The effect of sawdust as a bulking agent on the in-vessel composting of food waste in a manually-turned drum

Abstract

Composting is one approach for recycling organic waste, that mostly consists of kitchen and food residue waste. This can be done at household level by use of in-vessel composters. Sawdust as a bulking agent was used to assess the effect of bulking agent:food waste (BA:FW) ratio on the stabilising process of food waste in an in-vessel composter drum. The drum was turned manually at hourly interval at 2 rpm in 5 minutes. Three BA:FW v/v ratios were studied; 2:1,3:1, and 4:1 using more or less same food waste composition. Temperature, bulk density, moisture, pH and porosity were monitored over a period of 15 days. Temperature generally rose to above 45oc within the first 5 days in all the ratios and started to fall after 10days except for 2:1 ratio that remained high even at the 15th day. The moisture content increased during the process with the highest values occurring in the 2:1ratio. There was an semi-logarithmic relationship between the bulk density and porosity across all BA:FW ratios. The pH increased from the initial value of about 4.5 to between 6 and 7.5. Except for less rapid attainment of thermophilic temperature and sustainability, the 4:1 ratio generally achieved the best composting conditions. This study appears to suggest that well rationed BA:FW mixture may be stabilised rapidly in an in-vessel composter enabling a high turn-over to handle the food waste generated in a household.