Topic

As the amount of land available for growing bio energy plants in Central Europe is limited, it is particularly important to examine the suitability of by-products for biogas production. Currently, about half a million horses are kept in Germany, producing approximately 4.5 million tonnes of horse manure per year. Hitherto this material has barely been used as a means of generating energy because it has not been authorised as a fuel and because its high fibre content has led to problems in processing the material when it is used to generate biogas. The University of Hohenheim has therefore set itself the goal of developing a functioning process for producing biogas from horse manure with particular emphasis on examining the mechanical processing of horse manure. At the same time, an assessment was to be made of the feasibility of the process as well as an energetic, ecological and economic assessment.

Aims

• Increase the usable part of horse manure in biogas plants by shredding the horse manure to increase its surface area and thus the working surface for the microorganisms that break down the manure
• Providing an optimum supply of micronutrients to the microorganisms
• Determination of special requirements that have to be met for the digestion of horse manure by systematic tests and process engineering tests in the laboratory

Measures

• Recording of the methane yield potential from the digestion of differently prepared horse manure substrates of different origins and composition by batch tests
• Examination, whether the content of trace elements is sufficient for a stable biogas process where there is a high proportion of horse manure or whether this content needs to be supplemented
• Determination and definition of the optimum conditions for the digestion of horse manure on a laboratory scale by variations in processing, substrate composition and process temperatur
• These tests were conducted in digesters operating on a continuous basis.
• Further tests were to take place on an industrial scale at the research biogas plant of the University of Hohenheim.
• An energy balance of the process was to be carried out during these tests.

Focus

• Transfer of the results to industrial scale
• Mechanical preparation of the horse manure at the research biogas plant of the University of Hohenheim with a cross-flow shredder
• Comparsion of a prepared substrate with a untreated horse manure in digesters running in parallel
• Recording of the energy required for the processing during the tests
• Evaluation of the cost-effectiveness of the digestion of horse manure
• Survey with operators who use horse manure as a substrate