10.4.9 Air quality issues: NMVOCs and combustion emissions
Landfill gas contains trace concentrations of aromatic, chlorinated and fluorinated hydrocarbons, reduced sulphur gases and other species. High hydrocarbon destruction efficiencies are typically achieved in enclosed flares (>99%), which are recommended over lower-efficiency open flares. Hydrogen sulphide is mainly a problem at landfills which co-dispose large quantities of construction and demolition debris containing gypsum board. Emissions of NOx can sometimes be a problem for permitting landfill gas engines in strict air quality regions.
At landfill sites, recent field studies have indicated that NMVOC fluxes through final cover materials are very small with both positive and negative fluxes ranging from approximately 10-8 to 10-4 g/m/d for individual species (Scheutz et al., 2003a; Bogner et al., 2003; Barlaz et al., 2004). In general, the emitted compounds consist of species recalcitrant to aerobic degradation (especially higher chlorinated compounds), while low to negative emissions (uptake from the atmosphere) are observed for species which are readily degradable in aerobic cover soils, such as the aromatics and vinyl chloride (Scheutz et al., 2003a).
Uncontrolled emissions resulting from waste incineration are not permitted in developed countries, and incinerators are equipped with advanced emission controls. Modern incinerators must meet stringent emission-control standards in Japan, the EU, the US and other developed countries (EIPPC Bureau, 2006). For reducing incinerator emissions of volatile heavy metals and dioxins/dibenzofurans, the removal of batteries, other electronic waste and polyvinyl chloride (PVC) plastics is recommended prior to combustion (EIPPC Bureau, 2006).