Global Warming Potential of Biomass-to-Ethanol: Review and Sensitivity Analysis through a Case Study

Abstract

In Europe, ethanol is blended with gasoline fuel in 5 or 10% volume (E5 or E10). In USA the blend is 15% in volume (E15) and there are also pumps that provide E85. In Brazil, the conventional gasoline is E27 and there are pumps that offer E100, due to the growing market of flex fuel vehicles. Bioethanol production is usually by means of biological conversion of several biomass feedstocks (first generation sugar cane in Brazil, corn in the USA, sugar beet in Europe, or second-generation bagasse of sugarcane or lignocellulosic materials from crop wastes). The environmental sustainability of the bioethanol is usually measured by the global warming potential metric (GWP in CO2eq), 100 years time horizon. Reviewed values could range from 0.31 to 5.55 gCO2eq/LETOH. A biomass-to-ethanol industrial scenario was used to evaluate the impact of methodological choices on CO2eq: conventional versus dynamic Life Cycle Assessment; different impact assessment methods (TRACI, IPCC, ILCD, IMPACT, EDIP, and CML); electricity mix of the geographical region/country for different factory locations; differences in CO2eq factor for CH4 and N2O due to updates in Intergovernmental Panel on Climate Change (IPCC) reports (5 reports so far), different factory operational lifetimes and future improved productivities. Results showed that the electricity mix (factory location) and land use are the factors that have the greatest effect (up to 800% deviation). The use of the CO2 equivalency factors stated in different IPCC reports has the least influence (less than 3%). The consideration of the biogenic emissions (uptake at agricultural stage and release at the fermentation stage) and different allocation methods is also influential, and each can make values vary by 250%.

Co-production of biofuels and value-added compounds from industrial Eucalyptus globulus bark residues using hydrothermal treatment

“…Lignocellulosic materials are the only renewable raw material in sufficient amount to partially replace fossil sources, which are cheaper and usually do not compete with food crops [3]. However, and because they present a very recalcitrant structure for most of the cases, their conversion also involves more complex operations, such as the application of an initial pretreatment [4].…”

A waste-to-wealth initiative exploiting the potential of Anabaena variabilis for designing an integrated biorefinery

“…However, the emissions from fossil-fuel-driven energy production cannot be disregarded, as electricity requirement remains indispensable for various operational stages of the production process. The GWP per kWh will depend upon the electricity mix of a particular region 47 . Nonetheless, from the LCA perspective, an integrated production system with quantitative coproduct generation is known to lessen the extent of ecological impact 48 .…”

High throughput method development and optimised production of leaf protein concentrates with potential to support the agri-industry

“…Based on the protein recoveries obtained, ethanol consumption would amount to 11.2 L/kg leaf protein. Conservative carbon footprint associated to ethanol production is reported to be approximately 0.4 kg/L [68,69]; although depending on the production method used, the value ranges from 1.3 to 0.2 kg/L [69]. The emissions associated to solvent use in production of 1 kg leaf protein would come to 4.5 kg CO 2 eq./kg leaf protein.…”