The greenhouse gases emissions and environmental impact profiles for bio-electromobility alternatives in Brazilian urban buses

The global transport sector remains a major contributor to greenhouse gas (GHG) emissions, urging the need for low-carbon pathways that go beyond full fleet electrification. In countries like Brazil, where biofuel production is mature and the electricity matrix is relatively clean, bio-electromobility can offer an effective alternative for decarbonizing urban public transport. This study assesses the environmental performance of seven scenarios composed by different bus types and energy use — conventional diesel, compressed natural gas (CNG), biomethane (bioCNG), hydrotreated vegetable oil (HVO) from soybean oil and from tallow, in internal combustion engine buses (ICEB), hybrid buses (HEB) and battery electric buses (BEB) configurations — through a cradle-to-grave Life Cycle Assessment (LCA). The analysis covers midpoint Global Warming Potential and endpoint damage categories: Ecosystem Quality, Human Health, and Natural Resources. Results show that buses powered by residue-based HVO or bioCNG in both internal combustion and hybrid configurations outperform BEBs in several environmental impact categories, challenging the narrative that “zero-emission” buses are always the optimal solution when upstream and mid-life emissions are considered. Limitations include data assumptions, partial regionalization, and infrastructure constraints that may affect large-scale deployment. The findings emphasize the need for diversified public policies that integrate biofuels and electrification, leveraging Brazil's biomass potential while expanding charging infrastructure sustainably. This study contributes to closing knowledge gaps in bio-electromobility's role and provides decision-makers with robust evidence to guide investments and regulatory frameworks toward a truly low-carbon urban transport system. • Bio-electromobility solutions can cut GHG emissions by up to 87 % compared to conventional diesel buses. • Hybrid buses using bioCNG or HVO outperform pure electrification in Ecosystem Quality, Human Health and Mineral Resources. • Policies combining biofuels and electrification could optimize the decarbonization of urban bus fleets.