Polyurethanes are synthesized from polyols, which can be fossil- or plant-sourced. The goal of this study was to investigate how the use of plant-sourced polyols, i.e., the ricinoleic acid triglyceride (the main component of castor oil, CO) and lignosulfonate, impacts the properties of the materials, as well as of their composites reinforced with sisal fibers. To reach this objective, the properties of polyurethanes from plant-sourced polyols were compared with those of their counterparts synthesized using fossil-sourced diethylene glycol (DEG) and polyethylene glycol (PEG). As far as is known, this approach is unheard-of. Polyurethanes and lignopolyurethanes (neat PUs and LigPUs) were synthesized under temperature and compression molding from CO, DEG, and PEG (PUs), and in LigPUs, 30 % of the polyols were replaced by lignosulfonate. Under the same conditions, composites were formed simultaneously with the syntheses after adding sisal fibers (30 % by weight, 3 cm in length) to the reagents. A notable characteristic is the impact strength of the neat PU and PU sisal composites in which PEG (approximately 750 Jm−1and 850 Jm−1, respectively) and CO (unfractured and approximately 850 Jm−1, respectively) were used. Flexural tests showed that the use of CO as a polyol in the synthesis of the neat PUs and LigPUs and composites imparted elastomeric characteristics to the materials. Similar properties were noted when PEG was used as a polyol, except when it was used together with lignosulfonate in the sisal reinforced composite. A high content of renewable raw material was used in the LigPU sisal fiber composites, meeting expectations regarding the sustainability of the processes, as well as the potential to contribute to the development of the bioeconomy. The materials were prepared using renewable reagents largely available, with no solvent or catalyst use, through a simple process, and no byproducts generated. These features favor the scaling-up of the process. Also, the bio-based materials exhibited good and diverse properties, which qualify them for various applications in which polyurethanes obtained only from fossil-sourced raw materials are used.