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Biofiltration of methane emissions from a dairy farm effluent pond
Abstract
Dairy farm effluent ponds are a source of methane (CH4), a potent greenhouse gas. Biofiltration, whereby CH4 is oxidised by methanotrophic bacteria, is a potentially cost-effective CH4 mitigation technology. We report on the performance of a field-scale biofilter treating dairy farm effluent pond CH4 emissions for 16 months. This study is the first to report on the feasibility of using biofiltration to mitigate dairy waste CH4 emissions. The 70-L filter comprised a 1:1 volumetric mixture of volcanic soil from a landfill and perlite. Biogas collected in a floating cover on a 4-m2 section of the pond was directed through the biofilter's base. Air was pumped through the filter to supply oxygen to the methanotrophs. The filter's maximum CH4 removal rate was 16 g m−3 h−1 (or 53 μg g−1 h−1), which is high compared with literature landfill soil oxidation rates (typically <1 to 40 μg g−1 h−1). At the trial's conclusion, the filter experienced acid accumulation, due to oxidation of H2S in the inlet biogas (evidenced by low pH [3.9] and high sulphate-S [1079 mg−1 kg−1] at the base of the filter compared with the top [pH = 4.6, sulphate-S = 369 mg−1 kg−1]). Nonetheless, the filter's oxidation rate peaked at the end of the experiment indicating negligible H2S impact on overall performance over the 16-month period. The results showed that a 50-m3 filter would be needed to offset CH4 emissions (approximately 720 g h−1) from a typical 1000-m2 dairy effluent pond. As this calculation is based on the efficiency of a single experimental filter, field testing of replicate biofilters is needed to accurately establish full-scale filter sizing. Nonetheless, this study has shown that biofilter technology is feasible to mitigate dairy effluent pond CH4 emissions. Current research is underway to make the filter more economically viable through design optimisation.
... The use of hybrid packing materials in a biofiltration system takes advantage of the beneficial properties of both materials and may improve the performance of the system (Hernandez et al., 2015). More importantly, they are much simpler to operate since an external supply of nutrients is not required (Brandt et al., 2016;Pratt et al., 2012a). For instance, compost in hybrid systems has been shown to perform comparably to pure compost systems (Haubrichs and Widmann, 2006) due to its rich source of nutrients. ...
... In a study by Streese and Stegmann (2003), a hybrid mixture of compost, peat, and wood fibers was observed to eliminate more CH 4 over the course of a 1-year operation than pure compost by maintaining steady operation. Similarly, Pratt et al. (2012a) observed CH 4 elimination capacities of up to 384 g/ m 3 d using a 1:1 volumetric hybrid mixture of perlite and landfill-cap soil in a field experiment treating biogas from a farm effluent. The filter mixture provided a high porosity value of 84% which remained unchanged following the 16-month experiment and there was no sign of compaction or slumping at the end of the 16-month experiment. ...
... Similarly, Einola et al. (2008) observed severe drops in CH 4 removal efficiencies ranging from 0 to 22% in the winter on a field landfill lysimeter as a result of the presence of frost and snow suppressing the entry of O 2 . During the winter on a New Zealand farm effluent pond, Pratt et al. (2012a) observed almost no CH 4 oxidation as the ambient temperature dropped to −1°C. In comparison to biocovers, field biofilters offer a more controlled environment since they can be capped and insulated to minimize the effects of external variability. ...
The on-going annual increase in global methane (CH4) emissions can be largely attributed to anthropogenic activities. However, as more than half of these emissions are diffuse and possess a concentration less than 3% (v/v), physical-chemical treatments are inefficient as an abatement technology. In this regard, biotechnologies, such as biofiltration using methane-oxidizing bacteria, or methanotrophs, are a cost-effective and efficient means of combating diffuse CH4 emissions. In this review, a number of abiotic factors including temperature, pH, water content, packing material, empty-bed residence time, inlet gas flow rate, CH4 concentration, as well biotic factors, such as biomass development, are reviewed based on empirical findings on CH4 biofiltration studies that have been performed in the last decades.
... Before the start of the experiment, very low CH 4 removal rates were evident in the soil biofilter previously studied by Pratt et al. (2012) (data not shown). The low removal rates were probably either due to the drying out of the biofilter material (soil moisture 12.5 % water-holding capacity (WHC)) or to the temporary disconnection of the CH 4 feed line 2-3 months before the experiment began. ...
... The biofilter was reconstructed by using the soil medium from the biofilter established by Pratt et al. (2012) containing a 50/ 50 (v/v) mixture of volcanic pumice soil (Andisol) and perlite enriched with MOB and acidified to pH 3.72 by the oxidation of H 2 S produced from the dairy effluent pond over its 5-year use. This was done by gentle mixing and wetting the soil to about 60 % WHC (previously suggested by Pratt et al. (2012) and refilling the biofilter column (1 m high and 0.35 m in diameter) with 58 L of soil medium up to a height of 54 cm. ...
... The biofilter was reconstructed by using the soil medium from the biofilter established by Pratt et al. (2012) containing a 50/ 50 (v/v) mixture of volcanic pumice soil (Andisol) and perlite enriched with MOB and acidified to pH 3.72 by the oxidation of H 2 S produced from the dairy effluent pond over its 5-year use. This was done by gentle mixing and wetting the soil to about 60 % WHC (previously suggested by Pratt et al. (2012) and refilling the biofilter column (1 m high and 0.35 m in diameter) with 58 L of soil medium up to a height of 54 cm. The biofilter column had inlet port at the bottom, ten sample ports-spaced 5 cm apart down the side of the biofilter and an outlet port to facilitate gas sampling at various depths in the biofilter. ...
A biofilter made using volcanic pumice soil from a landfill in Taupo, New Zealand has been found to mitigate CH4 emissions from New Zealand dairy effluent ponds. However, the biofilter after drying out following almost 5 years of use removed little or no CH4. Furthermore, H2S present in the biogas (from the dairy effluent ponds) had increased the acidity (pH) in the soil biofilter from 5.2 to 3.72 during this 5-year period. In this study, we adjusted the soil moisture to 60 % water-holding capacity (WHC) and investigated the CH4-oxidising capacity of a reconstituted acidic soil biofilter operating at low pH (3.72) and characterised the abundance and diversity of methane-oxidising bacteria (MOB) using quantitative polymerase chain reaction (qPCR) and terminal-restriction fragment length polymorphism (T-RFLP). The acidic soil biofilter achieved a maximum CH4 removal rate of 30.3 g m–3 h–1. Both types I and II MOB communities, along with some uncultured novel MOB strains or species in the biofilter column, were present. Among these, Methylocapsa-like type II methanotrophs were significantly more prominent than the other MOB. Other MOB, Methylococcus (type I), Methylobacter/Methylomonas/Methylosarcina (type I) genera, Methylosinus and Methylocystis (type II), were least abundant. During the 90-day study, the population of Methylocapsa-like MOB increased 4-fold, demonstrating the ability of these soil microorganisms to grow under acidic pH conditions in the biofilter, whereas the populations of type I MOB remained stable, and the populations of type II MOB (except Methylocapsa) decreased. Our results indicated that (i) a soil biofilter can effectively regain efficiency if sufficient moisture levels are maintained, regardless of the soil acidity; (ii) changes in the MOB population did not compromise the capacity of the volcanic pumice soil to oxidise CH4; (iii) the more acidic environment (pH 3.72) tends to favour the growth and activity of acid loving Methylocapsa-like MOB while being detrimental to the growth of Methylobacter/Methylocystis/Methylococcus group of MOB; and (iv) novel species or strains of uncultured Methylomicrobium
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Methylosarcina/Methylobacter (type I MOB) could be present in the soil biofilter. This study has revealed the MOB population changes in the biofilter with acidification did not compromise its capacity to oxidise CH4 demonstrating that soil biofilter can operate effectively under acidic conditions.
... This study builds on the findings of Pratt et al. (2012b), demonstrating that the field soil biofilter operating at Massey No. 4 dairy farm pond can achieve high methane (CH 4 ) removal efficiency. The aim of the study was to characterise methanotroph (CH 4 -eating bacteria) abundance and diversity in the column biofilter that has been operating almost continuously for 5 years with little maintenance. ...
... Overall, the type I and type X populations of methanotrophs increased from day-0 to day-90, positively correlating with the increase in CH 4 removal. The maximum CH 4 removal rate achieved at the end of 90 days of study was 30.3 g m -3 h -1 , which is higher than earlier reported by Pratt et al. (2012b). This study demonstrated the importance of biofilter moisture content and pH in controlling CH 4 oxidation rates; and the effect of the acidic environment on changing active / inactive population dynamics of methanotrophs. ...
... Biofiltration study carried out by Pratt et al. (2012b) demonstrated high CH 4 removals up to 16 g m -3 h -1 from a field column biofilter operating at Massey No.4 dairy pond, Palmerston North. The focus of our current research is on the engine of the biofilter; in particular how methanotroph abundance and diversity have influenced biofilter performance since it began operating about 5 years ago. ...
This study builds on the findings of Pratt et al. (2012b), demonstrating that the field soil biofilter operating at Massey No. 4 dairy farm pond can achieve high methane (CH4)removal efficiency. The aim of the study was to characterise methanotroph (CH4- eating bacteria) abundance and diversity in the column biofilter that has been operating almost continuously for 5 years with little maintenance. The methanotroph abundance and diversity in the reconstituted biofilter were studied for 3 months using the molecular biology technique, quantitative polymerase chain reaction (qPCR). Biofilter parameters including moisture content, pH, microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) were measured. Results revealed that type I, type X, and type II communities of methanotrophs were present across the biofilter, but type X and type I were found to be dominant. Methylocapsa were significantly higher than type I and type II community, with p values of 0.075 and 0.089, respectively. Other subgroups were minor, and included Methylococcus and the Methylobacter/Methylomonas/Methylomicrobium/Methylosarcina genera belonging to type I; and Methylosinus and Methylocystis belonging to type II, as indicated by the respective gene copy numbers. Overall, the type I and type X populations of methanotrophs increased from day-0 to day-90, positively correlating with the increase in CH4 removal. The maximum CH4 removal rate achieved at the end of 90 days of study was 30.3 g m–3 h–1, which is higher than earlier reported by Pratt et al. (2012b). This study
demonstrated the importance of biofilter moisture content and pH in controlling CH4 oxidation rates; and the effect of the acidic environment on changing active / inactive population dynamics of methanotrophs.
