Quiet at the moment. The machines stand still. Revision. But not for long. On 17. September the machines will start up again. The biomass cogeneration plant in the sandreuth district of nurnberg, on the land of the N-ergie aktiengesellschaft energy company, uses wood chips to generate heat and electricity in a combined heat and power process.
Up to 20 trucks a day arrive at the plant to deliver new wood chips. After the incoming goods inspection, samples of the delivered wood are taken. Afterwards, the finished fuel is stored in one of the total of six boxes. The power plant uses only forest residues or wood chips for combustion. Fresh wood from landscaping. "We do not use waste wood because it is contaminated with pollutants, paint residues or oils", says production manager matthias klopfer.
The six boxes have a capacity of five to seven days, and up to 200 tons of fuel are stored in each of them. It will be transported from there to the biomass boiler. Due to the heat of combustion of the fuel resp. The woodchip evaporates the spinning water in the boiler. The resulting steam drives a heating turbine and generates electricity via a generator. The warmth generated is fed into the nurnberg district heating network.
51,000 tons of forest residues per year are required by the plant. The biomass-fired combined heat and power plant (CHP) thus generates 82 million kilowatt hours of oko-warmth per year. The quantity is enough to supply 7,000 three-person households. Additional 35 million kilowatt hours of eco-electricity produced. Energy from biomass can be obtained from all plants that can be grown for energy production. Plant and animal residues can also be used as energy producers. Biomass can be used as a solid, liquid or gaseous energy carrier and is used in biogas plants as well as biomass cogeneration plants.
The highest efficiency of use is achieved in the warm sector. This is particularly the case in heating plants that operate on the basis of logs, pellets or, like the biomass cogeneration plant in nurnberg, wood chips. But high efficiency can also be achieved in electricity generation through heat-powered cogeneration plants and on the basis of biogas from manure and residual materials.
28,000 tons of CO2 saved
All in all, the use of electricity and heat from the biomass cogeneration plant can prevent around 28,000 metric tons of carbon dioxide emissions per year, explains klopfer. However, this does not include the carbon dioxide emissions of the 20 trucks that drive to the plant every day. "Compared to what we are saving, the emissions from the trucks are minimal.", says the production manager.
The use of biomass has several advantages. By generating heat and electricity from bioenergy, an almost closed carbon dioxide cycle can be realized. The costs incurred by the use of organic residues and waste materials for the operators are rather low. In contrast to photovoltaics and wind energy, biomass is not dependent on wind or solar radiation.
"It is important to us that the wood is also supplied from the nurnberg region, from a radius of 80 kilometers on average", says franz walter, head of bioenergy at the nurnberg cogeneration plant.
However, the energetic use of biomass does not only mean the generation of heat and electricity, but also the production of fuels from biomull or plant oils.
With the "bioclimate" program of the technology and demand center (TFZ) in straubing, biomass cogeneration plants have been demanded at around 300 locations in bavaria so far. The TFZ wants to make an even greater contribution to climate protection. N-ergie aktiengesellschaft had invested about 36 million euros in the plant. However, there are also critics of energy production from biomass. In a study published in july, scientists from the environmental institute leopoldina in halle (saale) massively criticized its appropriateness. It has a poor environmental performance, and corn cultivation competes with other food crops.. It also states that biofuel and biogas should not be a key component of the energy transition.
Green politician christine stahl is also critical of biomass in some respects. "It's a long-running debate. I can understand the advantages and disadvantages of biomass." According to christine stahl, neither one nor the other renewable energy source can prevail in the long term. It needs an energy mix. "I don't think it's a good idea to focus on one type of energy. The energy-saving possibilities are coming up short and the biomass is reaching its limits", says christine stahl.
Biomass is regenerative, but it is still problematic. Because the plants also have to be planted and grow first. Critics also fear that biomass will provoke monocultures of those plant species that have the best energy balance. At least that's what it says in the energy balance sheet of the low-energy forum. Ulrich maly (SPD), mayor of the city of nurnberg, on the other hand, sees a lot of room for improvement in renewable energies. "We will not be able to achieve the energy turnaround with biomass alone. It is a small component, like photovoltaics and wind energy", says maly.
Nevertheless: the bavarian energy concept envisages that nine percent of total energy consumption (currently seven percent) and ten percent of electricity consumption (currently six percent) should be covered by biomass in bavaria by 2021.