126 phosphate. The crop is capable of absorbing up to five times more phosphate and ten times more nitrogen per hectare than corn. Where there is significant acreage, this could be advantageous for recycling within the farm. Reducing emissions of greenhouse gases at the ECOFERM company is achieved on three fronts - the renewable electricity produced, the use of the heat, and the emissions that are avoided (methane). However, with the current prices of CO2 emission allowances, this does not really amount to very much. By adding duckweed to the diet, some savings in the feeding costs can be achieved. Calculations of the nutritional quality of duckweed have been based on the product being fresh (and therefore wet). This limits the proportion of duckweed in the diet. It is expected that with a certain degree of drying, more duckweed can be used, allowing for greater savings on the costs of the rations. However, these are offset by the drying costs. Any rise in the price of soya will have a positive effect on the ECOFERM ration savings. The costs of creating the cultivation system and the energy consumption of exploiting it are currently too high for ECOFERM to be economically viable. However, the large-scale production of duckweed is not a commonplace technique. The costs could be considerably reduced if greater efforts went into developing technology. In addition, the cultivation of duckweed in old and unused greenhouses, which are no longer suited for the production of vegetables, could give a completely different picture. Another higher-end market could come into view for duckweed as a fresh vegetable (water lentils) or as protein concentrate for the food industry. After all, the cultivation of and market for duckweed are still in their infancy. Given that a large number of societal goals are achieved in the ECOFERM concept − reductions in manure transport; fewer food and mineral imports; less use of land in the tropics and therefore less destruction of rainforest; strong increase in protein production per hectare (up to 10 times higher than with cultivating soya); circular business operations − it is worth considering to have a similar stimulation policy for the sustainable production of protein in the Netherlands as currently exists for sustainable energy. This would temporarily bridge the gap between costs and yields until the cultivation system has fully matured. an idea worth consideration. Calculations suggest that the CO2 emissions could then be markedly reduced. Using the heat from the animals to the full appears to compensate no less than 71 to 88% of the overall veal footprint. It is also conceivable that the nutrients can be used in the greenhouse to limit the fertilizer costs. This promising combination merits further research. References • Liere, J. van, G. Boosten, L. van Dijk, G. Hemke & A. Verschoor, 2011. ECOFERM De kringloopboerderij. Innovation Network, Utrecht. Report no. 11.2.248, ISBN 978–90–5059–432–5 There are also other ways of achieving valorization for the CO2 and heat that the calves produce. A link with a horticultural greenhouse is Pagina 133
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