Optimization of conditions for thermal treatment of rice bran using an accelerator including an organo-iron compound

A method for thermal conversion of raw organic waste (ROW) to a compost-like material (CLM) with higher levels of unsaturated carbohydrates, nitrogen- and oxygen-containing compounds was developed, in which rice bran and an organo-iron compound were employed as a model ROW and the accelerator, respectively. To evaluate the qualities of CLMs, organic substances of an acid insoluble fraction of alkaline extracts (AIAEs) from a CLM were structurally characterized by elemental analysis, pyrolysis–gas chromatography/mass spectrometry and FT-IR. The levels of unsaturated carbohydrates, and nitrogen- and oxygen-containing compounds in the CLM samples were increased by long-term treatment (60 °C for 5 days, 170 °C for 3 days). In particular, the high lipid content of the AIAEs, which was indicative of inadequate digestion of CLM components, was dramatically reduced in the presence of the accelerator.