A Review on Biogas Interception Processes in Municipal Landfill

摘要

Biogas in landfill is being captured by natural and engineered processes. The natural processes are represented by biological activities such as bacterial methane oxidation and plant uptake for carbon dioxide at topsoil layer. Landfill gas is transported through soil layers in landfill top or in nearby areas before being released to the atmosphere. Whilst transported in the soil layers the biogas is mixed with atmospheric air and the methane may hence be oxidized by the methanotrophic bacteria in the soil using oxygen from atmosphere. Methane oxidation is affected by different environmental factors such as; temperature, water content, nutrients, substrate and oxygen concentrations. One of the ways to decrease greenhouse emissions in the future is to plant fast growing woody crops thereby sequestering carbon and displacing fossil fuels by harvesting woody biomass for bio-energy, or by storing carbon in long-lived woody products. Plant uptake for carbon dioxide is affected by some parameters such as; CO₂ concentration, nitrogen concentration, water content and temperature. The engineered processes are represented by various physical biogas extractions; gas is collected using network of collection pipes and wells. The gas collection efficiency in landfills is between 40-90%. Landfill gas can be collected by either a passive or an active collection system. Passive gas collection systems use existing variations in landfill pressure and gas concentrations to vent landfill gas into the atmosphere or a control system. Active gas collection is considered a good means of landfill gas collection. An active collection system composed of extraction wells connected to header pipe to a pump that delivers gas for energy recovery.