Reducing running costs through significantly lower energy consumption

The Mecklenburg community of Ivenack is famous for its ancient, thousand year-old oaks, which are some of the oldest in Europe. This spot, so strongly influenced by nature, is where the vision of supplying the entire community with self-generated renewable energy originated. In addition to the 140-kilowatt photovoltaic system, the biogas plant, which was specially constructed in 2006, is the key to a standalone power supply for the village.

Since then, the plant, which has an installed power of 626 kW, has generated not only electricity from a substrate mix of cattle slurry (30 %) and maize & cereals (70 %), but heat for the specially constructed local heating network. The owner of the plant since 2018 has been BALANCE Erneuerbare Energien GmbH, a wholly owned subsidiary of the energy group VNG AG based in Leipzig.

Comprising a digester and a fermentation residue store, the plant’s capacity utilisation was at least 90 percent. Nevertheless, rising substrate prices, amongst other difficulties, have meant that it has been impossible to operate the plant economically in recent years.

Extensive investment required – but not lucrative

Legislation, including the new German Fertilisers Regulation (DüV), threatened operation of the biogas plant with significant economic losses. In order to satisfy the legal requirements, construction of a new fermentation residue store became necessary. As essential modernisation measures, the charger and gas tank were also replaced. The problem thus arose that the total investment was not offset by any additional income.

Fit for the future with a new concept

The operators found a competent partner in Schmack Biogas Service GmbH, which was commissioned to develop and implement a solution concept. Schmack specialists identified potential, developed a logical optimisation concept and took the following steps to ensure that the plant would be futureproof and remain profitable in the long term.

Step 1:
Change substrates to poultry manure and solid cattle manure rather than cattle slurry.
Result:
Reduction in the substrate quantity and, in turn, a reduction in the fermentation and storage volume needed, thus rendering construction of an expensive fermentation residue store unnecessary. By fermenting the stackable substrate mix, the plant, which is covered by the German Renewable Energy Sources Act (EEG) 2004, is now eligible to receive the technology bonus for dry fermentation of 2 cent/kWh. This led to significant additional revenues.

Step 2:
Extensive technical conversion (required in part due to the TF bonus) was carried out for modernisation, including replacement of the agitators, gas tank and chargers, as well as integration of separation into the plant technology
Result:
A reduction in running costs due to significantly lower energy consumption and longer service life of the new components.

Implementing the optimisation concept from Schmack Biogas Service and converting to the technology bonus will allow the investment costs to be amortised and enable economically efficient operation under the new approval requirements . Consequently, the plant is well equipped for operation until at least the expiry of the German Renewable Energy Sources Act (EEG) at the end of 2026.

September 2020