Studie: Retrofit könnte Europas Busflotte 15 Jahre früher elektrifizieren

A new study suggests that retrofitting existing diesel buses with battery-electric systems could accelerate the electrification of Europe’s bus fleet by approximately 15 years. The research, conducted by the Swiss Federal Laboratories for Materials Science and Technology (Empa) as part of the EU-funded CircEUlar project, was published in the journal Environmental Research: Infrastructure and Sustainability. According to the study, even if only emission-free buses were allowed after 2035, the European bus fleet would not reach over 95% electrification until 2057 due to the typical 20-year lifespan of urban buses. As of 2023, less than three percent of all buses operating in Europe were fully electric. The process known as E-Retrofitting involves removing the engine, transmission, fuel tank, and exhaust system and replacing them with batteries, an electric motor, and auxiliary electrical components. The body, chassis, and interior remain unchanged. Because there are few large-volume models in the city bus sector, the Empa researchers suggest that standardized retrofit kits can be developed. This would allow individual conversions to take place within just a few days. Components removed during the retrofitting process are primarily made of steel and aluminum, which can be recycled. Harald Desing, a researcher at Empa’s Department of Technology and Society in St. Gallen, summarized the approach: “If we retrofit existing buses for electric operation instead of replacing them with new ones, we can achieve complete electrification of the bus fleet around 15 years earlier, and save emissions and raw materials in the process.” According to lifecycle analysis, E-Retrofitting produces roughly half the greenhouse gas emissions compared to manufacturing a new battery-powered bus. Each retrofitted vehicle emits about 58 tons of CO₂ equivalents less. The costs associated with retrofitting are also about half the purchase price of a new electric bus. Since operational costs for electric buses are lower than those for diesel buses, transport companies could reduce both investment and maintenance expenses in the long term. Depending on the scenario, the study estimates cost savings ranging from 2.2 to 3.2 percent of total bus transportation costs by 2100. When extrapolated to the entire European bus fleet, the potential carbon dioxide savings amount to up to 300 million tons by 2100. This figure is comparable to Spain’s annual greenhouse gas emissions, which stand at around 270 million tons of CO₂ equivalents. According to the study, this approach would also reduce the demand for primary raw materials, cumulative energy consumption, water usage, and fine particulate emissions. Only about one percent of today’s automotive mechatronics professionals in Europe would be needed to retrofit up to 75,000 buses annually. With five percent of these specialists, the existing European diesel bus fleet could theoretically be fully electrified within less than three years. Freed-up capacities could later be expanded to trucks and other commercial vehicles. There are already initial projects underway in practice. Since early 2025, a ten-year-old MAN A 21 Lion's City bus operated by the Transdev Group has been running in Schwäbisch Hall after being converted to electric drive using technology from Voith, Orten Electric Trucks, and ToZero electric vehicles. In Cologne, Willms Touristik has retrofitted 18 sightseeing buses, and in Berlin, former BVG double-deckers are being electrified for tourism purposes. However, the study acknowledges that several key issues remain unresolved. The setup of charging infrastructure was only briefly addressed. Questions regarding the approval of retrofitted vehicles, warranty claims, and the standardization of retrofit kits have yet to be resolved definitively. Actual conversion costs will likely vary depending on the vehicle platform, battery concept, and desired range. The economic viability of retrofitting depends heavily on factors such as the age of the bus, its current condition, and local regulatory requirements. Some stakeholders argue that retrofitting might not be suitable for older buses with extensive wear and tear, while others emphasize the environmental benefits despite higher upfront costs. The long-term sustainability of retrofitting programs also hinges on the availability of skilled labor and the development of robust supply chains for retrofit components.