The Use of Landfills for the Long-Term Storage of Biogenic Organic Carbon

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1 The Use of Landfills for the Long-Term Storage of Biogenic Organic Carbon Morton A. Barlaz, Ph.D., P.E. Distinguished University Professor and Head Department of Civil, Construction, and Environmental Engineering North Carolina State University

2 Outline and Objectives Design features Carbon flow in landfills Gas production and collection Leachate production and composition Waste decomposition and carbon storage available data on wood Research needs

3 Design Features Heights of feet Excavation depth dictated by the water table Highly engineered cost of $300 - $500,000/acre for liner and cover Many site-specific considerations Leachate and gas controls Fill plan

4 Design and Operation Components Soils and hydrogeology Site layout and landfill operations Containment systems: liners and covers Water management Gas Production Leachate quality Groundwater Post-Closure monitoring Regulation

5 Landfill Cross Section (simplified) Monitoring Wells Gas Collection Vegetation Cover System Gas Collection Waste Leachate Collection System Liner System Water Table

6 Conceptual Landfill Liner System 6 in. top soil 1 ft. drainage layer 0.06 in. geomembrane 2 ft. clay 1 ft. soil single liner ft. waste 1 2 ft. drainage layer 0.06 in or 60 mil geomembrane 2 ft. clay

7 CO 2 H 2 0 heat O 2 Biological Polymers ulose Hemicellulose Soluble Monomers Sugars Amino Acids Fermentative Alcohols Butyric Acid Propionic Acid Hydrolytic Carbon Flow during Anaerobic Biodegradation Acetogens H 2,CO 2 CH 4 CO 2 Acetic Acid Methanogens Organic matter + SO > CO 2 + H 2 S

8 Carbon Flow In Landfills CO2, Energy Offset Emissions Gas Capture Fugitive Emissions Gas (CH4, CO2, VOCs) Decomposing Waste Residential Industrial Commercial Biosolids Stored Carbon Leachate (CO 2, VOCs)

9 Role of C Storage on C Balance in Landfills Slower biodegradation is better GHG emissions for waste components and average MSW by process and expressed per wet Mg Published in: James W. Levis; Morton A. Barlaz; Environ. Sci. Technol. 2011, 45,

10 Landfill Gas Modeling Q n = k L 0 n 0.9 i= 0 j= 0.0 M i 10 e k t i, j Q n is annual methane generation for a specific year t (m 3 CH 4 /yr); k is first order decay rate constant (1/yr) L 0 is total methane potential (m 3 CH 4 /ton of waste); M i is the annual burial rate (wet tons) t is time after initial waste placement (yr); j is the deci-year time increment Landfill Gas Emissions Model (LandGem)

11 Methane Production Rate Curve for Five Years of Waste Methane Rate (m3/yr) 1.50E E E E E+06 Year 1 Year 2 Year 3 Year 4 Year 5 total 0.00E Time (Yr)

12 Effect of Decay Rate (k) on Methane Production % of Cumulative Methane Wood ~ yr -1 0 Based on 286,000 short tons of refuse annually for 20 years and Lo = 1.5 Year ft 3 /wet lb (93.5 m 3 /wet Mg)

13 Leachate Generation: Liner and Cover Performance Eastern Landfill: gallons/acre-day during operation

14 Leachate Treatment Alternatives On-site treatment with NPDES permit On-site pretreatment followed by WWTP (wastewater treatment plant) Truck or pipe to WWTP Will WWTP accept leachate and for how long? Evaporation (in regions with an extended dry season and little rain) Recirculation

15 Leachate Composition Organics BOD = biochemical oxygen demand COD = chemical oxygen demand The BOD is always lower than the COD In fresh waste, the BOD/COD could be ~ In well decomposed waste is will be <~0.15 Major organic constituents: decomposition intermediates (carboxylic acids, humic matter) trace organics not likely associated with wood

16 Leachate Composition Metals generally quite low though occasionally a problem with one or more metals (Se, As) Ammonia always elevated (~ mg/l) released from engineered wood products

17 Laboratory Measurements Reactor Experiment High solids conditions optimized to maximize decomposition Temperature: 37 C Particle size: 2 cm by 5 cm Leachate neutralization and recirculation Nutrients addition as needed o NH 4+ -N: 100 mg of N/L o PO P: 5 mg of P/L 8 L reactor with gas and leachate collection bags.

18 Biochemical Methane Potential (BMP) Anaerobic biodegradability of substrates under optimal conditions Standard BMP o T = 37 C o Grind to <1 mm o Solids to liquid (S/L): <1 gm in ~100 ml liquid o Time = 60 days o 160 ml serum bottle used

19 Decomposition of Wood and Branches Wood lumber and engineered products: a. Hardwood lumber b. Softwood lumber c. Plywood (PW) d. Oriented strand board (OSB) e. Particle board (PB) a c e b d f f. Medium-density fiberboard (MDF) Hardwood (HW) from angiosperms, normally contains less lignin than SW Softwood (SW) from gymnosperms, SW lignin more condensed due to guaiacyl lignin subunit.

