We hope that the large-scale project will contribute to promote the use of particulate filters.

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1 Preface This report finalises the official part of the large-scale project with particulate filters in Odense. In several ways the activities of the project will continue. Odense Municipality will continue to purchase vehicles with particulate filters. Work is still being carried out to ensure a more efficient operation and other transport companies will continuously be encouraged to purchase filters. We hope that the large-scale project will contribute to promote the use of particulate filters. Especially during the first year, the project was characterised by a number of running-in and teething problems for some of the filters in the project. However, after two years the filters are still in working order on the majority of the vehicles. And much improved knowledge of what is required to become satisfied with a retrofitted filter has been obtained. The steering group would like to thank all the employees at the three operational departments in Odense, namely Odense Public Bus Transportation (Odense Bybusser), Odense Parks and Roads Management (Park- og Vej Service) and Odense Waste Management Ltd. (Odense Renovationsselskab A/S) for their competent and committed participation in the project. The Steering Group 1

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3 Contents 1 Summary The background of the project Regulation of air pollution in general Particulate pollution Regulation of motor vehicle emissions, EU legislation Health conditions Effects of particulate filters Filter technology and filter types The large-scale project in Odense Measurements of the effects of the project Cleaning efficiency of the particulate filters Measurements in the street canyon Interview with citizens who frequent the city centre Questionnaire completed by employees Experience General overview of operational experience Requirements to the vehicle and evaluation of its suitability for retrofitting of particulate filters Fitting Servicing of filters, handling of additives Monitoring of filters in operation Health and safety at work Teething troubles Operational problems Co-operation with manufacturers and distributors Fuel consumption and additives The environmental plan of Odense Municipality Conclusions from the project Filter efficiency Prerequisites for filter operation without substantial problems References...63 Enclosure 1: Course of the project...65 Enclosure 2: Members of steering group, working group and technician group...77 Enclosure 3: Overview of filters and vehicles...79 Enclosure 4: Exhaust gas measurements Odense public buses...83 Enclosure 5: Working environment instructions

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5 1 Summary Background The emission of particulates from heavy-duty diesel vehicles contributes to one of the most substantial environmental problems in cities. In a number of investigations a connection has been ascertained between particulate pollution and life-shortening lung and cardiovascular diseases. In a number of directives, the EU has implemented regulations concerning emissions from heavyduty diesel vehicles. In the directive containing the requirements to emissions from heavy-duty diesel vehicles which are effective from 1 October 2006 (Euro 4) sharpened particulate emission requirements also appear. In order to meet the emission requirements stated in this directive new heavy-duty diesel vehicles will presumably have to be equipped with particulate filters from that date (1 October 2006). In 1998, the Danish Road Safety and Transport Agency decided to promote an early use of particulate filters on existing heavy-duty diesel vehicles and in 1999 the Agency started a cooperation with Odense Municipality to test and demonstrate filter technology on a large scale. The main objective of the project has been to investigate the efficiency as well as the possibilities of particulate filter retrofitting on heavy-duty diesel vehicles. The project has run over nearly 3 years with a working period of two years and was finalised in the first quarter of This report describes the course of the project and the results that were obtained. Course of the project As part of the project, particulate filters were fitted on the heavy-duty diesel vehicles owned by Odense Municipality that were suited for retrofitting. In addition, other transport companies in Odense have been able to apply for support for partial payment of expenses connected with the purchase of filters and three transport companies have made use of the offer. As part of Odense Municipality's environmental plan other initiatives have been implemented to disseminate environmentally friendly vehicle technology with the objective to improve the air quality in the city. All in all, particulate filters were fitted on approximately 120 vehicles. 8 of the vehicles were privately owned. Four different types of filters were purchased. Furthermore, additional testing of systems that also reduce the emission of NO x has taken place. The project had a budget of DKK 11 million, which was financed by the Danish Ministry of Transport through funds for traffic measures. Beyond that budget, Odense Municipality financed a considerable workload in connection with fitting, operation and maintenance of filters and the collection of experience in connection with the preparation of the final report. During the project data has been collected about operational and environmental conditions that apply to the different types of filters. In addition, measurements have been made of the filter efficiency as well of the air quality in the selected street canyons and analyses concerning citizen and employee reactions have been carried out. 5

