The Marselisborg Wastewater Treatment Plant in Aarhus, Denmark, produces over150% more electricity than is required to run the plant. The plant generates energy from the biogas it creates from household waste water and sewage. Carbon is extracted from the waste water and pumped into bio-digesters kept at 38°C. The bacteria on the bio-digesters produce methane which is burned to make heat and generate electricity. In 2015, Marselisborg WWTP had a total energy production of 9,628 MWh/ year and consumed 6,311 MWh/year, giving an equivalent net energy production of 153 percent.
Over the past five years focus has been placed on energy savings and energy production. At the Plant, energy-saving technologies such as an advanced SCADA control system, a new turbo compressor, sludge liquor treatment based on the anammox process, and a fine bubble aeration system have optimised processes, reduced energy consumption and fine-tuned systems. The energy production has also been improved through implementation of new energy efficient biogas engines (CHP), resulting in an increase in electricity production of approximately 1 GWh/year. Furthermore, a new heat exchanger has been installed with the aim of selling surplus heat to the district heating grid, which represents approx. 2 GWh/year. This has resulted in a reduction in power consumption of approximately 1 GWh/year which corresponds to about 25 percent in total savings.