Around 2,700 tons of waste are burned every day in units 1 and 3 of the North thermal power station, built in 1964, at more than 850 degrees Celsius. Between 230 and 480 deliveries land in front of the gates every day. The numbers vary depending on the week, year or vacation time, the Munich waste management company (AWM) reports on request. But now the combined heat and power plant may be facing a shortage of an important catalyst material: ammonia water, a by-product of natural gas production.
It’s about large quantities: 312,382 tons of garbage came from Munich households in 2021, plus bulky waste and commercial waste. Deliveries are also made from the district of Munich, the area of the Donau-Wald waste management association, the districts of Freising, Bad Tölz-Wolfratshausen, Weilheim-Schongau, as well as from neighborhood help and, in emergencies, from south-eastern Bavaria and Ingolstadt.
Residual waste is therefore always present. So far, waste and sewage sludge incineration has been considered a stable factor in heat and power supply. According to Stadtwerke München (SWM), in the past 2021/22 heating period, their share in Munich’s district heating was almost ten percent, almost as much as geothermal energy contributes. 30 percent is generated with coal, 50 percent with natural gas.*
Without ammonia, the limit values cannot be met
Ammonia water is a by-product of natural gas production and is used in all three blocks of the North combined heat and power plant – including the one with coal combustion – to reduce pollutants. “Without ammonia, the systems cannot be operated with the currently applicable limit values,” says a spokeswoman for the public utility company. There are no alternatives.
Bavarian operators already feared delivery bottlenecks, as reported by Bayerischer Rundfunk. That could mean: switching off the system or emitting more exhaust gases. In any case, Stadtwerke München share the concerns. “We also see possible difficulties here, since the producers are dependent on larger quantities of gas for the production of ammonia. Delivery by rail must also be ensured, since the routes for coal transport have priority for the coming winter,” says one written answer. Ammonia is an important factor in flue gas cleaning – it reduces nitrogen oxides from the flue gas and reacts with the nitrogen oxides in the catalytic converter to form the harmless substances elementary nitrogen and water. 785 tons were consumed in 2020 in SWM’s thermal power station north in Unterföhring. The Stadtwerke obtain it from a provider from Saxony-Anhalt.
According to the Association of the Chemical Industry in Frankfurt (VCI), companies have already reduced the production of some products, including ammonia, because of the “extremely high gas prices in Germany”. “The sharp increase in the price of ammonia indicates that supply is tight compared to demand. It is unclear whether this will lead to supply bottlenecks in the value chain, since ammonia can also be imported,” according to the current estimate.
The waste heat is also used for Munich’s heat supply
According to a spokeswoman, the sustainable thermal utilization of residual waste and sewage sludge will also play a role for the municipal utilities in the future energy mix of Munich district heating. Since garbage can no longer be stored in landfills in Germany, it must be incinerated in any case – by means of cogeneration, the waste heat is still used for Munich’s heat supply in the combined heat and power plant north.
As a short-term reaction to the current supply situation, SWM resumed its coal supply contracts for Block 2 in the North combined heat and power plant and postponed the planned conversion of this block to natural gas with the approval of the Munich City Council. Oil burners that had already been shut down were also reactivated in two heating plants. The Stadtwerke cannot make any more specific statements at this time. However, they do not rule out price increases. In the long term, SWM intends to continue the “renewable energies” offensive launched in 2008 and massively expand in the areas of electricity and heating. A ten million euro package to accelerate the expansion of district heating in Munich was only recently launched.
Although waste incineration plays a role in the supply mix, the AWM sticks to its declared goal of waste avoidance: the reduction of residual waste has been anchored in the waste concepts for years. So it was formulated long before the current energy crisis. Whether and to what extent waste incineration will contribute to energy supply and in particular to district heating in the future must be decided politically.
*An earlier version stated that the thermal power plant north is responsible for 10 percent of Munich’s district heating. This was an editorial error, which we apologize for.