Effect of bulking agents on maturity and gaseous emissions during kitchen waste composting

• Composting of kitchen waste with BA formed mature compost and reduced mature time.
• Composting of kitchen waste with BA decreased CH4 and N2O emissions.
• Composting of kitchen waste with BA had little impact on NH3 emissions.

This study investigated the effect of bulking agents on the maturity and gaseous emissions of composting kitchen waste. Three different bulking agents (cornstalks, sawdust, and spent mushroom substrate) were used to compost kitchen waste under aerobic conditions in 60-L reactors for a 28-d period. A control treatment was also studied using kitchen waste without a bulking agent. During the experiment, maturity indexes such as temperature, pH value, C/N ratio, and germination index were determined, and continuous measurements of leachate and gaseous emissions (CH4, N2O, and NH3) were taken. The results showed that all of the composts with bulking agents reached the required maturity standard, and the addition of spent mushroom substrate gave the highest maturity (C/N ratio decreased from 23 to 16 and germination index increased from 53% to 111%). The bulking agents also reduced leachate production and CH4 and N2O emissions, but had little impact on NH3 emissions. Composting with sawdust as a bulking agent was found to emit less total greenhouse gas (33 kg CO2-eq t−1 dry matter) than the other treatments.