From Euro III to Clean Buses: Real-world Emissions and Decarbonization Pathways for an Ecuadorian BRT System

Many large cities, particularly in Latin America, have adopted Bus Rapid Transit (BRT) systems to reduce emissions from individual road transport, yet their impacts on air quality are rarely evaluated. This study aims to estimate fuel consumption and emissions from the BRT fleet in Guayaquil and to explore several decarbonization scenarios.

The study applies macroscale Tier 1, Tier 2, and Tier 3 methodologies from the European Environment Agency to estimate fuel consumption and emissions of the Guayaquil BRT fleet. Several “what if” decarbonization scenarios are assessed, including upgrading emission-control technologies, switching to low-sulfur fuels and higher biodiesel blends, and incorporating air-conditioning systems. The analysis also accounts for refrigerant leakage and key upstream CO₂ emissions from fuel desulfurization and biodiesel production.

The results reveal substantial uncertainty in pollutant inventories. For example, NO_X emissions range from 433 to 724 tons per year, depending on the applied methodology. Current palm-oil biodiesel output (16,259 tons per year) is sufficient to supply the Guayaquil BRT fleet without requiring additional land.

Although the local biodiesel supply can support the Guayaquil BRT system, extending this bioenergy BRT strategy nationwide would likely generate significant upstream environmental pressures. The findings also highlight variability across emission estimation methods.

The study shows that while the Guayaquil BRT system can be supplied with existing biodiesel production and evaluated through established emission methodologies, scaling such strategies requires careful consideration of upstream environmental impacts and methodological uncertainty.