Calculations of gaseous and particulate emissions from German agriculture 1990-2017 report on methods and data (RMD) submission 2019.
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 GAS-EM as well as input data, emission results and uncertainties of the emission reporting submission 2018 for the years 1990-2017. 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 emissions of methane (CH4) and nitrous oxide (N2O) from German agriculture (including the anaerobic digestion of energy crops) decreased by 16.3% from 79.2 Tg CO2eq in 1990 to 66.3 Tg CO2eq in 2017. This reduction is a consequence of the following emission changes of partial sources (rounded figures): * decrease of 9.8 Tg CO2eq (-27.8%) as CH4 from enteric fermentation, * decrease of 2.5 Tg CO2eq (-20.5%) 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 2.0 Tg CO2eq (-7.0%) as N2O from agricultural soils, * decrease of 0.55 Tg CO2eq (-20.3%) as CO2 from liming (agriculture and forest), * increase of 0.30 Tg CO2eq (+60.3%) 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 not considered with regard to compliance with internationally agreed emission ceilings. Omitting the emissions originating from anaerobic digestion of energy crops and spreading of the pertinent digestate, the 2017 NH3 emissions of the German agriculture were 578.2 Gg, which is 20.2% lower than in 1990 where the emissions amounted to 724.4 Gg. While anaerobic digestion of energy crops (including spreading of the resulting digestate) was negligible in 1990, it led to NH3 emissions of 61.1 Gg in 2017. Hence, total NH3 emissions from agriculture in 2016 were 639.8 Gg, which is 11.7% less than 1990.