M. Barlaz

The report presents an empirical model to estimate global methane (CH4) emissions from landfills and open dumps, based on EPA data from landfill gas (LFG) recovery projects. CH4 produced by the anaerobic decomposition of waste buried in landfills and open dumps is a significant contributor to global CH4 emissions, with estimates ranging from 10 to 70 Tg/yr. Methods of managing

Methane production from municipal refuse represents a rapidly developing source of energy which remains underutilized. Part of the problem is the small amount of methane which is typically collected relative to the refuse's methane generation potential. This study was undertaken to define the parameters which affect the onset of methane production and methane yields in sanitary landfills. Ultimately, we need

Population development of key groups of bacteria involved in municipal refuse conversion to methane was measured from the time of initial incubation through the onset of methane production. Hemicellulolytic bacteria, cellulolytic bacteria, hydrogen-producing acetogens, and acetate- and H(2)-plus-CO(2)-utilizing methanogens were enumerated by the most-probable-number technique with media containing oat spelt xylan, ball-milled cellulose, butyrate, acetate, and H(2) plus CO(2), respectively. Refuse decomposition was monitored in multiple replicate laboratory-scale sanitary landfills. A laboratory-scale landfill was dismantled weekly for microbial and chemical analysis. Leachate was neutralized and recycled to ensure methanogenesis. The methane concentration of the sampled containers increased to 64% by day 69, at which time the maximum methane production rate, 929 liters of CH(4) per dry kg-year, was measured. Population increases of 2, 4, 5, 5, and 6 orders of magnitude were measured...

Laboratory-scale reactors containing mixtures of municipal solid waste and wastewater treatment biosolids were monitored to assess the effect of biosolids on refuse decomposition and on phosphorus (P) cycling and speciation among orthophosphate, acid-hydrolysable P, and organic P. The co-disposal of 10 to 20% (by wet weight) aerobically-digested biosolids with residential refuse was compatible with refuse decomposition although the biosolids did not increase either the maximum methane production rate or the cumulative yield, and did not reduce lag times to the onset of methane production. The results of this study indicated that dissolved reactive phosphorus (DRP) was the dominant dissolved P fraction throughout refuse decomposition and that it was negatively correlated with the methane production rate and pH (r² = 0.35 for both). P was not found to limit methane production. Biosolids increased dissolved P as well as ammonia-N in some reactors, but this did not have a significant impact on maximum methane production rates. The maximum tolerated Na+ and K+ concentrations during active methane production were at least 4100 mg Na+ L⁻¹ and 800 mg K+ L⁻¹, respectively.

Five landfills were analyzed to provide a perspective of current practice and technical issues that differentiate bioreactor and recirculation landfills in North America from conventional landfills. The bioreactor and recirculation landfills were found to function in much the same manner as conventional landfills, with designs similar to established standards for waste containment facilities. Leachate generation rates, leachate depths and temperatures, and liner temperatures were similar for landfills operated in a bioreactor/recirculation or conventional mode. Gas production data indicate accelerated waste decomposition from leachate recirculation at one landfill. Ambiguities in gas production data precluded a definitive conclusion that leachate recirculation accelerated waste decomposition at the four other landfills. Analysis of leachate quality data showed that bioreactor and recirculation landfills generally produce stronger leachate than conventional landfills during the first two to three years of recirculation. Thereafter, leachate from conventional and bioreactor landfills is similar, at least in terms of conventional indicator variables (BOD, COD, pH). While the BOD and COD decreased, the pH remained around neutral and ammonia concentrations remained elevated. Settlement data collected from two of the landfills indicate that settlements are larger and occur much faster in landfills operated as bioreactors or with leachate recirculation. The analysis also indicated that more detailed data collection over longer time periods is needed to draw definitive conclusions regarding the effects of bioreactor and recirculation operations. For each of the sites in this study, some of the analyses were limited by sparseness or ambiguity in the data sets.

... Samples representative of residential refuse were decomposed under conditions designed to simulate decomposition in both control and bioreactor landfills. ... In bioreactor landfills, decomposition is accelerated, which increases the rearrangement of waste particles. ...

ABSTRACT Four mesophilic, irregular, rod-shaped methanogenic bacteria were isolated from decomposing refuse recovered from laboratory-scale reactors and a municipal solid waste landfill. H2/CO2 was the only substrate on which the isolates could grow in a complex medium. Isolates grew between either 25° or 30° and 45°C and between pH 6 and 8. One isolate exhibited growth at pH 5. Growth of each isolate was enhanced by yeast extract and inhibited by anaerobic sewage sludge supernatant fluid. No isolate showed greater than 25% lysis on exposure to 1% sodium dodecyl sulphate (SDS) for 24 h, as is typical of methanogens with a proteinaceous cell wall. The physiological traits of the methanogens isolated here are similar to many previously characterized isolates.

... Dale T. Lane STS Consultants, Ltd. Madison, Wisconsin, USA James M. Rawe Science Applications International Corporation (SAIC) Under Contract No. 68-C-00-179 Hackensack, NJ, USA David Carson Thabet Tolaymat Ph.D. David Carson Project Officers ...

ABSTRACT The Deer Track Bioreactor Experiment (DTBE) was a field-scale experiment conducted in a drainage lysimeter (8.2-m height, 2.4-m diameter) to assess the physical, chemical, and biological response of municipal solid waste with leachate addition. The experiment was operated for 1,067 days, with leachate dosing initiated on Day 399. Fresh leachate collected from a full-scale landfill was used for each dose. The ratio of cumulative leachate effluent to influent volume increased during dosing and leveled off at approximately 80%, indicating field capacity was achieved. Peak Darcy flux ranged from 2 x 10(-7) m/s to 4x10(-5) m/s, with larger flux computed for the last four doses when waste saturation was higher. During the experiment, the average dry unit weight of the waste increased 28% and the dry-weight water content (w(d)) increased 18%; field capacity of the waste was 44 to 48% on a dry-weight basis. Biochemical methane potential decreased from 51.4 to 3: 4 mL-CH4/g-dry, indicating that 93% of the potential methane embodied in the waste was removed. The pH of the effluent increased, whereas biochemical oxygen demand (BOD), chemical oxygen demand (COD), and BOD:COD all decreased during dosing. Immediate compression occurred for 1-2 weeks following waste placement, and the immediate compression ratio C'(c) was 0.23. The average rate of time-dependent compression (C'(alpha)) ranged between 0.048 and 0.35 and varied systematically with waste temperature (increasing C'(alpha) with increasing temperature). DOI: 10.1061/(ASCE)GT.1943-5606.0000636. (C) 2012 American Society of Civil Engineers.