Control of Landfill Gases Emission with Particular Emphasis on Btex
Landfilling is the most popular way for waste disposal and has been widely applied globally. A large quantity of volatile organic compounds (VOCs) is released from landfills. Among them, BTEX (benzene, toluene ethylbenzene and xylene) is a major group of pollutants, which have now become a cause for concern worldwide because of their toxic properties. For this reason, strict regulations have come into force which induce researchers to find methods to reduce their emissions. This article contains descriptions of several aerobic metabolic pathways for the degradation of BTEX, which are provided by two enzymatic systems (dioxygenases and monooxygenases). Special attention was paid to biofiltration - a method for improving the efficiency of treatment of BTEX released from landfills.
Uncontrolled emissions of landfill gas may contribute significantly to climate change, since its composition represents a high fraction of methane, a greenhouse gas with 100- year global warming potential 25 times that of carbon dioxide. Landfill cover could create favourable conditions for methanotrophy (microbial methane oxidation), an activity of using bacteria to oxidize methane to carbon dioxide. This paper presents a brief review of methanotrophic activities in landfill cover. Emphasis is given to the effects of cover materials, environmental conditions and landfill vegetation on the methane oxidation potential, and to their underlying effect mechanisms. Methanotrophs communities and methane oxidation kinetics are also discussed. Results from the overview suggest that well-engineered landfill cover can substantially increase its potential for reducing emissions of methane produced in landfill to the atmosphere.