What to do with industrial waste heat considering a water-energy nexus perspective

is generally accepted that waste heat recovery from industrial processes is an enabler of energy efficiency and CO2 emission reduction. Options for industrial waste heat recovery include power generation, heat upgrading, and distribution through district energy networks to meet a remote heating demand. Particularly in presence of subsidies, even technologies with relatively low conversion efficiencies may become feasible. In the last few years, however, novel concerns arose as to the links between primary energy consumption, carbon equivalent emissions and blue water consumption. The water-energy nexus concept is well known in energy planning and in water infrastructure planning, has been however hardly examined in the industrial sector. In a recent work, the impact of an industrial absorption cooling project based on waste heat recovery on both energy and bluewater consumption has been evaluated for the EU-15. It was found that, depending on the national energy mix and market situation, alternatives with higher energy savings but increased water consumption compared with baseline operation were preferred in some countries. Building upon that study, in this paper the water footprint of district heating options for recovering low grade industrial waste heat is investigated. The sum of direct and indirect bluewater consumption, carbon emissions and primary energy demand are evaluated. A parametric study of economic feasibility is performed in order to evaluate under which circumstances the additional water and carbon footprint, produced by district energy systems construction and operation, is offset by the reduction in fossil fuel consumption, caused by the substitution of remote boilers. Switching values and trade off curves are presented and a comparison is drawn between district heating technologies, and energy conversion via Organic Rankine Cycles, so as to answer the research question posed in the title.