CH4 Oxidation Capacity Research Articles

Effects of no-till duration on the methane oxidation capacity of Alfisols

Frequent tillage negatively affects the methane (CH4) oxidation capacity of agricultural soils. The restoration of that capacity of soils through no-tillage (NT) adoption has been suggested, but is not well documented. With the expectation of increased CH4 oxidation with longer NT duration, a tillage chronosequence study was conducted at paired sites in Ohio under conventional tillage (or plow till, PT) and NT for 9, 13, 36, and 48 years. Nearby deciduous forests were also included to estimate the maximum oxidation capacity of undisturbed local soils. Surface soil samples (0–5, 5–10, 10–20, 20–30 cm) were collected in April (soil moisture 29 %) and in August 2010 (moisture 19 %), sieved (6.3 mm), and incubated (initial CH4 5 μl L−1) to determine the CH4 oxidation capacity. The results showed a significant effect of tillage practice on CH4 oxidation. With the exception of the site under NT for 9 years, the CH4 oxidation rates were consistently higher (2–40 times) in NT than in PT soils during both the April and August sampling dates. A similar effect of NT was also observed when incubation was conducted with intact soil cores, but the rates were lower, perhaps due to restriction of CH4 diffusion in the cores. Across the sampling dates and depth, the CH4 oxidation capacity increased linearly with NT duration averaging 3.2, 4.2, 11.5, and 13.6 μg CH4-C kg−1 soil day−1 at sites under NT for 9, 13, 36, and 48 years, respectively. While the CH4 oxidation rate in PT soil was 10–12 % of the level in the forest soils, it was 36–37 % at sites under NT for >30 years. These results demonstrate the positive effect of NT on the CH4 oxidation in soils and the potential impact of continued NT maintenance on the CH4 sink strength of agricultural soils.

Effects of ammonia on methane oxidation in landfill cover materials

The effects of ammonia (NH3) on CH4 attenuation in landfill cover materials consisting of landfill cover soil (LCS) and aged municipal solid waste (AMSW), at different CH4 concentrations, were investigated. The CH4 oxidation capacities of LCS and AMSW were found to be significantly affected by the CH4 concentration. The maximum oxidation rates for LCS and AMSW were obtained at CH4 concentrations of 5% and 20%(v/v), respectively, within 20 days. CH4 biological oxidation in AMSW was significantly inhibited by NH3 at low CH4 concentrations (5%, v/v) but highly stimulated at high levels (20% and 50%, v/v). Oxidation in LCS was stimulated by NH3 at all CH4 concentrations due to the higher conversion of the nitrogen in NH3 in AMSW than in LCS. NH3 increases CH4 oxidation in landfill cover materials.

Assessment of methane emission and oxidation at Air Hitam Landfill site cover soil in wet tropical climate

Methane (CH₄) emissions and oxidation were measured at the Air Hitam sanitary landfill in Malaysia and were modeled using the Intergovernmental Panel on Climate Change waste model to estimate the CH₄ generation rate constant, k. The emissions were measured at several locations using a fabricated static flux chamber. A combination of gas concentrations in soil profiles and surface CH₄ and carbon dioxide (CO₂) emissions at four monitoring locations were used to estimate the CH₄ oxidation capacity. The temporal variations in CH₄ and CO₂ emissions were also investigated in this study. Geospatial means using point kriging and inverse distance weight (IDW), as well as arithmetic and geometric means, were used to estimate total CH₄ emissions. The point kriging, IDW, and arithmetic means were almost identical and were two times higher than the geometric mean. The CH₄ emission geospatial means estimated using the kriging and IDW methods were 30.81 and 30.49 gm(−2) day(−1), respectively. The total CH₄ emissions from the studied area were 53.8 kg day(−1). The mean of the CH₄ oxidation capacity was 27.5 %. The estimated value of k is 0.138 year(−1). Special consideration must be given to the CH₄ oxidation in the wet tropical climate for enhancing CH₄ emission reduction.