... Depending on its concentration, H 2 S can have both positive and negative effects on CH 4 oxidation efficiency. At low concentrations, H 2 S may provide sufficient nutrients for the growth of methanotrophs in the biofilm, whereas at high concentrations, it could inhibit bio-oxidation of CH 4 due to its toxicity and changing the pH of the system (Yu et al., 2009, Pratt et al., 2012Caceres et al., 2014). In the presence of water and air, H 2 S oxidizes to sulphuric acid resulting in pH reduction that can inhibit the growth and activity of methanotrophs (Nikiema et al., 2007;Pratt et al., 2012). ...
... At low concentrations, H 2 S may provide sufficient nutrients for the growth of methanotrophs in the biofilm, whereas at high concentrations, it could inhibit bio-oxidation of CH 4 due to its toxicity and changing the pH of the system (Yu et al., 2009, Pratt et al., 2012Caceres et al., 2014). In the presence of water and air, H 2 S oxidizes to sulphuric acid resulting in pH reduction that can inhibit the growth and activity of methanotrophs (Nikiema et al., 2007;Pratt et al., 2012). In addition to growth inhibition, H 2 S can also negatively impact the methanotroph's ability to oxidize CH 4 due to its high solubility in water at neutral pH, which has been found to be 3.85 g per kg of water at 1 atm and 20°C (Caceres et al., 2014). ...
... If mineral soils are to be used as MOL material, a texture dominated by the sand fraction or artificial mineral substrates such as porous clay (Gebert et al., 2003;Gebert et al., 2009) or perlite (Pratt et al., 2012) are excellent candidates to be employed in methane oxidation systems, given the above criteria. Supplementary Material S2 provides values for air capacity, field capacity, and available field capacity for a large range of particle size distributions (textures) of mineral soils, useful to deduce gas conductivity and diffusivity (air capacity, in connection with Gas transport), water retention (field capacity) and its plant available share (available field capacity). ...
Landfill methane currently represents the largest global source of greenhouse gas emissions from the solid waste sector. Emissions are expected to increase due to increasing waste generation, particularly in countries still landfilling biodegradable wastes. As a complementary measure to gas extraction with subsequent flaring or energy conversion, or for emissions reduction from old landfills or from landfills containing wastes with a low gas potential, microbial methane oxidation systems (MMOS) are considered a promising technology. Numerous studies relating to controlling factors and enhancement of microbial methane oxidation in biocovers, biowindows or biofilters, both in laboratory and in large scale field settings, have been published. The design of optimized MMOS requires thorough understanding of the involved processes, specifically the biological ones and of those related to the transport of gas and water in porous media, and of the impact of material properties and external environmental factors on these processes. Consequently, the selection of materials that are suitable from a biogeochemical and from a geotechnical point of view, meeting the required water and gas transport properties, are key aspects in the design process. This paper reviews the scientific background of the relevant concepts and processes dictating MMOS performance, and provides guidance on layout and design steps, including choice of materials and quality control. Further, a decision tree to support the choice of MMOS is proposed. This paper provides the scientific foundation for upcoming technical guidance documents.
... The maximum removal efficiencies recorded in FBB and FB were 26 % and 17 %, respectively, with EC comparable to those reported by Lebrero et al. [12] for a fungal-bacterial biofilter (35 g m −3 h -1 ). The EC achieved in this work was higher than the 16 g m −3 h -1 attained by Pratt et al. [28] in a biofilter inoculated solely with a methanotrophic bacterial consortium. Fig. 3 shows the CH 4 EC recorded at the different methane loading rates applied in both biofilters. ...
Methane is an important contributor to global warming and especially for dilute emissions, its oxidation to carbon dioxide can be difficult and expensive. Methane abatement was studied in a biofilter inoculated solely with the filamentous fungus Fusarium solani and compared to a biofilter inoculated with a consortium of methanotrophic bacteria (Methylomicrobium album and Methylocystis sp.) and F. solani.
Results showed that F. solani degrade methane as the sole carbon source, achieving a maximum elimination capacity of 42.2 g m-3 h-1, nearly half of the maximum elimination capacity of the fungal-bacterial consortium. The second Damköhler number indicates that under the prevailing operational conditions, the fungal biofilter performance was bioreaction limited meanwhile external mass transport limitation was found on the fungal/methanotrophic bacteria biofilter.
Results support the hypothesis that the beneficial effect of F. solani during CH4 biofiltration is mediated by biomass hydrophobicity rather than by an increase in the mass transfer area.
... Odorous compounds are emitted from many sectors of human activity, including wastewater treatment plants, communal waste landfills, agriculture and plenty of industrial facilities e.g., crude oil refineries, pulp and paper mills and various chemical industries. Additionally, the need for indoor air treatment is gaining interest [6][7][8][9][10][11]. Such emissions are controlled by various deodorization techniques. ...
Due to increasingly stringent legal regulations as well as increasing social awareness, the removal of odorous volatile organic compounds (VOCs) from air is gaining importance. This paper presents the strategy to compare selected biological methods intended for the removal of different air pollutants, especially of odorous character. Biofiltration, biotrickling filtration and bioscrubbing technologies are evaluated in terms of their suitability for the effective removal of either hydrophilic or hydrophobic VOCs as well as typical inorganic odorous compounds. A pairwise comparison model was used to assess the performance of selected biological processes of air treatment. Process efficiency, economic, technical and environmental aspects of the treatment methods are taken into consideration. The results of the calculations reveal that biotrickling filtration is the most efficient method for the removal of hydrophilic VOCs while biofilters enable the most efficient removal of hydrophobic VOCs. Additionally, a simple approach for preliminary method selection based on a decision tree is proposed. The presented evaluation strategies may be especially helpful when considering the treatment strategy for air polluted with various types of odorous compounds.
... This value is significantly higher than removal efficiency previously reported for field-scale biofilter systems. A biofilter with a 1:1 volumetric mixture of volcanic soil from a landfill and perlite only achieved a 16 g m −3 h −1 CH 4 removal rate when treating a dairy farm effluent pond (Pratt et al. 2012). Moreover, a field-scale biofilter filled with sand, gravel or clay treating residual landfill methane and achieved 80 g m −3 h −1 CH 4 removal rate (Gebert and Gröngröft 2006). ...
Low methane (CH4) emission reduction efficiency (< 25%) has been prevalent due to inefficient biological exhaust gas treatment facilities in mechanic biological waste treatment plants (MBTs) in Germany. This study aimed to quantify the improved capacity of biofilters composed of a mixture of organic (pine bark) and inorganic (expanded clay) packing materials in reducing CH4 emissions in both a lab-scale experiment and field-scale implementation. CH4 removal performance was evaluated using lab-scale biofilter columns under varied inflow CH4 concentrations (70, 130, and 200 g m−3) and corresponding loading rates of 8.2, 4.76, and 3.81 g m−3 h−1, respectively. The laboratory CH4 removal rates (1.2–2.2 g m−3 h−1) showed positive correlation with the inflow CH4 loading rates (4–8.2 g m−3 h−1), indicating high potential for field-scale implementation. Three field-scale biofilter systems with the proposed mixture packing materials were constructed in an MBT in Neumünster, northern Germany. A relatively stable CH4 removal efficiency of 38–50% was observed under varied inflow CH4 concentrations of 28–39 g m−3 (loading rates of 1120–2340 g m−3 h−1) over a 24-h period. The CH4 removal rate was approximately 500–700 g m−3 h−1, which was significantly higher than relevant previously reported field-scale biofilter systems (16–50 g m−3 h−1). The present study provides a promising configuration of biofilter systems composed of a mixture of organic (pine bark) and inorganic (expanded clay) packing materials to achieve high CH4 emission reduction.
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... One third of the sample (34%) are small plants that treat low flows (less than 5 L s -1 ); many of them do not properly manage the biogas produced, releasing it to the atmosphere, transferring pollution from water to air. Some authors have reported that small wastewater treatment plants may present operational problems due to low technical and financial resources, resulting in effluents of low quality and, in the case of anaerobic reactors, the unburned venting of biogas (Nikiema et al. 2005;Pratt et al. 2012;Tanaka et al. 2012). Anaerobic systems operated in countries with temperate climates (temperature around 20 °C) could release dissolved methane in the effluent (Noyola et al. 1988;Souza et al. 2011;Daelman et al. 2012). ...
... This concept was later confirmed using a biofilter where almost all the CH4 emissions produced from an average (ca. 450 cows) dairy farm waste pond could be removed (Pratt et al. 2012b). This biofilter has operated successfully with minimal maintenance on an effluent pond, over more than three years, removing up to 16 g CH4 m -3 h -1 (Pratt et al. 2012a). ...
... [14,16] The bulking properties of the packing material affect methane loading rate and oxidation efficiency which has flow-on consequences for PHA or C 16 /C 18 contents, but only very few studies reported pilot-scale testing. [12,17,18] In summary, the selection of active MOB-heterotrophs and testing of suitable packing material in biofilters are critically important to facilitate high rates of CH 4 removal from point emission sources, that is, landfills, coal mines, animal farming, anaerobic ponds, etc. As a systematic approach, the present study established a mixed methanotrophic consortium (MMC) from a marine sediment (proven robust inoculum [19]) to establish bio-filter characteristics and operational parameters for the remediation of low concentration CH 4 from coal mine ventilation air (<1% v/v in air) in an industrypartnered research project funded through the Advanced Manufacturing Cooperative Research Centre (AMCRC) at James Cook University (JCU), Australia. ...
