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© Thünen-Institut
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Institute of

AT Agricultural Technology


Fertilizer concentrates from residuals (DüaR)

The illustration shows the interior of the composting container when liquid manure is being applied to a bed of straw
© Thünen-Institut
The illustration shows the interior of the composting container when liquid manure is being applied to a bed of straw

Development and testing of an innovative and environmetally sound manure and digestate processing for the production of a solid humus product with phosphorus enrichment and simultaneous nitrogen separation in a transportable form as a liquid fertilizer.

In some regions of Germany livestock produces more nitrogen and phosphate as can be used for fertilizing. In other regions these nutrients are required. The Thuenen institute is investigating how manure transport  can be  made marketable.


Background and Objective

In regions with intensive livestock huge amounts of nitrogen and phosphate accumulate. On basis of tightened demands for fertilizing these key nutrient amounts cannot be used completely for fertilizing in the local area because nutrient surpluses may contribute to environmental impacts. In other regions these nutrients are required. However, the liquid manure transport is inefficient so far because of high water contents and missing storage capacities.

Aim of the project is the production of nutrient concentrates which are marketable, transortable and well calculabe in fertilizing effects using a technical conditioning process. Within the process a solid humus product should be produced with preferably high phosphate and potassium contents one the one hand and a high concentrated ammonium sulphate as a liquid ferilizer on the other.

In the process manure mixed with structure materials as straw should be composted under thermophilic conditions. Odorants should be degraded and unwanted seeds be inactivated. An extensive water evaporation is aimed to gain concentrated nutrients. The exhaust air from composting will be cleaned in a two-step chemically operating scrubber to produce a high concentrated soluble ammonium sulphate.


Target Group

  • Animal farmers with nutrient surplus
  • Producers of composting and exhaust air treatment operations
  • Consulting institutions for animal keeping (chambers of agriculture, agricultural organisations)
  • Fertilizer trading enterprises


The research project should be realized in practical scale on a animal farm in cooperation with the Chamber of Agriculture in Lower Saxony and a farmer. Following project steps are planned:

1. Planning and dimensioning of the testing plant.

2. Concluding release of planning documents

3. Construction and startup of the testing plant

4. Test operation

5. Final report and deconstruction of the test facility

In the project frame mass and nutrient balances will be determined using different raw materials, process data as tempertaure runs will be registered and the entire process will be assessed. An economic process assessment will be made by the chamber of agriculture. The economic assessment of the process will be made by the chamber of agriculture.


Data and Methods

Input and output materials will be recorded in view of mass, nitrogen and phosphorus. Outgoing from these data mass and nutrient balances will be calculated for the projected material mixings used in the composting process. The exhaust air from the composting process will be cleaned in a two-step srcubber, in which a liquid and concentrated ammonium sulphate is be produced. The ammonia separation efficiency will be calculated by online measurements in raw and outlet gas over a longer time period. The composting process will be controlled by temperature sensors.

Our Research Questions

Is it possible to realize a stable working manure and structure material composting resulting in marketable products with the designed process?

Is it possible to secure a stable working ammonia separation in  a thermophilic working scrubber and which nitrogen concentrations can be achieved in the liquid phase?

Preliminary Results

13,700 liter (72 %) of liquid manuer and 5,400 kg (28 %) of straw were combined fo form a compost during a three month trial period. At an average internal compost temperature of approx. 40 °C 3.4 tons of water could be evaporated. This equates to approx. 25 % of the water in the compost material. Approx. 13 % of the nitrogen contained in the compost were separated and collected completely in the chemical working scrubber.

A permanent process operation was not possible so far due to several technical problems in the composting process.

Involved external Thünen-Partners

Funding Body

  • European Union (EU)
    (international, öffentlich)


2.2019 - 4.2023

More Information

Project funding number: 276034030000096
Funding program: Innovationsförderung
Project status: ongoing

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