Water Consumption in the Production of Ethanol and Petroleum Gasoline

Abstract

We assessed current water consumption during liquid fuel production, evaluating major steps of fuel lifecycle for five fuel pathways: bioethanol from corn, bioethanol from cellulosic feedstocks, gasoline from U.S. conventional crude obtained from onshore wells, gasoline from Saudi Arabian crude, and gasoline from Canadian oil sands. Our analysis revealed that the amount of irrigation water used to grow biofuel feedstocks varies significantly from one region to another and that water consumption for biofuel production varies with processing technology. In oil exploration and production, water consumption depends on the source and location of crude, the recovery technology, and the amount of produced water re-injected for oil recovery. Our results also indicate that crop irrigation is the most important factor determining water consumption in the production of corn ethanol. Nearly 70% of U.S. corn used for ethanol is produced in regions where 10-17 liters of water are consumed to produce one liter of ethanol. Ethanol production plants are less water intensive and there is a downward trend in water consumption. Water requirements for switchgrass ethanol production vary from 1.9 to 9.8 liters for each liter of ethanol produced. We found that water is consumed at a rate of 2.8-6.6 liters for each liter of gasoline produced for more than 90% of crude oil obtained from conventional onshore sources in the U.S. and more than half of crude oil imported from Saudi Arabia. For more than 55% of crude oil from Canadian oil sands, about 5.2 liters of water are consumed for each liter of gasoline produced. Our analysis highlighted the vital importance of water management during the feedstock production and conversion stage of the fuel lifecycle.

Investigation of biochemical biorefinery sizing and environmental sustainability impacts for conventional bale system and advanced uniform biomass logistics designs

“…6), similar to that of conventional oil sands production. 35 Switchgrass-derived ethanol (Case 3) requires less blue water than corn stover-derived ethanol (Case 1 or 2) because of savings from switchgrass irrigation. Export bioelectricity contributes a 1 gal/gal water credit to the blue water footprint, reducing total blue water use by 12-20%.…”

Coproduction of Acetaldehyde and Hydrogen during Glucose Fermentation by Escherichia coli

“…Currently, most fuel ethanol is purified by distillation, which requires large amounts of water and energy (40). Water used for cooling distillation towers usually accounts for over 50% of total water consumption, and the energy needed for heating distillation columns consumes about 75% of total process heat (18,20,41). However, potential savings would need to be weighed against the cost of chemical conversion of acetaldehyde and H 2 to ethanol.…”

Potential water requirements of increased ethanol fuel in the USA

“…The average value (weighted by 2007 ethanol production) was 142 L/L, although as the authors pointed out, national average values are not relevant in understanding bioethanol's water implications at a local scale. Also in 2009, Wu et al published a life-cycle report confirming that crop irrigation is the most important factor determining total water consumption in providing corn ethanol in the USA and demonstrating the large regional variability of irrigation requirements [21]. Results showed that 70% of the corn used to produce ethanol in 2009 was grown in regions that required 10-17 L/L; whereas 19% of the corn was grown in regions that required over 300 L/L.…”

“…Results taken from five recent life-cycle assessment (LCA) studies are summarized graphically in Fig. 2 [21,[26][27][28][29]. As shown here, the consumptive water use of corn ethanol in the USA is 1-2 orders of magnitude higher than that of petroleumbased fuels.…”