Robust methanotrophic consortia for methane (CH4) remediation and by-product development are presently not readily available for industrial use. In this study, a mixed methanotrophic consortium (MMC), sequentially enriched from a marine sediment, was assessed for CH4 removal efficiency and potential biomass generated by-product development. Suitable packing material for bio-filters to support MMC biofilm establishment and growth was also evaluated. The enriched MMC removed ∼7-13% CH4 under a very high gas flow rate (2.5 L min-1; 20-25% CH4) in continuous stirred tank reactors (CSTR; ∼ 10 L working volume) and the biomass contained long chain fatty acids (i.e., C16 and C18). Cultivation of the MMC on plastic bio-balls abated ∼ 95-97% CH4 in pilot-scale non-sterile outdoor operated bio-filters (0.1 L min-1; 1% CH4). Contamination by cyanobacteria had beneficial effects on treating low level CH4, by providing additional oxygen for methane oxidation by MMC, suggesting that the co-cultivation of MMC with cyanobacterial mats does not interfere with and may actually be beneficial for remediation of CH4 and CO2 at industrial-scale.
... In a methane biofilter setup, MOB are immobilized on a carrier material in a fixed bed system. Although a full scale biofilter application has not been established yet, several lab scale tests have been conducted to remove methane emission from livestock housing (Girard et al., 2012;Pratt et al., 2012a;Veillette et al., 2012a). ...
Methane is the most important organic greenhouse gas emitted to the atmosphere for its contribution to the global warming. The gas has a strong infrared absorbance (i.e., 25 times more efficiently than carbon dioxide) which makes it a more effective greenhouse gas than carbon dioxide although having a shorter lifetime in the atmosphere (~9 years). Driven by the anthropogenic emission due to the increase of global population and energy demand, methane emission is set to increase in the future. Several anthropogenic methane emission mitigation has been applied in various sectors (agriculture, energy, and waste). The use of a biochemical reactor can be an alternative to remediate methane emission at low concentration (< 1 % (v/v)) as it environmentally friendly and economically more beneficial. In the biochemical oxidizer, Methane Oxidizing Bacteria (MOB) are used as the biocatalyst. MOB are part of methylotrophic bacteria, a group of bacteria capable of utilizing one carbon compounds as their carbon and energy sources. For gaseous waste having low solubility like methane, the typical bioreactor used to treat methane gas waste is biofilter where MOB are immobilized on a carrier material.
When designing a biofilter, carrier material selection is arguably the most crucial step. The preferred carrier materials possess a high porosity and surface area to provide space for the bacteria to grow and to increase the contact area between the bacteria and methane, respectively. Based on these criteria, building materials have the potential to be a good carrier material for a methane biofilter. Using this concept of “housing” MOB on building material, another biotechnological application of the bacteria was explored. Microbiologically Induced Carbonate Precipitation (MICP) is the production of carbonate mineral driven by environmental condition (e.g., pH) alteration as a result of microbial activity. In the construction industry, the typically applied urea hydrolysis based MICP poses several disadvantages such as ammonia release to the air and nitric acid production. In this thesis, the capacity of MOB to induce calcium carbonate precipitation as the basis for a more environmentally friendly biogenic building material surface protection was also explored. Therefore the thesis is divided into two parts: Part 1 deals with the exploration of building material utilization as the carrier material for methane biofiltration (Chapter 2 to 4) whereas Part 2 deals with the exploration of MOB application on building materials as an alternative biocatalyst for the material surface treatment (Chapter 5 and 6).
In Chapter 2 a screening of different building material and MOB culture was done to select the combination of both which allow the bacteria to exhibit the highest methane removal capacity. Experiments were performed with different MOB inoculated on building materials at high (~20 % (v/v)) and low (~100 ppmv) methane concentrations. Methylocystis parvus in Autoclaved Aerated Concrete (AAC) exhibited the highest methane removal rate at high (28.5 ± 3.8 μg CH4 g-1 building material h-1) and low (1.7 ± 0.4 μg CH4 g-1 building material h-1) methane concentration. Due to the higher volume of pores with diameter > 5 μm compared to other materials tested, AAC was able to adsorb more bacteria which might explain for the higher methane removal observed. The total methane and carbon dioxide-carbon in the headspace was decreased for 65.2 ± 10.9 % when M. parvus in AAC was incubated for 100 hours. AAC was therefore selected for the carrier material for the subsequent methane bioremediation studies (Chapter 3 and 4) and M. parvus was selected as the MOB strains for MICP studies (Chapter 5 and 6).
In Chapter 3, the methane removal capacity of mixed MOB culture in a biofilter setup using AAC as a highly porous carrier material was tested. Although it was found that M. parvus exhibited the highest methane removal capacity on AAC (Chapter 2), mixed MOB culture was the selected culture for the biofilter inoculation in this study. This was based on the fact that non-aseptic practice was preferred to keep the operating cost lower if the biofilter was to be applied to remove methane in places with high methane emission (atmospheric concentration < 1 % (v/v)). Batch experiment was performed to optimize MOB immobilization on the AAC specimens where optimum methane removal was obtained when calcium chloride was not added during bacterial inoculation step and 10 mm thick AAC specimens were used. The immobilized MOB could remove methane at low methane concentration (~1000 ppmv) in a biofilter setup for 127 days at an average Removal Efficiency (RE) of 28.7%. MOB also exhibited a higher abundance at the bottom of the filter, in proximity with the methane gas inlet where a high methane concentration was found. It was concluded here that a reasonably efficient and a more environmentally friendly methane biofilter performance can be obtained using AAC as the carrier material. Hence, the setup was used in a field test application (Chapter 4).
The performance of MOB immobilized on AAC to remove methane from ruminants effluent gas was investigated in Chapter 4. A biofilter employed in Chapter 3 was used as the biofilter in this study. Two dairy cows were housed in respiration chambers for two days where the exhaust gas from the chambers was used as the biofilter feed. MOB consumed methane at an average RE of 17.52 % and elimination capacity (EC) of 67.3 g m-3 d-1. Several factors that might cause the lower RE and EC compared to the lab scale study (RE = 28.7 %) in Chapter 3 are: (a) the lower methane concentration and (b) the presence of ammonia in the livestock effluent gas, (c) the higher gas flow rate into the biofilter, and (d) the lowering humidity level in the biofilter. By using AAC as carrier material, carbon dioxide in the effluent gas as well as the one from the methane oxidation by MOB were removed by the carbonation reaction with AAC. Thus, complete carbon sequestration from methane was obtained. Overall, in part 1 of this thesis (Chapter 2 to 4) it was concluded that a more environmentally friendly methane biofilter than the ones previously tested could be achieved when using ACC as the carrier material.
An alternative MICP from calcium formate by Methylocystis parvus OBBP is presented in Chapter 5. To induce calcium carbonate precipitation, M. parvus was incubated at different calcium formate concentrations and starting culture densities. Up to 91.4 % ± 1.6 % of the initial calcium was precipitated in the methane amended cultures compared to 35.1 % ± 11.9 % when methane was not added. Because the bacteria could only utilize methane for growth, higher culture densities and therefore calcium removals were exhibited in the cultures when methane was added. A higher calcium carbonate precipitate yield was obtained when higher culture densities were used but not necessarily when more calcium formate was added. This was mainly due to salt inhibition of the bacterial activity at a high calcium formate concentration. A maximum of 0.67 ± 0.03 CaCO3 Ca(CHOOH)2-1 (g/g) calcium carbonate precipitate yield was obtained when 109 cells mL-1 and 5 g L-1 of calcium formate were used. Compared to the current strategy employing biogenic urea degradation as the basis for MICP, the approach in this study presents significant improvements in terms of pollutant emission reduction if applied in the construction industry. The process was subsequently applied on building material as an alternative surface treatment (Chapter 6).
The effectiveness of MICP from the formate oxidation by Methylocystis parvus as an alternative concrete surface treatment was investigated in Chapter 6. MICP was induced on AAC by immersing the material in 109 M. parvus cells mL-1 containing 5 g L-1 of calcium formate. A 2 days immersion of the material gave the highest weight increase of the specimen due to the calcium carbonate deposition. The deposition mainly occurred on the wall of the pores on the surface of the specimen. Due to this surface deposition, a significantly lower water absorption was observed in the bacterially treated specimens compared to the non-treated ones (i.e., up to 2.92 ± 0.91 kg m-2). A concomitant atmospheric methane removal (152.2 ± 40.1 μg of CH4 m-2 h-1) was also observed in the bacterially treated specimens. Overall, in part 2 of this thesis (Chapter 5 and 6) it was concluded that compared to the currently employed biogenic processes, the formate-based MICP by M. parvus offers a more environmentally friendly approach for the biotechnological application to protect concrete surface.
The results obtained from part 1 and 2 in this thesis were subsequently positioned in their related biotechnology field and the outlook for the respective researches was presented in Chapter 7. The AAC-based methane biofilter had lower methane removal efficiency compared to the previously reported biofilters, although the other biofilters operated with higher Empty Bed Residence Time (EBRT) which might increase the overall methane conversion in the biofilter. The AAC-based methane biofilter, however, offers an advantage of carbon dioxide sequestration and this advantage is not found in the other biofilters. For the formate-oxidation based MICP by M. parvus, it was found that, on per cell basis, the optimum biomineralization rate obtained in Chapter 5 (i.e., at 5 g L-1 calcium formate and 109 cells ml-1) was still approximately three times lower than the maximum urea based biomineralization rate by B. pasteurii ATCC 6453. Moreover, unlike the urea-based MICP where a high urea / calcium source concentration could be employed, the influence of the formate-oxidation based MICP on the building material characteristics was smaller. Nevertheless, the resulting calcium carbonate deposition could effectively lowered water intrusion into the material. Based on the results obtained, several suggestions were made. To construct the biofilter like the “green façade” concept, MOB should be applied by brushing / spraying on existing building material with consecutive applications of nutrient applications to sustain the MOB growth on the building structure. For the MOB-based MICP, the application on natural stones to test the effectiveness of the process as the surface treatment for this type of material should be performed. Future studies should also look into the use of mixed culture MOB as it may lower the cost of this type of application.
