Optimized design of a compost layer in a landfill biocover for CH4 oxidation

Abstract

In this study, the mixture of two compost materials, including Yard Waste and Leaf Compost (YWLC) and Biosolids Compost (BSC) was optimized for methane (CH4) oxidation to be suitable for a field-scale landfill biocover. Laboratory column tests were conducted with CH4 and carbon dioxide (CO2) flowing through the column at 50:50 v:v to assess the CH4 oxidation in the vertical profile of the compost. The variation in CO2:CH4 ratio, indicating methanotrophic activity, was assessed during three column trials considering two different mixing ratios of 1:1 and 1:4 YWLC:BSC, moisture contents (MC) of 60%, 35%, and 40% ww, and the addition of a methanotroph-enriched compost extract. It was found that the main restricting factors for effective CH4 oxidation were high MC, Exopolymeric Substance (EPS) formation, and fine texture of the materials that limited oxygen (O2) diffusion into the biocover. Based on CH4 mass balance in the columns, the highest CH4 oxidation efficiency of 40% was observed in the column trial with the 1:4 mixing ratio of composts at a MC of 40% ww, with CH4 being oxidized throughout the entire height of the column. It can be concluded that this optimized design for YWLC and BSC mixture, removing a significant portion of the CH4 flowing through the landfill biocover, had the potential to be used in the real field conditions.