Analysis of emission profiles from charcoal produced from selected tree species by different pyrolysis methods

Abstract

The use of charcoal is associated with indoor air pollution where users are continually exposed to combustion pollutants with detrimental effects to their health. This study analyzed the emission profiles of selected domestically used charcoal produced by different pyrolysis methods. Charcoal samples from three tree species Acacia polyacantha, Acacia xanthophloea and Eucalyptus grandis, produced by both efficient and traditional pyrolysis were collected from charcoal producers in rural Kenya. The volatile organic compounds were collected using a fabricated chimney placed on clay cook stove such that smoke was vented to a glass cannula and condensed. Extracted volatiles were analyzed by gas chromatography-linked mass spectrometry. Twenty-two polycyclic aromatic hydrocarbons were identified together with other hydrocarbons. Polycyclic aromatic hydrocarbons found in the smoke extracts with known health effects included naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, fluorene, phenanthrene, anthracene, 1-methylphenanthrene, fluoranthene, benzo(a)anthracene and chrysene. There were significant differences in the concentrations of fluorine, naphthalene and pyrene emitted from Acacia polyacantha and Acacia xanthophloea prepared by traditional pyrolysis. From Acacia polyacantha, concentrations were naphthalene (110 µg/g), fluorine (72 µg/g) and pyrene (60 µg/g), while from Acacia xanthophloea, concentrations were naphthalene (140.42 µg/g), fluorene (97.35 µg/g) and pyrene (71.82 µg/g). Charcoal prepared by traditional pyrolysis emitted the highest number of polycyclic aromatic hydrocarbons and also had higher concentration of polycyclic aromatic hydrocarbons relative to the accepted 0.1–0.2 mg/m³ levels, while those prepared by efficient pyrolysis produced the lowest concentration. Therefore, there is need to use efficient pyrolysis methods of charcoal production.