Evaluation of methane oxidation activity in waste biocover soil during landfill stabilization

Biocover soil has been demonstrated to have high CH4 oxidation capacity and is considered as a good alternative cover material to mitigate CH4 emission from landfills, yet the response of CH4 oxidation activity of biocover soils to the variation of CH4 loading during landfill stabilization is poorly understood. Compared with a landfill cover soil (LCS) collected from Hangzhou Tianziling landfill cell, the development of CH4 oxidation activity of waste biocover soil (WBS) was investigated using simulated landfill systems in this study. Although a fluctuation of influent CH4 flux occurred during landfill stabilization, the WBS covers showed a high CH4 removal efficiency of 94–96% during the entire experiment. In the LCS covers, the CH4 removal efficiencies varied with the fluctuation of CH4 influent flux, even negative ones occurred due to the storage of CH4 in the soil porosities after the high CH4 influent flux of ∼137gm−2d−1. The lower concentrations of O2 and CH4 as well as the higher concentration of CO2 were observed in the WBS covers than those in the LCS covers. The highest CH4 oxidation rates of the two types of soil covers both occurred in the bottom layer (20–30cm). Compared to the LCS, the WBS showed higher CH4 oxidation activity and methane monooxygenase activity over the course of the experiment. Overall, this study indicated the WBS worked well for the fluctuation of CH4 influent flux during landfill stabilization.

Landfill CH4 oxidation by mineralized refuse: Effects of NH4+[sbnd]N incubation, water content and temperature

Mineralized refuse, excavated from a municipal solid waste (MSW) landfill that had been closed for more than 10years, was incubated in livestock wastewater for 150d to accumulate ammonia-oxidizing bacteria and also co-oxidize methane (CH4). The extent of CH4 oxidation and carbon dioxide (CO2) emissions from the incubated mineralized refuse (IMR) were investigated to assess its applicability as a bio-cover material at landfill sites for minimizing total greenhouse gas emission equivalents. From the initial 200mg nitrogen (N) kg−1 incubated for 120h, the nitrate-N content produced in the IMR was twice (P<0.05) that of the untreated original mineralized refuse (OMR) and 3.81 (P<0.05) times that of soil. For an initial CH4 concentration of approximately 10% by volume in the headspace, CH4 consumption and net emission of CO2 from the soil, IMR and OMR all agreed well with first-order and zero-order kinetics models for a 120-h incubation (R2=0.667 and R2=0.995, respectively). Similar to N turnover, the rate of consumption of CH4 by the mineralized refuse was some 50.0% higher than for soil (P<0.05). Based on the net rate of CO2 generation, the CH4 oxidation rate by IMR was 14.2% (P>0.05) greater than for OMR and 56.1% (P>0.05) higher than for soil. Variation of water content and temperature produced substantially higher CH4 consumption rates by IMR than by either OMR or soil. After treatment by livestock wastewater, the CH4 oxidation capacity of mineralized refuse was moderately improved, due to the enhancement of CH4 adsorption by retained suspended solids and the subsequent co-oxidation by the accumulated ammonia-oxidizing bacteria. By correlation analysis for the three experimental materials, CH4 oxidation rate was significantly correlated with specific surface area and organic matter content (P<0.05), and was positively correlated with CO2 generation, NH4+N nitrification and NO3–N generation rate (P>0.05).

Effect of biocover equipped with a novel passive air diffusion system on microbial methane oxidation and community of methanotrophs

A novel biocover with passive air diffusion system (PADS) was designed in this study. Its effect on landfill gas components in the macrocosms of simulated biocover systems was also investigated. The results show that O2 concentration increased in the whole profile of the macrocosms equipped with PADS. When simulated landfill gas (SLFG) flow rate was no more than 40 mL min−1, the methane oxidation rate was 100%. The highest CH4 oxidation capacity reached to 31.34 mol m−3 day−1. Molecular microbiology analysis of the soil samples taken from the above macrocosm showed that the growth of type I methanotrophs was enhanced, attributable to enhanced air diffusion and distribution, whereas the microbial diversity and population density of type II methanotrophs were not so affected, as evidenced by the absence of any difference between the biocover equipped with PADS and that of the control. According to a phylogenic analysis, Methylobacter, Methylosarcina for type I, and Methylocystis, Methylosinus for type II, were the most prevalent species in the macrocosm with PADS. Implications Semiaerobic landfill technology was reported to be an effective in situ CH4 emission reduction method. A semiaerobic status is achieved through a continuous supply of fresh air sucked passively through the open end of a leachate collection pipe, with a temperature gradient created by organic matter degradation. In this research, a novel passive air diffusion system (PADS) was designed, and O2 concentration increased in the whole profile of the microcosms equipped with PADS. The constant supply of fresh air reduced CH4 production and enhanced biodegradation. Through molecular microbiology analysis, it was found that growth of methanotrophs was enhanced, and species of prevalent methanotrophs were found. Supplemental Materials Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for a list of abbreviations and PCR protocol.

