This section presents the fundamentals of electric public transport, addressing its operation, main components, and benefits compared to traditional combustion models. The environmental and economic impacts of this technology are discussed, including the reduction of greenhouse gas (GHG) emissions and operational costs. Additionally, a life cycle analysis of electric buses is conducted, highlighting their energy efficiency and sustainability. Finally, national and international experiences in electric mobility for public and university transportation are explored, emphasizing the applicability of this model in the context of UFPB.
2.2. Economic and Sustainability Indicators
The adoption of electric buses represents a promising alternative to reduce the environmental and economic impacts of public transportation. Regarding sustainability, electric motors can significantly contribute to reducing air pollution, minimizing the emission of both local and global pollutants. According to IPEA (2016) [
13], the main vehicular pollutants that directly affect human health include particulate matter (PM), nitrogen oxides (NOx), and sulfur dioxide (SO
2), which are often present in soot emitted by exhaust systems, brakes, tires, and road surfaces. Meanwhile, global pollutants such as carbon dioxide (CO
2) are responsible for exacerbating the greenhouse effect and global warming, highlighting the urgency of adopting cleaner alternatives for urban transportation.
Studies indicate that replacing conventional fleets with electric vehicles can lead to significant reductions in CO
2 emissions. In an analysis of the environmental impact of urban transportation electrification, the potential variations in CO
2 emissions resulting from replacing urban buses with electric models were quantified [
10]. The authors point out that urban buses and minibuses account for 9% of emissions from the road transport sector, equivalent to approximately 19.08 million tons of CO
2. Using data from the Ministry of the Environment on diesel consumption for these vehicles, the study concluded that these emissions correspond to 25.114 million MWh of diesel consumption [
10,
14].
Based on these values, the Ministry of Science, Technology, and Innovation (MCTI) estimated that CO
2 emissions from each MWh of electricity generation in Brazil amounted to 0.0653 tons, considering the energy mix in operation at the time. By multiplying this emission factor by the energy consumption of urban buses and minibuses, the total CO
2 generated for charging electric vehicles would be approximately 1.64 million tons. Thus, when comparing environmental impacts, replacing conventional vehicles with electric ones could result in a reduction of 17.44 million tons of CO
2, representing a 91.4% decrease in emissions for the year 2012 [
15].
Beyond reducing air pollution, electric motors create quieter urban environments, as they generate less noise than internal combustion engines. This aspect is crucial for mitigating noise pollution, a recurring problem in major urban centers. Studies suggest that excessive urban noise not only affects hearing but can also lead to sleep disorders, cardiovascular problems, and psychological conditions, including headaches, anxiety, depression, and cognitive difficulties in children [
16]. Thus, the electrification of public transport can play a crucial role in enhancing urban quality of life, reducing prolonged exposure to harmful noise levels [
16].
Regarding economic indicators, one key factor that may encourage the replacement of diesel buses with electric models is the difference in fossil fuel and electricity prices. According to [
17], oil prices are expected to rise in the coming decades due to increasing extraction costs in non-conventional regions and rising global demand. As petroleum supply becomes more constrained, frequent price hikes may make diesel an increasingly expensive input for public transport operators [
17].
Conversely, the authors state that although electricity prices may also fluctuate, the expected increase will likely be less pronounced than that of petroleum. Furthermore, carbon policies and environmental regulations will likely introduce additional costs for fossil fuels, further encouraging transport electrification. Even though electric bus acquisition still represents a high initial investment, projections indicate that this cost will decline in the coming years. According to Bloomberg New Energy Finance (2018) [
18], electric bus prices are expected to equalize with diesel models by 2030. This shift will be driven primarily by the declining cost of batteries, which accounted for 26% of the vehicle’s total price in 2016 but are expected to drop to just 8% by 2030.
Given this scenario, the electrification of public transport not only reduces environmental impacts but also emerges as an economically competitive alternative in the medium and long term. The combination of lower pollutant emissions, public health benefits, and the expected decrease in electric vehicle costs reinforces the need to expand discussions on transitioning to a sustainable and energy-efficient mobility model.
