Comparison of the energy efficiency to produce agroethanol between various industries and processes: The transport stage

The different modes of transport used in the agroethanol industry and their energy efficiencies have been studied. Their specific consumption of fuels t_trans in MJ (t_load km)⁻¹ is assessed from raw data and from friction force laws. t_trans depends on the mode characteristics, fuel/engine performance, velocity, geometry, total mass, actual load… Lack of precision on them increases the uncertainty on t_trans (variation by a factor up to 8 for pipeline depending on the flow velocity).From t_trans is deduced the consumption of the mode in the industry R_trans in J for 100 J of the energy content of ethanol E_etoh produced from the load. R_trans takes also into account the distance of shipment d and the weight of the load in E_etoh, w_load. Trucks, t_trans from 7 to 1.4 MJ(tload·km)⁻¹, can present the best R_trans, lower than 0.5 J for 100 J of ethanol, because of trips over small d (less than 100 km) and of low w_load (less than 0.04  for farm inputs and ethanol). R_trans of the plant transport to the factory by trucks ranges to 3 J due to larger w_load (up to 0.56  for sugar cane). Large part of the ethanol is moved from the factory to the local storages over 1000 km more or less depending on the proximity of consumption centers. Efficient modes such as pipeline and sea ships, t_trans as low as 0.05 MJ (t_load·km)⁻¹ when optimized, can compensate for these distances with R_trans around 1 J. R_trans to export ethanol from Brazil to France would represent less than 5 J, much lower than the difference of consumptions R between sugar cane and sugar beet based ethanol productions.