Fabrication and Evaluation of House Scale Green Waste Composting Machine

In this study, a U-shaped reactor with aeration, heating and stirring systems was designed for composting process. The length, width and height of reactor were 110, 66 and 70 cm respectively. The experiment was carried out at different aeration rate (0.2, 0.4 and 0.6 Lit/min.Kg DM) and time (0, 19, 38, 57, 76, 96 hour). The agitation speed and temperature for the purpose of this experiment was; 55 and 1 rpm respectively. In order to adjust the C/N ratio and humidity of compost, two additives namely: zeolites and rice bran was used. The initial moisture content of waste material was between 60 to 65 percent in all operations. Results showed that the changes in the EC, germination index, and C/N ratio were significant. The EC of compost declined and the pH value increased at the end of process for all operations. The average C/N ratio of compost materials changed from 28 to 20.9 after 96 hours in the reactor. In traditional method, the C/N ratio reached to 19.8 after 21 days. Composting process time has a significant effect on germination index. The maximum germination index occurred at the aeration rate of 0.4 Lit/min. Kg DM which was 85 percent. Also the results indicated that the designed reactor with continuous rotating agitator, heating and air pressure was able to convert the food waste to compost within 96 hours. Results indicate that the proposed composting system can create a suitable environment for the growth and performance of micro-organisms in order to accelerate the decomposition of food waste.