Methane Production In Landfill Research Articles

Greenhouse gas reporting data improves understanding of regional climate impact on landfill methane production and collection.

A critical examination of the US Environmental Protection Agency’s (US EPA’s) Greenhouse Gas Reporting Program (GHGRP) database provided an opportunity for the largest evaluation to date of landfilled waste decomposition kinetics with respect to different US climate regimes. In this paper, 5–8 years of annual methane collection data from 114 closed landfills located in 29 states were used to estimate site-specific waste decay rates (k) and methane collection potentials (Lc). These sites account for approximately 9% of all landfills required to report GHG emissions to the US EPA annually. The mean methane collection potential (Lc) for the sites located in regions with less than 635 mm (25 in) annual rainfall was significantly (p<0.002) lower than the mean methane collection potential of the sites located in regions with more than 635 mm (25 in) annual precipitation (49 and 73 m3 methane Mg-1 waste, respectively). This finding suggests that a fraction of the in-place biodegradable waste may not be decomposing, potentially due to a lack of adequate moisture content of landfills located in arid regions. The results of this evaluation offer insight that challenges assumptions of the traditional landfill methane estimation approach, especially in arid climates, that all methane corresponding to the total methane generation potential of the buried solid waste will be produced. Decay rates showed a significant correlation with annual precipitation, with an average k of 0.043 year-1 for arid regions (< 508 mm (20 in) year-1), 0.074 year-1 for regions with 508–1,016 mm (20–40 in) annual precipitation, and 0.09 year-1 in wet regions (> 1,016 mm (40 in) year-1). The data suggest that waste is decaying faster than the model default values, which in turn suggests that a larger fraction of methane is produced during a landfill’s operating life (relative to post-closure).

Evaluation of the Temperature Range for Biological Activity in Landfills Experiencing Elevated Temperatures

There have been reports of municipal solid waste landfills with waste and gas wellhead temperatures of at least 80–100 °C, which is in excess of temperatures reported at typical landfills. Landfills experiencing heat accumulation over a broad area present a number of challenges involving leachate and gas quality and quantity, and the associated collection infrastructure. The objectives of this research were to evaluate the impact of temperature on methanogenesis and fermentation in landfills, and to evaluate the extent to which microbial populations acclimate when perturbed to either lower or higher temperatures relative to their in situ temperature. Samples excavated from two landfills exhibiting elevated temperatures were utilized as inocula for small- and reactor-scale experiments. The optimum temperature for methane generation in the thermophilic range was 47.5–57.5 °C, with yields reduced by ∼37 and 75% at 62.5 and 67.5 °C, respectively. While microbial populations did not acclimate above 67.5 °C, methanogenic activity resumed when waste was cooled. 16S rRNA sequencing revealed that Methanothermobacter likely plays a key role in facilitating methane production in landfills operating in the thermophilic range and that microbial community diversity decreased at higher incubation temperatures. There was evidence that fermentation occurs up to 77.5 °C, well above the upper limit for methanogens measured in this study. Model simulations predict that fermentation reactions contribute a ∼3–10 °C rise in waste temperature.

Methane–hydrogen fuel blends for SI engines in Brazilian public transport: Potential supply and environmental issues

In the last decades, the whole world has been feeling the effects of environmental pollution, especially air pollution in large cities, with the transport sector as a major contributor to this scenario. In this sense, Brazil presents 27 states with great potential for biogas generation from landfills through anaerobic digestion. Only in the year 2016, the calculations presented in this paper point to a methane production in landfills of 5.57E+09 m3. On the other hand, the high number of rivers and hydroelectric dams in the country makes possible the generation of electricity that reached 90.27 TWh in 2016. However, the water that is drained by the floodgates to control the level of the reservoirs becomes an interesting wasted energy source for other uses, such as the production of other clean fuel, hydrogen, through classical processes such as electrolysis. It is pointed out the possibility of producing 2.76E+06 tons of hydrogen only with the energy drained in these hydroelectric plants. These two fuels together can be used to fuel vehicles powered by the hydrogen–methane blends, like HBio95 and HBio60. The promise of harmful and CO2 emissions by focusing on mixture of gases has recently attracted the interest of vehicle manufacturers and transport operators. In this scenario, this work presents an analysis on the use of mixture of gases in the urban bus fleet of the 27 Brazilian states, using as energy source derived from secondary energy from Brazilian hydroelectric plants and biogas from sanitary landfills, comparing this scenario with the use of only methane from landfills or only H2 from hydroelectric plants, assessing issues such as pollutant emissions, engine performance and deployment facilities.