6 Project results In general it can be ascertained that the filters function well and they have proved to be operational during the entire two-year project period. On the basis of the measurements it can be documented that all filters after some time have had a particulate emission of g/kwh. Measurement of particulate size distribution shows that the filters have efficiency on particulates in all sizes. The measurements also show that the CRT type filters under a very heavy load (and thus high temperatures) emit a considerable number of particulates in sizes between 10 and 100 nm (nanoparticles) which presumably consist of condensed sulphate compounds. Among the 120 filters that were fitted at the beginning of the project or during the first 6 months more than 80% worked well or were acceptable. However, the remaining filters had operational problems. Problems especially arose in connection with the just under 10% buses 1 that had too low exhaust temperature and too high particulate emissions for the filters to function properly. In the light of the current knowledge it must be assumed that it will be possible to obtain satisfactory operation also on the service buses. It is considered that 10% of the remaining vehicles had engines that had not been maintained satisfactorily and would be disproportionately expensive to repair. The project has given essential knowledge of the requirements to vehicles and filters during retrofitting of particulate filters. It has been possible to obtain satisfactory filter operation for all filter types fitted on vehicles with a driving profile that gives high exhaust temperatures. However, it is essential that the vehicle has been satisfactorily maintained - otherwise, considerable requirements to maintenance might arise. If a filter is used in connection with lower exhaust temperatures and if it is well-suited for these temperatures, then satisfactory operation can be obtained. It might be a question of filters based on additives being added to the engine fuel or of filters with electric regeneration. During the first year of the project a lot of effort was put into operational problems of which some were mechanical teething troubles and others were running-in problems. That resulted in quite a few filter replacements. Most of the problems were solved within the first working year, which seems to suggest that filter technology at the beginning had not been sufficiently developed for retrofitting. The second year of the project went much smoother and it was possible to arrive at the conclusion that particulate filter retrofitting can be carried out on most heavy-duty diesel vehicles in Denmark. During the project, knowledge has been collected about the demands to fitting, maintenance and operation. Special demands are made to the working environment when filters are handled. In order to obtain good particulate filter operation it is necessary to check the condition of the filter and to ensure that the filters are maintained on a regular basis. The condition of the filters has been checked by means of back-pressure and opacity measurements and in the case of too high backpressure the filters are cleaned on a specially developed filter cleaner and afterwards they are reversed. In connection with vehicles that are in good repair the service intervals prescribed by the suppliers seem to be correct. A smaller group of vehicles that were poorly maintained will require more frequent maintenance of the filter. 1 Short city buses that are well-suited for urban driving. 6

7 Parallel with the project, back-pressure alarms have been developed and they can contribute to improved monitoring. It has been ascertained that if the risk of filter core melt down has to be reduced then a back-pressure alarm should be installed. Back-pressure alarms have not been tested during this project. The experience gained during the project has been passed on to the suppliers and in that connection subjects such as working environment and filter monitoring have been discussed. As part of the project, citizens from Odense were interviewed about their attitude to the project. The interview revealed that the project has received considerable attention. The citizens were satisfied with the municipality's commitment and they knew a lot about the problem. However, the citizens have in general not noticed that the air quality has improved owing to the use of particulate filters, which also agrees with the measurements carried out in the street canyon. Some citizens have registered the smell of swimming pool, which can be traced back to the increased emission of NO 2 from certain filters. The questionnaire completed by people employed in the Municipality and involved in the project showed that an improved air quality has been obtained, which is also confirmed, as the garages have become cleaner. Evaluation of the general working environmental impacts has mainly been positive with the exception of filter handling and maintenance. All in all, the large-scale project in Odense has shown that it is possible to retrofit particulate filters on a considerable share of the heavy-duty diesel vehicles. However, the project has also demonstrated that not all vehicles have a driving profile or state of maintenance that permits efficient operation of retrofitted filters. About this report In chapter 2 the background of the project is described; the existing knowledge of the impacts of particulate pollution, EU legislation within the field and filter technology. In chapter 3 the results of the various measurements carried out as part of the project are discussed and in chapter 4 the experience gained in the course of the 2 years of operation are described. In chapter 5 conclusions are drawn. Enclosure 1 gives a more detailed description of the course of the project starting with the plan of action which the Danish Road Safety and Transport Agency prepared in 1998 for planning, invitation to tender and collection of experience. 7

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9 2 The background of the project This chapter describes the background of the project including the existing and planned EU regulation of air pollution and emissions from vehicles. In addition, some of the most important terms connected with emissions into air and their measurement are defined and explained. A brief evaluation of the health related conditions and particulate filter impacts as well as a brief description of the course of the project is given. Chapters 2.1 to 2.6 are partly a summary of chapter 2, 3 and 4 in the interministerial report 2 "Particulate filters on heavy-duty diesel vehicles". There are no deliberate differences in the contents. In the following, the report is called "Report from the inter-ministerial working group". 2.1 Regulation of air pollution in general Since 1980, the EU has - through the adoption of several directives - fixed limits for the air quality. The limits have been transferred to Danish legislation in the form of executive orders issued according to legislation on environmental protection. The limits have been fixed on the basis of estimates on health effects combined with an assessment of technical, financial and political considerations. Ongoing revision is carried out and new limits will be in force from year 2005 or 2010 depending on which substances are in question. The ongoing revision of the limits has its starting point in a decision from 1996 concerning a new EU framework directive for air quality 3. The directive will be completed with sub-directives for the individual substances and for particulates. In addition to the limits, which in most cases are sharpened the sub-directives will include requirements to the measurement methods, publication of results etc. In 1999, a sub-directive was adopted for sulphur dioxide, nitrogen dioxide, particulates and lead 4. As part of the implementation of the directives, Denmark has carried out preliminary evaluations of the air quality with regard to planning a measurement programme. The objective is to identify the areas where the limits might be exceeded and afterwards to establish air observation posts and to carry out a more detailed evaluation of the air quality in the specific areas. 2 Particulate filters on heavy-duty diesel vehicles Report from the working group to illustrate how the use of particulate filters for trucks and buses in Denmark can be encouraged. Danish Ministry of Transport, Danish Road Safety and Transport Agency, Council Directive 1996/62/EC of 27 September 1996 on ambient air quality assessment and management. 4 Council Directive 1999/30/EC of 22 April 1999 relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead in ambient air. 9

