Atmospheric methane removal by methane-oxidizing bacteria immobilized on porous building materials

Abstract

Biological treatment using methane-oxidizing bacteria (MOB) immobilized on six porous carrier materials have been used to mitigate methane emission. Experiments were performed with different MOB inoculated in building materials at high (~20 % (v/v)) and low (~100 ppmv) methane mixing ratios. 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 mixing ratio. 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 Ytong was incubated for 100 h. This study showed that immobilized MOB on building materials could be used to remove methane from the air and also act as carbon sink.

Biofiltration of methane from ruminants gas effluent using Autoclaved Aerated Concrete as the carrier material

“…Firstly, methane at lower concentration (other studies were between 0.08% (v/v) to 10% (v/v) [10,24,25]) was fed into the filter. The activity of the immobilized MOB on building material followed the hyperbolic Michaelis-Menten kinetic model and at low methane concentration, smaller activity was exhibited by the bacteria [13]. Secondly, the biofilter in this study operated at a low EBRT (other studies were between 4 min and 180 min [21,26,27]).…”

“…4d). This could be attributed to the carbonation reaction of carbon dioxide with the binder material of AAC (i.e., tobermorite À1.1 nm) [13]. Hence, complete carbon sequestration from the removed methane was achieved.…”

“…The methane biofilter was a hollow tube filled with AAC specimens inoculated with MOB mixed culture enriched from circum-neutral agricultural soil (pH $ 7.9) originating from Ghent, Belgium used in previous study [13]. Prior to the test, methane gas at $1000 ppmv concentration was fed into the biofilter via the bottom part of the filter for 127 days in order to have a high MOB enrichment in the biofilter.…”

“…Different carrier materials have been tested to achieve an optimum methane removal by the MOB. Previously, we showed that different MOB cultures exhibited a high methane removal when immobilized on Autoclaved Aerated Concrete (AAC) [13]. AAC is a lightweight building material exhibiting porosity up to 80% pore volume where more than 40% of the pore diameter is between 5 and 100 lm [13].…”

“…Previously, we showed that different MOB cultures exhibited a high methane removal when immobilized on Autoclaved Aerated Concrete (AAC) [13]. AAC is a lightweight building material exhibiting porosity up to 80% pore volume where more than 40% of the pore diameter is between 5 and 100 lm [13]. With bacteria diameter around 1 to 2 lm, this makes AAC a suitable carrier material to immobilize MOB in the biofilter setup as it can accommodate a high number of bacteria per gram of material [14].…”