2.3. Emission and Life Cycle Indicators
A Life Cycle Assessment (LCA) consists of a comprehensive study of the mass and energy consumption of a given product, identifying its environmental impacts from raw material extraction, through its use, to the final disposal of its waste throughout the entire process. In other words, it is a “cradle-to-grave” analysis (
Figure 1). This method has been employed to evaluate the integration of different vehicle types into urban transportation fleets, comparing various powertrains and fuel sources. Such methodology prevents zero-exhaust-emission technologies, like electric vehicles (EVs), from being generalized as having no environmental impact.
This study focuses on greenhouse gas (GHG) emissions, measured in gCO2eq, and their applications in transportation planning. The goal is to provide planners and decision-makers with more effective tools to optimize energy consumption and emission reductions in public bus transportation systems. The study compares diesel-powered and battery electric buses (BEBs), analyzing their powertrain emissions. Hydrogen fuel cell buses and other fuels, such as natural gas (GNV) and hydrotreated vegetable oil (HVO), were excluded due to the maturity of these technologies for buses in Brazil.
The metrics and data used to calculate GHG emissions are described in
Table 2 and
Table 3, detailing input parameters used in calculations for the university bus fleet, including route data (bus type, quantity, average mileage, weight, average yield) and emissions data.
The 2016 Mascarello GranMidi bus, designed for urban and intermunicipal use, exhibits structural characteristics typical of medium-sized models, featuring a carbon steel metal frame and a diesel-powered chassis (
Table 4). Although precise emission data from its manufacturing process are not publicly available for this specific model, its environmental impact can be estimated based on Life Cycle Assessment (LCA) studies of similar buses, taking into account the production, maintenance, and disposal and/or recycling phases.
The emission factors for ICE buses were obtained from the JEC Well-To-Wheels Reports, which provide CO
2 equivalent emission values for heavy-duty diesel engines, including buses. The data is a result of a collaborative study by the Joint Research Center of the European Commission (JRC), the European Council for Automotive R&D (EUCAR), and CONCAWE (CONservation of Clean Air and Water in Europe) [
20]. The CO
2 equivalent emissions reported for ICE buses are as follows: fuel production: 12.8 gCO
2eq/t·km, fuel combustion: 50.2 gCO
2eq/t·km, and total ICE emissions: 63.0 gCO
2eq/t·km.
For internal combustion engine buses (ICEBs), the development of the emission factor within the LCA framework considers two fundamental stages: fuel production, which includes its manufacturing, transportation, and storage, and fuel use, corresponding to its combustion by the vehicle. Thus, the greenhouse gas (GHG) emissions from combustion engine buses are determined as the sum of the emissions from the production stage and the use (combustion) stage, as shown in Equation (1):
where GEE
ICEB represents the total greenhouse gas emissions from an ICE bus, expressed in CO
2eq/km; GEE
production and GEE
use refer to the emissions from fuel production and combustion, respectively (gCO
2eq/ton·km); and P is the total weight of the bus, in tons.
The LCA process for battery electric buses (BEBs) follows a similar methodology but consists of two main stages: (i) Energy extraction and transportation—mining of energy sources and their transportation to power plants. (ii) Electricity transmission and consumption—energy transfer from the grid to the bus and its use for traction [
21].
Thus, the GHG emissions for BEBs (measured from well-to-wheel) are calculated as the sum of emissions from mining and electricity use, as expressed in Equation (2):
where GEE
BEB represents the total GHG emissions generated by the energy supply chain or national electricity mix, measured in (gCO
2eq/km), GEE
mining and GEE
use refer to the GHG emissions per kWh from energy extraction and electricity consumption, respectively, and η represents the energy efficiency of the electric bus (km/kWh).
The GEE
extraction emission factor follows the methodology proposed by [
22], who conducted a comprehensive review of 167 LCA studies evaluating GHG emissions from different energy sources. GEE
use for BEBs was not considered in this study since battery electric buses do not generate direct exhaust emissions [
23].
The composition of Brazil’s national electricity mix was considered to account for the emissions associated with electricity generation. The Brazilian electricity grid is predominantly based on renewable sources, with the following distribution: hydropower: 58.9%, wind power: 13.2%, biomass: 5.2%, solar power: 7.0%, coal and derivatives: 4.9%, petroleum and derivatives: 2.7%, nuclear energy: 2.0%, natural gas: 5.3% (includes domestic production and imports) [
24].