10 2.2 Particulate pollution Particulates The designation particulates comprises a complex combination of solid components that vary with regard to physical properties (size, surface etc.) and chemical composition. The original source can be natural as well as man-made. Particulates can be emitted directly to the air (primary particulates) or they can be created in the air from other types of pollution (secondary particulates). The primary particulates originate from both man-made and natural sources. The man-made sources are traffic, coal-fired power plants, industrial plants etc. The natural sources are trees (pollen), wind-swept soil etc. The secondary particulates primarily consist of sulphate, nitrate and different organic compounds that are created slowly when the air is carried over long distances. The original source could be SO 2 and NO x produced through the combustion of fossil fuels. The particulate content in air typically appears in three clearly separated sizes: Ultra-fine particulates ( micrometer or nanometer), fine particulates ( micrometer) and coarse particulates (> 2.5 micrometer), cf. figure 1. Figure 1. Typical size distribution of particulates in air Particulates from cars PM 10 PM 2.5 Particulates carried over long distances Wind-swept dust W hirled up road dust C PAH metal ++ SO 4 -- N O 3 - Si Ca Fe Ultra-fine Fine Coarse Diameter (M icrometer) The shape of the curve depends on the chosen unit on the vertical axis. If the unit is weight (mass) of particulates, the ultra-fine part of the distribution will disappear. The same is the case for the coarse part of the distribution if the unit is number of particulates. The ultra-fine particulates typically originate from car engines. They have either been formed at high temperatures in the engine, through exhaust pipe condensation or immediately after emission to the atmosphere. The fine particulates are typically formed from the ultra-fine particulates through coagulation and adsorption of gaseous material from the atmosphere on existing particulates. 10

11 The secondary particulates also belong to this group. The coarse particulates are typically created mechanically (wind-swept dust, whirled up road dust and wear products from tires and brakes) 5. Measurements of the particulate content in air During the period from , the measurements at the Danish air observation posts have shown a general decline in the measured particulate concentrations of between 30 and 50%. The decline comprises both coarse and fine particulates. In connection with coarse particulates the reason is believed to be improved "housekeeping" near construction sites and green fields during winter. In connection with fine particulates the reason is believed to be improved cleaning of power plant smoke, the introduction of unleaded petrol and reduced particulate emissions from diesel vehicles. The ultra-fine particulates emitted from petrol and diesel vehicles only contribute a little to these measurements, which are based on weight. In connection with ultra-fine particulates methods have to be used that make it possible to measure the number of particulates. The Danish National Environmental Research Institute (DMU) has by means of special measuring equipment carried out measurements at heavily trafficked streets in Copenhagen (Jagtvej) and in Odense (Albanigade) 6. By means of special calculation methods it has been possible to estimate the amount of ultra-fine particulates emitted from petrol and diesel vehicles, respectively. On the basis of these calculations, DMU has concluded that a diesel car emits app. 25 times more ultra-fine particulates than a petrol car. Only a few diesel cars drive on Jagtvej and therefore the result is that the two types of cars almost contribute equally to pollution with ultra-fine particulates. In Albanigade the contribution from diesel cars is considerably higher than the contribution from petrol cars. From the measurements on Jagtvej, DMU has concluded that close to 90% of the ultra-fine particulates in the street canyon in Denmark originate from the traffic. In connection with the measurements carried out on Jagtvej it has also been ascertained that the amount of ultra-fine particulates from diesel vehicles was diminished by one half from The reason is believed to be that the sulphur content in diesel fuel during the same period was reduced from 500 ppm to 50 ppm 7. 5 With regard to measuring technique different particulate definitions are used. Until a few years ago the measurements solely comprised the content of suspended particulates (TSP, total suspended particulates ) and soot in air. TSP typically includes all particulates with a diameter of up to app. 25 micrometer. The amount is determined by means of weighing after collection on a filter. Soot comprises coloured (black) particulates that mainly are created through combustion of fossil fuels. The soot content is determined empirically from the blackening of a white filter. In recent years, attention has concentrated on the smaller particulates and the measurement of the PM 10 content in air (particulates with a diameter of less than 10 micrometer). In addition some measurements of PM 2.5 (particulates with a diameter of less than 2.5 micrometer) are being carried out. As it appears from figure 1, PM 10 is not the most appropriate method of measurement for the smallest particulates as the dividing line is in the middle of the fraction that is called coarse particulates. PM 2.5 is a better measurement, as it precisely comprises the total of fine and ultra-fine particulates. As the smallest particulates only contribute insignificantly to the weight of the total particulate mass, more accurate future health related evaluations will presuppose that information about the number of the smallest particulates is available. 6 Measurements in Albanigade in Odense have been carried out as part of this project. 7 ppm = parts per million, i.e. 1 ppm is %. 11