... This approach requires additional inputs in the form of industrial-or plantwaste biomass because methanogenesis from manure alone may not produce sufficient quantities of methane (Prapaspongsa et al. 2010). For smaller scale farms (herds of 100–350 animals), a more cost-effective means to reduce methane emissions may be via the use of biofilters, which filter methane from an anaerobic source and oxygen through an artificial soil MOB community (Melse and Van der Werf 2005; Pratt et al. 2012). The implementation of such mitigation strategies depends largely on construction and energy costs, and government incentives for investment in renewable energy technology (Wilkinson 2011). ...
Methane is a potent greenhouse gas with a global warming potential similar to 28 times that of carbon dioxide. Consequently, sources and sinks that influence the concentration of methane in the atmosphere are of great interest. In Australia, agriculture is the primary source of anthropogenic methane emissions (60.4% of national emissions, or 3 260 kt(-1) methane year(-1), between 1990 and 2011), and cropping and grazing soils represent Australia's largest potential terrestrial methane sink. As of 2011, the expansion of agricultural soils, which are similar to 70% less efficient at consuming methane than undisturbed soils, to 59% of Australia's land mass (456 Mha) and increasing livestock densities in northern Australia suggest negative implications for national methane flux. Plant biomass burning does not appear to have long-term negative effects on methane flux unless soils are converted for agricultural purposes. Rice cultivation contributes marginally to national methane emissions and this fluctuates depending on water availability. Significant available research into biological, geochemical and agronomic factors has been pertinent for developing effective methane mitigation strategies. We discuss methane-flux feedback mechanisms in relation to climate change drivers such as temperature, atmospheric carbon dioxide and methane concentrations, precipitation and extreme weather events. Future research should focus on quantifying the role of Australian cropping and grazing soils as methane sinks in the national methane budget, linking biodiversity and activity of methane-cycling microbes to environmental factors, and quantifying how a combination of climate change drivers will affect total methane flux in these systems.
... Considering the low methane concentration in the ruminant effluent gas, biotechnological applications are economically beneficial and environmentally friendly strategies to treat the gas [8,9]. Biofiltration, a typical biotechnological application for methane remediation, has been applied previously to mitigate ruminant methane emissions [10,11]. Methane-Oxidizing Bacteria (MOB) are the biocatalysts used to degrade methane in the biofilter. ...
... For example, secondary N 2 O emissions from dairy effluent ponds in NZ are not accounted for in the national GHG inventory. Yet, in a study by Pratt et al. (2012), measured NH 3 emissions from an anaerobic dairy effluent pond indicated a nationwide secondary N 2 O production rate of 0.4 Mt CO 2 -e/year (usingTable 1 F Animal Production Sciencefactor). The accuracy of this estimate is compromised by the extremely short monitoring period (2 days) on a 4-m 2 section of one pond, and the questionable appropriateness of the secondary N 2 O emission factor. ...
Australia's and New Zealand's major agricultural manure management emission sources are reported to be, in descending order of magnitude: (1) methane (CH4) from dairy farms in both countries; (2) CH4 from pig farms in Australia; and nitrous oxide (N2O) from (3) beef feedlots and (4) poultry sheds in Australia. We used literature to critically review these inventory estimates. Alarmingly for dairy farm CH4 (1), our review revealed assumptions and omissions that when addressed could dramatically increase this emission estimate. The estimate of CH4 from Australian pig farms (2) appears to be accurate, according to industry data and field measurements. The N2O emission estimates for beef feedlots (3) and poultry sheds (4) are based on northern hemisphere default factors whose appropriateness for Australia is questionable and unverified. Therefore, most of Australasia's key livestock manure management greenhouse gas (GHG) emission profiles are either questionable or are unsubstantiated by region-specific research. Encouragingly, GHG from dairy shed manure are relatively easy to mitigate because they are a point source which can be managed by several 'close-to-market' abatement solutions. Reducing these manure emissions therefore constitutes an opportunity for meaningful action sooner compared with the more difficult-to-implement and long-term strategies that currently dominate agricultural GHG mitigation research. At an international level, our review highlights the critical need to carefully reassess GHG emission profiles, particularly if such assessments have not been made since the compilation of original inventories. Failure to act in this regard presents the very real risk of missing the 'low hanging fruit' in the rush towards a meaningful response to climate change.
... As already commented on, the very rapid recovery of type II methanotrophs when soil used for agriculture but formerly under forest was reforested (Fig. 1) illustrate this trait (e.g., Singh et al., 2009;Nazaries et al., 2011). Populations of type I methanotrophs appear very responsive to substrate availability in environments where disturbances are common, for example, as shown in Arctic tundra soil (Liebner et al., 2009;Yergeau et al., 2010), rice paddy soils (Ho et al., 2011), and engineered biofilters (e.g., Pratt et al., 2012). ...
... Four areas of research are promoted: mitigation of enteric methane emissions, mitigation of nitrous oxide emissions, soil carbon research, and integrated low GHG-emitting farm systems. Few mitigation techniques are available to offset CH 4 emissions from effl uent ponds, but research to develop a cost-effective biofi ltration technology using methanotrophic bacteria is well advanced (Pratt et al. 2012). In general, methods used to quantify climate regulation involve biogeochemical regulation (e.g. ...
This chapter reviews all stocks and fl uxes of carbon in New Zealand, and reviews biophysical regulation through surface albedo. The terrestrial environment provides a climate-regulation service by assimilating, transforming, and adjusting to emissions of greenhouse gases that could otherwise lead to undesirable changes in global climate. Quantifying this service requires accounting for both stocks and flows. While greenhouse gas emissions and removals are reported in the national inventory, this inventory accounts only
for human-induced changes in greenhouse gases, and omits some natural processes and ecosystems; for example, indigenous forest and scrub are not included but represent the largest biomass carbon pool in New Zealand. Emissions are mainly attributed to the energy and agricultural sectors, while removals come from exotic forestry and natural shrubland regeneration. Erosion plays a role as a carbon sink through natural regeneration of soil carbon on slopes. Biophysical regulation occurs through absorption or reflection of solar radiation (albedo). Forests tend to absorb more radiation than crops or pasture, thus contributing to a lesser extent to global warming. Government currently provides some mechanisms to incentivise sustainable land management in favour of increased forest area on lands unsuitable for agriculture. However, carbon stocks are also at risk of being lost through degradation of natural ecosystems, and this requires active management and mitigation strategies.
Methanotrophs are Microorganisms that are able to utilize Methane as the electron donor and carbon source. For long, Methanotrophs have been widely studied for their application in Environmental biotechnology, due mainly to the exclusive ownership of the unique Enzymes that mediate Oxidation of Methane to Methanol, namely the Particulate methane monooxygenases (pMMO) and soluble methane monooxygenases Soluble methane monooxygenase (sMMO). Utilizing these Methane monooxygenases, Methanotrophs are capable of Co-oxidizing a broad range of Organic pollutants including Chlorinated ethenes. Thus, Methanotrophs have long been studied and utilized as Biocatalysts for In situBioremediation of soil and aquatic environments contaminated with these Xenobiotic compounds. Due to the growing concerns in anthropogenically induced Climate change and Global warming, Methanotrophs have increasingly gained attention also for greenhouse gas mitigation purposes. Active Methane removal using MethanotrophicBiofilters of diverse configurations have proven to be effective for treatments of gases with relatively high Methane concentrations, e.g., landfill Landfill gases (LFG) and animal husbandry tank exhausts. Furthermore, improving the atmospheric Methane sink capability of agricultural soils has been one of the foremost foci of climate-smart Climate-smart soils research. This chapter provides an extensive overview of scientific and engineering breakthroughs geared towards practical applications of Methanotroph biotechnology in managing impending environmental problems.
Hydrogen sulfide (HS) contamination in biogas produced from animal wastes limits its use to cooking and precludes it from being used for heating, lighting, or electricity generation. This limitation results in the release to the atmosphere of between 3 and 51% of total biogas produced. Biogas contains 50 to 70% methane (CH), a potent greenhouse gas that contributes to global warming. This study aimed to develop a cost-effective HS filtering system using local materials rich in iron as iron oxide (FeO), which reacts readily with HS and forms adsorbed iron sulfide (FeS) when gas is passed through it. Here we tested the performance of seven New Zealand soils and sand, each at five different gas flow rates (59, 74, 94, 129, and 189 mL min). We found that three materials (allophanic soil, brown soil, and black sand) had stable HS removal efficiencies close to 100% at all gas flow rates, followed by typic sand (89-99%), raw sand (76-99%), acidic sand (48-89%), and podzol soil (58-87%). These results show that inexpensive and simple filters to remove HS from biogas can be made using local soils. Used soil in the filters can then be easily regenerated by exposure to the atmosphere and reused to achieve sustained HS removal efficiency. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.
The accurate quantification of the carbon footprints of animal products and the related development of greenhouse gas (GHG) mitigation strategies are of interest to consumers, the general public, and the academic community. The objective of this review was to summarize recent advances in GHG emission quantification, life‐cycle assessment applications, and mitigation technologies for animal production in the USA, to assist the development of system‐based solutions for mitigation of GHG emissions from animal production. The GHG emissions from animal production mainly come from feed production, enteric fermentation, and manure management. Opportunities to mitigate emissions from feed production largely rely on continuous improvements in animal and feed production efficiency. This is in general agreement with the economic interest of the industry. To mitigate emissions from manure, many technologies can be chosen, depending on the given economic and regulatory environments. It is possible to minimize GHG emissions from manure through manure energy recovery when this is economically feasible. For enteric emissions, there are limited opportunities to reduce GHG emissions through dietary manipulation, feed management, or feed supplementations. Improving environmental stewardship of consumers and reducing food waste will reduce animal protein demand and are important bottom‐line strategies to mitigate GHG from animal production systems. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.
