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 ofenergy from a given feedstock using energy equivalency or produce the equivalent amount of mass of acarbon-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 ethanolequivalent (EEx) indicating that the ethanol equivalent also includes the use of 1 unit of bioethanol toproduce x units of bioethanol. Thus, the abbreviation EE2.3used in this paper shows a 2.3 output/inputbioethanol ratio or efficiency. Calculations of the corresponding mass of corn and size of landwere basedon 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, theEE2.3of a production process or even a total technology can be estimated. We show that the EE2.3couldbe used as a translational tool between fossil- and biomass-based feedstocks, products, processes, andtechnologies. Since the EE2.3can be readily determined for any given biomass-based technology, therequired mass of biomass feedstock, the size of land, and even the volume of water can be calculated.Scenario analyses based on EE2.3could better visualize the demands of competing technologies on theenvironment 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 landneeded to produce the same amount of energy or mass via different technologies is more straightforward.