Statement of the Bavarian Farmers' Association: Animal husbandry is a decisive component of a sustainable nutrient cycle.
Myth: Animal agriculture is a decisive component of biogeochemical cycles.
Closed-loop agriculture is based on the idea that the nutrients removed from the soil through the cultivation and consumption of plants are returned to the soil. Consequently, all primary, secondary and final consumers must return their metabolic products and finally their (residual) bodies to the soil .
A closed biogeochemical cycle is not present in the Bavarian agriculture, as in practically every modern agriculture. The cycle of an agriculture with animal husbandry is broken several times.
(i) According to the closed-loop agriculture, nutrients must be returned to the removed soil via excreta, but also animal and human bodies. However, mainly liquid manure and certain slaughterhouse waste from the animals are applied to the fields, but hardly any animal products that are consumed and digested by humans and pets (meat, milk, eggs). Human excrement is collected via sewage treatment plants, in which important nutrients are removed from the cycle by conversion into gases or discharge to industry (, p.57). Only a very small proportion of sewage sludge may be used in agriculture because of problematic components (industrial, household, drug residues and pathogens) (, p.42). Animal products that are not consumed by humans but are used elsewhere (animal skins, blood, bones, fats) are completely removed from the cycle. It is practically and ethically difficult to return the bodies of pets and humans to agricultural land.
(ii) The animals are fed nutrients from foreign soils via imported plants. Throughout Germany, the foreign share of digestible protein in the feed is 33% (, p.10). No exact figures are publicly available for Bavaria, but the proportion is likely to be similarly high. There is no return of nutrients, so that the countries (primarily USA, Brazil, Argentina) are irretrievably deprived of nutrients via this broken cycle. On the other hand, the oversupply of nitrogen and phosphorus in Bavaria leads to numerous health and environmental problems. Firstly, it causes over-fertilization of the soil in Bavaria. The oversupply of nitrogen  regularly leads to an exceeding of the EU limit values for harmful nitrate pollution of groundwater (, S2). Secondly, nitrogen and phosphorus also reach lakes and seas via rivers, where they cause eutrophication. In addition, the biodiversity of various ecosystems is disturbed and air quality decreases due to particulate matter produced by ammonia (, p.105 ff).
(iii) The enormous demand for animal feed requires an intensification of agriculture using artificial fertilizers and pesticides. In Germany, for example, more than half (56%) of the nitrogen fertilizer is artificial fertilizer (, S.63). Sales of pesticides for agriculture in Germany in 2016 were over 32 thousand tons of active ingredient (, p.54 ). No sales figures are available for Bavaria, but the threshold values for herbicides, fungicides and insecticides in groundwater were exceeded more than twice as often in the period 2009-2012 (approx. 10% of the samples) than on average for all of Germany (, p. 33).
Animal agriculture is therefore not a necessary component of a nutrient cycle, but rather a resource-intensive factor that brings the material flow balance into disequilibrium.
Without the recycling of human excrements and bodies, agriculture without animal use (vegan organic agriculture) is not a completely closed nutrient cycle either, but it can be practiced sustainably without the addition of synthetic fertilizers and pesticides. Legumes can fix the most important macronutrient nitrogen in sufficient quantities from the air via a symbiosis with nodule bacteria. Through regular green manure with legumes and the additional application of self-produced, biocyclic humus and mature compost, bound nitrogen and all other macro- and micronutrients can be added to the soil. The production of humus and compost can be achieved on the one hand via cyclic fruit rotations (, chapter 18.104.22.168) and on the other hand via a part of the areas previously required for animal feed (, Kp. 3.6). Any nutrient deficits that may arise can be compensated with naturally available additives (e.g. rock phosphate, potassium sulfate, magnesium sulfate) ,.