2000 Compost spreader

Due to the increasingly strict legal regulations regarding the handling and utilization of organic waste as spreading material on agricultural land, greater attention will be paid in future to compliance with maximum area-related spreading quantities.

At present, compost is spread using universal spreading vehicles. These spreaders are primarily designed for spreading various types of solid manure and sewage sludge. However, the physical properties of these differ considerably from those of composts such as fresh or finished compost from composting plants. As a result, the universal spreader wagons can only be used under optimum conditions for precise dosing and even distribution. The spreading problem is further exacerbated by the high susceptibility of the distribution to the effects of crosswinds, which occurs to a greater extent with the low density of the finished compost.

The aim of a project funded by the German Federal Environmental Foundation and carried out in cooperation with the Bergmann company in Goldenstedt was to develop an exact distribution device for spreading organic compost. This spreading device is to be integrated into a conventional universal spreading vehicle. The following development goals were set:
- better quantity dosing, tolerance < 15 wt.%,
- more even quantity distribution, lengthwise and crosswise to the direction of travel with a VK < 15 %,
- spreading option in standing crops,
- working width corresponding to a tramline spacing of 12 m,
- low susceptibility to crosswinds,
- low odor emissions,
- near-series prototype, can be produced in series,
- adaptation of the spreading system to a series vehicle.

As the low mass of the spreading material means that targeted and wide trajectories are not possible, the development goals cannot be achieved by further development and optimization of the conventional spreading technology alone. For this reason, a new concept for the entire spreading device was developed using preliminary tests and design methodology tools. Both mechanical and pneumatic systems were considered in the system evaluation. The evaluation decided in favor of a mechanical system. The reasons for this are the bulky and powdery spreading material components and the strong cohesive properties with increased material moisture.

The properties of the grit also make it necessary to fulfill the sub-tasks of dosing, distribution and transport to the distribution units using separate sub-systems. Due to the low bulk density of approx. 300-500 kg/m³, it is only possible to achieve the given development goals by using several decentralized distribution systems. In terms of functional safety, effort and costs, the system of a bunker discharge screw was considered to be the most suitable for dosing. The advantage of this subsystem lies in its functional reliability, even with unfavorable spreading material properties such as increased moisture and sometimes bulky material components. These considerations also led to the use of augers as a transport system to the distribution equipment, with the auger troughs taking over the function of the booms. Turntables equipped with a blading system proved to be the most suitable distribution device. This functional principle could be adopted from conventional agricultural distribution vehicles. In order to achieve a symmetrical spreading pattern from the overlap of the individual spreading patterns, four individual turntables were distributed across the width of the vehicle, with the outer turntables located at the ends of the retractable augers. Guide plates are fitted at a short distance from the turntables in order to produce a more controlled spreading pattern with fewer segregation phenomena and to achieve lower crosswind sensitivity by increasing the kinetic energy of the substrate particles shortly before they hit the target surface. To reduce the construction and financing costs, the dosing screws were designed so that they also take over the transport to the inner turntables. Here you can see a sketch of the system: 1-Dosage augers / unloading and dosage augers, 2-Transport augers / conveyor augers, 3-Drehteller / rotating disks.

In order to be able to maintain the required distribution accuracy with different spreading material properties, the rotary discs are pivot-mounted, allowing the feeding area of the material on the rotary disc and its inclination to be changed. To further influence the spreading pattern, the speed of the turntables can be continuously adjusted. The mass flow is controlled by regulating the speed of the metering screws. The drives are integrated into a separate hydraulic system to realize the infinitely variable speed change and to provide the necessary drive power. This system consists of a PTO-driven hydraulic pump, a control valve block, the tank and the drive motors. The link between the crop mass flow and the volume flow of the metering screws is established by means of a calibration test. For this purpose, the vehicle is equipped with a weight measuring system. The adaptation of the mass flow to changing driving speeds is realized by a speed measuring system. In the final phase of the project, a computer-aided control system on board the vehicle is planned for setting the control variables.

The research project ended in 1999.

Publications :

• Stieg, D.; Wagner, G. and Krause, R. : Exaktstreuer für Bioabfallkompost - Entwicklung eines Exaktdosier- und Verteilsystems in Landtechnik 1, 53. Jg., Fachzeitschrift für Agrartechnik und ländliches Bauen, 10-11, 1998, Darmstadt, ISSN 0023-808
• Stieg, D. and Krause, R. : Spreading compost with precision. Eilbote - The magazine for agricultural machinery. No.20, 46. vol., 26-27, 1998, Winsen/Luhe
• Stieg, D.; Wagner, G. and Krause, R. : Compost spreading with high precision. VDI Report No. 1356, 97-100, 1997, Braunschweig, ISBN 3-18-091356-8
• Stieg, D. : Distribution systems of compost spreaders: With tines, chains and flails, profi-magazin für agrartechnik. No. 9, 1998, Münster ISSN 0937-1583
• Wilmer. H. : Big all-rounders ?! Three 18 t high-capacity spreaders compared. - profi-magazin für agrartechnik. No. 6, 1999, 20 - 25 , Münster, ISSN 0937-1583

Project work : Wille, Volker : Possibilities of an improved transverse and longitudinal distribution of compost, FG Agrartechnik, 1994

With the kind support of :

Company Fehr, Kassel - Company Bergmann, Goldenstedt - Deula, Witzenhausen