The Catalan Government issued an air quality decree stipulating that all Euro II and III buses in Catalonia must be upgraded to a minimum standard of Euro IV by 2014. In that context, Transports Metropolitans de Barcelona (TMB) has selected a combined Selective Catalytic Reduction (SCR) and Diesel Particulate Filter (DPF) retrofit technology to help them cut emissions from 363 buses. This has now become Europe’s largest retrofit program to target both PM and NOx. Independent testing at homologation test centre Idiada, confirmed that the retrofit system could help achieve EEV (Enhanced Environmentally Friendly Vehicle) standards with removal from the exhaust of over 90% of particulate matter, hydrocarbons and carbon monoxide and more than 70% of nitrogen oxides. Retrofitting was chosen for economic reasons since ‘for the price of one new bus, it was possible to upgrade over 15 buses to Euro V and EEV standards’ commented a TMB official.
On-board emissions measurements conducted by TÜV Nord on Berlin Cityline M27 showed that NOx emissions were reduced from 15.1 g/km down to 6.9 g/km. Berliner Verkehrsbetriebe (BVG), the public transport company of Berlin, said at the “Clean Solutions – Clean Emissions – Clean Cities” event in the European Parliament on 20 June 2013 that it is retrofitting 91 Euro IV Cityline M49 double deck buses with SCR systems in 2013, achieving emissions reductions of 76% NOx, 92% NO2 and 2% CO2.
Buses in Copenhagen, Denmark
In 2016, nearly 300 buses (from Euro III to Euro V and EEV) operated in Copenhagen, Denmark have been retrofitted to the Euro VI standard with a deNOx technology capable of converting 95-99% of NOx from the diesel engine exhaust during city operation without increasing fuel consumption and CO2 emissions. The retrofit technology used relies on a Selective Catalytic Reduction (SCR) catalyst and gaseous ammonia injection into the exhaust stream which is also possible at low temperature. The ammonia is carried on board in cartridges containing a material that has been certified as safe for transportation by the UN. In addition, each retrofitted bus is capable of reporting performance data in real-time allowing both bus operators and the authorities to keep track of exactly how much NOx is removed on a daily basis.
Buses in Umeå, Sweden
In 2016, five EURO IV buses from 2007 were upgraded to EURO VI by retrofitting an SCRT system. In addition to removing particles, this combine system can remove 95-99% of NOx emissions from the exhaust without increasing fuel consumption and CO2 emissions, thereby allowing the existing buses to operate in the Low Emission Zone of Umeå. Apart from an overall high deNOx efficiency, the system performs particularly well in slow city driving conditions at arctic temperatures. The system relies on gaseous ammonia injected into the exhaust stream. The ammonia is safely stored in cartridges containing an ammonia-absorbing salt and released to the exhaust by a special dosing unit. Each bus is reporting performance data in real-time allowing both the bus operator and authorities to keep track of exactly how much NOx has been removed.
Flemish Buses in Belgium
Flanders public transport operator De Lijn has been fitting combined Diesel Particulate Filter and Selective Catalytic Reduction systems on 247 buses, including city buses in Antwerp, Ghent and Bruges plus regional and inter-city buses. The systems eliminate more than 70% of Nitrogen Oxides (NOx) and virtually eliminate all Particulate Matter (PM) to achieve emissions standards equivalent to the Euro V standard on vehicles as old as Euro II. Trials started at De Lijn in November 2006. The bus had a data-logger and modem that continuously monitored high NOx reduction in real-time and in real world operating conditions. The system has proved its reliability throughout the 50 000 km covered during the trial, which was key to De Lijn.
La Rochelle Buses
Since January 2004, 47 Heuliez GX Euro I and II buses of La Rochelle city are equipped with a passive retrofit system using Fuel-Borne Catalyst (FBC), a Diesel Oxidation Catalyst and Silicon Carbide Diesel Particulate Filter (DPF). The combination of a DPF and FBC has proven its efficiency over a long-term field experience.
In 2006, Transport for London (TfL) selected the single-decker 3.9 litre Dennis Dart for a field trial with a combined SCR and DPF retrofit system. Two bus operators were selected by TfL for the trial to ensure that the technology would be tested on a wider variety of routes. 14 buses which had already been operating successfully with a particulate filter were fitted with an integrated package that included SCR catalysts, NOx sensors, a urea tank, pump and dispensing system, as well as an electronic control unit. Due to the low temperatures prevalent in these city bus applications and due to the need to avoid increases in secondary emissions, a NOx conversion target of 65% was set and achieved. Improvement of the commercially available components selected for the trial enabled achievement of more than 98% operating reliability across the fleet during the final nine months of the trial.
According to the London’s European Office speaking at the Clean Solutions – Clean Emissions – Clean Cities event in the European Parliament on 20 June 2013, Diesel Particulate Filters have now been installed on all pre-Euro IV buses. It has helped reduce PM10 emissions from the TfL bus fleet from 200 tonnes in 1997 to 17 tonnes in 2013. Following successful trials, in which 88% NOx reduction was achieved on both the Denis Dart and Volvo Double Deck buses, SCR equipment is now also being installed on up to 1000 buses (approximately 12% of the fleet). A 50% reduction in NO2 emissions, relative to engine out levels, is achieved at the tailpipe.
In 2016 and 2017, 55 Metroline EURO V buses were retrofitted with a gaseous ammonia injection system. Without changing the existing SCR catalyst, NOx reduction is now living up to EURO VI levels. Apart from an overall high efficiency, the system performs particularly well in slow city driving conditions at low catalyst temperatures. The solution relies on gaseous ammonia injected into the exhaust stream. The ammonia is safely stored in cartridges containing an ammonia-absorbing salt and released to the exhaust by a special dosing unit. Each retrofitted bus is reporting performance data in real-time allowing both the bus operator and authorities to keep track of exactly how much NOx has been removed.
The Madrid public transportation company, EMT, has already retrofitted 209 Euro III buses with DPF and SCR combined systems (118 Scania Omnicity, 33 MAN NL 263 F, 29 Mercedes Citaro, and 29 Iveco Cityclass). The selected SCRT® system reduces NOx emissions by more than 75%, below the Euro V standard, and reduces particles emissions by about 90%. More buses will be retrofitted, up to a total of 485 buses by June 2014. As presented at the Clean Solutions – Clean Emissions – Clean Cities event in the European Parliament on 20 June 2013, the measures taken by EMT will allow emissions in the Low Emissions Zone of Madrid to be reduced by more than 10 tonnes/year of particles and 500 tonnes/year of NOx.
In July 2008 Norfolk County Council established a Low Emissions Zone in the city of Norwich, UK, requiring an increasing number of buses to meet Euro III NOx limits. By 1 April 2010, this applied to all bus services with both terminal points within the LEZ and 50% for those than go outside the LEZ. In order to meet the requirements of the LEZ, 25 Euro II buses operated by First Eastern Counties have been retrofitted with SCR (Selective Catalytic Reduction) technology to reduce their NOx emissions by up to 64%.
Refuse Truck in France
A Euro II 20-tons refuse truck (Renault Trucks Premium MIDR 62045) with a 6-cylinder 9.84 liters engine was retrofitted with 6 Silicon Carbide filter units (20m² of filtration area) placed in the existing muffler volume. The truck was evaluated with standard diesel fuel (350ppm Sulfur) over a 12-month national program. A Catalytic Fuel Combustion technology and Fuel Borne Catalyst were used in this project.
Source: “The Ecologic Refuse Trucks: data and references” ADEME, 2003