Service Portal Plant Tour

How does the waste incineration plant work?

How does a waste-to-energy plant work?

The Rothensee waste-to-energy plant receives household and commercial waste as well as sewage sludge. These materials are mixed in a closed system to ensure that combustion takes place evenly and efficiently. The waste is incinerated at temperatures of 850 to 1,000 °C. This produces hot steam, which forms the basis for energy generation at the waste-to-energy plant. High-performance turbines are driven and electricity is fed into the public grid. District heating reliably supplies large parts of Magdeburg with energy.

The Rothensee waste-to-energy plant is equipped with a multi-stage flue gas cleaning system. This filters out dust particles, heavy metals and acidic gases. Emissions are well below the legal limits. The residue left over after combustion – the slag – is processed at the plant. Metals are sent for recycling, whilst mineral components are reused, for example in road construction.

Learn more about the Rothensee waste-to-energy plant

The Rothensee waste-to-energy plant in Magdeburg is a striking example of how modern waste management and energy generation go hand in hand. Here, waste is converted into heat and electricity. Anyone wondering, “How does a waste-to-energy plant work?” will find the answer at the Rothensee plant. The facility combines safe waste disposal with modern energy generation and actively contributes to climate protection.

Just below this text, you will find an interactive animation that takes you through, step by step, how the Rothensee waste-to-energy plant works – from the delivery of waste to energy generation.

  • Household and commercial waste goes through process steps 1–8.
  • Sewage sludge follows steps a–e and is transferred to the flue gas cleaning system from step 5 onwards.

Sewage sludge delivery: Well insulated

In addition to waste, the Rothensee waste-to-energy plant also incinerates sewage sludge. The sewage sludge is delivered with a dry matter content of around 24%, in a semi-solid rather than liquid state. The sewage­sludge is delivered via a sepa­rate sewerage sludge dumping­bunker. It is sealed with a flap to pre­vent odour­emissions. The sewage sludge falls through a discharge grate, where it is broken up.  

Waste delivery: Waste bunker

This is where the waste is delivered. More than 120 refuse collection vehicles empty their loads into the waste bunker every day. The weighbridge at the entrance to the waste-to-energy plant records the exact quantities of waste in the vehicles as they enter and leave.

Inside the bunker, crane operators transfer the waste from the tipping bunker to the stacking bunker, where it is sorted and layered in an optimal configuration for incineration. For safety reasons, three high-performance fire­extinguishing systems are installed in the waste bunker.

Crane and control room: the control centre of MHKW

The crane control console is integrated into the control room, from where both the cranes and the plant processes are controlled. The cranes are responsible for mi­xing the incoming waste and feeding it into the hoppers.

In the control room, the operations of all plant systems are monitored around the clock and managed by a shift ­team of 11 staff members. A modern process control­ system handles the largely auto­mated control functions.

Slag bunker: 
What remains at the end

Around 30% of the mass of the in­cine­rated waste remains as raw ­slag and is stored in the slag ­bunker. However, the raw slag is full of valuable materials such as aluminium, copper, steel and stainless steel. Even coins can be recovered from it. 

Solid-handling pumps – Saxlund pumps: Conveying­ system for sewage sludge

Two hydraulically driven pumps transport the sewage­ sludge from the discharge hopper to the silo and on to the dryer. Duplex piston pumps, each with two delivery cylinders, are used for this purpose. To reduce wear, the pumps are equipped with a water reservoir. In addition, water is used as a lubri­cant to prevent blockages and pressure losses. A coarse solids separator removes larger foreign objects from the sludge prior to pumping.  

Fluidised-bed furnace: Mono­sewage sludge­incineration

Mono-sewage sludge ­incineration involves the exclusive combustion of sewage­ sludge, free from any foreign matter, in a fluidised-bed furnace. Quartz sand ensures stable combustion, and the combustion air is introduced from below via a windbox. The plant processes up to 55,000 tonnes of sewage sludge per year. The resi­dual ash contains concentrated phosphorus and is used for reco­very. The pollutants produced during combustion are then fed into the flue gas cleaning system. 

Boiler: Waste is turned into energy

In the boiler, the sorted waste from the waste bunker is incinerated at temperatures of over 900 °C. The inside of the boiler is fitted with pipes filled with water. The heat from combustion heats the water, and the resulting steam is fed to the turbines to generate electricity, into the district heating network for households in our city, or to businesses that require steam for their processes.   

Sewage sludge ash: 
Ash becomes a raw material

The incineration of sewage sludge produces ash with a high phosphorus content. The ash is removed from the flue gas in an electrostatic precipitator and temporarily stored in a separate silo until it is sent for phosphorus recy­cling. Recovered phosphorus reduces depen­dence on im­ports and is essential for fertilisers, animal feed and medi­cines.

Sewage sludge storage silo:  
Fuel supply

The sewage sludge is fed via pipes into a silo with a capacity of 500 m³. It is fed in through three inlets at different heights, which ensures better mixing and homogenisation of the sewage sludge. As the silo is located outdoors, it is additionally fitted with trace heating to ensure the quality of the sewage sludge even at low temperatures. 

Flue gas cleaning plant:  
Turning flue gas into clean gas

The pollu­tants produced during the ­incineration of waste and sewage sludge are filtered out thoroughly and safely. Acidic gases are separated using lime slurry, heavy metals are captured by activated carbon filters, and fabric filters collect even the finest dust – thus turning exhaust gas into clean gas. These emission levels are monitored 24/7. The waste-to-energy plant is proud to fall well below the legal limits.

Chimney/Clean gas: 
White smoke

Following complex filtration processes, the clean gas is released from the 60- and 70-metre-high chim­neys at the end of the value­ chain. The term ‘clean gas’ sums it up perfectly, as the concen­tration of pollu­tants is not only monitored around the clock in the control room of the waste-to-energy plant, but also online via a dedicated line by the relevant authority.

District heating and heat ­storage: Better solutions for more vehicles

Magdeburg’s district heating network reliably sup­plies over 50,000 households and businesses with hot water. The heat comes from the combined heat and power plant and is trans­por­ted to consumers via well-insulated, under­ground pipes belonging to the Städtische Werke Magdeburg (SWM) network. The cooled water then flows back to the combined heat and power plant and is reheated.    

Nine heat storage tanks and two hot water generators are available to cover peak loads. This saves large quantities of oil. 

Electricity from waste: 
Regulating voltage

The energy generated during incineration is used to produce green electricity via combined heat and power generation. Turbines drive generators, and the electricity they produce is regulated via transformers to the correct voltage – reduced for internal use, increased for fee­ding into the SWM grid. The waste-to-energy plant supplies almost 50,000 house­holds, and thus almost the entire SWM electricity grid.

It is green electricity because the majority of the waste processed consists of biogenic material. This saves large quantities of fos­sil fuels.