Concerns about biogas from landfills are reviewed in terms of biogas generation, composition, and elimination. Biogas is mainly composed of methane and carbon dioxide but it also contains a few hundred non-methane organic compounds. The solutions available to reduce its harmful effects on the environment and on human health are valorization as electricity or heat, flaring, or biofiltration. The main parameters affecting the biofiltration of methane are reviewed: temperature, moisture content, properties of the packing material, nutrient supply, oxygen requirements, formation of exopolysaccharides, and gas residence time. An analysis is performed on the co-metabolic properties and the inhibition interactions of the methane-degrading bacteria, methanotrophs.
BACKGROUND: Biofiltration of methane is of particular interest to contribute to limiting the greenhouse gas effect of biogas emissions from landfills. The complexity of the biogas mixture from landfills has underlined the importance of the presence of non-methane organic compounds. The aim of this study was to determine the effect of toluene on the microkinetic and macrokinetic parameters of methane biodegradation using an inorganic filter bed.
RESULTS:Two concentrations of toluene were tested, 0.7 and 3.4 gC m −3 , and compared with the case of methane biofiltration alone. The specific growth rates of methane decreased from 0.793 to 0.574 to 0.278 d −1 when the toluene concentration was increased from 0 to 0.7 to 3.4 gC m −3 , respectively. The maximum elimination capacity of methane decreased from 39.4 to 5.6 gC m −3 h −1 when toluene concentration was increased from 0 to 3.4 gC m −3 . The half-saturation constants decreased from 4.6 to 1.6 gC m −3 and from 4.6 to 0.7 gC m −3 , respectively.
CONCLUSIONS: Results show that an inhibition occurred on methane biodegradation when toluene was introduced into the biofilter.
Methane is a greenhouse gas (GHG) 21 times more contributing to global warming than carbon dioxide (CO 2 ) and originates mainly from the energy, agriculture and landfill sectors. Methane can be valorized via combustion or transformed by catalytic processes into products like methanol. When valorization cannot be applied because of inappropriate flow rates or methane concentrations, biofiltration is a biotechnology well adapted to control the methane emissions. Biofiltration is a triphasic biotechnology, which uses microorganisms to reduce pollutants like volatile organic compounds (VOCs) or volatile inorganic compounds (VICs) or GHG like methane. Several studies have been published over the last three decades about VOC and VIC biofiltration, but fewer studies are available about methane control.At the Université de Sherbrooke, research is being conducted to control methane emissions originating from landfills or livestock productions. The biofilter used in this study is a laboratory-scale bioreactor of 0.018 m 3 divided into 3 sections. An inorganic packing material is used as the filter bed and a nutrient solution is supplied to irrigate the biofilter once daily.The objective of the present study is to determine the operating conditions to obtain high removal efficiencies at methane inlet concentrations around 7000 ppmv. The biofilter is operated under a nitrogen concentration of 0.
Landfi ll gas emissions contribute to the greenhouse effect due to the presence of methane (CH 4 ). CH 4 emissions from old and small landfi lls can be reduced by using biofi ltration. The objective of this study was to optimize parameters that control CH 4 removal in a biofi lter. Temperature is one of the important parameters as well as the amount of nutrient solution (NS) supplied. The effects of the carbon dioxide (CO 2 ) concentration on CH 4 biofi ltration were also studied. Four biofi lters using an inorganic fi lter bed were studied under similar conditions: an inlet CH 4 concentration of 7000 ppmv and an air fl ow rate of 0.25 m 3 /h. A NS was supplied daily. The temperature was varied from 4°C to 43°C. The highest performance was obtained in the range of 31-34°C with an elimination capacity (EC) of 30 g CH 4 /m 3 /h for an inlet load (IL) of 80 g CH 4 /m 3 /h. The effect of the amount of NS supplied to the biofi lter at ambient temperature was also analyzed. The EC was 23 g CH 4 /m 3 /h for both 101 L NS /m 3 V bed /d and 34 L NS /m 3 V bed /d, but it fell to 17 g CH 4 /m 3 /h at 17 L NS /m 3 V bed /d. CO 2 concentrations were varied from 650 to 18,500 ppmv and no effect was noticed on the EC which remained constant at 18 g CH 4 /m 3 /h for an inlet load of 72 g CH 4 /m 3 /h.
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