نبذة مختصرة : The main objective of the project was the identification and analysis of new technical concepts for centralized biogas plants, which would make them less dependant on organic waste supplies, and thus be economically self sustained mainly on manure supplies. The analyses have been carried out as system analyses, where plant concepts have been evaluated in connection with agricultural areas. 8 scenarios where analyzed, of which 2 were reference scenarios. One without a biogas plant, but with on-farm separation in order to reach phosphorous balance in the area by exporting fiber fraction (Scenario 0) to other regions, and one with a conventional centralized biogas plant with a post separation facility, likewise to enable the export of surplus phosphorous (Scenario 1). The remaining 6 scenarios are: 1a. Serial digestion in two digesters, and partial post separation of digested manure so phosphorous balance in the area is obtained. 1b. Conventional centralized biogas plant, post separation and recycling most of the fiber fraction. Export of fiber fraction till phosphorus balance in the area is obtained. 2. On farm separation of major parts of pig manure. Fiber fraction supplied to the biogas plant and mixed with remaining conventional slurry until a dry matter content of 10% in the biogas plant has been reached. The thin fraction remains on the farms and is utilized as a fertilizer. Post separation of the digested manure, pretreatment (wet oxidation) and recycling most of the fiber fraction to the digesters. The remaining fiber fraction is exported until phosphorus balance in the area is reached. 2a. Same as 2, but pressure boiling of the fiber fraction in stead of wet oxidation. 2b. Same as 2, but no on farm separation, which means that the entire manure amount in the area is supplied to the biogas plant. 2c. On farm separation until 10% dry matter content in input is reached, no pretreatment but post separation until phosphorus balance in the area is obtained.
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