12 According to evaluations carried out by Danish Technological Institute an average 13% reduction in particulate emissions, measured on weight basis (TSP) 8, can be expected for the mentioned reduction in sulphur content. Some analyses have indicated that modern engines with reduced particulate emission (weight) could emit more ultra-fine particulates than older engines. However, the most recently published analyses do not support that conclusion. Analyses exist on passenger cars that show that new engines emit less particulate mass as well as less particulate number. For heavy-duty engines recent analyses conclude that Euro 2 heavy-duty engines (1996) emit more nanoparticles (10-70 nm) than Euro 1 engines (1993). The new Euro 3 heavy-duty engines (2001) have a reduction in both mass and number. Particulate emission distribution on sources No official figures exist of the total Danish emission of particulates and its distribution on sources. However, the European Commission has carried out calculations that comprise all sources (traffic, power stations, boilers, industry, agriculture etc.). The calculations show that in 1995, diesel vehicles 9 contributed with app. 11% of the total emission 10 of primary particulates. The contribution from petrol cars and from tires and wear and tear are estimated to amount to 3% and 2%, respectively, of total emissions, so the contribution from traffic when secondary particulates are not taken into account amount to app. 16% of total particulate emissions. It should be stressed that these figures are based on weight and therefore they do not take the special impacts from the ultra-fine particulates into account. In connection with the annual reporting to EU on air pollution in Denmark, DMU prepares statements of particulate emissions in Denmark from diesel vehicles. The development of the emissions from appear from table 1. Table 1: Particulate emissions from Danish road traffic (tons) Passenger cars Vans 2,500 2,400 1,700 Trucks/buses 1,700 1,600 1,400 Total 4,800 4,400 3,500 In the 90s, the total emission of particulates was reduced by app. 25%. 8 Possibilities for environmental improvements of diesel vehicles, Danish Technological Institute (for the Danish Environmental Protection Agency), May The statement only comprises emissions from the exhaust, cf. later. 10 The calculation is based on the measurement of weight and therefore nothing is indicated about the amount of ultrafine particulates. 12

13 Diesel car emissions DMU has grouped the emissions 11 of diesel vehicles according to vehicle category and driving conditions. The fragmentation appears from table 2. Table 2: Diesel car emissions in Denmark 1999, grouped according to vehicle category and driving conditions No. of Particulate emission (tons) vehicles Town Highway Motorway Total Passenger cars 104, Vans 206, ,740 Trucks t 5, Trucks t 10, Trucks t 17, Trucks exceeding 32 t 15, Buses 4, Tourist buses 5, Total 1,580 1, ,540 It appears from table 2 that diesel vans emit the most substantial amount of emissions in cities and they represent 55% of emissions while trucks and buses constitute app. 33% and passenger cars 10%. 2.3 Regulation of motor vehicle emissions, EU legislation In December 1987, the EU adopted a directive on measures to reduce the emission of pollutants from diesel engines 12. The basis of the directive was various recommendations concerning the emission of harmful gases as well as particulates. An amendment of the directive in meant that the Council of the European Union made the emission limits binding and sharpened them in two stages as of 1993 and 1996 (Euro 1 and 2). At the same time, the directive introduced maximum limits for the emission of particulates from trucks that gradually had become a serious problem in city traffic. As of 1 October 1993, there has been a binding maximum limit in the EU for the emission of NO x, HC, CO and particulates from trucks and buses. The most recent amendment of the directive took place in and concerns new requirements in three stages of which the first (Euro 3) was implemented on 1 October The statements of the emissions do not comprise petrol vehicles. Other vehicle related emissions (tire wear and tear, material from brake lining, whirled up road dust etc.) are not included either. Calculations show that the contribution from petrol cars and from wear and tear cannot be ignored as the contributions are estimated to amount to app. 20% and 10%, respectively, of total emissions. In total, the contribution from diesel cars is estimated to amount to app. 70% of the road traffic's total particulate pollution. 12 Council directive 88/77/EEC of 3 December 1987 on the approximation of the laws of the Member States relating to the measures to be taken against the emission of gaseous pollutants from diesel engines for use in vehicles /542/EEC of 1 October 1991 amending directive 88/77/EEC on the approximation of the laws of the Member States relating to the measures to be taken against the emission of gaseous pollutants from diesel engines for use in vehicles. 14 Directive 1999/96/EC of the European Parliament and the Council of 13 December 1999 on the approximation of the laws of the Member States relating to measures to be taken against the emission of gaseous and particulate pollutants from compression ignition engines for use in vehicles, and the emission of gaseous pollutants from positive ignition engines fuelled with natural gas or liquefied petroleum gas for use in vehicles and amending Council Directive 88/77/EEC. 13

