Energy and carbon assessment of advanced bioethanol-based fuel pathways for low-carbon passenger vehicle mobility in Brazil

Brazil’s light-duty fleet is predominantly flex-fuel and already operates with high-ethanol blends. Further greenhouse gas (GHG) mitigation can be achieved by coupling ethanol with low-carbon synthetic gasoline intermediates. This study investigates the environmental and energy performance of the renewable fuel blend E93eG7, composed of 93% w/w anhydrous ethanol (E100) and 7% w/w synthetic gasoline (eGasoline) produced via the Ethanol-to-Gasoline (ETG) process. Three synthetic gasoline pathways were evaluated, based on different ethanol feedstocks: first-generation corn ethanol (EtOH 1G-C), first-generation sugarcane ethanol (EtOH 1G-S), and second-generation sugarcane bagasse ethanol (EtOH 2G-S). Well-to-tank (WTT) carbon intensity values were combined with vehicle fuel-consumption data to estimate per-kilometer and lifetime CO 2 eq emissions under Brazil-specific conditions. Fossil Brazilian type C Gasoline (E30) exhibited the highest emissions (124.25 g CO 2 eq km −1 ), whereas Hydrous Ethanol Fuel (HEF) and E100 showed substantially lower emissions (41.60 g CO 2 eq km −1 and 40.97 g CO 2 eq km −1 , respectively). The E93eG7 blends achieved intermediate emissions strongly influenced by the ethanol feedstock: EtOH 1G-C (42.37 g CO 2 eq km −1 ), EtOH 1G-S (41.63 g CO 2 eq km −1 ), and EtOH 2G-S (39.53 g CO 2 eq km −1 ). Over a 200,000 km vehicle lifetime, E93eG7 2G-S reduced cumulative emissions to 7.91 t CO 2 eq, representing a 68.2% reduction compared to E30 (24.85 t CO 2 eq). Furthermore, E93eG7 2G-S increased vehicle autonomy by 8.21% relative to HEF due to the higher energy density of its eGasoline fraction. These results demonstrate that blending ethanol with a small fraction of synthetic gasoline—particularly derived from second-generation feedstocks—can simultaneously improve energy efficiency and reduce greenhouse gas emissions, providing a viable low-carbon fuel option for Brazil’s light-duty vehicle fleet under the assumed Brazilian 2024 electricity mix and 200,000 km lifetime.