Issues ECOFERM! consists of a new combination of partially existing techniques for daily manure removal, air treatment, manure fermentation, manure treatment and algae cultivation. Before we could start integrating these components, several critical issues in this concept were studied in greater detail. This concerned the following questions: 1. Is it technically possible to release minerals in sufficient quantities from the manure and urine for algae cultivation? 2. Is it technically possible to increase algae production to such an extent that the economic profitability is radically increased? 3. Is it legally permitted to cultivate algae with raw materials from manure and to subsequently feed these to pigs? If so, what is the value of algae as pig feed? 4. What are the chances of ECOFERM! being economically viable, i.e.: what does the business model look like and what are the critical issues there? To answer these questions, experiments in small-scale test set-ups were carried out at pig farms and several laboratory experiments were performed. In addition, interviews were also conducted with practitioners as well as legislative and inspection authorities. The data from the laboratory experiments were used to develop and evaluate an overall concept for technical and economic feasibility. The study paid only marginal attention to the utilization of ammonia, heat and CO2 emissions in the stalls. The experiments in this area must still take place. 111 Manure treatment Various techniques are available for treating manure. SUSTEC Consulting & Contracting BV investigated a process consisting of various steps for ECOFERM! Concept. Broadly speaking, this process involves separating the manure into a thin and a thick fraction. The thin fraction is stripped with steam, thus removing most of the nitrogen. Next, water is separated via inverted osmosis from the thin fraction for use as scrubbing or rinsing water. The thick fraction and the remainder of the thin fraction are mixed and then undergo thermo-chemical digestion before being fermented into biogas. The biogas, in turn, is purified and used for the production of electricity and heat. Finally, the phosphorus released by digestion and fermentation is taken from the thin fraction after separating the digestate using lime milk. By not only fermenting but also treating the manure, most of the nitrogen, phosphorus and CO2 becomes available in a relatively pure form as nutrients for the algae, thus strongly reducing the risk of pathogens being transferred from the manure to the algae. Fermentation without further treatment is also possible. In this case the digestate is fed directly into the algae pond. The algae produced in this manner may not be used as animal feed, but are suitable for use as e.g. biofuel. These algae fetch a lower price than those suitable for animal feed. Pagina 119
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