14 An overview of the development in emission standards for heavy-duty diesel vehicles is given in table Table 3: Emission standards for diesel trucks and buses (g/kwh) Commencement NO x Hydrocarbons (HC) Carbon monoxide (CO) Particulates (PM) EC directive 88/77 Euro 0 1/ (1.0) EC directive 91/542 Euro 1 Euro 2 EU directive 99/96 Euro 3 Euro 4 Euro 5 1/ / / / / It is the general assumption that the requirements in Euro 4 in practice will imply that heavy-duty diesel vehicles will have to be delivered with particulate filters. Already today, trucks, buses and passenger cars can be delivered with factory-mounted particulate filters. In 2001, the European Commission submitted a proposal for an additional reduction of the sulphur content in petrol and diesel from the 50 ppm 16 that will become compulsory in The proposal implies that as of year 2005 sulphur-free fuels shall be marketed (sulphur content less than 10 ppm) and a complete transition to sulphur-free fuels will take place at the end of EU calculations have shown that the sharpened standards (incl. the sharpened requirements to stationary sources) will result in a decline in total particulate emissions of app. 30% from The reduction is calculated to be app. 80% for diesel vehicles. For this reason, the total emission of particulates from diesel cars is expected to be reduced to app. 3% of total particulate emissions against the current 11%. In its white paper 17 on transport, the European Commission has concluded that the air quality in the cities has improved due to the technical requirements that were introduced through the 90s. 2.4 Health conditions The health hazards attached to particulate pollution (probably especially fine and ultra-fine particulates) give rise to concern. Through investigations in USA and Europe it has been documented that air pollution with particulates or dust in cities involves serious health hazards. However, the implemented investigations have mainly concerned the impact of particulates from the total particulate mass It should be noted that the method of measurement that forms the basis of the below emissions varies from the method that is used to carry out measurements in the street canyon which means that there is a difference between what is measured as particulates e.g. condense etc. 16 ppm = parts per million, i.e. 1 ppm is %. In Denmark, the sulphur content in "low sulphur diesel" is <50ppm. 17 The European transport policy up to 2010 the difficult choices. White paper from the European Commission (KOM(2001)370). 14

15 A comprehensive survey in the USA that indicates a considerable impact on the number of cases of lung cancer implies that especially the fine and ultra-fine particulates are carcinogenic. However, it is still unclear which properties make particulates unhealthy. Particulates above 10 micrometer will mainly be deposited in the upper respiratory passages (nose/throat), while particulates with a diameter below 10 micrometer will be deposited further down in the bronchial tubes. Particulates smaller than 5 micrometer can reach down into the pulmonary (alveoli). Particulates that are deposited in the bronchial tubes are removed rather quickly due to the movement of the cilia while the particulates that reach the alveoli are exposed to an encapsulation that means that the retention time can be long. Which damages are caused to a high degree depends on the particulate size itself and on the chemical composition, i.e. which substances might be adsorbed on the surface of the particulates. The particulates partly influence the lung tissue and partly the viscosity of the blood and the cardiac function. The importance of the calculated values for increased mortality can be illustrated via calculations carried out by WHO in the light of the investigations carried out among Americans. WHO has calculated that the increased mortality that can be expected when the PM 2.5 level increases 10 microgrammes/m³ will shorten the average life expectancy by app. 1 year. Danish evaluations contain preliminary and uncertain estimates showing that a reduction in the particulate level of app. 30% would mean that from among children, fewer children would suffer from bronchitis symptoms. In the evaluation of the extent of the health hazards it is emphasised that all calculations also concerning increased mortality are related to the general occurrence of particulates and do not include any special evaluation of the contribution from traffic. In 1999, calculations were carried out in the municipality of Copenhagen and they showed that between 100 and 280 premature deaths are due to the exposure to PM 10. The figures are based on a conservative evaluation and might be much higher. The calculations from Copenhagen also show that the exposure to PM 10 leads to additional hospitalisations especially among people with pulmonary diseases and older people. 2.5 Effects of particulate filters 18 The specification of health related impacts from particulate pollution are connected with considerable uncertainty. Therefore, the health related specification of what is gained by using particulate filters on heavy-duty diesel vehicles in Denmark is also connected with considerable uncertainty. An expert group has evaluated the health-related impacts through a hypothetical situation where all trucks and buses in Denmark are equipped with particulate filters. In such a situation the health related impacts (expressed as avoided, annual premature deaths) have been estimated to 22. The modest impact is related to the fact that the calculations were based on urban background PM 10, which primarily consists of fine and coarse particulates that only are reduced a little when 18 The expert group that is referred to carried out a project to illustrate the effect on air quality and health by mounting filters on all heavy-duty diesel vehicles (more than 3.5 tons) in Denmark. The expert group consisted of representatives from DMU, the University of Copenhagen and the Danish Cancer Society. 15

