Sewage sludge and sewage gas
Purified wastewater leaves traces: sewage sludge and also sewage gas, which are valuable residual materials from the wastewater treatment process, and simultaneously raw materials for energy generation.
In the final phase of wastewater treatment, large volumes of energy-rich sewage gas are produced in the digesters of the wastewater treatment plants. This gas can be used as a fuel in combined heat and power units, which simultaneously produce electricity and heat. We preferentially use this in our own plants. Thus, for example, the combined heat and power unit of the LIPPEVERBAND at the Dorsten wastewater treatment plant covers the majority of the electricity requirements of the facility, and additionally heats the plant buildings. The same applies e.g. to the wastewater treatment plant of the EMSCHERGENOSSENSCHAFT in Bottrop. This saves natural resources, puts the sewage gas to good use, and lowers operating costs.
Sewage gas as an innovative raw material
Processed into gas of natural gas quality, or into hydrogen, sewage gas can be used for many purposes: to fuel vehicles, heat buildings, or supply electricity. The pilot project 'EuWaK' (a German acronym for 'Natural Gas and Hydrogen from Wastewater Treatment Plants') is operated by the EMSCHERGENOSSENSCHAFT at the Bottrop wastewater treatment plant, where all three options will be used. Dimensioned for 1.34 Million population equivalents, the wastewater treatment plant has one of the largest sewage sludge processing capacities in Germany, and is therefore particularly suitable as a development and test environment.
In an age of diminishing oil and natural gas reserves, hydrogen represents the fuel of the future. Thus far, hydrogen has typically been extracted from fossil fuels, and has therefore been unable to bring to bear ist great advantage as a CO2-neutral, clean source of energy. Biogas from wastewater treatment plants offers the opportunity to generate large volumes of CO2-neutral "natural gas", from which hydrogen can be extracted in a second stage. Both gases can be used for energy generation in the wastewater treatment plant itself, but also for the electricity and heat supplies of neighbouring housing developments. A third option is the construction of fuel stations for vehicles that run on natural gas or hydrogen.
Sewage sludge as a fuel and raw material
Alongside sewage gas, sewage sludge is a further important raw material. It is either burned and used to generate electricity, or it is used in agriculture and landscaping. Due to its content of valuable soil nutrients, e.g. phosphor, the sludge is suitable for use as fertiliser. A proportion of the sewage sludge is therefore applied to agricultural land, in compliance with strict statutory conditions. Smaller quantities are also used in landscaping work.