Performance of mature compost to control gaseous emissions in kitchen waste composting

Highlights: • Mature compost could mitigate gaseous emissions during kitchen waste composting. • Mixing mature compost reduced 58.0%NH₃, 44.8%CH₄, and 73.6%N₂O emissions. • Mixing mature compost reduced total greenhouse gas emissions by 69.2%. • Mature compost covered on the composting pile contributed to less gas reduction. • Mixing mature compost conserved nutrients and thus enhanced the compost quality. -- Abstract: This study investigated the performance of mature compost to mitigate gaseous emissions during kitchen waste composting. Cornstalk was mixed with kitchen waste at a ratio of 3:17 (wet weight) as the bulking agent. Mature compost (10% of raw composting materials on the wet weight basis) was mixed into or covered on the composting pile. A control treatment without any addition of mature compost was conducted for comparison. Results show that mature compost did not significantly affect the composting process. Nevertheless, gaseous emissions during kitchen waste composting were considerably reduced with the addition of mature compost. In particular, mixing mature compost with raw composting materials reduced ammonia, methane, and nitrous oxide emissions by 58.0%, 44.8%, and 73.6%, respectively. As a result, nitrogen could be conserved to increase nutrient contents and germination index of the compost product. Furthermore, the total greenhouse gas emissions during kitchen waste composting were reduced by 69.2% with the mixture of mature composting. By contrast, a lower reduction in gaseous emissions was observed when the same amount of mature compost was covered on the composting pile.