Secretary of State for Transport (): Today, I am providing
an update regarding the retrofitting of buses with selective
catalytic reduction (SCR) technology to reduce
emissions of nitrogen oxides (NOX ).
Through a series of trials between 2013 and 2015, the previous
government explored the potential of reducing emissions or
improving fuel economy in older buses and other large vehicles
through a range of retrofit technologies. Retrofitting
SCR technology
was found to be the most effective in reducing the levels of
NOX emitted from older
buses. Allowing for some variation based on the Euro standard of
the retrofitted bus, reduction of NOX using SCR technology in trials
averaged around 90%
The clean vehicle retrofit accreditation scheme (CVRAS) was
launched in 2017 to accredit retrofit technologies that could
reduce NOX emissions from
buses to close to Euro VI levels. Between 2017 and 2019, £64
million was allocated to the clean bus technology fund for bus
upgrades and retrofits. A further £31 million was provided to
local authorities in the government's NO2programme. Approximately 9,000 buses
in England have been retrofitted with CVRAS-accredited
SCR
technology.
In 2021, the government was made aware of new evidence from
Scotland suggesting that real-world emission reductions from
retrofitted buses were lower than expected. In 2022 a roadside
monitoring campaign was commissioned to measure NOX emissions from retrofitted buses in
3 areas in England which reported in early 2023. The findings
were similar to those in Scotland. Government funding for bus
retrofits was paused in April 2023 while further research was
carried out to understand the causes of poor performance and
assess the scope for improvement.
This research was overseen by the Department for Transport (DfT)
and Department for Environment, Food and Rural Affairs (Defra)
Chief Scientific Advisers, assisted by an external independent
expert group. Today I have placed the Bus retrofit performance
report, containing the findings of this research, in the
Libraries of both Houses. This performance report was
commissioned by the government and finalised in November 2023. In
the interest of transparency, I am now releasing this report
today.
The report concludes that real-world performance of bus retrofit
SCRtechnology
is highly variable, achieving 80 to 90% NOX reductions in some cases, but having
a minimal effect in others. There is an average 11% reduction in
NOX emissions overall from
retrofitted buses compared to non-retrofitted Euro V buses, which
is significantly lower than the 80% reduction anticipated.
The research shows that a number of contributing factors can lead
to poor performance, including incorrect functioning of retrofit
systems, the condition of bus engines and low catalyst operating
temperatures. Based on these findings, I am announcing today a
permanent end to further government funding for retrofit and the
closure of the clean vehicle retrofit accreditation scheme to
further accreditations.
Moving forward, we will work with bus operators and retrofit
suppliers to encourage a step change in monitoring and
maintenance of retrofit systems to get the best possible
performance from the retrofitted buses currently in service. This
will include ensuring that buses are providing live data showing
retrofit performance so that operators and depots can prioritise
and target essential maintenance on the poorest performing buses.
Providing this data will be a condition of the buses remaining on
the list of CVRAS-accredited
vehicles.
Air pollution is the biggest environmental threat to human
health, and this government recognises the need to take
preventative public health measures to tackle the biggest killers
and support people to live longer healthier lives. We will
continue to work closely with the relevant local authorities to
identify alternative measures to deliver compliance with legal
NO2 limits in the shortest
possible time.
