Generators and pumps powered by either gas or diesel engines are widespread, and can be collectively referred to as stationary engines. The emissions of stationary engines in the range of 1-50 mW are regulated by the recently-announced Medium Combustion Plant Directive (MCPD).
Generators can be divided into continuous, prime-power, mobile and standby operations. Continuous and prime-power generators are used intensively and therefore the exhaust emissions are of concern because of the sheer quantities involved in a single location. Standby generators often don’t clock up many hours, but may be sited in a place where excessive exhaust pollution is unacceptable, for example near an existing pollution hotspot. Mobile generators by definition can be used almost anyway, and may be used intensively meaning that the quantum of pollutants is inappropriate for the location.
Problems with the emissions from engine-driven pumps often arise where these are located in densely populated areas or near large buildings such as office blocks and hospitals.
The emissions regulations which apply to stationary engines are usually a stage behind those which apply to non-road mobile machinery and two stages behind heavy-duty road vehicles. This means that major benefits in terms of air quality can be obtained by retro-fitting these engines with the latest exhaust-gas aftertreatment systems.