Attentive readers have been able to follow the public discussions about the planning and construction of the thermal residue treatment and energy utilisation plant, or TREA for short, in the media over the last few days. This topic has raised a number of questions both among the population and in local politics. Stadtwerke Gießen AG (SWG) would like to provide answers to these questions. Reinhard Paul, Technical Director of Stadtwerke Gießen AG, used a press conference organised yesterday to help objectify the public debate.
"The TREA is often referred to as a waste incineration plant. But that is wrong. TREA is not a waste incineration plant," explains Reinhard Paul. "The TREA, or more precisely the Thermal Residue Treatment and Energy Utilisation Plant, is a heating plant that serves our district heating supply," says Paul. As in any other heating plant, fuel is used. Sorted and processed residual materials are used as fuel for the TREA to generate heat. The TREA boiler plant is connected to SWG's district heating network so that the heat can be transported to the heating customers in the form of heating water.
Which fuels are used?
In the TREA, Stadtwerke uses fuels that are obtained by processing commercial waste from the region. Prior to this, a certified specialist company from the region carries out the processing, i.e. the sorting of the waste. Odour-emitting substances are reduced. What remains is commercial waste such as wood, cardboard, pallets or paper. This fuel can therefore be considered a renewable energy source to a certain extent. This does not include metals or plastics, which are not incinerated in the TREA. Residual waste and hazardous waste must be sent to separate hazardous waste incineration plants.
Value cycle
Waste generated in the region is also incinerated here by Stadtwerke Gießen's TREA. The sorting plant required for processing is to be located at a distance of around one kilometre from the TREA site on the former Gail site. This will keep the transport distances for the fuel very short.
SWG pursues environmental protection
At no time during the planning phase of the TREA did the municipal utilities ignore the issue of the environment. "Protecting the environment is our top priority despite all economic necessities," says Paul. "We want to put our district heating supply on a clean energy footing". For this reason, SWG's district heating experts have developed an operating concept that will ensure low air, water and noise emissions in particular during all phases of operation. Thanks to the TREA, the municipal utilities could increase the proportion of heat supply from the current 4% from renewable energies to 15%.
But that's not all. Stadtwerke covers 41 % of Giessen's current heating requirements alone by supplying district heating. Last year, SWG fed 444 thousand megawatt hours (MWh) into its heating network. This corresponds to the heating requirements of around 17,700 single-family homes. SWG generates the required heat in environmentally friendly heating systems and combined heat and power plants such as gas turbines and a large number of smaller combined heat and power plants. By using combined heat and power generation, SWG achieves energy savings of 38 to 40 % compared to the separate generation of electricity and heat. As a result, 153 thousand MWh less was consumed in 2006 alone. This is also associated with carbon dioxide (CO2) savings - 64,000 tonnes less CO2 were released into the air in Giessen.
State-of-the-art technology
The state of the art is also frequently discussed. The planned plant is state-of-the-art, particularly in terms of flue gas cleaning. The municipal utilities are using the most effective filter method currently available by means of a bag dust filter. The plant is designed in such a way that it will comply with the limit values stipulated in the German Immission Control Act. SWG even anticipates that it will fall well below the legal requirements. In addition, following a discussion with representatives of the Giessen Green Party, Paul has called in an independent expert to analyse the flue gas cleaning concept for possible improvements.
TREA supplies heat for 6,000 households
With the planned Am Atzelbusch plant, SWG aims to be able to generate 75 thousand MWh of usable heat and thus heat for 6,000 households. The TREA would thus save the burning of 7 million litres of heating oil in individual furnaces. Looking at SWG's entire district heating supply, the TREA is only a small plant. The municipal utilities have installed 257 MWh in their network, and the TREA represents a small part of this with only 10 MWh.
The fact that the TREA is more of a small plant is also shown by the comparison with other plants that burn 300,000 tonnes or more per year. TREA, on the other hand, only incinerates 25,000 tonnes of residual materials.
Advantages
- less climate-damaging CO2 is released during the incineration of residual materials compared to the incineration of fossil fuels
- Fossil energy sources (valuable raw materials) are conserved
- Dependence on energy imports is reduced by using domestic fuel
- the volume of waste is considerably reduced, which means that less landfill capacity is required.
Further information
All information about TREA can be found on the homepage of Stadtwerke Gießen at www.stadtwerke-giessen.de.