Biogas as a Fuel for City Buses

Abstract

Research and/or Engineering Questions/Objective: The road transport in Europe almost fully depends on fossil fuel. Diversification of the road transport fuels will be a key attribute for road transport in the coming years. Biogas is one of alternative renewable fuels. Actually in Poland biogas is used for generating electricity and heat. In some countries (for example in Sweden), upgraded biogas to natural gas quality (biomethane) is used as a vehicle fuel too. In this chapter estimated biogas production potential in Baltic See Region countries: Germany, Poland and Sweden. It is one of the purposes of European Project Baltic Biogas Bus, realized presently. Methodology: Authors of the paper discussed ecological results of biogas (biomethane) application for fuelling city buses. Comparative studies of exhaust emissions from city buses powered by diesel and CNG engine were carried out. The study was conducted under real traffic conditions in southern Polish city Rzeszow. Due to the lack in-service city buses with emission level Euro V in Rzeszow, comparative studies of this type of city buses powered by diesel and CNG engine was conducted in SORT I test. Determined mean values of road emissions in g/km for the city buses operated in Rzeszow. Estimated value of the total road emissions in the case that would be replaced half the fleet of city buses (40 CNG buses and about 35 % of the diesel engine powered buses, meet Euro III emission standard) by the CNG-powered (biomethane) city buses, complying with Euro V (EEV) emission standard. Results: It was found, inter alia, that the above-mentioned exchange half the fleet of city buses in Rzeszow for CNG-powered buses that meet Euro V (EEV) emission standard, reduced by about 10 %, first of all, the total CO₂ emissions. The reason is to use during test SORT I the bus with engine of small displacement (downsizing). Also significantly reduced the total emission of CO and NO_x (54 %) and (44 %), while THC emissions increased (70 %). Road PM emission is, as is the case in vehicles powered by CNG (biomethane), very small. The use of biomethane instead of CNG, as a fully renewable energy source, will reduce CO₂ emissions compared to diesel fuel supply very significantly, taking into account the emission from the well to the wheel. The paper presents the estimated potential of biogas in Baltic See Region countries: Germany, Poland and Sweden, too. Limitations of this study: A limitation of the study was, inter alia, lack possibilities of research in real traffic conditions in Rzeszow, exhaust pollutant emissions from city buses with the Euro V level of emissions. These buses are not operated here. The lack Portable Particulate Measurement Device (PPMD) also prevented a more accurate measurement of particulate emissions during tests city buses in Rzeszow. What does the paper offer that is new in the field in comparison to other works of the author: Comparative works discussed in this chapter as well as estimates of biogas potential production in above-mentioned the Baltic Sea Region countries, the authors earlier have not conducted. Conclusion: The new transport White Paper recommends an ambitions target of 60 % reduction of greenhouse gas emissions from transport up to 2050 in comparison to 1990. In this publication is forecasted that biomethane will be alternative road transport fuel for passenger/light duty cars, heavy duty (city) vehicles and heavy duty (long distance) vehicles in short term period (2020), mid term period (2030) and long term period (2050—only for passenger/light duty cars and heavy duty (city) vehicles). Prospect of application of biogas (biomethane) as a city fuel buses is significant.

F2012-B01-037