Energy usage varies from country to country, depending on economic development, geopolitical conditions, resource availability, climate, industrial profile, and other relevant factors [
25].
This issue is also relevant in battery production and recycling emissions for BEBs. According to [
26], the manufacturing process of lithium-ion batteries accounts for 45% to 60% of total emissions. The study concludes that the carbon footprint of battery production strongly depends on the energy mix of the manufacturing country. The same report estimates that battery production emissions range from 150 to 200 kgCO
2eq/kWh, particularly in countries where fossil fuels account for 50–70% of electricity generation, such as China, the main supplier of lithium-ion batteries used in Brazil.
In this study, Chinese manufacturing emissions were considered, adopting a 200 kgCO2eq/kWh emission factor. A battery pack of 3000 cycles was assumed, with an efficiency of 0.775 kWh/km and a range of 200 km per charge.
Additionally, an average battery degradation rate of 0.008% per cycle was used, based on established vehicle models listed in
Table 4. Thus, the total production impact per kilometer traveled is a function of the battery life cycle. In this study, the resulting impact was 58.71 gCO
2eq/km, assuming a total lifespan of 528,000 km.
For the recycling and disposal phase, only the battery of the battery electric bus (BEB) is considered for its first useful life (500,000 km). It is estimated that this process accounts for approximately 5 to 10% of total emissions. Battery recycling remains a challenge, as less than 50% of the materials from lithium batteries are currently recovered globally [
27]. Advanced reuse and recycling technologies may help reduce this environmental footprint in the future.
Many studies have explored the reuse of these batteries, as they still retain approximately 80% of their initial capacity (plug-in 400 kWh) [
28]. However, the market for battery reuse and recycling remains highly uncertain [
26].
During the manufacturing process, it is estimated that approximately 40 to 45% of total CO
2 emissions are generated, with the production of lithium-ion batteries being the primary contributor to the environmental impact [
29]. The extraction and refining of materials such as lithium, cobalt, and nickel significantly contribute to these emissions [
30].
Research indicates that manufacturing emissions of an urban bus also depend on the energy matrix of its origin. A medium- to large-sized bus results in emissions ranging from 40 to 60 tons of CO
2 equivalent (tCO
2e), considering the production of the body, chassis, engine, and battery of the electric bus [
26,
31,
32].
Maintenance of electric buses accounts for between 5 and 15% of total CO
2 emissions over their lifetime, as these vehicles have fewer moving parts and require fewer mechanical interventions than traditional buses [
33]. However, for a future study, an extended useful life (20 years) could be considered, and we would then add battery replacement over the total useful life of the bus, which would increase this share of emissions [
28].
For combustion buses, preventive measures such as oil, filter, tire, and brake pad changes were considered during the maintenance phase, which represents 10 to 20% of overall emissions [
34].
2.4. Electric Mobility: Advances in Public and University Transportation
The transition to electric bus fleets has been driven in various parts of the world as a strategy to reduce pollutant gas emissions, improve energy efficiency, and modernize urban systems. The implementation of electric buses has shown significant positive impacts, promoting environmental sustainability and reducing operational costs in the medium and long term. Different cities and institutions have adopted various approaches to enable this transition, including tax incentives, public–private partnerships, and integration with renewable energy sources. The following sections present successful cases of electric bus deployment and the main challenges that still need to be overcome.
China leads the global electric bus market, accounting for a significant portion of the worldwide fleet. Between 2015 and 2021, the country experienced substantial growth, reaching approximately 700,000 units in operation and over 1000 models available for sale [
35]. One of the most widely used models, the K9 BEB, has a range of over 400 km at a constant speed of 40 km/h. Meanwhile, models equipped with lithium batteries for fast charging can reach distances exceeding 150 km, with 50% of these units surpassing 260 km of autonomy [
21].