16 particulate filters are used because the traffic's share of total emissions of fine and coarse particulates is limited. New investigations suggest greater health related impacts from ultra-fine particulates. The traffic's share of ultra-fine particulates is high. Therefore, particulate filters can reduce the total emission of ultra-fine particulates considerably. The expert group could not evaluate the effect quantitatively but stated a presumed upper limit of the positive effects of particulate filters on heavy-duty vehicles on the basis of ultra-fine particulates. The estimated upper limit that is connected with a much greater uncertainty corresponds to avoided premature deaths. At the same time it is believed that the use of particulate filters can reduce the number of hospitalisations connected with circulatory diseases and respiratory diseases and can reduce the number of bronchitis cases and asthma attacks. The assessment of these effects is also connected with great uncertainty. 2.6 Filter technology and filter types Basically, a particulate filter works by collecting soot particulates from the engine exhaust gas. The particulate filter is constructed of many small channels made of ceramics. The neighbouring channels are closed at the opposite ends so the exhaust gas is forced to pass through the channel wall where the particulates are caught. Even though the particulates are small the filter will quickly become clogged with soot, if the filtration is not combined with a method to remove the soot. Removal takes place through ongoing burning of the collected soot. The process is called regeneration of the filter. Some filter systems have passive regeneration (i.e. it is spontaneous), others have active regeneration (i.e. it requires help to burn off the particulates e.g. by supplying electricity). Figure 2: Particulate filter design Normally, a temperature of app. 600 o C is required to carry out soot combustion. That is higher than the temperatures that are obtained in the exhaust system which can vary from o C. However, ignition of the soot particulates collected in the filter can take place at much lower temperatures ( o C). That can i.a. be obtained by combining the filter with a catalyst that produces large amounts of NO 2, by using an additive in the fuel or by adding additional energy (from the car's electric system). Which system is best to a high degree depends on the vehicle in question and how the vehicle is used. 16

17 Filter types There are many different filter products in the market. Common to them all is that the efficiency on the particulate emission is declared to be 95-99% under laboratory conditions and more than 80% under practical conditions. Some of the filters are combined with an oxidation catalyst and therefore they can also reduce the emissions of HC and CO. The greatest difference between the particulate filters is how the collected particulates are removed (burned) i.e. how the filter is regenerated. In addition, technologies exist that can reduce NO x and they are often used together with particulate filters. Below, different types of filters are briefly described. Filter types that formed part of the Odense project Johnson Matthey, CRT 19 Johnson Matthey is one of the largest catalyst and filter producers in the world. The CRT filter (Continuous Regenerated Trap) was originally developed by Emissionsteknik in Sweden, which now is part of Johnson Matthey. CRT is the most well-known particulate filter and with a sale of app. 12,000 units it is also the most widespread in the European market. In Europe, the CRT filters are made under license by Eminox in England and they are sold as Eminox CRT. The filter is also sold by Volvo as Volvo CRT for original or retrofitting on buses and trucks. Johnson Matthey, CRT filter CRT is a passive filter that is regenerated by means of NO 2, which is produced in a pre-catalyst. Johnson Matthey requires fuel with less than 75 ppm sulphur. Engelhard DPX Engelhard is also a large producer of catalysts and particulate filters. At the beginning of the project, Engelhard DPX filters were made under license by Ferrita in Sweden, but subsequently they are made under license by Dinex in Denmark. DPX is a passive filter that is regenerated by means of NO 2, which is produced in the catalytically covered filter itself. Contrary to CRT, the filter has no pre-catalyst. Engelhard also recommends fuel with less than 75 ppm sulphur. 19 All the applied product names are (or can be) registered trademarks of the respective companies. 17

18 Engelhard DPX filter Silentor On an international scale, Silentor is a small Danish company and mufflers are their speciality. Silentor makes particulate filters with monoliths from NoTox. Silentor is a passive filter that is regenerated by means of an additive, which is added to the fuel. Today, Silentor uses the additive Octel Optimax 4804, which contains 4% Iron and 1% Strontium. Normally, the additive is dosed with 200 ppm during summer and 400 ppm during winter. Silentor is available with or without an oxidation catalyst. Energietechnik Bremen, ELR ETB makes particulate filters with electric regeneration and they are called ELR. This type of filter makes it possible to use filters at low exhaust temperatures as the collected soot particulates are burned continuously by means of power from the vehicle's generator. DeNO x systems that formed part of the additional tests Svensk Turbo Teknik EGR The company Svensk Turbo Teknik (STT) has developed an EGR (Exhaust Gas Recirculation) system for retrofitting and it is used in combination with a Johnson Matthey CRT filter. The EGR system recirculates part of the exhaust gas to the engine's inlet air and in that way reduces the NO x emission. The recirculated exhaust gas is cooled in a heat exchanger. The STT system uses an electronically controlled EGR valve and its operation has to be programmed to the engine in question and therefore the system is adapted to a limited number of engines. Volvo sells Johnson Matthey CRT filters and STT EGR systems as original Volvo auxiliary equipment under the name VEC. 18

