Water, Energy, and Carbon Footprints of Bioethanol from the U.S. and Brazil

Authors

Mesfin Mekonnen, University of Nebraska - LincolnFollow
Thiago L. Romanelli, University of São Paulo
Chittaranjan Ray, University of Nebraska-LincolnFollow
Arjen Y. Hoekstra, University of TwenteFollow
Adam Liska, University of Nebraska - LincolnFollow
Christopher M. U. Neale, University of Nebraska-LincolnFollow

ORCID IDs

Mesfin M. Mekonnen: 0000-0002-3573-9759

Date of this Version

11-14-2018

Citation

Published in Environmental Science & Technology 52 (2018), pp 14508−14518.

doi 10.1021/acs.est.8b03359

Comments

Copyright © 2018 American Chemical Society. Used by permission.

Abstract

Driven by biofuel policies, which aim to reduce greenhouse gas (GHG) emissions and increase domestic energy supply, global production and consumption of bioethanol have doubled between 2007 and 2016, with rapid growth in corn-based bioethanol in the U.S. and sugar cane-based bioethanol in Brazil. Advances in crop yields, energy use efficiency in fertilizer production, biomass-to-ethanol conversion rates, and energy efficiency in ethanol production have improved the energy balance and GHG emission reduction potential of bioethanol. In the current study, the water, energy, and carbon footprints of bioethanol from corn in the U.S. and sugar cane in Brazil were assessed. The results show that U.S. corn bioethanol has a smaller water footprint (541 L water/L bioethanol) than Brazilian sugar cane bioethanol (1115 L water/L bioethanol). Brazilian sugar cane bioethanol has, however, a better energy balance (17.7 MJ/L bioethanol) and smaller carbon footprint (38.5 g CO₂e/MJ) than U.S. bioethanol, which has an energy balance of 11.2 MJ/L bioethanol and carbon footprint of 44.9 g CO₂e/MJ. The results show regional differences in the three footprints and highlight the need to take these differences into consideration to understand the implications of biofuel production for local water resources, net energy production, and climate change mitigation.