Optimizing the System P .4 Material Flow Analysis The Material Flow Analysis for this test case greenhouse is as complete as we could make it, considering a number of uncertainties remaining in the system design. We made particular efforts to track not just the overall quantity of green waste traveling out of the system and then returning as compost, but to actually make estimates as to its elemental composition. We modeled estimates for N, P K, and C , breakdowns whenever available. In addition, we were able to model the generation of heat and CO2 from the animal, mushroom, and compost modules. The CO2 production from mushrooms and chickens alone is only around 2,4% of the level of output achieved by a commercial CO2 generator. However, the additional source provided by compost is very large and easily scalable, which means that it could be adjusted to provide the necessary supplemental CO2. Our conclusions are that the system can easily supply its own nutrients if it contains a livestock module. We have calculated that the nutrients contained in the compost stream relative to the demands of all the crops are more than fully satisfied, largely as a result of the chicken manure. In fact, the number of chickens in the model is quite a bit too high from a nutrient cycling perspective; they are largely included for their value as secondary products. In the next iteration of the design the number should probably be reduced quite significantly. To fully close the nutrient loop, we would ideally find a means of producing all fish and chicken feed on site. Both the fish and the chicken can consume some of the vegetable waste generated in the system to provide some of their nutrients. Vegetable waste is lower quality than commercially available feed, so it cannot be considered a complete source. Because tilapia are vegetarian, fish feed for their consumption can easily be generated by growing algae or other suitable plant matter. Chicken manure can be readily used as a fertilizer for algae. This is something that could be added into a subsequent model of the system. We have made rough estimates on electricity inputs, assuming that we have a moderate amount of supplemental lighting into the facility. We have assumed that the greenhouse will also be equipped with a FiWiHex system, reducing or eliminating its heat requirements. However, the energy aspects of this model are the least accurate. Polydome: High Performance Polyculture Systems 87 Pagina 86
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