Utilization of rice straw ash during composting of food waste at different initial C/N ratios for compost quality

The increases in rice productivity and size of paddy areas have led to the huge excess of rice straw in paddy field after the harvesting season. Rice straw can be used as a soil conditioner by composting process instead of on-farm burning that been practice by farmer which can caused pollution. Nevertheless, it required a long time for the decomposition process to happen since the main fraction of rice straw is lignocellulose which was difficult to degrade. Thus, the objective of this study was to evaluate the effect of different initial C:N ratio used (20,25,30) during composting of rice straw ash and food waste towards compost quality in term of pH, temperature, moisture content, C:N ratio and germination index. A laboratory-scale bin composter reactor was used during 30 days of composting period. The composting mixture with initial C:N ratio of 30 maintained the temperature exceeding 55°C for more than 3 days but the composting mixtures with initial C:N ratios of 20 and 25 did not meet the requirement of pathogen destruction. The maximum final C:N ratio and germination index obtained at a composting mixture with initial C:N ratios of 30 compared to the other two composting mixtures. The pH and moisture content value in three composting mixture was recorded in a range of 7-9 and 40-60% for mature compost to establish.