Realization of a prototype aimed at investigating the degradation potential of landfill gas in bio-covers

Landfill gas (LFG) diffuse emissions into the atmosphere and landfill leachate (LL) uncontrolled discharges into the environment represent two of the major issues in landfill management. Recent research approaches to reduce the LFG emissions and the related environmental impacts and costs, focus on: (i) application of biochemical methane potential tests, aimed at effectively predicting the LFG generation from the deposited waste categories, with consequential optimization of the engineering systems for LFG collection and energy recovery; (ii) improvement of the efficiency of possible bio-covers in degrading CH4 and non-methane volatile organic compounds (VOCs) and reducing meteoric water infiltration. For the realization of lab-scale prototypes designed to investigate new bio-cover systems, different concepts have been reported in literature, such as: (i) columns filled with treated soil and equipped with a pump that allows the flushing of synthetic LFG mixtures from the column base, to study the LFG degradation efficiency of the bio-cover; or (ii) columns filled with a layer of waste covered with soil and equipped with a LL recirculation system, to study the effects of LL on waste degradation and LFG production. Here, a novel prototype to reliably investigate the capability of bio-covers for degrading LFG components is presented. The developed prototype consisted of a maceration chamber (i.e. landfill body producing the LFG), made with a 20 L tank filled with a mixture of selected waste category and anaerobic sludge (inoculum to provide microorganisms for anaerobic degradation process), connected to a column (i.e. landfill cover soil), constituted of 105 cm high dark PP cylinder (7 cm inner diameter), filled with soil. The column is equipped with 4 ports as pertaining sampling points, placed along the vertical axis (spaced 22 cm, with the upper one 9 cm from the top and the lowest one 30 cm from the bottom), hosting 5.5 cm long PA tubes (4 mm inner diameter), equipped with three-way stopcocks, and inserted in the column. Another sampling port is placed in the silicone tube connecting the maceration chamber with the column. Periodical gas sampling from both maceration chamber and column is performed using a plastic syringe and gas is stored in 12 cc vials equipped with a pierceable rubber septum. Analysis of VOCs composition is carried out by gas chromatography coupled with quadrupole mass spectrometry. The obtained analytical dataset describes temporal evolution of VOCs produced in the maceration chamber and passing through the soil column. Such experimental setup, coupled with comprehensive chemical analyses of gas samples from the maceration chamber and the soil column, allows to investigate and describe the influence of many physicochemical parameters and conditions (e.g. soil moisture and characteristics, temperature, possible addition with dewatered sewage sludge, possible LL recirculation) on VOCs degradation capacity of bio-cover systems.