Biopolymer production and end of life comparisons using life cycle assessment

This paper presents an attributional life cycle assessment of biopolymers and traditional plastics using real world disposal methods based on collected data and existing inventories. The focus of this LCA is to investigate actual disposal methods for the end of life phase of biopolymers and traditional fossil-based plastics relative to their corresponding production impacts. This paper connects commonly available methods of disposal for traditional fossil-based plastics and the compostability of polylactic acid and thermoplastic starch to compare these materials not just based on production impacts but also on various scenarios for recycling, composting, and landfilling. Additionally, three traditional resins were evaluated (PET, HDPE, and LDPE) using fossil and bio-based production pathways to assess the performance of bio-based products in the recycling stream. The results demonstrate real environmental tradeoffs associated with agricultural production of plastics and the consequential changes resulting from shifting from recyclable to compostable products. The potential for methane production in landfills is a significant factor for global warming impacts associated with biopolymers while recycling provides major benefits in the global warming and fossil fuel depletion categories. A sensitivity analysis was conducted to investigate the relative importance of locale-specific factors such as travel distances and sorting technologies to the end of life treatment methods of recycling, composting, and landfilling. The results show that composting has some advantages, especially when compared to impacts associated with landfilling, but that recycling provides the greatest benefits at end of life.

Archaeal community diversity in municipal waste landfill sites.

Despite the pivotal role of archaea in methane production in landfills, the identity, ecology, and functional diversity of these microorganisms and their link to environmental factors remain largely unknown. We collected 11 landfill leachate samples from six geographically distinct landfills of different ages in China and analyzed the archaeal community by bar-coded 454 pyrosequencing. We retrieved 121,797 sequences from a total of 167,583 sequences (average length of 464 bp). The archaeal community was geographically structured, and nonabundant taxa primarily contributed to the observed dissimilarities. Canonical correlation analysis (CCA) suggested that the total phosphorous (TP), nitrate, and conductivity are important drivers for shaping the archaeal community. The hydrogenotrophic methanogens Methanomicrobiales and Methanobacteriales greatly dominated 9 of 11 samples, ranging from 83.7 to 99.5 %. These methanogens also dominated the remaining two samples, accounting for 70.3 and 58.8 %, respectively. Interestingly, for all of the studied Chinese landfills, 16S rRNA analysis indicated the predominance of hydrogenotrophic methanogens.

The prediction of the methane production in landfill affected by the temperature

The functional relationship between the generation rate coefficient and temperature was developed for quantitative prediction of the temperature effect in this paper. The methane production of the landfill was predicted under the condition of the seasonal variation. The results showed that considering the temperature effect, the methane production is higher than the methane production without temperature effect of the 0.14×106 m3~0.28×106m3.With the depth increasing, the effect of the atmospheric temperature fluctuation on the temperature change of the landfill was weakened. The temperature has a significant effect on the methane production in the landfill. The temperature effect should be considered when simulate the long time effect of the landfill methane production.

Methane production in simulated hybrid bioreactor landfill

The aim of this work was to study a hybrid bioreactor landfill technology for landfill methane production from municipal solid waste. Two laboratory-scale columns were operated for about ten months to simulate an anaerobic and a hybrid landfill bioreactor, respectively. Leachate was recirculated into each column but aeration was conducted in the hybrid bioreactor during the first stage. Results showed that leachate pH in the anaerobic bioreactor maintained below 6.5, while in the hybrid bioreactor quickly increased from 5.6 to 7.0 due to the aeration. The temporary aeration resulted in lowering COD and BOD5 in the leachate. The volume of methane collected from the hybrid bioreactor was 400 times greater than that of the anaerobic bioreactor. Also, the methane production rate of the hybrid bioreactor was improved within a short period of time. After about 10 months’ operation, the total methane production in the hybrid bioreactor was 212L (16L/kgwaste).

