Definition and application of ethanol equivalent: Sustainability performance metrics for biomass conversion to carbon-based fuels and chemicals

Ethanol equivalent (EE) is defined as the mass of ethanol needed to deliver the equivalent amount of energy from a given feedstock using energy equivalency or produce the equivalent amount of mass of a carbon-based chemical using molar equivalency. The production of ethanol from biomass requires energy, which in a sustainable world could be produced from biomass. Therefore, we also define a real ethanol equivalent (EE_x) indicating that the ethanol equivalent also includes the use of 1 unit of bioethanol to produce x units of bioethanol. Thus, the abbreviation EE_2.3 used in this paper shows a 2.3 output/input bioethanol ratio or efficiency. Calculations of the corresponding mass of corn and size of land were based on the first generation corn-based bioethanol technology as commercially practiced in the US in 2008.Since the total energy and essential materials requirements of a given process can be calculated, the EE_2.3 of a production process or even a total technology can be estimated. We show that the EE_2.3 could be used as a translational tool between fossil- and biomass-based feedstocks, products, processes, and technologies. Since the EE_2.3 can be readily determined for any given biomass-based technology, the required mass of biomass feedstock, the size of land, and even the volume of water can be calculated. Scenario analyses based on EE_2.3 could better visualize the demands of competing technologies on the environment both for the experts and to the general public. While differentiating between 1, 1000, and100,000 BTUs for different options is rather difficult for most people, comparing the amount of the land needed to produce the same amount of energy or mass via different technologies is more straightforward. © 2014 Elsevier B.V. All rights reserved.