116 Electricity consumption The ECOFERM not only produces a lot of electricity, it also consumes a great deal. There are 27 ventilators which, running for 8,400 hours a year, consume 390,000 kWh. The true amount is actually some 20% lower as a result of regulating the frequency. Apart from the ventilators, the amount of electricity consumed is 368,000 kWh. The ventilators use up a lot of energy in order to transport the air to the greenhouse via the biobed of wet wood chippings. In order to reduce the emission of ammonia using a different method and thus cut the amount of electricity consumed, an ionization experiment was held in 2015, using carbon brushes. Although this had the effect of substantially reducing the concentration of fine particles, the concentration of ammonia was hardly reduced. Other equipment that use electricity includes the manure scraper, the fermenter, and the CHP unit, as well as the pumps in the duckweed pond (see the following table). Ventilation Separating manure Fermenter and power unit Duckweed production Total consumption by farm 8,400 7,500 8,400 2,500 hours/year 312,000 kWh/year hours/year hours/year hours/year 20,700 kWh/year 40,000 kWh/year 2,500 kWh/year 375,200 kWh/year Because it produces 400,000 kWh of electricity every year from the fermentation process, the ECOFERM is completely self-sufficient, and is actually able to provide around 7% of its electricity to the national grid. CO2 production The production of CO2 by the 3,500 calves amounts to 6,494 tons a year. A hectare of duckweed producing 25 tons every year is capable of absorbing more than 30 tons of CO2 in that time. Some 29 tons of oxygen per hectare are produced. That means that just a small proportion of the CO2 is usable in the cultivation of the duckweed. A description of closed cycles In summary, the closed cycles on the ECOFERM farm can be described as follows. Due to the removal of fresh manure and the fermentation of the solid fraction, an 80% reduction in methane emissions has been achieved in the new building. This is a reduction across the farm as a whole of around 35%. The formation of ammonia has been cut by 50% by separating manure under the slatted floors in the new building, after which another 70% of the remaining emissions is removed from the air. The reduction in ammonia emissions in the new building therefore amounts to 85%. The fermenter provides 107% of the farm’s own electricity needs, and also produces heat that is used elsewhere. In addition, some of the heat and the CO2 from the animals was used for the growth of the duckweed. Pagina 123
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