECTS

IMPROVING LANDFILL METHANE RECOVERY -- RECENT EVALUATIONS AND LARGE SCALE TESTS 1

IMPROVING LANDFILL METHANE RECOVERY -- RECENT EVALUATIONS AND LARGE SCALE TESTS 1 Don Augenstein A, Ramin Yazdani B, Paul Imhoff C, Morton Barlaz D Bentley E and John Benemann A Harold A. Institute for