Heterogeneity of biochar amendment to improve the carbon and nitrogen sequestration through reduce the greenhouse gases emissions during sewage sludge composting

- Biochar additions increased the dehydrogenase activity during composting.
- Biochar have a potential impact on reduction of N losses and gaseous emissions.
- Biochar amendments shorten the thermophilic phase period.
- Biochar additions increased CO2 emission and reduce the ammonia losses.
- Biochar additions have significant correlation with carbon and nitrogen losses.

This study was performed to investigate the effects of biochar as an amendment to a gaseous emissions and sewage sludge (SS) composting dynamics. Six dosage of biochar [low dosage of biochar (LDB) - 2%, 4% and 6%; and higher dosage of biochar (HDB) - 8%, 12% and 18%] were amended to a mixture of SS and wheat straw (4:1 ratio on dry weight basis) and compared to control or without additive. The HDB significantly reduced CH4, N2O and NH3 emission by 92.85-95.34%, 95.14-97.30% and 58.03-65.17%, but not the CO2 emission. Meanwhile, humification results indicated that humic and fulvic acid 35-42% and 24-28% higher in the HDB amended treatments than those in the LDB and control treatments. The HDB significantly decreased total nitrogen losses and greenhouse gas emission, while LDB had significantly (p < 0.001) higher CH4 and N2O emissions. Due to effective performance of HDB, the 12% biochar was recommended to be used in SS composting practice.

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