In Europe, the electrification of public transport has progressed significantly, driven by the European Green Deal, which aims to make the continent carbon neutral by 2050. In 2019, the European electric bus fleet reached approximately 4000 units, including battery-powered models, plug-in hybrids, IMC trolleybuses, and fuel cell buses [
36]. The transport sector accounted for 15% of net CO
2 emissions in Europe in 2018, with 11% originating from road transport [
37]. At the municipal level, Gijón, Spain, incorporated six electric buses into its fleet in 2025 as part of a plan to gradually replace diesel vehicles with electric and hybrid models by 2027. The direct benefits of this transition include a 50% reduction in CO
2 emissions, 16 h operational autonomy, and lower maintenance costs due to the simpler structure of electric motors [
38].
Outside Europe, the island of Barbados, in the Caribbean, adopted a public transportation modernization plan in 2020, incorporating 33 electric buses in Bridgetown. The project aims to reduce dependence on fossil fuels and encourage the use of renewable energy sources for vehicle recharging. As a result, there was a 30% reduction in fossil fuel consumption, an improvement in public transportation quality, and a decrease in operational costs [
39].
In Latin America, Santiago, Chile, stands out as one of the leading examples of public transport electrification. Since 2018, its electric fleet has grown progressively, surpassing 800 electric buses in operation. This initiative was made possible through a partnership between the Metbus operator, the energy company Enel X (Rome, Italy), and the manufacturer BYD (Shenzhen, China), resulting in a 70% reduction in operational costs compared to diesel buses, as well as a significant decrease in CO
2 emissions and noise pollution [
34]. Following this trend, Bogotá, Colombia, established itself as a reference by acquiring 406 electric buses in 2020, becoming one of the largest fleets in Latin America. As part of a transportation modernization plan, this initiative led to a 60% reduction in GHG emissions, improved air quality, and lower operational costs in the medium term [
39,
40].
The electrification of public transport in Brazil has been advancing, albeit at a slower pace compared to other Latin American countries. São Paulo leads the sector, with 201 electric buses in operation in 2025 [
41]. The city government established a plan to gradually replace diesel buses by 2038, with the goal of reducing 50% of public transport emissions by 2030. The adopted public concession model enables this transition through subsidies and tax incentives [
42]. In Curitiba, electric bus testing began in 2023, prioritizing high-demand routes. The project is supported by research institutions and private companies, and initial results indicate a 60% reduction in energy consumption compared to diesel models [
5].
In the academic sector, electric mobility has also been implemented. The Federal University of Santa Catarina (UFSC) developed eBus, a 100% solar-powered electric bus, which has been transporting the academic community between the Trindade Campus and Sapiens Parque since 2017. The vehicle completes five daily trips, covering over 5000 km per month, without charging passengers. In addition to being a sustainable mode of transport, eBus serves as a research laboratory for electric mobility and energy efficiency studies [
2]. Similarly, the State University of Campinas (UNICAMP) introduced an electric bus powered by solar energy in 2020, as part of the Campus Sustentável project, in partnership with CPFL Energia. The model contributes to reducing the university’s carbon footprint while promoting research on sustainable mobility [
42].
In the study conducted by Fidelis (2021) [
43], sustainable urban mobility alternatives for the UFPB Campus I were analyzed. Through bibliographic research across various university campuses, the author examined the mobility situation at UFPB and emphasized the need for alternatives that are safe, accessible, and of high quality. However, the acceptance of this non-traditional model, such as the electric model, depends not only on the availability of adequate infrastructure but also on the commitment of external stakeholders, who play a crucial role in the implementation and maintenance of the system.
Despite the numerous advantages associated with fleet electrification, challenges remain that hinder the adoption of this system. In [
10], three main obstacles are identified: (1) high initial investment costs, (2) scalability and operational flexibility, and (3) limited experience with this technology.
Although the total cost of ownership of an electric bus may be lower than that of a diesel model, many cities face budget constraints for initial investments, even with government subsidies. Additionally, the reduced range of electric buses can be a challenge for long-distance routes or continuous 24 h operations.
A viable alternative to overcome these challenges is the implementation of electric buses in university campuses, where distances are shorter and travel times are reduced. In addition to contributing to sustainable mobility, this approach allows universities to serve as test centers, analyzing the feasibility of electrification for future large-scale applications.