Environment ministry adds seven water-heat sources to Korea's renewable energy list

South Korea's environment ministry said Tuesday it will add seven untapped water-heat sources, including water from industrial use, to the resources recognized as renewable energy, widening a technology it says can cut building energy use by more than 30 percent.

The Ministry of Climate, Energy and Environment said a revision to the enforcement decree of the Renewable Energy Development, Use and Distribution Promotion Act was approved at a Cabinet meeting the same day and takes effect Nov. 17. A separate notice designating the scope of water-heat energy will be issued at the same time.

Water-heat energy draws on the fact that water is cooler than the air in summer and warmer in winter, and the ministry says it can supply heating and cooling at about 30 percent less energy than conventional systems. Paris, Tokyo and northern Europe have used river, sewage and wastewater heat for urban heating and cooling for 20 to 30 years.

Korea folded river water into the category in 2019 and has run pilot projects and a large cluster in Gangwon Province, but those efforts have been confined largely to rivers, dam areas and places served by trunk water mains. The changes are meant to bring the technology to dense urban districts and inland industrial parks where heat demand is concentrated.

They include the roughly 581,000 tons of leaked groundwater that emerges each day from subways, tunnels and large buildings, water that stays at an average of 15 degrees Celsius year-round and can be connected on site. Sewage and industrial wastewater, at 12 to 15 degrees in winter and 20 to 25 degrees in summer, can also yield heat for district heating or process hot water.

The ministry estimates that using all discharge from the country's sewage plants handling at least 500 cubic meters a day, some 20.09 million tons daily, would provide 3 million gigacalories a month, enough to heat about 3 million households. Industrial water can supply heating and cooling within industrial complexes; only its heat is taken, with the water returned entirely to existing process use, so supply is possible without consuming the resource.

"Water-heat energy, whose effects have been demonstrated through pilot projects at the Korea World Trade Center and Lotte World Tower, will spread widely to consumption sites near urban buildings and industrial complexes across the board, using this institutional overhaul as a springboard," said Song Ho-seok, head of the ministry's water management policy office.

He added that the changes are the first institutional result of the ministry, launched in October 2026, managing water and energy together under a single goal.