Casting. Using biogas to generate energy is an economically viable and environmentally sound technology. Stadtwerke Gießen (SWG) is convinced of this and refers to its experience with its own biogas plants.
In doing so, SWG is firmly contradicting a statement by the chairman of the Giessen Tenants' Association. In a newspaper article, he had spoken out in favour of stopping the promotion of biogas plants via the Renewable Energy Sources Act. He considers the alternative of photovoltaics, which according to figures from the Federal Ministry for the Environment is more heavily subsidised than biogas, to be much more land-efficient. Biogas producers drive up methane and nitrous oxide emissions and thus increase the greenhouse effect. In addition, the cultivation of crops for energy production increases the global price of maize and wheat.
Good environmental balance of biogas
Stadtwerke Gießen disagrees with this: Biogas is clearly climate-neutral and methane and nitrous oxide are only released into the atmosphere during production if fermentation or storage tanks are operated improperly. SWG rules this out for Giessen. Corresponding test protocols of the plant sensors approved by TÜV have documented the reliability without any gaps. In practice, however, nitrous oxide is mainly produced when biomass reaches the field as fertiliser and is decomposed there by bacteria.
SWG also takes a clear stance against the extraction of biomass by regional agriculture. Company spokeswoman Ina Weller recommends taking a close look at the topic of biogas: "It is important to understand that biogas will only ever be part of the energy mix. On the scale and in the composition in which we use biomass as a climate-neutral energy source at SWG, it makes perfect sense." We are not promoting a monoculture of energy crops, nor are we aiming to convert the whole of Germany to biogas. "It is a misconception that biogas production in Germany is driving up the global market price for food. Germany has been overproducing grain by around 50 per cent for years. What's more, the area under biogas production in Germany accounts for just 0.19 per cent of the global area under wheat, barley and maize," calculates Ina Weller.
High efficiency through combined heat and power generation
SWG uses biogas because it is a safe and, above all, already functioning technology for climate-friendly energy generation. The company produces electricity and heat simultaneously in combined heat and power plants, thereby making an important contribution to the energy transition in the region. Ina Weller explains: "Building solely on photovoltaic and wind power plants that produce electricity depending on the weather is not enough. It is not for nothing that the German government has set itself the target of increasing the proportion of electricity from combined heat and power generation to 25 per cent by 2020. We still need types of generation that are capable of meeting base load requirements and at the same time have a positive environmental balance."
When planning the SWG biogas plants, the engineers pay attention to many different criteria that are decisive for this positive environmental balance: The experts take into account access and delivery routes as well as the exact mix of biomass. In addition, a research project is currently underway with the THM (Technische Hochschule Mittelhessen) with the aim of optimising the fermentation processes and thus further increasing energy efficiency.
"At Stadtwerke, we understand that a major project such as the energy transition inevitably raises fears of the unknown," assures Ina Weller. "If there are concerns, we take them seriously and are happy to enter into dialogue. We have therefore invited residents to open days on several occasions, where they can see our energy systems for themselves. On these occasions, we repeatedly explain the positive climate balance."
The biogas plant in Großen-Buseck alone helps to reduce CO2 emissions by around 1200 tonnes every year, making it an important component of SWG's strategy. As early as 2010, the company voluntarily committed itself to reducing greenhouse gas emissions that are harmful to the climate and to promoting the local energy transition as part of the "Charter for Climate Protection" of the state of Hesse.