19 When deno x systems are used in connection with particulate filters that are regenerated by means of NO 2 there is a natural limit to the efficiency of the deno x system as NO x can only be reduced so much so there is enough NO 2 to regenerate the filter. In practice that means that the NO x efficiency should not exceed 40-45%. Otherwise, there is a risk of damaging the filter. Ferrita EGR Another Swedish company, Ferrita, has also developed an EGR system for retrofitting - at first together with Engelhard DPX filters. Ferrita's system is purely mechanical and an orifice that is adapted to the individual engine type limits the EGR amount. Ferrita's EGR system also has a heat exchanger for cooling of the recirculated exhaust gas. The same considerations as above apply to efficiency. Ceryx, QuadCat Ceryx was a small American company (now closed down) that produced an active filter called QuadCat. It was regenerated through secondary fuel injection, i.e. a small amount of fuel is injected into the exhaust before the filter. A patented heat exchanger is incorporated in the system, which reduces the energy consumption to some degree. QuadCat also has an oxidation catalyst that removes HC and CO and a deno x -catalyst that reduces NO x. The catalyst should have an efficiency of 25-40% depending on how much fuel is used in secondary injection. Typically, additional consumption is 2-6%. Other filter types The above-mentioned products are the most important in the market, but there are also other products in the market or they are on their way into the market. In that connection we would like to mention: Unikat Swedish UNIKAT AB supplies a filter system where the burning of particulates takes place by means of electricity from the grid. This system requires the vehicle to be connected to the grid (400 volt) for 8 hours every time it has driven 8-10 hours and the use of the system limits the use of the vehicle. 19

20 2.7 The large-scale project in Odense In connection with the negotiation of the EU directive 99/96, the Danish Road Safety and Transport Agency carried out various considerations about expediting the use of particulate filters. The considerations resulted in a proposal for the implementation of a large-scale project concerning retrofitting of particulate filters. Project planning Tender for filter purchase Filter fitting Measurement of filter effects Monitoring Street canyon measurement Figure 3: General timetable of the project Reporting etc. April Quarter 1999 July Quarter 1999 October Quarter 1999 January Quarter 2000 April Quarter 2000 July Quarter 2000 October Quarter 2000 January Quarter 2001 April Quarter 2001 July Quarter 2001 October Quarter 2001 January Quarter 2002 The project was to cover operation with one or several different types of particulate filters on a large group of heavy-duty diesel vehicles. Odense Municipality was chosen as co-operation partner and it was agreed that particulate filters were to be retrofitted on the main part of the Municipality's heavy-duty diesel vehicles. Through political initiatives and agreements with private transport companies, Odense Municipality was to ensure that using filters became more widespread among carrier and distribution services, taxis and private buses. The objective of the project has been to illustrate the environmental impacts as well as the operational and financial conditions that arise when filter technology is used. Odense Municipality and the Danish Road Safety and Transport Agency have jointly been responsible for the project. A steering group that also had the main financial responsibility has handled the superior management of the project. A working group has been in charge of the project's daily management and for involving external parties with specialised knowledge (Danish Technological Institute, the Danish National Environmental Research Institute (DMU) etc.). The composition of the steering group and the working group appears from enclosure 2. The project has comprised the main activities described in the general timetable, figure 3. Below, the purchase of filters is described. A more detailed description of the course of the project appears in enclosure 1. 20

21 EU tender concerning filter purchase The purchase of filters took place in the form of a public EU tender. As far as possible, the tender comprised the purchase of different types of filters. In addition to the filters, the delivery also included guiding and instructing the garage staff in connection with fitting and servicing of the filters. The tender comprised filters adapted to specific vehicles. The filter suppliers had to guarantee that the filters would work for at least 2 years/200,000 km. Table 4 includes an overview of the purchased and tested filters. Enclosure 3 gives a detailed overview of vehicles and filters. Table 4: Overview of purchase of filters In connection with tender Filter type Make No. Odense Public Bus Parks and Roads Odense Waste Transportation Management Management Ltd. Johnson Matthey, Eminox CRT CRT Volvo CRT Engelhard, DPX Ferrita Silentor Silentor Additional testing of electrically regenerated filters Filter type Make No. Energietechnik Bremen, ELR Energietechnik Bremen, ELR Odense Public Bus Transportation Parks and Roads Management Odense Waste Management Ltd All filtertypes Filter type Make No. Additional purchase for other transport companies Odense Technical College "Odense Fragtcentral" (carrier service) Silentor Silentor 3 3 Engelhard, DPX Ferrita 3 3 Johnson Matthey, CRT Post Denmark Volvo CRT 2 2 In total, 121 filters were purchased for the project. In addition, deno x systems were tested on 9 vehicles, cf. table 5. Table 5: Additional testing of deno x systems Type Filter No. Odense Public Bus Transportation Ferrita EGR Ferrita 3 3 STT EGR Eminox CRT 3 3 Ceryx Quad CAT Ceryx Quad CAT

