1.A.4 - Small Combustion: Stationary Sources (OVERVIEW)

Short description

Source category 1.A.4 comprises stationary combustion systems in the sectors Commercial and Institutional (1.A.4.a), Residential (1.A.4.b), and Agriculture (1.A.4.c).

NFR-Code Name of Category
1.A.4 Small Combustion
including / consisting of sub-categories
1.A.4.a i Commercial and Institutional - Stationary Combustion
1.A.4.b i Residential - Stationary Combustion
1.A.4.c i Agriculture, Forestry, Fishing - Stationary Combustion


Activity data

Activity data in source category 1.A.4 are based on the Energy Balance for the Federal Republic of Germany prepared by the Working Group on Energy Balances (AGEB) 1). For the period prior to 1995, separate Energy Balances are used for the new and old German Länder. Lines 66 (residential) and 67 (commercial, trade, services and other consumers) of the Energy Balance are of primary importance.

Since large quantities of wood fuels, used in households and in commerce and trade, are purchased privately or obtained from system owners' own forest parcels, data are outside official statistics. For this reason, additional studies are used by the Working Group on Renewable Energy Statistics (AGEE-Stat). The results for the residential sector are based on surveys of wood consumption carried out in the framework of the “Rohstoffmonitoring Holz” (“Monitoring of raw materials – wood”) project 2). That project collected data both on firewood purchased via commercial sellers and wood gathered in forests. For interim years, a regression model is applied that takes account of numbers of degree days, the price indexes for conventional fuels, and the heating systems, broken down by types, used in residential buildings. Conversions of volume units into energy units are carried out in conformance with the accepted conversion conventions of AGEE-Stat. Wood consumption in heat-generation-only systems of the commercial and institutional sector is derived via a remainder calculation. In the process, the data on total wood consumption (outside of private households), as determined via the “Rohstoffmonitoring Holz” surveys and via regression models, are blended with the relevant wood-quantity data from official energy statistics and the applicable wood-quantity data given by other relevant models. The wood consumption data derived via this approach, which relate to data on heat generation by CHP systems, are also part of the data on total wood consumption in the commercial and institutional sector.

Energy data and emissions from small engines using biomass as fuel are reported in source category 1.A.1.a, since all the plants feed electricity into the local network. However a small amount of biogas and liquid biofuel, used for heat production, is reported in source category 1.A.4.

The determination of these fuel activities is a result of a comprehensive evaluation of invoicing data of the EEG (Renewable Energy Law), provided by the Federal Network Agency. The EEG-accounting system contains primarily electricity generation data, but also additional information, since a bonus is paid for heat extraction. For the calculation a typical power to heat ratio is necessary according to manufacturers specification.

Emission factors

The database for the emission factors used for NOx, SO2, NMVOC, CO, TSP, PM10, PM2.5, heavy metals, PCDD/PCDF and PAH is the research report “Efficient provision of current emissions data for purposes of air quality control” (“Effiziente Bereitstellung aktueller Emissionsdaten für die Luftreinhaltung”; Struschka 2008) 3). Within the context of that project, appliance-related and source-category-specific emission factors for the combustion systems in the residential and commercial/ institutional sectors were calculated, with a high level of detail, for all important emission components for the reference year 2005.

In 2016 the revision of the emission factors for the main pollutants was necessary due to changes in legislation. Data source for emission factors of several pollutants from 2010 onwards is the research report “Ermittlung und Aktualisierung von Emissionsfaktoren für das nationale Emissionsinventar bezüglich kleiner und mittlerer Feuerungsanlagen der Haushalte und Kleinverbraucher”; Tebert, 2016) 4)

The determination of emission factors is based on a source-category-specific “bottom-up” approach that, in addition, to differentiating (sub-) source categories and fuels, also differentiates appliance technologies in detail. In the process, several technology-specific emission factors are aggregated in order to obtain mean emission factors for all systems within the source categories in question. Use of system-specific / category-specific emission factors ensures that all significant combustion-related characteristics of typical systems for the various categories are taken into account. The procedure is in keeping with the Tier-2 and Tier-3 methods, respectively.

The emission factors are structured in accordance with the relevant fuels involved in final energy consumption in Germany:

  • Light Heating Oil,
  • Natural gas,
  • Lignite (briquettes from Rhine and Lausitz areas, and imported briquettes),
  • Hard coal (coke, briquettes, anthracite) and
  • Wood (unprocessed wood, wood pellets, residual wood).

In addition, emission factors for combustion systems are determined in accordance with device design, age level, output category and typical mode of operation. The emissions behaviour of the combustion systems in question were determined via a comprehensive review of the literature, in an approach that distinguished between results from test-bench studies and field measurements. Transfer factors were used to take account of the fact that emissions in a test-bench environment tend to be considerably lower than those of corresponding installed systems.

The description of the structure for installed combustion systems was prepared using statistics from the chimney-sweeping trade. These data were used to estimate the energy inputs for various system types, to make it possible to determine sectoral emission factors weighted by energy inputs.

The SO2 emission factors for natural gas and lignite briquettes is calculated by the sulfur content of the fuel which is determined by measurents. In terms of light fuel oil the limit values were used. Since 2008 there are two qualities of light fuel oil available: fuel oil with a sulfur content of 1000 mg/kg and fuel oil with a sulfur content of 50 mg/kg. In small combustion plants nowadays almost exclusively low-sulfur fuel oil is used. the share of the different light fuel oil qualities is annually available from the oil statistic. Regarding lignite briquettes can be assumed that 10 % of the sulfur were stored in the ash while 90 % were emitted as SO2. Since the sulfur content of lignite briquettes depends on the region, a weighted average emission factor has been calculated.

Black carbon emission factors are given by the EMEP EEA Guidebook 2019.

For more detailed information on specific acitivity data, emission factors, emissions trends, recalculations and planned improvements, please refer to the sub-chapters linked above.

1) AGEB, 2022: National energy balance and Satellite balance for renewable energy: https://ag-energiebilanzen.de/en/data-and-facts/energy-balance-2000-to-2030/
3) Struschka, 2008: Struschka, Dr. M., Kilgus, D., Springmann, M.; Baumbach, Prof. Dr. Günter: Effiziente Bereitstellung aktueller Emissonsdaten für die Luftreinhaltung; UBA Forschungsbericht 205 42 322; Dessau, 2008. https://www.umweltbundesamt.de/en/publikationen/effiziente-bereitstellung-aktueller-emissionsdaten
4) Tebert, 2016: Christian Tebert, Susanne Volz, Kevin Töfge, Christian Friedrich: Ermittlung und Aktualisierung von Emissionsfaktoren für das nationale Emissionsinventar bezüglich kleiner und mittlerer Feuerungsanlagen der Haushalte und Kleinverbraucher (unpublished)