Algae in animal feed For hygienic reasons it is forbidden to use manure directly for the cultivation of algae that are intended to be used as animal feed. This could cause the feed that is given to pigs – and possibly also consumers of pork – to be contaminated with pathogens. For this reason, manure is treated in the ECOFERM! concept to ensure that nitrogen and phosphorus are the only minerals used for algae cultivation. The organic fraction, which could contain pathogens, is largely converted into biogas for a CHP installation. Our study revealed nothing that stands in the way of algae being used in animal feed. One important condition is that the algae cultivators are GMP-certified (GMP = Good Manufacturing Practice). The use of minerals from manure as a nutritional source is also no longer banned. However, permission for this use can only be obtained after the process undergoes a thorough risk analysis, including relevant measurements. 113 Nutritional value of algae Algae are healthy for pigs and possibly also for chickens and farmgrown fish. Depending on the type of algae, they contain a high level of proteins (up to more than 50%), lots of iron and large amounts of healthy omega-3 and omega-6 fatty acids. In addition, they contain anti-oxidants such as beta carotene (a precursor of vitamin A), sterols and substances with an anti-bacterial and infection-inhibiting effect. In view of these latter properties, the use of algae as animal feed could make a substantial contribution towards reducing the use of antibiotics in animal farming. There appears to be a sufficiently large market for algae as an ingredient in feed for fish and agricultural animals. Given current prices, the value based on nutrients and fatty acids is €550- 600 per tonne of algae when used as feed for fish and young pigs and chickens. On top of that, the presence of health-promoting components could potentially add a further €100 to 300 per tonne of algae. Technical and economical feasibility As noted, ECOFERM! is a concept – a challenging concept that has not yet been realized in practice. Many of the techniques, such as manure separation, fermentation and stripping and algae cultivation are already applied in practice. The big challenge is to combine them into an effective ECOFERM! system. The technical evaluation shows that the cycles can be closed to a reasonable degree. Only the reclamation of sufficient nitrogen remains a problem with the selected route. Algae absorb nitrogen and phosphorus in the ratio of 7:1 whereas the N/P ratio from manure treatment is 3:1. Another critical point concerns the precipitation of phosphorus in the form of calcium phosphate. During this process, quite a lot of organic material ends up in the precipitate, so there is a small risk of pathogenic contamination. If only pig manure is fermented, then the production of electricity from biogas will be insufficient to meet ECOFERM!’s own Pagina 121
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