‘Quick win’ clean bus technologies identified

Buses retrofitted to use exhaust treatment technologies such as selective catalytic reduction (SCR) or electric powertrains are likely to be the most effective at reducing NOx emissions, government-backed research has suggested.

Commissioned by the government’s Joint Air Quality Unit (JAQU), the findings were presented by the Low Carbon Vehicle Partnership (LowCVP).

Buses, vans and HGVs are thought to contribute over half of UK national average roadside concentration of nitrogen dioxide

Release of the findings comes as local authorities are being asked to bid for funding as part of a £30 million scheme to reduce bus emissions. Authorities have been given until 17 November to apply for funding as part of the latest stage of the Clean Bus Technology Fund — with an initial funding start date of 5 January 2018.

LowCVP has assessed findings from trials in over 25 local authority projects, involving five vehicle types and over seven technologies, analysing a range of vehicle testing data, before and after retrofit equipment was fitted and when in service.


The organisation has claimed that the highest NOx emission reductions — between 80%-100% — were seen for retrofit SCR after-treatment and diesel bus engine conversion to using an electric powertrain.

It added that moderate NOx emission reductions (25%-29%) were achieved by retrofit thermal management and flywheel hybrid technologies, while low NOx emission reductions (3%-6%) were achieved by mild hybrid, hybrid assist and dual fuel CNG conversions.

The majority of retrofit SCR systems were fitted with particle filters, also resulting in high reductions (>75%) in particulate (PM) emissions, the LowCVP added.

The LowCVP’s Evaluation Report can be found here.

LowCVP is running a Clean Vehicle Retrofit Accreditation Scheme (CVRAS) to provide a standard for emission-reduction technology for buses to meet requirements set out in the government’s Clean Air Zone Framework (see story).

Eminox SCR technology

This is intended to aid local authorities bidding for funding for retrofit technologies from the government’s Clean Bus Technology Fund which opened this month and aims to support “rapid, cost-effective and reliable emissions-reduction retrofit programmes in bus fleets”.

Commenting on the findings, LowCVP’s head of projects, Gloria Esposito, said: “The LowCVP work has highlighted the need for robust and independent vehicle emission testing to demonstrate the performance of retrofit technologies in terms of both air pollutants and greenhouse gas emissions.

“The Clean Vehicle Retrofit Accreditation Scheme builds upon our earlier work, enabling technology providers and vehicle users to focus on a nationally recognised independent system of equipment quality, durability and performance.

“LowCVP’s work in developing retrofit technology accreditation over a number of years provides one important part of the solution to tackling the urgent problem of cutting air pollution in our cities.”


UK-based emission reduction specialist Eminox has become the first company approved for the CVRAS with its SCR technology. According to Eminox, the SCR technology can reduce NOx and NO2 by 99%, and particulate matter by 95%, resulting in emissions equivalent to Euro VI.

Carlos Vicente, business development manager for Eminox, said: “To be named as the first ever company to become CVRAS approved is a fantastic achievement for Eminox.

“We can now help operators who want to retrofit to meet the requirements of many new Euro VI level emission zones across the UK.

A Go Ahead bus retrofitted as part of the government’s Clean Bus Technology Fund

“We have worked hard to make sure that the company stays ahead of the latest technology and be the first to provide certified retrofit equipment that meets the latest demanding standards.”

Government has identified retrofitting of older, more polluting buses as a key area for targeting improvements in emissions in towns and cities, with the July Air Quality Plan having stated that local authorities should “consider the impact retrofitting could have on their pollution levels and meeting local air pollution levels.”

Vantage Power, which designs and manufactures hybrid retrofit systems for buses, has welcomed the latest round of funding.

Alex Schey, chief executive of Vantage Power, said: “Solving the air quality problem in this country is one of the great problems of our time, and it’s pleasing to see the Government recognise this with funding to support fleet upgrades. We look forward to working with operators and local authorities to tackle poor air quality and lower CO2 and noise emissions with a truly novel and cost-effective solution.”

Related Links

LowCVP – Clean Bus Technology Assessment Report
Clean Vehicle Retrofit Accreditation Scheme


Comments are closed.

Help us break the news – share your information, opinion or analysis
Back to top