5.B.2 - Biological Treatment of Waste: Anaerobic Digestion at Biogas Facilities

Within NFR category 5.B.2, ammonia (NH₃) emissions from the anaerobic digestion at biogas facilities are reported.

Separately collected organic waste (biowaste) from e.g. households, public garden and park service, food industry, restaurants, canteens and from agriculture can be treated in two different ways:
aerobically (composting) and anaerobically (biogas production).

The aim of the treatment is the production of digestate, leading to the recycling of nutrients and organic matter.

The produced digestate is used as fertilizer or soil improver in agriculture or horticulture and also in private gardening. In Germany, about 40% of the organic waste is treated in anaerobic digestion plants and ammonia (NH₃) is an important emission to air.

Emissions from anaerobic digestion at biogas facilities are not a key source and of minor priority.

Official statistical data (Statistisches Bundesamt, Fachserie 19, Reihe 1: Abfallentsorgung (Waste management), Table 2.1; ¹⁾) are used for the estimation. The data are published on a yearly basis with an exception for the actual year of reporting. The activity data for the actual year of reporting are obtained, initially, by carrying the relevant data from the previous year forward, in unchanged form. In the following year, when the actual activity data for the given year becomes available, they replace the data that were carried forward. This procedure has only a very small impact on the total emissions in the relevant current report year.

The emission factor used for calculating NH₃ emissions is based on emission data from a research project ²⁾. The NH₃-EF is 274 g/t and used for the whole time series (which is starting in 1998).

The AD from Statistisches Bundesamt have an uncertainty of ±2% whereas the uncertainty for the EF is -18/+920% (ibid.).

When preparing the current inventory data, statistical data are only available for the previous reporting year. The current reporting year must therefore be extrapolated on the basis of the previous year. The result of this approach is revised by the correct data in the following year. For this reason, annual recalculations are required for the previous year.

Table 1: Revised biowaste activity data, in [kt]

Table 2: Accordingly revised NH₃ emissions, in [t]

Currently no improvements are planned.