Water Footprint and Water Pinch Analysis in Ethanol Industrial Production for Water Management

Heng Liu,Huimin Zhuo,Sanze Fu,Lijun Ren

doi:10.3390/w11030518

Abstract

Fuel ethanol is considered to be a clean alternative fuel to meet increasing energy demands and mitigate environmental pollution. Faced with challenges in terms of energy security and environmental pollution, China is vigorously developing fuel ethanol. However, ethanol-manufacturing is a water-intensive industry; it consumes large volumes of fresh water and generates a corresponding amount of waste water. Expansion of this industry can reduce water quality and cause water stress. This study aims to combine the water footprint (WF) with a water pinch analysis technique to manage water consumption and sewage discharge systematically in an ethanol plant. A well-operated cassava ethanol plant in China was chosen as a case study. The WF of industrial ethanol production was evaluated. The total WF was 17.08 L/L ethanol, comprised of a 7.69 L blue water footprint (BWF), and a 9.39 L gray water footprint (GWF). The direct WF was 16.38 L/L ethanol, and the indirect WF was 0.70 L/L ethanol. Thereafter, a water pinch analysis was conducted, and the optimal direct water reuse scheme was studied. After the water network was optimized, the BWF was reduced by 0.98 L/L ethanol, while the GWF was reduced by 1.47 L/L ethanol. These results indicate that the combined use of WF and pinch analysis can provide the starch-based ethanol industry with an effective tool to improve its water management.

Highlights

Fuel ethanol is a kind of renewable energy
After the water network was optimized, the blue water footprint (BWF) was reduced by 0.98 L/L ethanol, while the gray water footprint (GWF) was reduced by 1.47 L/L
Was 7.69 L/L ethanol, which is less than the 8.30–18.97 L/L ethanol BWF of a cassava-based ethanol plant in Thailand [38], and close to the result of a study in Guangxi, which was 7.60 L/L ethanol [13]

Summary

Introduction

Fuel ethanol is a kind of renewable energy. Fuel ethanol can be blended with gasoline to form ethanol gasoline. Ethanol contains 35% oxygen, which enables a more efficient burning of gasoline, resulting in reduced emissions of particulate matter (PM), nitrogen oxides, hydrocarbons, and carbon monoxide [1]. Bioethanol has been widely used in several countries, including the United States, Brazil, Thailand, China, Australia, and Mexico. In China, fuel ethanol production was initiated late but is developing rapidly. China has become the third largest producer of fuel ethanol after Brazil and the United States

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Conclusion