Methane (CH4) is the second greatest contributor to anthropogenic climate change. Emissions have tripled since pre-industrial times and continue to rise rapidly, given the fact that the key sources ¬– food production, energy generation and waste management – are inexorably tied to population growth. Until recently, the pursuit of CH4 mitigation approaches has tended to align with opportunities for easy energy recovery through gas capture and flaring. Consequently, effective abatement has been largely restricted to confined high-concentration sources such as landfills and anaerobic digesters, which do not represent a major share of CH4’s emission profile. However, in more recent years we have witnessed a quantum leap in the sophistication, diversity and affordability of CH4 mitigation technologies on the back of rapid advances in molecular analytical techniques, developments in material sciences and increasingly efficient engineering processes. Here, we present some of the latest concepts, designs and applications in CH4 mitigation, identifying a number of abatement synergies across multiple industries and sectors. We also propose novel ways to manipulate cutting-edge technology approaches for even more effective mitigation potential. The goal of this review is to stimulate the ongoing quest for and uptake of practicable CH4 mitigation options; supplementing established and proven approaches with immature yet potentially high-impact technologies. There has arguably never been, and if we don’t act soon nor will there be, a better opportunity to combat climate change’s second most significant greenhouse gas.
Mitigating methane (CH4) emissions from New Zealand dairy effluent ponds using volcanic pumice soil biofilters has been found to be a promising technology. Because the soil column biofilter prototype previously used was cumbersome, here we assess the effectiveness of volcanic pumice soil-perlite biofilter media in a floating system to remove high concentrations of CH4 emitted from a dairy effluent pond and simultaneously in a laboratory setting. We measured the CH4 removal over a period of 11 mo and determined methanotroph population dynamics using molecular techniques to understand the role of methanotroph population abundance and diversity in CH4 removal. Irrespective of the season, the pond-floating biofilters removed 66.7 ± 5.7% CH4 throughout the study period and removed up to 101.5 g CH4 m⁻³ h⁻¹. By contrast, the laboratory-based floating biofilters experienced more biological disturbances, with both low (~34%) and high (~99%) CH4 removal phases during the study period and an average of 58% of the CH4 oxidized. These disturbances could be attributed to the measured lower abundance of type II methanotroph population compared with the pond biofilters. Despite the acidity of the pond biofilters increasing significantly by the end of the study period, the biofilter encouraged the growth of both type I (Methylobacter and Methylomonas) and type II (Methylosinus and Methylocystis) methanotrophs. This study demonstrated the potential of the floating biofilters to mitigate dairy effluent ponds emissions efficiently and indicated methanotroph abundance as a key factor controlling CH4 oxidation in the biofilter. © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. 5585 Guilford Rd., Madison, WI 53711 USA. All rights reserved.
The dairy industry is rapidly growing, which raises the problem of disposal of the effluent generated from farm to factory. If this effluent is not treated correctly, eutrophication of waterways can take place. Biofilms can have both positive and negative effects. Biofilms present in processes such as sludge reactors help with the removal of heavy metals and nutrients. Irrigation of effluent on to fields is a relatively new method for disposal; however, the extracellular polymeric substances (EPS) excreted by biofilms cause the entrapment of particles, such as clay, blocking the irrigator heads. We do not yet know the full potential of biofilms to cause problems in dairy wastewater systems or the combination of conditions that will result in their formation. We also do not fully understand the potential for biofilms in the treatment of dairy wastewater.
Previous studies have demonstrated the effective utility of volcanic pumice soil to mitigate both high and low levels of methane (CH4) emissions through the activity of both γ-proteobacterial (type I) and α-proteobacterial (type II) aerobic methanotrophs. However, the limited availability of volcanic pumice soil necessitates the assessment of other farm soils and potentially suitable, economical and widely available biofilter materials. The potential biofilter materials, viz. farm soil (isolated from a dairy farm effluent pond bank area), pine biochar, garden waste compost and weathered pine bark mulch, were inoculated with a small amount of volcanic pumice soil. Simultaneously, a similar set-up of potential biofilter materials without inoculum was studied to understand the effect of the inoculum on the ability of these materials to oxidise CH4 and their effect on methanotroph growth and activity. These materials were incubated at 25 °C with periodic feeding of CH4, and flasks were aerated with air (O2) to support methanotroph growth and activity by maintaining aerobic conditions. The efficiency of CH4 removal was monitored over 6 months. All materials supported the growth and activity of methanotrophs. However, the efficiency of CH4 removal by all the materials tested fluctuated between no or low removal (0–40 %) and high removal phases (>90 %), indicating biological disturbances rather than physico-chemical changes. Among all the treatments, CH4 removal was consistently high (>80 %) in the inoculated farm soil and inoculated biochar, and these were more resilient to changes in the methanotroph community. The CH4 removal from inoculated farm soil and inoculated biochar was further enhanced (up to 99 %) by the addition of a nutrient solution. Our results showed that (i) farm soil and biochar can be used as a biofilter material by inoculating with an active methanotroph community, (ii) an abundant population of α -proteobacterial methanotrophs is essential for effective and stable CH4 removal and (iii) addition of nutrients enhances the growth and activity of methanotrophs in the biofilter materials. Further studies are underway to assess the feasibility of these materials at small plot and field scales.
Abstract The livestock and poultry production industry, regulatory agencies, and researchers lack a current, science-based guide and data base for evaluation of air quality mitigation technologies. Data collected from science-based review of mitigation technologies using practical, stakeholders-oriented evaluation criteria to identify knowledge gaps/needs and focuses for future research efforts on technologies and areas with the greatest impact potential is presented in the Literature Database tab on the Air Management Practices Tool (AMPAT). The AMPAT is web-based (available at www.agronext.iastate.edu/ampat) and provides an objective overview of mitigation practices best suited to address odor, gaseous, and particulate matter (PM) emissions at livestock operations. The data was compiled into Excel spreadsheets from a literature review of 266 papers was performed to (1) evaluate mitigation technologies performance for emissions of odor, volatile organic compounds (VOCs), ammonia (NH3), hydrogen sulfide (H2S), particulate matter (PM), and greenhouse gases (GHGs) and to (2) inform future research needs.
There is growing international concern about the increasing levels of greenhouse gases in the atmosphere, particularly CO2 and methane. The emissions of methane derived from human activities are associated with large flows and very low concentrations, such as those emitted from landfills and wastewater treatment plants, among others. The present work was focused on the biological methane degradation at diffuse concentrations (0.2% vv(-1)) in a conventional biofilter using a mixture of compost, perlite and bark chips as carrier. An extensive characterization of the process was carried out at long-term operation (250 days) in a fully monitored pilot plant, achieving stable conditions during the entire period. Operational parameters such as waterings, nitrogen addition and inlet loads and contact time influences were evaluated. Obtained results indicate that empty bed residence times within 4-8 minutes are crucial to maximize elimination rates. Waterings and the type of nitrogen supplied in the nutrient solution (ammonia or nitrate) have a strong impact onto the biofilter performance. The better results compatible with a stable operation were achieved using nitrate, with elimination capacities up to 7.6 ± 1.1 g CH4 m(-3) h(-1). The operation at low inlet concentrations implied that removal rates obtained were quite limited (ranging 3 - 8 g CH4 m(-3) h(-1)), however, these results could be significantly increased (up to 20.6 g CH4 m(-3) h(-1)) at higher inlet concentrations, which indicates that the mass transfer from the gas to the liquid layer surrounding the biofilm is a key limitation of the process.
Effective utilization of waste resources was a hot topic in recent years. In this study, three experiments were designed to study the application of dairy effluent on the flue-cured tobacco irrigation, they were: 1) the enlarge cultivation of EM stoste, 2) the application of EM culture solution on the dairy effluent cleansing, 3) the application of EM-treated dairy effluent on tobacco irrigation. The results showed that after the enlarge cultivation, the pH of EM culture solution was on a trend of decreasing, and the microbe quantity increased rapidly, T6 (the volume ratio of EM stoste, accounted by 6%, 8% and 86%, respectively) was chosen as the optimum cultivation formula on account of the reasonable pH (4.22), microbe quantity (7.28×107), and lower production cost; after EM culture solution applying to the dairy effluent for 12 days cultivation, the COD degradation and deodorization effect was satisfactory, the COD degradation rate of H1, H2, H3 was 33.92%, 30.99% and 27.78%, respectively, and at the 12th day, the mixed liquor of H1 and H2 had sweet smell, H3 was generally odorless; applying the EM-treated effluent on the tobacco irrigation, the crop performance was desirable in comparison with the normal irrigation, H2 (the volume ratio of EM/effluent = 1/1500) was selected as the optimum EM/ effluent ratio, since the leaf area (42, 220 cm2) and the yield (169.3 g) of single tobacco plant with H2 ratio were largest.
Biofiltration, whereby CH(4) is oxidized by methanotrophic bacteria, is a potentially effective strategy for mitigating CH(4) emissions from anaerobic dairy effluent lagoons/ponds, which typically produce insufficient biogas for energy recovery. This study reports on the effectiveness of a biofilter cover design at oxidizing CH(4) produced by dairy effluent ponds. Three substrates, a volcanic pumice soil, a garden-waste compost, and a mixture of the two, were tested as media for the biofilters. All substrates were suspended as 5 cm covers overlying simulated dairy effluent ponds. Methane fluxes supplied to the filters were commensurate with emission rates from typical dairy effluent ponds. All substrates oxidized more than 95% of the CH(4) influx (13.9 g CH(4) m(-3) h(-1)) after two months and continued to display high oxidation rates for the remaining one month of the trial. The volcanic soil biofilters exhibited the highest oxidation rates (99% removal). When the influx CH(4) dose was doubled for a month, CH(4) removal rates remained >90% for all substrates (maximum = 98%, for the volcanic soil), suggesting that biofilters have a high capacity to respond to increases in CH(4) loads. Nitrous oxide emissions from the biofilters were negligible (maximum = 19.9 mg N(2)O m(-3) h(-1)) compared with CH(4) oxidation rates, particularly from the volcanic soil that had a much lower microbial-N (75 mg kg(-1)) content than the compost-based filters (>240 mg kg(-1)). The high and sustained CH(4) oxidation rates observed in this laboratory study indicate that a biofilter cover design is a potentially efficient method to mitigate CH(4) emissions from dairy effluent ponds. The design should now be tested under field conditions.
