The present study reports mathematical modelling of palm oil mill effluent and palm-pressed fiber mixtures (0% to 100%) during vermicomposting process. The effects of different mixtures with respect to pH, C:N ratio and earthworms have been optimized using the modelling parameters. The results of analysis of variance have established effect of different mixtures of palm oil mill effluent plus palm press fiber and time, under selected physicochemical responses (pH, C:N ratio and earthworm numbers). Among all mixtures, 60% mixture was achieved optimal growth at pH 7.1 using 16.29 C:N ratio in 15 days of vermicomposting. The relationship between responses, time and different palm oil mill waste mixtures have been summarized in terms of regression models. The obtained results of mathematical modeling suggest that these findings have potential to serve a platform for further studies in terms of kinetic behavior and degradation of the biowastes via vermicomposting.
By growing urban population, Iran faces numerous environmental issues and solid waste management is on the top of these problems. Studies showed that a daily average of 700-1000 g of wastes are produced per person in Iran, in which organic waste accounts for a significant amount. On the other hand, hospital waste represents a part of the wastes, which need careful consideration from the environmental point of view. In the present study, the amount, composition, and management of urban and hospital wastes were evaluated in 7 Iranian metropolises, which account for about 30% of the population and produce about 35% of the country wastes. Based on prior surveys, landfill method is the current main method for waste management in these cities, which is generally not completely sanitary and therefore causes many environmental problems. The other common methods for waste management in these cities are composting of organic wastes, and the use of waste conversion methods to energy. However, the latter is ongoing only in Tehran which also includes some limitations. Therefore, the study also evaluated the future perspectives and feasibility of waste-to-energy conversion as a promising economic route for waste disposal.