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Industrial Water Footprint Assessment: Methodologies in Need of Improvement Yifan Gu,† Jin Xu,† Hongtao Wang,*,†,‡ and Fengting Li†,‡ †
College of Environmental Science and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, China ‡ Key Laboratory of Yangtze River Water Environment, Ministry of Education, Shanghai 200092, China hypothetical pollution volume. Thus, water footprints can be used to determine freshwater consumption and assess the environmental impact of wastewater on industries. However, some defects are present in these footprints when applied in industries. In daily routine production, water withdrawal is applied as a major indicator in many enterprises; this application is similar to the concept of blue water footprint (consumption of surface and groundwater). The calculation of green water footprint remains unclear in previous studies;5 this parameter is also not observed in most industries because green water is defined as rainwater insofar as it does not become a runoff. The distinction between blue and green water can be considered to allocate water for agricultural purposes, but this distinction has no practical significance in industrial processes. Furthermore, blue and gray water footprints are described as the total water footprint of industrial processes that are not environmentally meaningful or informative for manufacturers.5 This parameter increases the incomparability of water footprints. Instead of the total water footprint, blue and gray water footprints can be used to evaluate freshwater appropriation and environmental impact separately. Wastewater discharged from industrial activities significantly oekstra1 introduced water footprint to quantify and map influences local aquatic environments. Gray water footprint is water use. For years, whether or not water footprint an indicator to evaluate the effects of water quality. However, should be a volumetric indicator of freshwater appropriation or the current model of this footprint possesses several limitations. an impact-based measure remains a topic of debate.2,3 Boulay et The results of gray water footprint that are calculated from al.4 highlighted the common grounds and differences among water quality standards cannot be used to accurately evaluate water footprint methodologies developed by the Water the effects on aquatic environments because some standards are Footprint Network (WFN) and life cycle assessment (LCA) performed in large areas; these results may also be inapplicable community. However, Pfister et al.5 emphasized pitfalls in other places. Current gray water footprint cannot be applied to evaluate the impact of wastewater discharge on local water between these common grounds. We believe that this pressure. In this method, variations in environmental residence controversy is attributed to different goals and objectives of time are disregarded.5 The methodology using gray water water footprint assessment. WFN-based water footprint is footprint should be improved by considering the quality, informative to improve strategies and engagements in national quantity, and time effects. and regional virtual water flow and trade; this method can also Energy consumption is crucial in industrial enterprises. help improve water management in the agricultural sector and WFN1 uses energy water footprint to link energy with water, allocation as volumetric indicators. However, various industries which makes it possible to assess the virtual water consumption are more sensitive to wastewater than agricultural sectors. The through the usage of energy. However, the nexus between environmental impact of industrial processes is the key to water and energy is discrepant in different regions. Energy properly assessing the corresponding water footprints and water footprints have been investigated in few areas. However, water risk. Problems are amplified when water footprint strives industrial companies are equipped with separate energy to show water consumption and pollution in industries consumption evaluation index systems. Thus, assessment is simultaneously. Current problems in water footprint methodpossibly meaningless if virtual water in energy is inaccurately ologies may result in defects to assess industrial water calculated. Further studies on water-energy relationship are footprints; hence, methodologies should be improved. In the WFN approach, water footprint is categorized into blue, green, and gray.1 Blue and green water footprints refer to Received: May 2, 2014 Published: May 21, 2014 water consumption volumes; gray water footprint refers to the
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© 2014 American Chemical Society
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dx.doi.org/10.1021/es502162w | Environ. Sci. Technol. 2014, 48, 6531−6532
Environmental Science & Technology
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Figure 1. Queries of water footprint assessment of industry enterprises.
and Linping Xu. We also thank Mr. Yang Aihui from World Wide Fund For Nature for his help.
necessary to support the assessment of industrial water footprints. In the LCA approach, water footprint is used to analyze a product’s impact on water resource-related processes, including raw material acquisition, supply chain, manufacturing, transportation, usage, and waste treatment during a product’s life cycle. Thus, LCA-based water footprints can be utilized to assess the effects of products or businesses on aquatic environments during the whole life cycle. Water footprint not only considers the water footprint of enterprise itself, but also takes the water footprint of external supply chain into account. As a sustainable enterprise, its supply chain also releases water footprint that should not be neglected, and this water footprint is related to the total water footprint of the enterprise. However, generally only water footprint used in relevant processes in production systems is considered. The water footprints of some inputs (e.g., raw materials and supply chain) in the upstream of production are difficult to obtain for enterprises. At the same time, water footprints for usage and waste treatment processes are difficult to calculate because of data availability. Therefore, production processes are usually utilized as the main body, which is the most important part that manufacturers should consider when they decide to alleviate water risk, in industrial water footprint assessments. In conclusion, water footprint methodologies exhibit drawbacks that impede industrial water footprint assessments; as such, misleading information is obtained (Figure 1). Therefore, this methodology should be improved to develop a highly accurate and feasible assessment for sustainable water management and cleaner production.
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REFERENCES
(1) Hoekstra., A. Y.; Chapagain., A. K.; M. M. Aldaya; Mekonnen, M. M. The Water Footprint Assessment Manual; Earthscan: Earthscan LLC: Washington, DC, 2011. (2) Berger, M.; van der Ent, R.; Eisner, S.; Bach, V.; Finkbeiner, M. Water accounting and vulnerability evaluation (WAVE): Considering atmospheric evaporation recycling and the risk of freshwater depletion in water footprinting. Environ. Sci. Technol. 2014, 48 (8), 4521−8. (3) Berger, M.; Finkbeiner, M. Methodological challenges in volumetric and impact-oriented water footprints. J. Ind. Ecol. 2013, 17 (1), 79−89. (4) Boulay, A. M.; Hoekstra, A. Y.; Vionnet, S. Complementarities of water-focused life cycle assessment and water footprint assessment. Environ. Sci. Technol. 2013, 47 (21), 11926−7. (5) Pfister, S.; Ridoutt, B. G. Water footprint: Pitfalls on common ground. Environ. Sci. Technol. 2014, 48 (1), 4.
AUTHOR INFORMATION
Corresponding Author
*Phone: +86 21-65980567; e-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This study was supported in part by the Fundamental Research Funds for the Central Universities (Grant No. 0400219184). We would like to express our gratitude to the members of our water footprint research group for their assistance: Yi Li, Dazhi Yuan, Ke Yang, Wen Tang, Shiyuan Zhao, Haiyan Tian, Yi Lan, 6532
dx.doi.org/10.1021/es502162w | Environ. Sci. Technol. 2014, 48, 6531−6532
