Biofilter with mixture of pine bark and expanded clay as packing material for methane treatment in lab-scale...

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. Graphic abstract ᅟ.