Model to determine greenhouse gas emissions of the urban railway system in the Northeast of Brazil

Abstract

The emission of greenhouse gases (GHGs) is an urgent environmental issue with significant implications for global climate change. Historically, the transportation sector has been a significant contributor to GHG emissions due to the predominant use of fossil fuels in vehicles. However, the railway system is widely recognized for being a more carbon-efficient mode of transportation compared to road and air transport. Nevertheless, despite the relative advantages of the railway system in terms of GHG emissions, there are still challenges to be addressed. The expansion and modernization of railway networks, especially in developing regions, may require substantial investments in infrastructure and technology, which should be considered within the context of a sustainable approach. In this context, this study conducted a retrospective bibliometric analysis spanning two decades in the railway sector, from 2002 to 2021, with the aim of deepening the understanding of the nuances of research in this field. To achieve this, the VOSviewer tool was employed to map connections between studied variables, revealing a marked increase in publications over this period. The standout work was that of Zhang, Y.T., identified as the most prolific author. The focus predominantly lay in engineering, with the Transportation Research Record being the most published journal. The leadership in this field was attributed to China, notably from the Southwest Jiaotong University. However, a gap in research regarding environmental impact and sustainability in railway systems was emphasized, pointing towards a promising area for future investigation. Based on the bibliometric analysis, the urgency for further exploration in the realms of sustainability and environmental impact in railway systems became evident. The study was directed towards the railway system in northeastern Brazil, aiming to assess the greenhouse gas (GHG) emissions associated with this system and juxtapose them with relevant international studies. Its core scope was to establish parameters for GHG emissions from this system and formulate effective mitigation strategies. To accomplish this goal, a comprehensive Life Cycle Assessment (LCA) approach was employed, providing meticulous scrutiny of the entire lifecycle of the railway system. This encompassed the collection of real data to construct a detailed inventory of GHG emissions. Furthermore, a comparison of GHG emissions in different urban railway transportation systems was conducted, yielding valuable contextual perspectives The results indicated that the total GHG emissions from the northeastern Brazilian railway system reached 11,996.11 tCO2e. Projections for a 50-year lifecycle estimated a total of 59,980,550 tCO2e of GHG emissions over the operational and maintenance cycle of the system. The study also highlighted the Sustainable Water and Energy Consumption Program (SWEC), established to address supply challenges in a Brazilian railway company. The program succeeded in reducing per capita water and energy consumption by 10% and 19%, respectively, and included the installation of photovoltaic systems, resulting in an average 56% reduction in energy consumption in 2022 and a 50% reduction in greenhouse gas emissions. Therefore, the railway system offers a valuable opportunity to decrease GHG emissions in the transportation sector. Electrification, the implementation of cleaner technologies, and operational optimization can contribute to mitigating these effects. However, it is important to adopt a holistic approach, considering all aspects of the railway system's value chain, in order to achieve more significant results in reducing GHG emissions and promoting environmental sustainability. This study not only demonstrates an effective approach to challenges related to water and energy consumption but also contributes to the global sustainability objectives outlined in the UN's 2030 Agenda. Its interdisciplinary emphasis underscores the importance of reducing air pollution and fostering sustainable practices, especially within the context of climate change and public policies. In a scenario where sustainability and climate change mitigation gain crucial relevance, this study plays a significant role in sustainable development, paving the way for a more sustainable railway transportation system through Life Cycle Assessment and an interdisciplinary approach.