Thermal desorption of creosote remaining in used railroad ties: Investigation by TGA (thermogravimetric analysis) and Py-GC/MS (pyrolysis-gas chromatography/mass spectrometry)

• A two-step pyrolysis of railroad tie recovered creosote and produced clean feedstock.
• 280 °C-treated tie produced 77–83% energy yield and high recovery of creosote.
• Pyrolysis of 280 °C-treated tie produced traceable creosote and high bio-oil quality.

A two-step thermal process, an initial thermal treatment at mild temperature followed by a fast pyrolysis step, was investigated to recover wood preservatives and produce preservatives-free wood for production of high quality bio-oil from used creosote-treated railroad ties. During the initial thermal treatment at temperature of 280 °C for 10–30 min, the treated wood ties underwent a 20–25% weight loss with energy yield (77–83%). Energy yield at 280 °C was lower than that at 200 and 250 °C (92–97%) but higher than that at the 300 °C (64–74%). Recovery level of creosote at 280 °C was comparable to that at 300 °C. Fast pyrolysis at 450 °C of the 280 °C-treated wood ties produced high amount of levoglucosan and phenolic compounds with a traceable amount (1.7–1.9% of the total peak area) of creosote compounds.