Calculations of gaseous and particulate emissions from German agriculture 1990 - 2019 : Report on methods and data (RMD) Submission 2021

Abstract

The report at hand (including a comprehensive annex of data) serves as additional document to the National Inventory Report (NIR) on the German green house gas emissions and the Informative Inventory Report (IIR) on the German emissions of air pollutants (especially ammonia). The report documents the calculation methods used in the German agricultural inventory model Py-GAS-EM as well as input data, emission results and uncertainties of the emission reporting submission 2021 for the years 1990 - 2019. In this context the sector Agriculture comprises the emissions from animal husbandry, the use of agricultural soils and anaerobic digestion of energy crops. As required by the guidelines, emissions from activities preceding agriculture, from the use of energy and from land use change are reported elsewhere in the national inventories. The calculation methods are based in principle on the international guidelines for emission reporting and have been continuingly improved during the past years by the Thunen Institute working group on agricultural emission inventories, partly in cooperation with KTBL. In particular, these improvements concern the calculation of energy requirements, feeding and the N balance of the most important animal categories. In addition, technical measures such as air scrubbing (mitigation of ammonia emissions) and digestion of animal manures (mitigation of emissions of methane and laughing gas) have been taken into account. For the calculation of emissions from anaerobic digestion of animal manures and energy crops (including spreading of the digestate), the aforementioned working group developed, in cooperation with KTBL, a national methodology. Total GHG emissions from German agriculture decreased from 76.5 Tg CO2eq in 1990 to 61.8Tg CO2eq in 2019 (-19.2 %). This reduction is a consequence of the following emission changes of partial sources (rounded figures): • decrease of 9.1 Tg CO2eq (-27.7 %) as CH4 from enteric fermentation, • decrease of 2.3 Tg CO2eq (-21.3 %) as CH4 and N2O from manure management, • increase of 1.6 Tg CO2eq as CH4 and N2O from anaerobic digestion of energy crops (digester + storage of digestate; 1990: 0 Tg), • decrease of 4.5 Tg CO2eq (15.3 %) as N2O from agricultural soils, • decrease of 0.41 Tg CO2eq (-15.2 %) as CO2 from liming (agriculture and forest), • increase of 0.04 Tg CO2eq (+8.8 %) as CO2 from application of urea. These changes are largely the result of the decline in animal numbers following reunification (reduction of oversized livestock numbers in Eastern Germany) and from the mid-2000s due to the limiting effect of the milk quota system (albeit with a renewed increase due to abolition of the milk quota system as of 31 May 2015). Increased nitrogen fertilization (mainly due to the application of increasingly larger amounts of digestate) led to an increase in greenhouse gas emissions from the mid- 2000s. By contrast, the increasing use of manure in biogas plants has contributed to a reduction in methane emissions from manure storage. The NH3 time series as well is a result of counteracting processes. Here too, one of the important governing quantities is the animal number the decrease of which after the German reunification is the main reason for the considerable decrease of the emissions from 1991 to 1992. Mitigation measures like emission-reduced storage and application of manure led to a reduction of emissions in subsequent years. However, opposite trends are caused by increase of animal performance and, for some years, animal numbers. In addition, emissions from application of synthetic fertilizer are higher than in 1990, even though the amount of synthetic fertilizer applied decreased (in units of nitrogen). The observed increase of emissions is due to the increasing share of urea, as urea has a considerably higher emission factor than other synthetic fertilizers. A major contributor to the increase in NH3 emissions in recent years has been the increase in anaerobic digestion of energy crops. Although emissions from the anaerobic digestion of energy crops and the application of the resulting digestates are reported, they are, at the time being, not considered with regard to compliance with internationally agreed emission ceilings. Omitting the emissions due to anaerobic digestion of energy crops (including spreading of digestates), the 2019 NH3 emissions of the German agriculture were 500.0 Gg, which is 26.6 % lower than in 1990 where the emissions amounted to 681.6 Gg and 9.4% lower than in 2005 where the emissions amounted to 551.6 Gg. Including anaerobic digestion of energy crops (including spreading of digestates) leads 2019 to total NH3 emissions from agriculture of 557.8 Gg, which is 18.2 % less than 1990 and 0.009% less than 2005.