Methane biofilter (MBF) technology, a cost effective method to control atmospheric emission of CH4, is usually developed as a passively aerated system to control low-volume point-source emissions such as those from landfills with gas collection systems. Actively aerated high-rate methane biofilter (HMBF) systems are designed to overcome the shortcomings of passively aerated systems by ensuring the entire filter bed is utilized for CH4 oxidation. Flow-through column experiments point to the fact that CH4 oxidation rates of actively aerated systems could be several times higher than that of passively aerated systems. However, reports of the performance of field HMBF systems are not available in literature. Furthermore, there are no studies that demonstrate the possibility of using laboratory data in the design and operation of field systems. The current study was conducted to fill this research gap and involve a comparative study of the performance of laboratory columns to field performance of a HMBF system using solution gas produced at an oil battery site as the CH4 source. The actively aerated column studies confirmed past results with high CH4 oxidation rates; one column received air at two injection points and achieved an oxidation rate of 1417 g/m3/d, which is the highest reported value to date for compost-filled columns. Subsequent studies at a specially designed field HMBF filled with compost showed a higher oxidation rate of 1919 g/m3/d, indicating the possibility of exceeding the high CH4 oxidation rates observed in the laboratory. The achievement of observed field oxidation rates being higher than those in the laboratory is attributed to the capability of maintaining higher temperatures in field HMBFs. Furthermore, results show that field HMBFs could operate at lower than stoichiometric air to CH4 ratios, and lower retention times than that of laboratory columns. Results indicated that laboratory columns may not truly represent field behavior, and said results could only be used in the preliminary design of field HMBFs.
Keywords: Active aeration; Greenhouse gas; High-rate methane biofiltration; Methane oxidation; Methanotrophic bacteria; Methanotrophy; Solution gas.