Fenton oxidation as pretreatment for biomass gasification condensate: cost and biomass inhibition evaluation

Gasification transforming organic compounds into energy-rich pyrolytic gas, is a climate-friendly treatment option for biological solid wastes. The condensates arising from the pyrolytic gas valorization is owing to high concentrations of small molecular phenols, cyanides, nitrogen-heterocyclics, aromatics and ammonium, posing an environmental and health hazard. In this paper, the watery phase of the biomass gasification condensate from spent mushroom compost (SMC), with a chemical oxygen demand (COD) of 16.4 g/L and total nitrogen of 2.3 g/L, was pretreated by Fenton oxidation. The experiments were conducted at room temperature with an initial pH value of 3, 5 and 8.9, hydrogen peroxide (H₂O₂) dosages between 15 and 100% of the normalized stoichiometric ratio (NSR), and Fe²⁺ dosages corresponding to molar ratio of H₂O₂:Fe²⁺ between 10 and 30. Through respiration inhibition assays, the best operational condition for detoxification was determined at an initial pH 5 with 30% NSR H₂O₂ dosage and molar ratio of H₂O₂:Fe²⁺ at 15:1. The specific operational cost of the Fenton oxidation was calculated at 2.17 €/kg COD_elimination. In respiration inhibition assay, the oxygen consumption of wastewater after Fenton oxidation was increased by 316% in 3 days. In a 20 days' biogas production test, the biogas production was increased by 81%.