A plant‐specific model approach to assess effects of repowering measures on existing biogas plants: The case of Baden‐Wuerttemberg

Abstract

Up to the latest versions of the German renewable energy act (EEG), there had been a constant growth of new biogas plants (BGPs). After reaching a stagnation in the last years, today the focus has shifted to improving the existing BGPs. Assuming that most plants have not reached the technical end of life, the question arises on how an operation can be realized beyond the initial EEG support period of 20 years. In addition, new legal and economic conditions require the implementation of adjustments, that is, “repowering measures.” Based on a method review, a plant‐specific model approach is presented to assess repowering measures for a wide range of BGPs differing in capacity, substrate mixture and agricultural structures. The techno‐economic model includes different performance indicators like levelized cost of electricity (LCOE) and temporal aspects like technical progress. Using a data set for BGPs in the state of Baden‐Wuerttemberg (Germany), results are illustrated for the different model modules and three repowering scenarios of an extended operation period of ten years. The scenarios regard different options to meet the requirements of the current EEG, namely the flexibilization and restrictions on energy crops, in comparison with a reference case. While in repowering scenarios, the number of plants decreases between 54% and 69% and the overall power capacity changes between −48% and 13% until 2035. The results further show a reduction potential in the specific area demand and GHG emission up to 12% and 24%, respectively. Technical progress, additional revenues and capacity premiums are shown to be an important factor for efficient substrate utilization, low LCOE and thereby the enabling of an extended operation period. The scenario results indicate that the agricultural areas for energy crop cultivation and the amount of manure used in BGPs will be reduced considerably, inducing new chances and challenges in the future.

Status quo and perspectives of biogas production for energy and material utilization

“…However, these advances are not enough to make biogas production able to compete on a large scale with other renewable energies in the future. This will be discussed later in the context of Güsewell et al, (). Further technological progress is therefore also needed in the field of fermentation and its process in order to achieve higher competitiveness (Achinas et al, ).…”

“…However, Tampio et al, () point out possibilities for future use. Still, biogas and the resulting end products have a major handicap: The production costs are still comparatively high despite a wide range of progress, as shown by the statements of Güsewell, Härdtlein, & Eltrop, ), while, for example, the electricity generation costs from wind and sun have been considerably reduced in recent years (IRENA, ). “The example of Germany shows clearly that biogas market dynamism is directly linked to the support schemes and the feed‐in tariffs implemented.” (Torrijos, ).…”

“…However, in many countries, subsidies have been significantly reduced in scope, so that after the expiration of the guaranteed subsidy periods (which in Germany amount to up to 20 years), there is uncertainty as to how things can continue if the cost of energy produced from biogas has to be borne much more strongly by market prices and less by subsidies. Güsewell, Härdtlein, & Eltrop, ) address this question with their article “A model‐based approach to assess effects of repowering measures on existing biogas plants: the case of Baden‐Wuerttemberg” and illustrate it using the example of existing biogas plants in Baden‐Wuerttemberg, Germany. Various forms of repowering techniques are analyzed.…”

“…Germany has another special feature in comparison with other countries. There is an increasing “overbuilding” of the plants, which can be connected with a considerable capacity increase but without producing more electricity and heat per biogas plant per year (Güsewell, Härdtlein, & Eltrop, ). The CHP output can, for example, be doubled in this “overbuilding” measure in order to produce the same amount of energy in half the annual operating time.…”

Downscaling of agricultural market impacts under bioeconomy development to the regional and the farm level—An example of Baden‐Wuerttemberg

“… Reference scenario (REF) from Güsewell, Härdtlein, and Eltrop (); Energy policy: German Renewable Energy Act (EEG, ). …”