The development of advanced new materials and technologies from bio-based products is immensely needed as the world is facing an ever-increasing variety of challenges due to increasing public concern about global sustainability. Polyurethane polymers present a broad spectrum of materials that are produced to meet the needs for various applications, from the automotive industry, building and construction to appliances, furnishing, marine and medicine. The general objective of the Thesis is to carry out comprehensive cradle-to-gate Life Cycle Assessment of rapeseed oil-based polyols suitable for polyurethane material production. The thesis is dived in three parts. Literature review (chapter I) aims to introduce the reader briefly with sustainability challenges, plastics with focus on polyurethane and state-of-the-art in natural oil-based polyurethanes and their environmental assessment. The methodological chapter (chapter II) aims to provide the reader with a description of the main Life Cycle assessment methodologies applied for rapeseed oil bio-polyol analysis. The results and discussion (chapter III) of this thesis are divided into four parts. Chapter III Part I presents Life Cycle Inventory of winter and spring rapeseed production in Latvia as a case study country in Northern Europe. In-depth and up-to-date agricultural practices used in the region under study data were provided by a large agricultural company located in Zemgale region in Latvia. Chapter III Part II presents an inventory of rapeseed oil mill stage with data provided by operation oil mill in Zemgale region. Different allocation methods are applied to further investigate the effect of different allocation methods on the environmental profiles of rapeseed oil-based bio-polyols and the consequences of applying these methods considering the main aims of the study. Chapter III Part III presents Life Cycle Impact Assessment of winter and spring rapeseed production and rapeseed oil production. Environmental performance is analyzed with Cumulative energy demand impact indicator along with the ReCiPe impact assessment methodology. The main environmental hotspots were identified. Sensitivity analysis was performed. Chapter III Part IV presents results of the Life Cycle Assessment of two rapeseed oil-based bio-polyols. Life Cycle Inventories were built on experimental data for polyol synthesis that were performed in a pilot-scale (50 L reactor). Bio-based polyols were compared with the petrochemical counterpart. The two developed rapeseed oil-based polyols were analyzed with three different modelling approaches for the bio-based feedstock stage. Sensitivity analysis was performed.