Analysis of legal regulations on direct effects for the nutrient management in Germany – impact assessment of EEG

The biogas plants currently in operation in Germany significantly contribute to the provision of renewable electricity and renewable heat. Since the amendment of the EEG (Renewable Energy Law) in 2014, the number of new biogas plants has declined sharply. It is therefore assumed that the development of existing plants is mainly driven by the EEG-remuneration. A decline in biogas production results in a reduction in the amount of digestate and can contribute to reduced nutrient balances, depending on the composition of the substrate (high renewable biomass proportions bring additional nutrient loads into the system).

However, the conventional storage of fertilisers inevitably leads to climate-relevant emissions. These emissions can be largely avoided by promptly transferring manure as a substrate to a biogas plant. The amount of avoided emissions varies depending on the type of manure and storage. The assumption is that a future phase out of the biogas plant stock will also lead to correspondingly lower GHG avoidance. If the stock higher installed capacities are maintained there is a correspondingly higher GHG avoidance in 2035. If, in the medium term, the number of plants and thus the energy recovery of animal excrement declines accordingly, the contribution to the avoidance of non-energy GHG emissions will also decrease. The following diagram illustrates the quantities of farmyard manure that will be released in the coming years, assuming the expiry of existing biogas plants regulated under the EEG.

This would be counterproductive for the achievement of the German climate protection targets, since some emission sources in the agricultural sector are difficult to reduce anyway and the agricultural sector in particular faces major challenges with very ambitious targets (95% GHG reduction by 2050 wrt 1990). In an extreme case, a reduction potential of approx. 1.75 million tonnes of CO2-eq (difference between non-energy GHG avoidance from 2020 and 2035) would be lost in this way by 2035, which would have to be compensated otherwise.

Thus, the positive climate protection effects achieved by the digestion of liquid manure or other biogenic residues would cease to exist if biogas plants were decommissioned.

Accordingly, the retention of the current legal situation in the coming years would lead to a sharp decline in the number of plants starting in 2023/2024, assuming the 20-year remuneration period expires. If GHG emissions from the storage and use of liquid and solid manure (methane in the case of liquid and solid manure, nitrous oxide primarily solid manure) can’t be avoided in the future, there will be an increase in indirect emissions in agriculture, which will counteract the implementation of the climate policy goals and the 10-point CO2 reduction plan presented in 2019.



  • IZES, DBFZ, UFZ (2019): Analyse der gesamtökonomischen Effekte von Biogasanlagen. Makrobiogas Wirkungsabschätzungen des EEG. Abschlussbericht, Saarbrücken und Leipzig.
  • IZES, ifeu (2016): Biogas – Quo vadis? Schärfung anstehender Forschungsfragen hinsichtlich der langfristigen Klimaschutzwirkung von Biogasanlagen. Endbericht, Saarbrücken.

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