In the last few years, the water-energy nexus concept has emerged as a global issue in the international research community. However, studies on European countries are relatively few, and often focused on the energy sector and agriculture, even though industry dominates water use in many European countries. Cooling purposes represent the main part of industrial water demand, and waste heat recovery is perceived as a main strategy to improve industrial resource efficiency. In this paper, we consider a real case study of low-temperature waste-heat recovery in an electric steelmaking industry and evaluate the impact of feasible interventions on primary energy and water consumption, as well as on CO2 equivalent emissions. Based on a Europe wide review of energy and water prices, of energy sources and corresponding resource efficiency indicators, a Monte Carlo model was developed to undertake a generalization of the case study to the EU-15. It was found that, in spite of common intuition, solutions with the lowest primary energy demand and the lowest CO2 equivalent emissions demonstrate the greatest water footprint. This is especially the case of southern European countries, where heat recovery projects with the highest water intensity are economically feasible due to high electricity and low water prices. As increasing carbon prices may exacerbate this phenomenon, inducing a switch to more water intensive technologies, policy instruments for supporting industrial energy efficiency or carbon emission reduction should be carefully designed.

Low grade waste heat is an underutilized resource in process industries, which may consider investing in urban symbiosis projects to make heating and cooling available to proximal urban areas through district energy networks. A long distance between industrial areas and residential users is a barrier to the feasibility of these projects, given the high capital intensity of infrastructure, and alternative uses of waste heat, such as power generation, may be more attractive in spite of electric efficiency. This paper introduces a parametric approach to explore the economic feasibility limits of industrial waste heat based district heating and cooling (DHC) of remote residential buildings in temperate climates. It also proposes a comparative water-energy-carbon nexus analysis of district heating and cooling and of Organic Rankine Cycles for power generation in an Italian and in an Austrian setting. The results show that, for a generic 4MW industrial waste heat flow steadily available at 95°C, district heating and cooling is the best option from an energy-carbon perspective in both countries. Power generation is the best option in terms of water footprint in most scenarios, and is economically preferable to DHC in Italy. Maximum DHC feasibility threshold distances are in line with literature, and may reach up to 30 km for waste heat flows of 30 MW in Austria. However, preferability threshold distances, above which waste heat-to-power outperforms DHC from an economic viewpoint, are shorter, in the order of 20 km in Austria and 10 km in Italy for 30 MW waste heat flows.

An increasing population with the need of new buildings in combination with global warming is important issues ahead. Hence, for defining a clear path towards a low and zero-emission building stock in the EU by 2050, as recently stated by the new EPBD recast, Nearly Zero Energy Buildings are one of many necessary measures for climate change mitigation. Finding cost optimal solutions are important, where a short time perspective and narrow concept for evaluation may be wrong. This study presents a Net Zero Energy Building in Sweden, with verified plus energy performance in the operation phase. Furthermore, it presents an economic analysis, based on life cycle costing (LCC), where additional cobenefits are included. The study shows that the discounted, cumulative annual cost reductions due to energy savings may exceed the initial extra costs after more than 20 years. However, when including additional green values and increased property value, breakeven may occur already after roughly five years.