COMPARISON OF METHANE OXIDATION POTENTIAL BETWEEN COMPOST AND BLACK SOIL AT JERAM LANDFILL

Landfills are significant sources of atmospheric methane (CH4) that contributes to greenhouse gas effect, and therefore there is a need to reduce the CH4 emissions from landfills. Small scale landfills in Malaysia and other developing countries generally do not generate enough CH4 for energy harvest. CH4 emission can be reduced by means of microbial oxidation enhanced by biologically engineered landfill covers. This is a promising cost-effective technology to enhance biological oxidation of CH4 in small scale landfills. The selection of suitable materials represents one of the key issues in constructing biotic CH4 oxidation systems. Composts and black soil have been proven to support CH4 oxidation and they represent a low cost alternative to other sandy or humic-rich soil substrate. This study was carried out to investigate the CH4 oxidizing capacity of compost and black soil under field conditions. Experiments with different flow rates of landfill gas have shown that compost has a higher oxidation capacity compared to black soil. At 100 cm of cover height and flow rate of 300 ml per minute, black soil has an oxidation capacity of 112.2 ml CH4 per minute. For compost, the oxidation capacity is 169.8 ml of CH4 per minute. From this study we concluded that compost has greater potential than black soil as landfill cover material due to the better CH4 oxidation capacity.

Response of methanotrophs and methane oxidation on ammonium application in landfill soils

To test the dose effect of ammonium (NH4+) fertilization on soil methane (CH4) oxidation by methanotrophic communities, batch incubations were conducted at a wide scale of NH4+ amendments: 0, 100, 250, 500, and 1,000 mg Nkg(dry soil(-1)). Denaturing gradient gel electrophoresis and real-time quantitative PCR analysis were conducted to investigate the correlation between the CH4 oxidation capacity and methanotrophic communities. Immediately after the addition of NH4+, temporal inhibition of CH4 oxidation occurred, and this might have been due to the non-specific salt effect (osmotic stress). After a lag phase, the CH4 oxidation rates of the soils with NH4+ fertilization were promoted to levels higher than those of the controls. More than 100 mg Nkg(dry soil(-1)) of NH4+ addition resulted in the reduction of type II/type I MOB ratios and an obvious evolution of type II MOB communities, while less than 100 mg Nkg(dry soil(-1)) of NH4+ addition induced nearly no change of methanotrophic community compositions. The NH(4+)-derived stimulation after the lag phase was attributed to the improvement of N availability for type I MOB. Compared with the controls, 100 mg Nkg(dry soil(-1)) of NH(4) (+) addition doubled the CH(4) oxidation peak value to more than 20 mg CH4kg(dry soil(-1)) h(-1). Therefore, an appropriate amount of leachate irrigation on the landfill cover layer might efficiently mitigate the CH4 emissions.

Kinetics of biological methane oxidation in the presence of non-methane organic compounds in landfill bio-covers

In this experimental program, the effects of non-methane organic compounds (NMOCs) on the biological methane (CH4) oxidation process were examined. The investigation was performed on compost experiments incubated with CH4 and selected NMOCs under different environmental conditions. The selected NMOCs had different concentrations and their effects were tested as single compounds and mixtures of compounds. The results from all experimental sets showed a decrease in CH4 oxidation capacity of the landfill bio-cover with the increase in NMOCs concentrations. For example, in the experiment using compost with 100% moisture content at 35 degrees C without any NMOCs the V(max) value was 35.0 microg CH4 h(-1)gwet wt(-1). This value was reduced to 19.1 microg CH4 h(-1) gwet wt(-1) when mixed NMOCs were present in the batch reactors under the same environmental conditions. The experimental oxidation rates of CH4 in the presence of single and mixed NMOCs were modeled using the uncompetitive inhibition model and kinetic parameters, including the dissociation constants, were obtained. Additionally, the degradation rates of the NMOCs and co-metabolic abilities of methanotrophic bacteria were estimated.

