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

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.