COMMENT pubs.acs.org/est
Water|Energy Energy|Water his issue of Environmental Science & Technology features articles addressing the concept of the “water energy nexus”. Perrone et al. invoke the concept in their title, in creating a tool to account for the “energy [used] for water and water [used] for energy” (Environ. Sci. Technol. DOI 10.1021/es103230n). In noting that the concept of a nexus is often “invisible”, they define the interrelationship explored by the articles noted below: “Water is withdrawn and consumed throughout the life cycle of an energy source and energy is consumed for extraction, distribution, and end-use of water resources.” Many articles in ES&T that explore the utility of biofuels speak to this interconnection of water resources and energy production. A recent example is Mishra and Yeh’s analysis that investigates the production of ethanol from corn and crop residue (Environ. Sci. Technol. DOI 10.1021/es104145m). In distinguishing between “green water” (sourced from natural precipitation) and “blue water” (sourced from ground and surface waters—i.e., irrigation), their manuscript indicates how nexus calculations can become rather intricate. Interested readers are also reminded that ES&T contributed to a virtual issue on biofuels, including the water energy nexus aspects, in autumn 2010 (http://pubs.acs.org/page/vi/2010/biofuels.html). Another ready example is this issue’s Feature by Li et al. on the use of water to cool (coal-fired) thermoelectrical energy production plants (Environ. Sci. Technol. DOI 10.1021/ es1040305). They note that freshwater diversion depletes that resource’s availability for other uses including drinking. Additionally, wastewater requires treatment, which can itself be an energy-intensive process producing more greenhouse gas emissions, as noted by Hall et al. (Environ. Sci. Technol. DOI 10.1021/es103939a). The Feature highlights how using wastewater instead of freshwater as a resource in energy production may afford higher system efficiencies. While this might seem straightforward, Li et al. note that the presence of waste in wastewater means biological and/or chemical fouling/scaling of the pipe interiors poses a challenge for implementation. An illustration of this aspect is found in He et al.’s investigation into the extent of insoluble fats collecting in sewer lines (Environ. Sci. Technol. DOI 10.1021/es2001997). As chemical and environmental engineers tackle the problem of inorganic scaling noted by Li et al., it is interesting to note that the presence of dissolved ions might additionally serve in energy production. Yip et al. discuss the potential of osmotic membranes to cull electricity from the salinity gradients found in natural waters (Environ. Sci. Technol. DOI 10.1021/es104325z). While a membrane engineered for use with brackish water might not be immediately suitable, there seems a potential (pun intended) for electricity generation using anthropogenic wastewater. Look for more content in ES&T on the water energy nexus, where such contributions are continually welcomed.
T
Darcy J. Gentleman Managing Editor
’ AUTHOR INFORMATION Corresponding Author
[email protected].
Published: May 12, 2011 r 2011 American Chemical Society
4194
dx.doi.org/10.1021/es201238t | Environ. Sci. Technol. 2011, 45, 4194–4194