Responses of oxidation rate and microbial communities to methane in simulated landfill cover soil microcosms

CH4 oxidation capacities and microbial community structures developed in response to the presence of CH4 were investigated in two types of landfill cover soil microcosms, waste soil (fine material in stabilized waste) and clay soil. CH4 emission fluxes were lower in the waste soil cover over the course of the experiment. After exposure to CH4 flow for 120 days, the waste soil developed CH4 oxidation capacity from 0.53 to 11.25–13.48μmol CH4gd.w.−1h−1, which was ten times higher than the clay soil. The topsoils of the two soil covers were observed dried and inhibited CH4 oxidation. The maximum CH4 oxidation rate occurred at the depth of 10–20cm in the waste soil cover (the middle layer), whereas it took place mainly at the depth of 20–30cm in the clay soil cover (the bottom layer). The amounts of the phospholipid fatty acid (PLFA) biomarks 16:1ω8c and 18:1ω8c for type I and II methanotrophs, respectively, showed that type I methanotrophic bacteria predominated in the clay soil, while the type II methanotrophic bacteria were abundant in the waste soil, and the highest population in the middle layer. The results also indicated that a greater active methanotrophic community was developed in the waste soil relative to the clay soil.

Methane fluxes on agricultural and forested boreal organic soils

Abstract. Annual methane fluxes from an organic soil in eastern Finland, originally drained and planted with birch (Betula pendula) and then later cultivated, were studied for two years using a chamber technique. The agricultural soils growing grass or barley or without vegetation, generally acted as sinks for CH4. Surprisingly, the agricultural soils emitted CH4 during a warm dry summer. The CH4 oxidation capacity and CH4 uptake rate of the forested site was three times that of agricultural soils. Also, the forest soil better retained its capacity to take up CH4 during a dry summer. Despite periods of CH4 emission, the agricultural soils were annual sinks for CH4, with uptake rate of CH4‐C varying from 0.1 to 3.7 kg ha−1 yr−1. The forested soil had a methane uptake rate of 3.9 kg CH4‐C ha−1 yr−1. All the soils acted as sinks for CH4 during winter, which contributed up to half of the annual CH4 uptake. The capacity of soils to transport gases did not explain the larger CH4 uptake rate in the forest soil. At the same gas filled porosity, the forest soil had a much larger CH4 uptake rate than the agricultural soil. Neither the soil acidity (pH 4.5 and 6.0) nor high ammonium content appeared to limit CH4 uptake. The results suggest that CH4 oxidation in agricultural organic soil is more sensitive to soil drying than CH4 oxidation in forested organic soil.

The effect of various environmental and design parameters on methane oxidation in a model biofilter.

Methane from landfills built with RCRA (Resource Conservation and Recovery Act) covers is frequently vented directly to the atmosphere. Alternatively, landfill gasses could be vented through a layer of soil that could serve as a biofilter to oxidize CH4 to carbon dioxide and water. Properly designed soil biofilters may reduce atmospheric CH4 emissions from landfills and help reduce the accumulation of greenhouse gasses in the atmosphere. This study was conducted to investigate the performance of a lab-scale model biofilter system using soil as the filterbed medium in packed columns to measure the effect of a variety of environmental and design factors on the CH4 oxidation capacity of a soil biofilter. Biofilter performance was tested under a variety of environmental and design conditions. The optimum soil moisture content for CH4 oxidation in a loamy sand was 13% by weight. Addition of NO3-N did not affect the CH4 oxidation rate. Soil depths of 30 cm and 60 cm were equally efficient in CH4 oxidation. When the CH4 loading rate was decreased, the percentage of CH4 oxidized increased. The maximum CH4 oxidation rate was 27.2 mol m(-2) d(-1) under optimum conditions.

The role of rice plants in regulating mechanisms of methane missions

Rice plants play a pivotal role in different levels of the methane (CH4) budget of rice fields. CH4 production in rice fields largely depends on plant-borne material that can be either decaying tissue or root exudates. The quantity and quality of root exudates is affected by mechanical impedance, presence of toxic elements, nutrient deficiencies, water status of growing medium, and nitrogenase activity in the rhizosphere. CH4 oxidation in rice fields is localized in the rhizosphere where the concentration gradients of CH4 and oxygen overlap. CH4 oxidation capacity is a function of the downward transport of oxygen through the aerenchyma, which, in turn, also acts as a conduit for CH4 from the soil to the atmosphere. The decisive step in the passage of CH4 through rice plant is the transition from root to stem. However, rice plants show an enormous variety of morphological and physiological properties, including differences in root exudation and gas transfer capacity. Comparative studies on different cultivars are deemed crucial for accomplishing a better understanding of the mechanisms of CH4 consumption in the rhizosphere and CH4 transport through the rice plant as well as the interaction of these processes. The results of such studies are considered tools for devising mitigation options.