Tropospheric methane (CH4) is oxidised by soil microbes called methanotrophs. We examined them in soil samples from a pristine Nothofagus forest located in New Zealand. Laboratory incubations indicated the presence of high-affinity methanotrophs that displayed Michaelis-Menton kinetics (K-m=8.4 muL/L where K-m is the substrate concentration at half the maximal rate). When the soil was dried from its field capacity water content of 0.34 to 0.16 m(3)/m(3), CH4 oxidation rate increased nearly 7-fold. The methanotrophs were thus metabolically poised for very high activity, but substrate availability was commonly limiting. When water content was held constant, CH4 oxidation rate nearly doubled as temperature increased from 5 to 12degreesC, a range found in the forest. By contrast, CH4 oxidation rate did not change much from 12 to 30degreesC, and it was zero at 35degreesC. When water content and temperature were held constant, the optimal soil pH for CH4 oxidation was 4.4, as found in the forest. Soil disturbance by nitrogen (N) and non-N salt amendment decreased CH4 oxidation rate, but this depended on the amendment species and concentration. The methanotrophs were adapted to native conditions and exhibited a great sensitivity to disturbance.
Livestock farming systems are major sources of trace gases contributing to emissions of the greenhouse gases (GHG) nitrous oxide (N2O) and methane (CH4), i.e. N2O accounts for 10% and CH4 for 30% of the anthropogenic contributions to net global warming. This paper presents scenario assessments of whole-system effects of technologies for reducing GHG emissions from livestock model farms using slurry-based manure management. Changes in housing and storage practice, mechanical separation, and incineration of the solid fraction derived from separation were evaluated in scenarios for Sweden, Denmark, France, and Italy. The results demonstrated that changes in manure management can induce significant changes in CH4 and N2O emissions and carbon sequestration, and that the effect of introducing environmental technologies may vary significantly with livestock farming practice and interact with climatic conditions. Shortening the in-house manure storage time reduced GHG emissions by 0–40%. The largest GHG reductions of 49 to, in one case, 82% were obtained with a combination of slurry separation and incineration, the latter process contributing to a positive GHG balance of the system by substituting fossil fuels. The amount and composition of volatile solids (VS) and nitrogen pools were main drivers in the calculations performed, and requirements to improve the assessment of VS composition and turnover during storage and in the field were identified. Nevertheless, the results clearly showed that GHG emission estimates will be unrealistic, if the assumed manure management or climatic conditions do not properly represent a given country or region. The results also showed that the mitigation potential of specific manure management strategies and technologies varied depending on current management and climatic conditions.
Evaluating multicomponent climate change mitigation strategies requires knowledge of the diverse direct and indirect effects
of emissions. Methane, ozone, and aerosols are linked through atmospheric chemistry so that emissions of a single pollutant
can affect several species. We calculated atmospheric composition changes, historical radiative forcing, and forcing per unit
of emission due to aerosol and tropospheric ozone precursor emissions in a coupled composition-climate model. We found that
gas-aerosol interactions substantially alter the relative importance of the various emissions. In particular, methane emissions
have a larger impact than that used in current carbon-trading schemes or in the Kyoto Protocol. Thus, assessments of multigas
mitigation policies, as well as any separate efforts to mitigate warming from short-lived pollutants, should include gas-aerosol
interactions.
Landfill gas containing methane is produced by anaerobic degradation of organic waste. Methane is a strong greenhouse gas and landfills are one of the major anthropogenic sources of atmospheric methane. Landfill methane may be oxidized by methanotrophic microorganisms in soils or waste materials utilizing oxygen that diffuses into the cover layer from the atmosphere. The methane oxidation process, which is governed by several environmental factors, can be exploited in engineered systems developed for methane emission mitigation. Mathematical models that account for methane oxidation can be used to predict methane emissions from landfills. Additional research and technology development is needed before methane mitigation technologies utilizing microbial methane oxidation processes can become commercially viable and widely deployed.
Methane-utilizing bacteria (methanotrophs) are a diverse group of gram-negative bacteria that are related to other members of the Proteobacteria. These bacteria are classified into three groups based on the pathways used for assimilation of formaldehyde, the major source of cell carbon, and other physiological and morphological features. The type I and type X methanotrophs are found within the gamma subdivision of the Proteobacteria and employ the ribulose monophosphate pathway for formaldehyde assimilation, whereas type II methanotrophs, which employ the serine pathway for formaldehyde assimilation, form a coherent cluster within the beta subdivision of the Proteobacteria. Methanotrophic bacteria are ubiquitous. The growth of type II bacteria appears to be favored in environments that contain relatively high levels of methane, low levels of dissolved oxygen, and limiting concentrations of combined nitrogen and/or copper. Type I methanotrophs appear to be dominant in environments in which methane is limiting and combined nitrogen and copper levels are relatively high. These bacteria serve as biofilters for the oxidation of methane produced in anaerobic environments, and when oxygen is present in soils, atmospheric methane is oxidized. Their activities in nature are greatly influenced by agricultural practices and other human activities. Recent evidence indicates that naturally occurring, uncultured methanotrophs represent new genera. Methanotrophs that are capable of oxidizing methane at atmospheric levels exhibit methane oxidation kinetics different from those of methanotrophs available in pure cultures. A limited number of methanotrophs have the genetic capacity to synthesize a soluble methane monooxygenase which catalyzes the rapid oxidation of environmental pollutants including trichloroethylene.
A fragment of the functional gene pmoA, which encodes the active-site polypeptide of particulate methane monooxygenase (pMMO), was PCR-amplified from DNA of the recently described acidophilic methanotrophic bacterium Methylocapsa acidiphila [corrected] B2. This methanotroph was isolated from an acidic Sphagnum peat bog and possesses a novel type III arrangement of intracytoplasmic membranes. Comparative sequence analysis revealed that the inferred peptide sequence of pmoA of Methylocapsa acidiphila [corrected] B2 belongs to a novel PmoA lineage. This lineage was only distantly related to the PmoA sequence cluster of type II methanotrophs, with identity values between 69.5% and 72%. The identity values between the PmoA of Methylocapsa acidiphila [corrected] B2 and PmoA sequences of type I methanotrophs ranged from 55.5 to 68%. However, the PmoA of this acidophilic methanotroph was more closely affiliated with the inferred peptide sequences of pmoA clones retrieved from various acidic upland soils showing atmospheric methane consumption. The PmoA identity values with these clones were 79.5-81%. Nonetheless, the apparent affinity for methane exhibited by Methylocapsa acidiphila [corrected] B2 was 1-2 microM, which is similar to values measured in other methanotrophic bacteria. This finding suggests that the pMMO of Methylocapsa acidiphila [corrected] B2 is not a novel enzyme specialized to have a high affinity for methane and that apparent "high-affinity" methane uptake is either the result of particular culture conditions or is performed by another pMMO type.
A greater understanding of the tightly linked trophic groups of anaerobic and aerobic bacteria residing in municipal solid waste landfills will increase our ability to control methane emissions and pollutant fate in these environments. To this end, we characterized the composition of methanogenic and methanotrophic bacteria in samples taken from two regions of a municipal solid waste landfill that varied in age. A method combining polymerase chain reaction amplification, restriction fragment length polymorphism analysis and phylogenetic analysis was used for this purpose. 16S rDNA sequence analysis revealed a rich assemblage of methanogens in both samples, including acetoclasts, H2/CO2-users and formate-users in the newer samples and H2/CO2-users and formate-users in the older samples, with closely related genera including Methanoculleus, Methanofollis, Methanosaeta and Methanosarcina. Fewer phylotypes of type 1 methanotrophs were observed relative to type 2 methanotrophs. Most type 1 sequences clustered within a clade related to Methylobacter, whereas type 2 sequences were broadly distributed among clades associated with Methylocystis and Methylosinus species. This genetic characterization tool promises rapid screening of landfill samples for genotypes and, therefore, degradation potentials.
Removal of methane from exhaust air of animal houses and manure storage has a large potential for the reduction of greenhouse gas emissions from animal husbandry. The aim of this study was to design a biofilter for methane removal at a full-scale livestock production facility. Air from the headspace of a covered 6 m3 liquid manure storage (air flow: 0.75-8.5 m3 m(-3) h(-1); CH4: 500-5500 mg m(-3)) was treated in an experimental biofilter (160 L). The filterbed, a mixture of compost and perlite in a 40:60 (v/v) ratio, was inoculated with activated sludge that had shown a good methane oxidation rate as compared to pure cultures in preceding laboratory tests. Methane removal up to 85% could be achieved in the experimental biofilter. The methane removal (g m(-3) h(-1)) appeared to be proportional to the concentration (g m(-3)) with k = 2.5 h(-1). Relatively low methane concentrations and high air flows, as reported for the exhaust air of animal houses, would require very large biofilter sizes. Extrapolation of the results showed that treatment of air from a 1000 m3 liquid manure storage with a methane concentration of 22 g m(-3) would require a 20 m3 biofilter for a desired emission reduction of 50%. The costs for such a biofilter are USD 26 per t of CO2 equiv reduction.