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23 3 Measurements of the effects of the project In this chapter, the results of the measurements that were carried out as part of the project are described. The measurements partly concern the cleaning efficiency of the filters in a test stand, air quality measurements in the street canyon and the interview/questionnaires among citizens in Odense who regularly frequent the city centre as well as among local municipal employees who participated in the project. 3.1 Cleaning efficiency of the particulate filters Emission measurements have been carried out on the tested filter types at Danish Technological Institute, Centre for Engine Technique, in Aarhus. The main objective of the emission measurements has been to follow the development of the filters in the course of time. Some filters have been tested three times: when the project started in January 2000, after app. 1 year (December 2000) and after app. 2 years (December 2001). Other filters that were fitted subsequently were tested once or twice. Besides, a measurement without filter has also been carried out on one bus in order to be able to evaluate the efficiency of the filter. Method of measurement The official method of measurement used to determine emissions from heavy-duty diesel vehicles is called 88/77/EEC with subsequent amendments. The engine is fitted in a test bench and measured in 13 stationary modes (13-mode test). The emission (g/s) and power (kw) measured at each mode is given a predetermined weight and summarised to produce a single value. (g/kwh). Measurement of bus on a chassis dynamometer. 23

24 Centre for Engine Technique has previously shown that a similar result can be obtained by measuring the vehicle on a chassis dynamometer in 5 different modes selected from the 13-mode test, but with different weight factors. This "5-mode test" has been used when measuring the emissions. The weight factors and loads are shown in table 6. Table 6: 5-mode test Mode no. Rpm Load % Weight % 1 Idling max. torque max. torque max. torque max. power mode load and weight factors. The following parameters were measured: NO x, NO 2, HC, CO and particulates as well as exhaust gas temperature, back-pressure, engine power and a number of other parameters for conversion and control of emissions. In the following, the results of the emission measurements carried out on the individual filter types are summed up and experience and conclusions from the measurements are emphasized. The technically interested reader is referred to the four measurement reports. 20 Johnson Matthey CRT Emissions from two types of CRT filters (Volvo CRT and Eminox CRT) have been measured. In principle, the filters are identical and therefore they are treated collectively. A total of 6 measurements have been carried out on a chassis dynamometer with CRT filters. As it appears from table 7, the CRT filters have given fluctuating and at times very high particulate results during emission measurements. (On one bus (no. 16) the filter was replaced and therefore two measurements are marked "1 st time"). In addition, the results of the measurements are shown graphically in figure The following measurement reports are in question: 1. Measurements of Emissions at project start, Danish Technological Institute, Centre for Engine Technique, May Follow-up on the Danish Road Safety and Transport Agency's Large Scale Particulate Filter Demonstration Project in Odense, Danish Technological Institute, Centre for Engine Technique, January Measurement of the "true" efficiency of a CRT filter, Danish Technological Institute, Centre for Engine Technique, May Follow-up on the Danish Road Safety and Transport Agency's Large Scale Particulate Filter Demonstration Project in Odense Emission measurements after 2 years of operation, Danish Technological Institute, Centre for Engine Technique, January

25 Table 7: Emission measurements CRT filters FILTER Vehicle Vehicle info Measurement Particulate emission (g/kwh) Volvo CRT - I Bus 16 Volvo B10 BLE 1999 (Euro 2) Volvo CRT - II Bus 16 Volvo B10 BLE 1999 (Euro 2) Filter "age" (Km in operation) 1 st Measurement ,862 1 st Measurement ,294 2 nd Measurement ,134 Eminox CRT Bus 139 Volvo B 10 M st Measurement ,471 (Before requirements) 2 nd Measurement ,097 3 rd Measurement ,012 After the first series of measurements in January 2000 the fluctuating measurement results and at times very high emission values were discussed in detail with the manufacturer Johnson Matthey, who gave an explanation of the phenomenon. In short, the explanation is that sulphate (formed of sulphur from fuel and lubricating oil) is stored in the washcoat 21 in the pre-catalyst of the CRT filter at temperatures below app. 375ºC and it is emitted at higher temperatures. If a vehicle with a CRT filter is used in a driving profile with low exhaust temperatures, e.g. urban driving, then sulphur will be stored in the system. When the vehicle subsequently is tested on a chassis dynamometer under a heavy load, sulphate will be released which is measured as particulates. Figure 4: Results of measurements on buses with CRT filters Bus 16, 1 st time Particulates [g/kwh] Bus139, 1 st time Bus 16, 1 st time Bus 139, 2 nd time Bus 139, 3 rd time 0.05 Bus 16, 2 nd time ,000 40,000 60,000 80, , , , ,000 Filter age [km in operation] 21 A washcoat is a material that is applied to the catalyst substrate, partly to increase the active surface and partly to bind the catalyst itself to the substrate. 25