Retrofitting Urban Buses to Reduce PM and NO2

In an attempt to improve ambient air quality, retrofit programmes have been encouraged; targeting reductions in PM emissions by means of diesel particulate filters (DPFs). However depending on the DPF design and operating conditions increased nitrogen dioxide (NO₂) emissions have been observed, which is causing concern. Previous work showed that retrofitting a DPF system employing a fuel borne catalyst (FBC) to facilitate regeneration, reduced NO₂ emissions. This paper outlines the investigation of a base metal coated DPF to enhance the reduction of NO₂. Such a DPF system has been fitted to older technology buses and has demonstrated reliable field performance.