Does vegetation affect the methane oxidation efficiency of passive biosystems?

Abstract

It is often reported in the technical literature that the presence of vegetation improves the methane oxidation efficiency of biosystems; however, the phenomena involved and biosystem performance results are still poorly documented, particularly in the field. This triggered a study to assess the importance of vegetation in methane oxidation efficiency (MOE). In this study, 4 large scale columns, each filled with sand, topsoil and a mixture of compost and topsoil were tested under controlled conditions in the laboratory and partially controlled conditions in the field. Four series of laboratory tests and two series of field tests were performed. 4 different plant covers were tested for each series: Trifolium repens L. (White clover), Phleum pratense L. (Timothy grass), a mixture of both, and bare soil as the control biosystem. The study results indicated that up to a loading equal to 100 g CH4/m(2)/d, the type of plant cover did not influence the oxidation rates, and the MOE was quite high (⩾ 95%) in all columns. Beyond this point, the oxidation rate continued to increase, reaching 253 and 179 g CH4/m(2)/d in laboratory and field tests respectively. In the end, the bare soil achieved as high or higher MOEs than vegetated biosystems. Despite the fact that the findings of this study cannot be generalized to other types of biosystems and plants and that the vegetation types tested were not fully grown, it was shown that for the short-term tests performed and the types of substrates and plants used herein, vegetation does not seem to be a key factor for enhancing biosystem performance. This key conclusion does not corroborate the conclusion of the relatively few studies published in the technical literature assessing the importance of vegetation in MOE.

Design of Microbial Methane Oxidation Systems for Landfills

“…This seems to indicate that θ a_occ could potentially be inferred from the optimum water content determined from the Standard Proctor test (ASTM D6-8 -12e2). However, for another substrate (fine sand) also successfully employed as MOL (Ndanga et al, 2015), Ahoughalandari et al (2018) found that the S r value associated with occlusion was greater than that given by the line of optima. As such, the simplification proposed, i.e.…”

“…In the case of mineral soils, the MOL can be constructed in two sublayers: the vegetated top part (usually composed of humic topsoil, constituting the main rooting zone) and the subsoil. Examples of an topsoil-subsoil layering are given in Gebert et al (2003), biofilter;Huber-Humer et al (2009), biocover test cell; Bour et al (2015), laboratory column study; Gebert et al (2015), biowindow; Röwer et al (2016a), biocover andNdanga et al (2015); laboratory and field tests of several biofilters. The CH 4 oxidation front (depth) may vary over time, depending on the depth of ingress of atmospheric air, the composition and height of the accruing landfill gas, and the environmental conditions that drive the microbial process (e.g., temperature, water tension).…”

“…areas of high CH 4 fluxes or uncontrolled emissions, at the surface of the landfill cover. Ensuring a more even distribution of the CH 4 loading greatly improves emissions abatement, with CH 4 oxidation rates attaining nearly 100% of the applied loading (Huber-Humer, 2004a;Bogner et al, 2007;Roncato and Cabral, 2012;Ndanga et al, 2015;Ndanga et al, 2016).…”

Biofiltration of Methane Fugitive Emissions from Landfills Using Scum from Municipal Wastewater Treatment Plants (Wwtp) as Alternative Substrate

“…Thus, various researchers have tested the most varied substrate materials (compost, sewage sludge, sand, garden waste, wood chips, expanded clay, etc. and their mixtures with the cover soil), biogas loading rates, climatic conditions, etc., always with the goal of studying and optimizing the methane oxidizing conditions in the land ll cover layer [6, 13,[24][25][26][27].…”

Detection and Analysis of Methane Emissions From a Landfill Using Unmanned Aerial Drone Systems and Semiconductor Sensors

“…Vegetation on a landfill's top cover may affect and be affected by LFG emissions, and irregularities in vegetation cover could indicate the presence of problematic spots. Plant roots can form channels and macropores in soil that facilitate O 2 diffusion and CH 4 supply to bacteria, stimulating CH 4 oxidation (Abichou et al, 2015, Ndanga et al, 2015. If the soil moisture content is sufficiently high, plant roots may also provide a favorable environment for CH 4 -oxidizing bacteria (Feng et al, 2017), which play a key role in reducing CH 4 emissions from landfills.…”