Identification and biotransformation of lignin compounds during co-composting of sewage sludge-palm tree waste using pyrolysis-GC/MS

•Lignin biotransformation during composting of sewage sludge-palm waste.•Lignin derivatives as precursors of humic fraction studied using Py-GC-MS.•Py-GC-MS method and composting maturity.

The biotransformation of lignin components during co-composting of sewage sludge activated with palm tree waste was studied for six months using Py-GC-MS. Two main groups of compounds were distinguished. The first includes 7 compounds which occurred during the co-composting process listed here in decreasing order of abundance: toluene, 2,4-dimethylbenzene, ethylbenzene, styrene, 1-ethyl-2-methylbenzene, 4-methylphenol and 2-methylnaphthalene. The reduction of their concentrations during the process is due to metabolization and biotransformation into other compounds. A second group of 4 components showed concentrations that increased with co-composting time: phenol, benzofuran, ethylmethoxyphenol and dimethoxyphenol. These lignin constituents are probably released parallel with lignin degradation to become incorporated into humic substances.