Development of the model for integrated organic waste management by applying the principles of circular economy

[A. Momčilović Ristanović]

[16], 184 str.

Biografija autora: str.193. Bibliografija: str.142 -152.

Waste management

Organic waste is a biodegradable resource with high potential for nutrient and chemically bound energy recovey yet mostly landfilled. To enable its sustainable use, a model for integrated organic waste management was developed. Based on circular economy principles, the model allows for optimized inclusion of locally available feedstocks into closed material and energy loops. The mathematical model is based on a physical model that links the sources of organic waste with the locations of its transformation through composting and anaerobic digestion, as well as with the points of nutrient recovery in the form of compost and digestate and the production of energy required for plant operation and transport. The mathematical formulation of the closed loop is developed through sections describing the material and energy flows of the system; the model itself is optimized in Wolfram Mathematica. Model analysis is conducted through six simulations organized into three research phases: exploratory, evaluative and validation. In the exploratory phase the model’s ability to determine optimal feedstock mixing ratios for anaerobic digestion and composting, and for assessing the potential for closing material and energy flows, is examined through multicriteria optimization. Within this phase, key system parameters are optimized: C/N ratio, minimum lignin content and minimum phosphorus content of 1% in the feedstock mixture; establishing conditions for sustainable treatment. The evaluative phase includes ten scenarios of organic waste management differing in the number of feedstocks and the combination of treatments. The efficiency of scenarios is assessed using a developed set of indicators: the degree of feedstock inclusion in circular economy flows, material and energy leakage and the degree of material and energy circularity. The results show that the scenario combining two treatment methods and two feedstocks achieve loop closure with low leakages and a high circularity rate, while adding an additional feedstock increases the inclusion rate but also leads to a higher material leakage in the form of compost. Increasing the number of feedstocks to four reduces the overall inclusion rate, indicating system limitations with introduction of larger number of feedstocks. A particular focus is placed on tracking the change of C, N, P and K and the transformation of their forms from organic to inorganic, plant-available fractions in compost, with the aim of satisfying the nutrient requirements of a specific crop. The results confirm that the model can optimize a composting mixture which composition meets the needs of barley. In the validation phase, modeled optimal feedstock mixtures are compared with experimentally obtained mixtures for defined C/N ratio in a biogas plant, confirming the applicability of the model under real operating conditions. Future research will focus on improving the mathematical model by incorporating a larger set of criteria, as well as on assessing the system’s circularity in relation to the number and types of included raw materials.

integralno upravljanje organskim otpadom, cirkularna ekonomija, matematički model, fizički model, odnos C/N Višekriterijumska optimizacija; Indikatori cirkularne ekonomije; Povraćaj nutrijenata

integrated organic waste management, circular economy, mathematical model, physical modelc, C/N ratio, multi-criteria optimization, circular economy indicators, nutrient recovery

628.473.4:556.013(043.3) 338.1:502.131.1(043.3)

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