20 HW - Eucalyptus reactors produced less methane than controls, suggesting toxicity Reactor Methane Yields of Various Wood Types Methane Yield, ml dry g -1 wood Time (days) HW-Red oak HW-Eucalyptus SW-Spruce SW-Radiata pine OSB-HW OSB-SW PW PB MDF HW - Red oak and OSB-HW exhibited relatively high yields in 2000 days

21 Material Lumber Carbon Conversion CH 4 Yield (ml dry g -1 ) C (%) C Conversion (%) CSF (g C dry g -1 ) HW - Red oak HW - Eucalyptus SW - Spruce SW - Radiata pine Wood Products OSB HW OSB SW Plywood (PW) Particleboard (PB) Medium density fiberboard (MDF) CSF = carbon storage factor

22 Carbon Conversion Material White oak Bough (HW 1) White oak Twig (HW 1) Willow oak Bough (HW 2) Willow oak Twig (HW 2) Loblolly pine Bough (SW 1) Loblolly pine Twig (SW 1) White pine Bough (SW 2) White pine Twig (SW 2) CH 4 Yield (ml dry g -1 ) C (%) C Conversion (%) CSF (g C dry g -1 )

23 Estimate of Stored Carbon in Landfilled Woods CSF, g C dry g -1 wood HW-Red oak HW-Eucalyptus Wood ID SW-Spruce SW-Radiata pine OSB-HW OSB-SW PW 10 million Mg (metric tons) of C stored in U.S. landfills due to discarded woods, using national and state-specific waste composition data Includes MSW and construction & demolition (C&D) only, excludes industrial waste PB MDF

24 Nitrogen Release from Wood Products MDF and PB contained 9.2 and 14.6% urea formaldehyde, a resin mainly used for pressed wood products MDF and PB had high NH 3 -N in reactor leachate. MDF and PB released 0.69 and 0.17 g NH 3 -N kg -1 wood, respectively over 28 days of leaching Upper estimate: 113 mg NH 3 -N may be contributed to each liter of landfill leachate Typical range: 500~2000 mg NH 3 -N L -1 in landfill leachate

25 Summary Biodegradability varies among wood lumber and engineered wood products Wood originated from hardwood and softwood showed different decomposition behavior due to lignin content and wood species High degradation of a HW and OSB made from HW Toxicity in a HW-eucalyptus Potential N contribution from certain resins Branches vary in their biodegradability and HW degraded more than SW

26 Research Needs and Design Considerations: How to Bury Large Quantities of Wood? How quickly will the entrained oxygen be consumed? Might it be necessary to add a small amount of carbon to develop reducing conditions? What is the impact of soil on seeding with anaerobic microorganisms? What is the impact of water on initiating decomposition? Is leachate generated and what is its composition? natural organic matter ammonia

27 Research Needs and Design Considerations: How to Bury Large Quantities of Wood? Build a test cell in a few climatic regions Geotechnical issues Stability Liner and cover punctures Methane management oxidation system design Wood chips and fires

28 References Wang, X., Padgett, J. M., De la Cruz, F. B. and M. A. Barlaz, 2011, Wood Biodegradation in Laboratory-Scale Landfills, Environ. Sci. and Tech., 45, 16, p De la Cruz, F. B., Chanton, J. P. and M. A. Barlaz, 2012, Measurement of Carbon Storage in Landfills from the Biogenic Carbon Content of Excavated Waste Samples, Waste Management, 33, 10, p Wang, X., Padgett, J. M., Powell, J. S. and M. A. Barlaz, 2013, Decomposition of Forest Products Buried in Landfills, Waste Management, 33, 11, p De la Cruz, F., Yelle, D. J., Gracz, H. and M. A. Barlaz, 2014, Chemical Changes during Anaerobic Decomposition of Hardwood, Softwood and Old Newsprint under Mesophilic and Thermophilic Conditions, J. of Ag. And Food Chemistry, 62(27), p De la Cruz, F., Dittmar, T., Niggemann, J., Osburn, C., and M. A. Barlaz, 2015, Adoption of Copper Oxide Oxidation for Quantification of Lignin in Municipal Solid Waste, Environ. Eng. Sci., 32, 6, p Ximenes, F., Björdal, C. Cowie, A. and M.A. Barlaz, 2015, The decay of wood in landfills in contrasting climates in Australia, Waste Management, 41, p

29 References Wang, X., De la Cruz, F., Ximenes, F. and M. A. Barlaz, 2015, Decomposition and Carbon Storage of Selected Paper Products in Laboratory-Scale Landfills, Science of the Total Environment, 532, 1, p De la Cruz, F., Osborne, J., and M. A. Barlaz, 2015, Determination of Sources of Organic Matter in Landfill by Analysis of Copper Oxide Oxidation Products of Lignin, J. Env.Eng., 142, 2 Wang, X. and M. A. Barlaz, 2016, Decomposition and Carbon Storage of Hardwood and Softwood Branches in Laboratory-Scale Landfills, Science of the Total Environment, 557, p Ximenes, F., Cowie, A and M. A. Barlaz, 2017, The decay of engineered wood products and paper excavated from landfills in Australia, accepted, Waste Management Wang, X. and M. A. Barlaz, 2016, Literature Review on Decomposition Factors for Harvested Wood Products Landfilled, prepared for Environment Canada, Pollutant Inventories and Reporting Division.

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