ABSTRACT
This chapter examines the environmental impact of internal combustion engines (ICEs), focusing on pollutant formation mechanisms, evolving emission directives, and the future role of ICEs in the transportation sector. ICEs have historically been central to passenger and freight mobility but are major contributors to air pollution and greenhouse gas (GHG) emissions, particularly in urban areas.
The chapter begins by analysing the formation of primary pollutants – such as carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter (PM) – within ICEs. It reviews advancements in emission control technologies, including three-way catalytic converters, fuel injection systems, and exhaust recirculation techniques, which have significantly reduced emissions over the decades. Differences in emission characteristics and technological evolution between spark ignition (SI) and compression ignition (CI) engines are also explored.
A detailed discussion of European emission standards from Euro 1 to Euro 6 illustrates the tightening of regulations and the shift towards real driving emissions (RDE) testing in response to challenges like the “Dieselgate” scandal. The introduction of stringent CO2 fleet-wide emission targets has accelerated the transition to hybrid and electric propulsion systems.
While ICEs continue to play a role in long-distance and heavy-duty transportation, the chapter highlights their declining relevance in urban applications due to zero-emission alternatives such as battery electric vehicles (BEVs). The chapter concludes by considering the future role of ICEs in a decarbonized transport landscape, balancing the technical advantages of ICEs in specific applications with the imperative to mitigate their environmental impacts.
