Recovering waste heat from greywater

Why recover heat from grey water? Still little known to the general public among renewable energies, it could take a prominent place in the French energy mix in the future. Waste heat, also called recovered heat, comes largely from industrial activities and represents an energy resource that is little exploited today given its potential. Waste heat is a source of heat generated by an activity that is not reused or exploited. There are various sources producing this heat: industries, data centres, incinerators, wastewater treatment plants, etc. Waste heat can be recovered in different ways. According to ADEME, there are “two complementary axes of thermal recovery”: - reusing this heat within the emitting company itself, - recovering it for external use, to heat other businesses or to produce electricity by cogeneration, for example. However, it is difficult to quantify how many tonnes of CO₂ will be saved by using this energy, because every installation is unique. How can heat from grey water be recovered? Heat recovery from grey water is carried out using a heat exchanger installed on the grey water pipe. The device is supplied with water from the mains network so that it is warmed before being heated by the domestic hot water tank or the boiler, for example. In this way, the amount of energy needed to heat the water in the tank to the desired temperature can be reduced by up to 60%. Several systems are available on the market. It is essential to check the quality and compliance of the chosen solution in order to guarantee the hygiene and safety of drinking water. A technical opinion from the Centre Scientifique et Technique du Bâtiment (CSTB) is a guarantee of a compliant and monitored product.

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France