A Paris swimming pool on Wednesday inaugurated a new heating system using warmth recovered from sewers in a bid to cut costs and reduce carbon emissions.
The Aspirant Dunand pool in Paris' 14th arrondissement is the latest in a series of French public buildings to use heat pumps to recycle residual warmth from showers, dishwashers and washing machines in its sewage pipes.
French waste and water group Suez, which has a 30-year contract to run the installation, already operates a dozen such heating systems around the country, including in pools in Paris suburb Levallois and in Annemasse, near the Swiss border, and in schools, apartment blocks and administrative buildings.
It is building three to four new installations per year.
"The potential is enormous. Wherever there are sewers, we can recover heat," said Bertrand Camus, head of Suez water in France.
France has some 400,000 kilometers of sewage networks, where the water temperature typically ranges between 13 degrees Celsius (55.4°F) in winter and 20 degrees (68°F) in summer.
With a stainless steel lining on the inside of sewage pipes, Suez recuperates 4 to 8 degrees of that warmth and boosts it to about 50 degrees for use in space heaters or as hot water. The technology is similar to low-temperature geothermal energy, already widely used in some countries to heat individual homes.
Suez says the cost ranges from 200,000 euros for a pool to one million euros ($1.12 million) for an apartment block, and that such projects pay for themselves over eight to nine years without subsidies and at normal energy prices.
Camus said the Aspirant Dunand installation covers nearly half of the pool' energy consumption.
Paris aims to reduce its greenhouse gas emissions, boost the share of renewables in the administration's energy use to 30 percent by 2020 and make better use of its 2,400 km long sewerage network.
($1 = 0.8912 euros)