Wastewater contains a remarkable amount of chemical and thermal energy. Since wastewater is reliably produced every day, this energy is renewable.
The following renewable energy sources are available at WWTPs:
- Wastewater heat: thermal energy can be extracted by heat pumps from raw sewage or plant effluent; in theory 10 % of all buildings could be heated with this energy.
- Hydropower: where wastewater flows downward, its energy can be used; where the drop is sufficiently steep, turbines, Archimedean screws or water wheels can be installed for power generation.
- Digester gas energy: by power and heat co-generation from digester gas the entire heat demand and a great portion of the power demand of a WWTP can be covered.
- Solar energy: large footprint plants lend themselves for installation of photovoltaic cells. Solar energy can also be directly used for sludge drying (See HUBER Solar Active Dryer SRT).
- Wind energy: some plants are located in flat and windy locations where installation of wind turbines for power generation is economical.