Anaerobic digestion offers an effective way to manage dairy manure by addressing the principal
problems of odor and environmental control while offering an opportunity to create energy from conversion of
biogas with a system of combined heat and power (CHP). The use of biogas as an energy source has
numerous applications. However, all of the possible applications require knowledge about the composition and
quantity of constituents in the biogas stream. This study provides data on composition of anaerobic digestion
biogas (ADG) over time (hourly, daily, weekly and year), results from the use of dairy-manure compost as a
biofilter to remove hydrogen sulfide (H2S) and an assessment of the feasibility of injecting ADG into the natural
gas pieline.
Results agrree well with often quoted generalized concentrations of 60% CH4, 40% CO2 and 600 BTU/ ft3 for
dairy-derived biogas. Also shown, depending on additives to the dairy manure and quality of farm water supply,
H2S concentrations can vary substantially from less than 1000 ppm to well over 6000 ppm. Utilization of cow-manure compost for removal of H2S from AD biogas, using small-scale reactors, was studied and shows
promise.. A technical and economic assessment of processing of biogas for injection to the natural gas
pipeline, while dependent on biogas quantity, price for processed biogas, proximity to the natural gas pipeline
and the interest rate, suggests that a real possibility exists for injecting biogas into the natural gas pipeline
dependent, of course, on the values of the parameters indicated.
A fragment of the functional gene pmoA, which encodes the active-site polypeptide of particulate methane monooxygenase (pMMO), was PCR-amplified from DNA of the recently described acidophilic methanotrophic bacterium Methylocapsa acidophila B2. This methanotroph was isolated from an acidic Sphagnum peat bog and possesses a novel type III arrangement of intracytoplasmic membranes. Comparative sequence analysis revealed that the inferred peptide sequence of pmoA of Methylocapsa acidophila B2 belongs to a novel PmoA lineage. This lineage was only distantly related to the PmoA sequence cluster of type II methanotrophs, with identity values between 69.5% and 72%. The identity values between the PmoA of Methylocapsa acidophila B2 and PmoA sequences of type I methanotrophs ranged from 55.5 to 68%. However, the PmoA of this acidophilic methanotroph was more closely affiliated with the inferred peptide sequences of pmoA clones retrieved from various acidic upland soils showing atmospheric methane consumption. The PmoA identity values with these clones were 79.5–81%. Nonetheless, the apparent affinity for methane exhibited by Methylocapsa acidophila B2 was 1–2 µM, which is similar to values measured in other methanotrophic bacteria. This finding suggests that the pMMO of Methylocapsa acidophila B2 is not a novel enzyme specialized to have a high affinity for methane and that apparent "high-affinity" methane uptake is either the result of particular culture conditions or is performed by another pMMO type.
The greenhouse gas emissions from agricultural systems contribute significantly to the national budgets for most countries in Europe. Measurement techniques that can identify and quantify emissions are essential in order to improve the selection process of emission reduction options and to enable quantification of the effect of such options. Fast box emission measurements and mobile plume measurements were used to evaluate greenhouse gas emissions from farm sites. The box measurement technique was used to evaluate emissions from farmyard manure and several other potential source areas within the farm. Significant (up to 250 g CH4 m−2 day−1and 0.4 g N2O m−2 day−1) emissions from ditches close to stables on the farm site were found.
Over 1000 anaerobic ponds are used in the treatment of wastewater from farms and industry in New Zealand. These anaerobic ponds were typically designed as wastewater solids holding ponds rather than for treatment of the wastewater. However, visual observation of these uncovered ponds indicates year-round anaerobic digestion and release of biogas to the atmosphere. The release of biogas may be associated with odour nuisance, contributes to greenhouse gas (GHG) emissions and is a waste of potentially useful energy. The aim of this study was to measure the seasonal variation in quantity and quality of biogas produced by an anaerobic pond at a piggery (8000 pigs) and a dairy farm (700 cows). Biogas was captured on the surface of each anaerobic pond using a floating 25m(2) polypropylene cover. Biogas production was continually monitored and composition was analysed monthly. Annual average biogas ( methane) production rates from the piggery and dairy farm anaerobic ponds were 0.84 (0.62) m(3)/m(2). day and 0.032 (0.026) m(3)/m(2). day, respectively. Average CH4 content of the piggery and dairy farm biogas was high (74% and 82%, respectively) due to partial scrubbing of CO2 within the pond water. The average daily volume of methane gas that could potentially be captured by completely covering the surface of the piggery and dairy farm anaerobic ponds was calculated as similar to 550m(3)/day and similar to 45m(3)/day, respectively ( assuming that the areal methane production rate was uniform across the pond surface). Conversion of this methane to electricity would generate 1650 kWh/day and 135 kWh/day, respectively (with potentially 1.5 times these values co-generated as heat) and reduce GHG emissions by 8.27 t CO2 equivalents/day and 0.68 tCO(2) equivalents/day, respectively. These preliminary results suggest that conventional anaerobic ponds in New Zealand may release considerable amounts of methane and could be a more significant point source of GHG emissions than previously estimated. Further studies of pond GHG emissions are required to accurately assess the contribution of wastewater treatment ponds to New Zealand's total GHG emissions.
Methanotrophs present in landfill cover soil can limit methane emissions from landfill sites by oxidizing methane produced in landfill. Understanding the spatial and temporal distribution of populations of methanotrophs and the factors influencing their activity and diversity in landfill cover soil is critical to devise better landfill cover soil management strategies. pmoA-based microarray analyses of methanotroph community structure revealed a temporal shift in methanotroph populations across different seasons. Type II methanotrophs (particularly Methylocystis sp.) were found to be present across all seasons. Minor shifts in type I methanotroph populations were observed. In the case of spatial distribution, only minor differences in methanotroph community structure were observed with no recognizable patterns (both vertical and horizontal) at a 5 m scale. Correlation analysis between soil abiotic parameters (total C, N, NH4 (+) , NO3 (-) and water content) and distribution of methanotrophs revealed a lack of conclusive evidence for any distinct correlation pattern between measured abiotic parameters and methanotroph community structure, suggesting that complex interactions of several physico-chemical parameters shape methanotroph diversity and activity in landfill cover soils.
In addition to it carbon source, bacteria require for growth a variety of nutrients such as phosphorus, potassium, and several other micronutrients including copper. The study described in this paper was conducted with the aim of determining the influence of phosphorus, potassium, and copper on methane elimination in a biofilter The study revealed that the particular phosphorus concentration leading to the greatest methane elimination capacity, which was 44 7 g m(-3) h(-1) at a methane inlet load of 75 g m(-3) h(-1), was 3.1 g/L The influence of the phosphorus concentration on the methane elimination capacities was also investigated for methane inlet loads of between 8 and 95 g m(-3) h(-1) The optimum range of the nitrogen-phosphorus mass ratios, determined during this study ranged from 0 5 to 2.5 It was established that, ill comparison with phosphorus, potassium does not seem to be a determining element for the biological removal efficiency and does not significantly affect the microorganisms' behaviour However, a Concentration of 0.076 g/L of potassium is recommended in the irrigation nutrient solution for an inlet load of 75 g m(-3) h(-1). The influence of the copper concentration was also studied by varying its concentration between the values of 0 and 0 006 g/L. The results have also shown that copper has a minor impact oil the biofiltration of Methane This paper is the first report describing the influence of several nutrients in a biofilter The knowledge provided by this study is necessary for the achievement of a biofilter indebted to methane control.
Landfills are considered to be an important global source of the greenhouse gas methane. These emissions are especially caused by inadequate gas collection systems, uncontrolled emissions from old dumps and unauthorized open dumping. The subsequent capturing and disposal of landfill gas from old landfills is technically difficult and very costly. A low-cost alternative to the conventional methods is the microbial oxidation of methane. For this purpose it is necessary to spread cover layers much in the same way as is done for large biofilters. This calls for sufficient knowledge about the biology of the methane oxidising microorganisms and the resulting requirements to be met by the substrate. Laboratory studies have proved municipal solid waste compost and sewage sludge compost to be suitable carrier substrates.
The production of biogas in landfills, its composition and the problems resulting from its generation are all reviewed. Biofiltration
is a promising option for the control of emissions to atmosphere of the methane contained in biogas issued from the smaller
and/or older landfills. A detailed review of the methane biofiltration literature is presented. The microorganisms, mainly
the methanotrophs, involved in the methane biodegradation process, and their needs in terms of oxygen and carbon dioxide utilization,
are described. Moreover, the influence of nutrients such as copper, nitrogen and phosphorus, and the process operating conditions
such as temperature, pH and moisture content of the biofilter bed, are also presented. Finally, the performance of various
filter beds, in terms of their elimination capacities, is presented for laboratory scale biofilters and landfill covers.
Agricultural crop and animal production systems are important sources and sinks for atmospheric methane (CH4). The major CH4 sources from this sector are ruminant animals, flooded rice fields, animal waste and biomass burning which total about one third of all global emissions. This paper discusses the factors that influence CH4 production and emission from these sources and the aerobic soil sink for atmospheric CH4 and assesses the magnitude of each source. Potential methods of mitigating CH4 emissions from the major sources could lead to improved crop and animal productivity. The global impact of using the mitigation options suggested could potentially decrease agricultural CH4 emissions by about 30%.
Though engineered covers have been suggested for reducing landfill methane emissions via microbial methane oxidation, little is known about the covers' function at low temperature. This study aimed to determine the methane consumption rates of engineered soil columns at low temperature (4–12°C) and to identify soil characteristics that may enhance methane oxidation in the field. Engineered soils (30 cm thick) were mixtures of sewage sludge compost and de-inking waste, amended with sand (SDS soil) or bark chips (SDB soil). At 4–6°C, we achieved rates of 0.09 gCH4 kgTS−1d−1 (0.02 m3 m−2d−1) and 0.06 gCH4 kgTS−1d−1 (0.009 m3 m−2d−1) with SDS and SDB soils, respectively. With SDS, good movement and exchange of oxygen in porous soil moderated the slowdown of microbial activity so that the rate dropped only by half as temperature declined from 21–23°C to 4–6°C. In SDB, wet bark chips reduced the soil's air-filled porosity and intensified non-methanotrophic microbial activity, thus reducing the methane consumption rate at 4–6°C to one fourth of that at 21–23°C. In conclusion, soil characteristics such as air-filled porosity, water holding capacity, quantity and stabilization of organic amendments that affect the movement and exchange of oxygen are important variables in designing engineered covers for high methane oxidation at low temperature.
