Gas-phase mass transfer processes in landfill microbiology

This report assesses gas-phase mass transfer processes in landfills with respect to their influence on waste biodegradation. Gas-phase transport must dominate in many regions of the waste because aqueous-phase transport is restricted, the environment is largely unsaturated, and substantial quantities of gas are produced. Analysis of landfill gas and landfill gas condensate at four municipal solid waste landfills in the eastern United States demonstrated that both volatile fatty acids and microorganisms are transported in the gas phase. The heterogeneity, mass transfer limitations, and significant thermal gradients in waste environments imply that gas-phase processes can play crucial roles in waste decomposition, for example by regulating local pH and distributing trace nutrients. A conceptual framework describing these processes is presented. Implications for waste management, landfill design, energy production, air emissions, and anaerobic microbiology are discussed.