G. H. EDULJEE

Introduction
All waste management activities have the potential to release emissions to atmosphere, perhaps along with releases to other environmental media such as groundwater or surface water. These emissions may be controlled (i.e. managed so as to minimize harm to the environment) or uncontrolled (i.e. not under the direct management of plant or site operators).1 In some waste management processes (for example incineration, gasiÞcation, pyrolysis) continuous and controlled emissions to atmosphere are an integral and essential consequence of the treatment, since the aim is to convert wastes to essentially gaseous, non-toxic products which can safely be released to the environment. In other waste management processes (physicochemical treatment, solidiÞcation, chemical recovery, etc.) the aim is not to permit releases to the atmosphere, and to contain the products within the reaction vessel. However, adventitious, uncontrolled releases could still occur if the reactions are not adequately monitored. In the landÞlling of biodegradable wastes, approximately 6 m3 of gas is released per tonne of waste deposited per year. Two gas management concepts are currently under discussion: maintaining dry conditions within the landÞll by preventing the ingress of air and water and thus slowing the generation of landÞll gas and leachate (the Ôdry tombÕ), or treating the landÞll as a bioreactor
and maximizing the generation and release of landÞll gas by optimizing air and water requirements.
In addition to these process-related emissions, uncontrolled releases to atmosphere could occur during any stage of the waste management cycle, for example during handling, transportation, inter-plant transfer, etc. illustrates the potential for releases from various types of waste management processes: landÞlls (representing an area source), combustion plant (stack emissions representing a point source), and tra¦c (representing a line source). Emissions can be continuous (as in the case of gases from incinerator stacks or of gas di¤using through the cover material of a landÞll) or discontinuous (as in thecase of releases from physicochemical treatment plants or from Þres and accidental spills).
In comparison to soil and ground or surface water, the atmosphere is a far more e¤ective carrier of pollution in that dispersion of emissions into the surrounding environment is multidirectional, relatively fast, and over longer distances.3 To persons living in the vicinity of waste treatment and disposal facilities, emissions to atmosphere are often the most obvious manifestation of waste management operations, because of visible emissions (steam and smoke from an incinerator stack), or because fugitive releases of dust, odours, litter, etc. have resulted in loss of amenity. Certainly, waste management processes that routinely discharge to atmosphere (in general, all thermal processes) have attracted more attention from environmental groups and the public due to anxieties over serious adverse health e¤ects than have other types of waste
treatment and disposal options. This article presents an overview of emissions to atmosphere from waste management operations. The discussion commences with a brief review of the regulatory control of such emissions, as it pertains in the UK. Next, the releases to atmosphere are characterized in terms of their sources, composition, and scale of release. The environmental impacts of such releases are then examined, di¤erentiating between national or global issues, and near-Þeld e¤ects which have the potential to produce more local impacts. Finally, measures which can be taken to mitigate the potential adverse e¤ects of emissions to atmosphere are discussed.