Study 47 – Joint utilisation of water and waste heat: challenges, potential and prospects in industry

French and European industry faces a two-fold environmental challenge: decarbonising its thermal energy use, which remains heavily reliant on fossil-fuel-generated heat, and reducing its water consumption, which is subject to significant constraints due to climate conditions and regulations.A cross-analysis of industrial water abstraction and waste heat sources shows that several sectors lie at the intersection of these two challenges. The chemicals and agri-food sectors thus account for more than 50 per cent of both waste heat sources and industrial water abstraction. These are closely followed by the paper and board sector, non-metallic materials (glass, cement, terracotta, etc.) and the metallurgy sector, each accounting for around 10 per cent of their respective categories.

This context, together with the observation that a significant proportion of waste heat sources also contain water, has led to the central question of this study: in what scenarios does the combined recovery of heat and water appear to be worthwhile?

This key question therefore raises a number of related issues concerning the feasibility, cost-effectiveness and competitiveness of these solutions in the industrial sector.

• The study aims, as a first step, to analyse the key components required to implement this type of project (equipment, studies, technologies, etc.) in order to identify the obstacles, barriers and opportunities from a technical, technological and regulatory perspective.
• The study then goes on to examine the key factors determining the environmental and financial impact of projects: it thus identifies three sets of factors that significantly influence profitability, and sets out favourable ranges for each of them. These may include contextual factors such as the number of operating hours per year, the reference price of heat or local water pressure, as well as factors relating to the characteristics of the waste heat stream in question (temperature, water content, etc.)
• Based on the conclusions drawn from the previous sections, the study provides an analysis and quantification of the potential of industrial sectors and sub-sectors, taking into account the key processes involved and the available sources of waste heat.

In order to illustrate and challenge the findings, the study presents a case study based on previous examples. The cases analysed confirm the technical feasibility of combined heat and water recovery, in line with the sectors identified as relevant.

The LIFE ZEUS project, implemented by MONIN (a French syrup manufacturer) at its Bourges site, demonstrates the industrial feasibility of water recycling in an agri-food context: the expected water savings are set to exceed 60 per cent of the site’s annual consumption, by reusing the entire 38,000 m³ of wastewater discharged each year.