Sewage Sludge Interview
22. April 2021 in News
The decentralized sewage sludge recovery for generating thermal energy makes an important contribution to disposal security and environmental protection. For this, the use of steam turbines is essential. In an interview, our project manager Wolfgang Ehrich explains the current developments and perspectives in this area.
1. The amendment of the Sewage Sludge Ordinance and the Fertilizer Ordinance and the resulting reduction in the amount of sewage sludge that can be used in agriculture are forcing operators of sewage treatment plants to rethink. How does this affect the steam turbine manufacturing industry?
With the implementation of the amendment, the trend from material to thermal utilization of sewage sludge will continue and intensify. While the use as a fertilizer for agriculture used to be an important aspect, today, against the background of increasing pollution with, for example, microplastics, heavy metals, drug residues or resistant bacterial strains, the resulting damage to the biological cycle is receiving more attention. The amendment requires the sewage treatment plant operators to submit appropriate concepts by 2023. This is noticeable in an increasing number of plans for sewage sludge incineration plants and the corresponding steam turbines.
2. Why is sewage sludge recycling important from a climate protection viewpoint? And how can steam turbine manufacturers make a contribution here?
Sewage sludge recycling also means that the constituents can continue to be used in a meaningful way. For example, the recovery of phosphorus is becoming increasingly important and must be carried out from 2029 in accordance with the Sewage Sludge Ordinance. In the case of thermal utilization, in addition to the recovery of resources and the reduced pollution of the soil in agriculture, the use of the energy stored in sewage sludge is also taken into account. Dried sewage sludge has roughly the same calorific value as dried lignite and is therefore suitable for the effective generation of water vapor. If appropriately efficient steam turbines are used, CO2 emissions can be saved elsewhere.
3. Can you explain the process of how sewage sludge and steam turbines come together?
There is currently a trend towards recycling in mono-incineration plants, i.e. the dried sewage sludge is not incinerated in existing power plants, but rather incinerated in fluidized-bed incineration plants that have been optimized for this purpose. In this process, an autothermal combustion without additional fuels, water vapor is generated. In the steam turbine, the energy in the steam is converted into motion and then converted into electrical energy in the generator.
4. What challenges / advantages can the construction of a turbine for sewage sludge utilization bring with it?
When implementing thermal recovery concepts, economic aspects are taken into account in the planning phase. This means that a suitable steam turbine has to be found for the planned incineration plant and not the other way around. With experience in the implementation of customer-specific requirements, M + M has always gladly accepted the challenge of finding the best solution for the overall process.
5. Is the incineration of sewage sludge also an international issue or are the inquiries restricted to German-speaking countries?
M + M's activities are currently focused on the German-speaking area, as more than 30 mono-incineration plants are being planned in Germany alone. But we hope that we can also be active internationally.