methane (CH4) and ammonia (NH3) in the stable. The losses in the new building are low, as a result of the immediate separation process and the removal of manure and urine. The amounts lost in the old buildings are greater. The slurry from the old building and the faeces from the new one go together to the manure fermenter. In practice, the composition of the faeces is produced, with a dry matter content of 12.8%. In reality, it is slightly less than this, because some of the manure is converted into 115 digestate is 6 to 7 g N/kg manure and 2.5 to 3 g P2O5/kg manure. The yields of biogas lay between 30 and 40 m³ per ton. With the help of a screw press or centrifuge, the digestate was separated into a solid fraction (3,244 tons a year) with 28% dry matter, and a liquid fraction (12,846 tons a year) with 5% dry matter content. Part of the solid fraction was dried using the residual heat from the gas turbines. The dried product is exported, in order to meet the new legislation that requires 35% of the excess phosphorus (in 2016) to be processed and send abroad. The liquid fraction is used in part for fertilising the duckweed. Various tests were carried out in 2015 for thermally or mechanically (using membrane distillation or ultrafiltration) separating the liquid fraction into pasteurized ammonia water (which can serve as a clean fertiliser for cultivating duckweed) and a pasteurized thick part (a syrup), which can be thickened even more (by being dried) and sold. The province of Gelderland financed these tests. They showed that it is technically possible to further separate the liquid fraction with the help of residual heat. However, the separation unit was very much liable to break down and therefore requires further development before being ready to be launched on the market. The suppliers are working on a more robust system. For that reason, the liquid fraction is still being spread directly onto the land. CH4 a year and 24 tons of NH3 a year. The fermenter regularly broke down due to blocked pumps, insufficient biological stability, and peaks in sulphur concentration levels. They ran at around 60% capacity for long periods of time in order to guarantee sufficient processing time. The capacity was slowly increased as 2015 progressed, to around 70% at the start of 2016. The overall production of electricity from biogas amounted to 400,000 kWh per year. Burning the biogas in the CHP unit not only produces electricity, but also releases heat. The heat from the exhaust gases (300°C) is reclaimed and transported to an adjacent farm via a heat network. A large quantity of water at 85°C is needed every day for this purpose. It goes towards providing warm milk for the white veal calves on the neighbouring farm. This additional use has lifted the overall efficiency from the turbines to around 82%. The calves also produce a considerable quantity of heat. This has been calculated at 43.8 MJ per calf per day (assuming an average size for the calves), based on 507 W per calf. This heat can be used for heating the air in the greenhouse. Energy production The losses in the stable caused by excretion and organic fermentation on the slatted floors amounted to 87 tons of manure a year, 37 tons of Pagina 122
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