Effect of Sawdust and Grass Clippings as Bulking Materials on the Quality of Compost

Abstract

The increase in student population has led to a corresponding increase in the generation of waste on the Campus of the Kwame Nkrumah University of Science and Technology. Composting of the biodegradable portion of waste is seen as a better option to reduce the volume of waste and manage it at the same time. This study hence aimed to investigate the effect of some bulking materials on the quality of compost after the decomposition of the biodegradable portion of the waste generated. Bin composting was employed for this analysis. Composting was conducted over a 60 -day period at the sewage treatment plant on the KNUST Campus. Wastes comprising of food waste, sawdust, and grass clippings were mixed in ratios of 1:1, 1:2, and 2:1 (v/v) ratio for sawdust/food waste (SSD 1:1, SSD 1:2, SSD 2:1) and grass clipping/food waste (SGC 1:1, SGC 1:2, SGC 2:1). Turning of compost was done manually at three days interval during which the volume was also recorded. Temperatures were taken on daily basis, three times within a day at 8 am, 12 pm and 4 pm respectively. Volume of all bins reduced as percentage organic matter decreased leading to an increase in percentage ash to between 39. % and 64.5 %. Percent organic matter loss was highest in the grass clipping/food waste treatments compared to the sawdust/food waste treatments. By the end of eight weeks of analysis, the grass clipping/food (SGC 1:1, SGC 1:2, and SGC 2:1) waste formulations were seen to decompose faster than the sawdust/food (SSD 1:1, SSD 1:2, and SSD 2:1) waste formulation. The grass clipping/food waste ratios (especially the SGC 2:1) therefore gave better compost in terms of the quality since rate of decomposition was faster compared to the sawdust/food waste.