Reply to: Brazilian ethanol expansion subject to limitations

摘要

Have we overly amplified ethanol's potential1? We say not. Ethanol at this level of production will displace crude oil. Despite the penetration of electric vehicles, liquid fuel demand for the light-duty-vehicle fleet is projected to increase 35%, globally, by 20352. Even in the EU, which has the most aggressive plans for decarbonizing the electricity supply, well-to-wheels analyses indicate that when total emissions resulting from generation and transmission costs are taken into account, the CO_2 emissions per kilometre would be 50% of gasoline-driven light duty vehicles by the 2050s3. In other regions, such as the European Union, the benefit may be smaller, but this requires that aggressive plans for decarbonization of electricity generation are achieved4-5. Therefore, in the best possible scenario, by 2050 electric cars would cause emissions of 250% more CO_2 per kilometre than light duty vehicles driven on sugarcane ethanol. Even with aggressive reductions in travel growth, shifts to mass transport modes, strong efficiency improvements and deep market penetration by electric vehicles, there remains a large projected demand for dense liquid fuels in 2050 (80% of transportation fuel) and 2075 (50%)6. Crude oil demand in 2050 is projected to at least equal that of 2015, with increased energy use offsetting efficiency gains7. At present, 48% of crude oil is converted into gasoline, as distillate and by cracking longer-chain fractions7. Offsetting gasoline demand with ethanol would allow changes at the refinery stage to produce a higher proportion of diesel and jet fuel from each barrel of crude oil, thereby decreasing the total crude demand8-9, should gasoline demand actually drop. While our analysis focused on the production of ethanol as a fuel, it should be noted that sugarcane has flexibility. The combustion of bagasse is now an important part of meeting Brazil's dry-season electricity demand. Should uptake of all-electric cars be faster than anticipated, this expansion of sugarcane would provide a decarbonized and fungible feedstock for the generation of electricity for this fleet. Finally, there is a broad consensus that biomass should, and will, supply a significant amount of future products that are currently manufactured from crude oil.