NaHaLi

Sustainable Lindenhof: Integration of new products and production from the farm's own organic materials into an existing farm system with arable farming, livestock breeding and biogas use

Laufzeit
01.01.2020 - 30.03.2020 

The objective is to find a solution to the problem of organic fertiliser surpluses on livestock farms by recycling them into C-rich functional materials, energy sources and fertilisers worthy of transport.

After species extinction and climate change, nitrogen (N) and phosphorus (P) pollution of ecosystems are considered global environmental problems No. 3 and 4 and contribute significantly to species extinction and climate change. The N, P surpluses are exported to other ecosystems (ground and surface waters, coastal waters, adjacent areas, etc.) and cause massive species change and impoverishment through eutrophication. According to the IPCC (2014), emissions of N2O (nitrous oxide) and CH4 (methane) contribute 6.2% and 16% respectively to the greenhouse effect (total: 22.2%).

The main source of N, P pollution is agriculture. Especially in intensive livestock farms, the purchase of concentrated feed (N, P import) results in surpluses that cannot be meaningfully utilised on the limited area of the farm. In Germany, 60% of total CH4 emissions and 80% of N2O emissions come from agriculture.

There is also a need for action on the part of farmers. The new Fertiliser Ordinance (DüV) 2017 regulates the application of N and P on fields more strictly and limits it upwards. Livestock farms now frequently exceed P soil contents of 20 mg/100 g soil P2O5 (CAL) and thus the limit value at which only withdrawal fertilisation is permitted.

Due to the P-limitation, on-farm organic fertiliser can then only be applied to a very small extent. Therefore, intensive livestock farms are often faced with the dilemma that they cannot use their own N, P fertiliser. Instead, they have to buy in mineral N fertiliser, because the N fertiliser requirement of the plants has to be covered anyway.

To solve the double environmental and operational problem, a) the N and P fertilizer flows must be decoupled and b) the disposal problem of the farm's own organic surplus must be solved.

Previous solutions have relied on redistribution by transporting organic fertilisers (liquid manure, biogas fermentation residues, etc.) to other farms with fertiliser needs. However, these fertilizers have a high water and low nutrient content. A transfer of the surpluses (N, P export) therefore often fails due to the costs, because organic fertilizers are only worth transporting over very short distances. From regions with high livestock density, however, it even has to be exported to other (federal) countries ("liquid manure tourism"). In addition, although the receiving farms are entitled to use the fertiliser, it does not make sense from an environmental and economic point of view.

Our proposed solution consists in a procedural separation of the material flows from organic operating surpluses into a carbon (C) flow to functional materials, e.g. for use in biogas purification, a P flow by separation to transportable mineral (N,) P fertilizer and a residual flow with greatly reduced C, P but high N residue and water for irrigation and N-fertilization of the farms own fields.

In this way, the required resources remain on the farm (small cycle) and the surpluses become marketable products (large cycle).

The project applied for is intended to test the feasibility / practicability of this solution on the actually existing farm "Lindenhöfe", an experimental farm of the University of Hohenheim. The Lindenhöfe are ideal because they have the same structural problems with livestock farming and biogas plant with surpluses as the practice farms. On the other hand, the possibilities of recording the material and energy flows and implementing and evaluating pioneering solutions on the farm premises are much greater. In addition, there is already cooperation on a small scale (pilot plant of the process engineers on site) between the relevant institutes and facilities, which were also involved in the conceptual design of the application from the very beginning.