AbstractThe acidic solvolysis of lignocellulose using a glycol solvent such as polyethylene glycol (PEG) is a promising process for separating its components and producing a valuable lignin product that can be used as thermoplastic and fusible materials. To decrease operational costs, a glycol solvent that is used as a solvolysis reagent must be recovered and reused. In the present study, PEG was recovered by the removal of water by evaporation from the supernatant after glycol lignin production by acidic solvolysis of Japanese cedar using PEG with an average molecular weight of 200 (PEG200). The recovered PEG200 worked as a solvolysis reagent and produced glycol lignin with appropriate yield. The thermomechanical analysis of glycol lignin from the fresh and recovered PEG200 systems exhibited two inflection points, which were assigned to a glass transition point (Tg) and a thermal softening point (Ts). The Ts of the glycol lignin from the recovered PEG200 system was higher than that from the fresh PEG200 system. These results suggest that the glycol lignin from the recovered PEG200 system had high thermostability as well as high thermal fusibility.