Co-composting bamboo powder and tea leaves affects the composting rate and improves compost quality

Abstract

The disposal of bamboo processing residues and spent tea leaves is an environmental concern, but their reuse as compost can be not only reduce the amount of waste, but can also convert the waste products into valuable resources that provide nutrients to crops and improve soil fertility. Combining bamboo, with its high C/N ratio, and tea leaves with high nitrogen content may produce high quality compost, but its effect on composting rate and nutrient content is unclear. This study evaluated the effect that co-composting of bamboo powder and tea leaves has on composting rate and quality. Three compost types were prepared: B100 (600 kg bamboo powder), B40 (240 kg bamboo powder and 360 kg tea leaves), and B20 (120 kg bamboo powder and 480 kg tea leaves), with two replicates each. The mixed materials were allowed to compost in an outdoor compost shed for 98 d. Peak composting temperatures occurred later for B40 and B20 than for B100, suggesting that the microbial activity of the co-composts may have been reduced during the early composting stage. However, the C/N ratio, NH₄⁺/NO₃⁻ ratio, chemical oxygen demand (measured in hot water extracts), and juvenile plant growth experiments using komatsuna (Brassica rapa var. perviridis) revealed that the composting rate was higher in B20 than in B40 and B100. Additionally, at the end of the composting period, B20 had a C/N ratio of approximately 10 along with high total nitrogen and NO₃⁻-N content, indicating an improved compost quality for use as a fertilizer.