A comparison of nanosilver and silver ion effects on bioreactor landfill operations and methanogenic population dynamics

Silver nanoparticles (AgNPs, nanosilver) and silver ions released from industry and various consumer products are eventually disposed in sanitary landfills. To compare the effects of these two forms of silver on landfill bioreactor operations with leachate recirculation, municipal solid waste (MSW) in six identical 9-L bioreactors was exposed to AgNPs (stabilized with 0.06% polyvinyl alcohol) or Ag+ at a silver concentration of 10 mg/kg solids. The landfill anaerobic digestion was operated and monitored for more than 200 days. There was no significant difference in cumulative methane volume or methane production rate between the groups of control and 10 mg/kg Ag+. However, MSW treated with 10 mg/kg AgNPs resulted in a reduced methane production (by up to 80%) and accumulation of volatile fatty acids in the leachates. This was accompanied by higher leachate Ag concentrations (an average of 3.7 ± 0.3 mg/L) after day 132 as compared to those in the groups of control and 10 mg/kg Ag+ at 0.7 ± 0.4 and 1.1 ± 0.3 mg/L, respectively. Quantitative PCR targeting 16S rRNA genes of methanogens indicated reduced methanogenic growth in the bioreactors exposed to nanosilver. The peak values of total methanogens in leachates were (1.18 ± 0.09) × 1010, (4.57 ± 2.67) × 1010 and (7.72 ± 0.78) × 108 (cells/mL) for the groups of control, Ag+ and AgNPs, respectively. The results suggest that silver ions have minimal impact on landfill methane production at the concentration of 10 mg/kg. However, nanosilver inhibits methanogenesis and is more toxic than its counterpart, likely due to slow and long-term Ag+ release from nanosilver dissolution yielding more bioavailability in landfill leachates.

Effect of quantity and composition of waste on the prediction of annual methane potential from landfills

A study was conducted to investigate the effect of waste composition change on the methane production in landfills. An empirical equation for the methane potential of the mixed waste is derived based on the methane potential values of individual waste components and the compositional ratio of waste components. A correction factor was introduced in the equation and was determined from the BMP and lysimeter tests. The equation and LandGEM were applied for a full size landfill and the annual methane potential was estimated. Results showed that the changes in quantity of waste affected the annual methane potential from the landfill more than the changes of waste composition.

A fractal-like kinetics equation to calculate landfill methane production

Landfill appears as a convenient choice to get rid of municipal solid waste while providing energy, due to methane generated through anaerobic fermentation. However, without capture and treatment landfill gas is considered an important source of atmospheric methane. The control and use of this gas require knowledge of both, current yield and long-term accumulative production. These values are usually calculated with mathematical expressions that consider 100% of conversion, and homogeneous chemical reactivity inside the fill. Nevertheless, fermentation in landfills is erratic and spatially heterogeneous. This work introduces a fractal-like chemical kinetics equation to calculate methane generation rate from landfill, Q CH 4 (m 3/year), in the way: Q CH 4 =L 0 ∑ j ∑ i M ijC ij 0k i(t j) −d s /2 exp[−k it j], where fermentable wastes are partitioned in readily, moderately and slowly biodegradable categories, L 0 is the potential of methane yield of refuse (m 3/tonne under standard conditions), d s is the solid-phase fracton dimension, k i is the reaction kinetics constant of waste category i (year −1), and t j is the time from the year of burying j (year), C ij 0 (kg/tonne) and M ij (kg) are the initial concentration and the mass of waste category i landfilled in year j, respectively. The idea behind this equation is that methane production kinetics is limited by the diffusion of hydrolyzed substrate into a heterogeneous solid-phase towards discrete areas, where methanogenesis occurs. A virtual study for a hypothetical case is developed. The predictions from this fractal approach are contrasted with those coming from two equations broadly used in the industrial work. The fractal-like kinetics equation represents better the heterogeneous nature of the fermentation in landfills.

EFFECT OF MOISTURE CONTENT AND CHEMICAL NATURE ON METHANE FERMENTATION CHARACTERISTICS OF MUNICIPAL SOLID WASTES

Effects of the moisture content and the chemical nature of solid wastes on their methane production in landfill were investigated using a solid bed incubated at 41°C. The solid-beds were filled with different moisture contents of meat, cabbage, sewage sludge cake, carrot, rice and potato. A simple model contained methane production potential, P, maximum methane production rate, Rm, and lagphase time, λ, was developed to fit the cumulative methane production curve in the batch experiment; and all the parameters in the model for various solid beds were estimated. For each proper solid waste, the lagphase time decreased, but the methanogenic activity increased with the increase of moisture content. The results reflect that the moisture content threshold limit (MSL) for the methane production in the solid bed was about 60%.