Field-Based Greenhouse Gas Emission Factors from Palm Kernel Shell Pyrolysis in Niger Delta

Palm kernel shells (PKS) are a major agricultural residue in the Niger Delta, commonly burned openly or left to decompose, releasing greenhouse gases into the atmosphere. While pyrolysis has been proposed as a cleaner alternative, no field-based emission data exist for operational PKS pyrolysis facilities in Nigeria or West Africa. This study measured greenhouse gas emissions from an operational pyrolysis facility in Cross River State, Nigeria. Stack emissions of CO2 and CH4 were monitored at the chimney outlet over 32 hours using a calibrated Aeroqual Series 500 monitor, while N2O was measured with a separate calibrated nitrous oxide detector, yielding 33 discrete measurements per gas. Mean concentrations were 677.24 ppm CO2, 46.88 ppm CH4, and 0.054 ppm N2O. Mass emission factors were 0.06064 t CO2/t PKS, 0.00153 t CH4/t PKS, and 0.0000050 t N2O/t PKS. Total emissions were 0.1048 t CO2e per tonne PKS, with CO2 contributing 57.86%, CH4 contributing 40.86%, and N2O contributing 1.27% of the climate impact. The measured CO2 emission factor was 36% lower than the IPCC Tier 1 default for biomass burning, while CH4 emissions were 62% lower, reflecting the controlled combustion conditions of pyrolysis. Uncertainty analysis yielded a 95% confidence interval of ±0.0089 t CO2e/t PKS for the total emission factor. This study provides the first empirical, field-based emission dataset for PKS pyrolysis in Nigeria, offering a validated input for national greenhouse gas inventories and life cycle assessments.