Several strains of methane-oxidizing bacteria were isolated and studied to determine their physiological suitability for removal of methane in coal mine atmospheres. One strain, Methylomonas fodinarum ACM 3268, was selected as the most suitable culture for use in the development of a continuous biofilter to be used as a ventilation air scrubber. The experimental biofilter utilising a biofilm of M. fodinarum was shown to reduce methane levels substantially provided the residence times were sufficiently long. In the range 0.25–1.0% methane in air, commonly experienced in coal mine atmospheres, more than 70% of the methane was removed with a residence time of 15 min, with a 90% reduction at 20 min. Even at a residence time of 5 min approximately 20% of the methane in air was removed. Equal quantities of O2 are consumed during the bacterial oxidation of methane and 1% methane is converted to 0.7% CO2. Scale-up and alternative biofilter packings are likely to reduce the residence times in the biofilter.
A biogas production assessment method based on the visual monitoring of biogas evolution events in an anaerobic waste stabilisation pond was developed and applied to an anaerobic pond treating farm dairy wastewater in New Zealand. Major biogas-induced perturbations at the pond surface were classified as either type 1 or 2 events and other observed biogas activities as small bubble events. Mean counts of types 1 and 2 events varied from 7·3 to 30·0 per hour and 4·3–34·0 per hour, respectively, over the pond surface and the frequency of events decreased as both organic loading and temperature increased. Preliminary estimates of areal gas production rates, obtained using the observational method, ranged from 0·002 to 0·015 m3 m−2 day−1 for major eruptions and 0·0004–0·024 m3 m−2 day−1 for small bubble events, giving a total range of 0·002–0·039 m3 m−2 day−1. Pond temperatures at 2·75 m depth showed relatively minor fluctuations on a diurnal basis and ranged between 13 and 15°C from days 1–60, reaching a maximum of 24°C at day 190. Refinements proposed for future method development include an increased number and range of event categories, the automatic recording of events and the use of an improved cover. Further work is required to assess the general applicability of the method to anaerobic ponds.
Biogas composition and variation in three different biogas production plants were studied to provide information pertaining to its potential use as biofuel. Methane, carbon dioxide, oxygen, nitrogen, volatile organic compounds (VOCs) and sulphur compounds were measured in samples of biogases from a landfill, sewage treatment plant sludge digester and farm biogas plant. Methane content ranged from 48% to 65%, carbon dioxide from 36% to 41% and nitrogen from <1% to 17%. Oxygen content in all three gases was <1%. The highest methane content occurred in the gas from the sewage digester while the lowest methane and highest nitrogen contents were found in the landfill gas during winter. The amount of total volatile organic compounds (TVOCs) varied from 5 to 268 mg m−3, and was lowest in the biogas from the farm biogas plant. Hydrogen sulphide and other sulphur compounds occurred in landfill gas and farm biogas and in smaller amounts in the sewage digester gas. Organic silicon compounds were also found in the landfill and sewage digester gases. To conclude, the biogases in the different production plants varied, especially in trace compound content. This should be taken into account when planning uses for biogas.
Animal wastewater can be a major contributor to the cultural eutrophication of surface waters. Constructed wetlands are under study as a best management practice to treat animal wastewater from dairy and swine operations. Preliminary results are promising when wetlands are a component of a farm-wide waste management plan, but they are ineffective without pretreatment of the wastewater. The feasibility of constructed wetlands varies with waste characteristics and climate. While the cost of wetland construction is low, the site must be maintained in order for the initial investment in the wetland to be worthwhile. In addition, several design iterations may be necessary before effective treatment is obtained. The design of animal wastewater treatment wetlands is still being researched and a number of the present projects will help provide recommendations for the use of constructed wetlands at animal operations.
Afforestation and reforestation of pastures are key land-use changes in New Zealand that help sequester carbon (C) to offset its carbon dioxide (CO2) emissions under the Kyoto Protocol. However, relatively little attention has been given so far to associated changes in trace gas fluxes. Here, we measure methane (CH4) fluxes and CO2 production, as well as microbial C, nitrogen (N) and mineral-N, in intact, gradually dried (ca. 2 months at 20 °C) cores of a volcanic soil and a heavier textured, non-volcanic soil collected within plantations of Pinus radiata D. Don (pine) and adjacent permanent pastures. CH4 fluxes and CO2 production were also measured in cores of another volcanic soil under reverting shrubland (mainly Kunzea var. ericoides (A. Rich) J. Thompson) and an adjacent pasture. CH4 uptake in the pine and shrubland cores of the volcanic soils at field capacity averaged about 35 and 14 μg CH4–C m−2 h−1, respectively, and was significantly higher than in the pasture cores (about 21 and 6 μg CH4–C m−2 h−1, respectively). In the non-volcanic soil, however, CH4–C uptake was similar in most cores of the pine and pasture soils, averaging about 7–9 μg m−2 h−1, except in very wet samples. In contrast, rates of CO2 production and microbial C and N concentrations were significantly lower under pine than under pasture. In the air-dry cores, microbial C and N had declined in the volcanic soil, but not in the non-volcanic soil; ammonium–N, and especially nitrate–N, had increased significantly in all samples. CH4 uptake was, with few exceptions, not significantly influenced by initial concentrations of ammonium–N or nitrate–N, nor by their changes on air-drying. A combination of phospholipid fatty acid (PLFA) and stable isotope probing (SIP) analyses of only the pine and pasture soils showed that different methanotrophic communities were probably active in soils under the different vegetations. The C18 PLFAs (type II methanotrophs) predominated under pine and C16 PLFAs (type I methanotrophs) predominated under pasture. Overall, vegetation, soil texture, and water-filled pore space influenced CH4–C uptake more than did soil mineral-N concentrations.
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 CH 4 to carbon dioxide and water. Properly designed soil biofilters may reduce atmospheric CH 4 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 filter-bed medium in packed columns to measure the effect of a variety of environmental and design factors on the CH 4 oxidation capacity of a soil biofilter.
Biofilter performance was tested under a variety of environmental and design conditions. The optimum soil moisture content for CH 4 oxidation in a loamy sand was 13% by weight. Addition of NO 3 -N did not affect the CH 4 oxidation rate. Soil depths of 30 cm and 60 cm were equally efficient in CH 4 oxidation. When the CH 4 loading rate was decreased, the percentage of CH 4 oxidized increased. The maximum CH 4 oxidation rate was 27.2 mol m ⁻² d ⁻¹ under optimum conditions.
In the long-term, landfills are producing landfill gas (LFG) with low calorific values. Therefore, the utilization of LFG in combined heat and power plants (CHP) is limited to a certain period of time. A feasible method for LFG treatment is microbial CH(4) oxidation. Different materials were tested in actively aerated lab-scale bio-filter systems with a volume of 0.167 m(3). The required oxygen for the microbial CH(4) oxidation was provided through perforated probes, which distributed ambient air into the filter material. Three air input levels were installed along the height of the filter, each of them adjusted to a particular flow rate. During the tests, stable degradation rates of around 28 g/(m(3) h) in a fine-grained compost material were observed at a CH(4) inlet concentration of 30% over a period of 148 days. Compared with passive (not aerated) tests, the CH(4) oxidation rate increased by a factor of 5.5. Therefore, the enhancement of active aeration on the microbial CH(4) oxidation was confirmed. At a O(2)/CH(4) ratio of 2.5, nearly 100% of the CH(4) load was decomposed. By lowering the ratio from 2.5 to 2, the efficiency fell to values from 88% to 92%. By varying the distribution to the three air input levels, the CH(4) oxidation process was spread more evenly over the filter volume.
A new biogas meter was developed to satisfy the need for an adjustable resolution meter that has minimal back-pressure and wide flow rate capability. The new meter had three main components; a timed bellows pump that delivered fixed volumes, a pressure sensor, and a data logger. The meter was built from off-the-shelf components and was thus easy to build and cost effective. The meter also proved to be accurate, precise, sensitive, and simple to calibrate.
Methods for chemical analysis of soils
- L C Blakemore
- P L Searle
- B K Daly
Blakemore, L.C., Searle, P.L., Daly, B.K., 1987. Methods for chemical analysis of soils. New Zealand Soil Bureau Scientific Report 80. NZSB, Lower Hutt.
New Zealand Dairy Statistics report An Evaluation of a Covered Anaerobic Lagoon for Flushed Dairy Cattle Manure Stabilisation and Biogas Production
- Lic
- Nz Dairy
- New Hamilton
- Zealand
- J H Martin Jr
Livestock Improvement Cooperation and Dairy New Zealand, 2008. New Zealand Dairy Statistics report 2007–2008, LIC and Dairy NZ. Hamilton, New Zealand. Martin Jr., J.H., 2008. An Evaluation of a Covered Anaerobic Lagoon for Flushed Dairy Cattle Manure Stabilisation and Biogas Production. Report submitted to the United States Environmental Protection Agency by Eastern Research Group Inc., Morrisville, North Carolina.
Managing methan-otrophs in an on-farm biofilter to reduce methane emissions
- C Pratt
- A Walcroft
- K Tate
- D Ross
- M Hills
- R Roy
Pratt, C., Walcroft, A., Tate, K., Ross, D., Hills, M., Roy, R., 2010. Managing methan-otrophs in an on-farm biofilter to reduce methane emissions. In: Fertiliser and Lime Research Centre Conference, Palmerston North, New Zealand.