Reviewing environmental life cycle impacts of biobased polymers: current trends and methodological challenges

摘要

Purpose The aim of this review is to evaluate previous life cycle assessment (LCA) studies of first- and second-generation bioplastics, to understand the state of the art and the main problems addressed during the development of new bioplastics. Furthermore, it provides an overview on land use change (LUC) impacts accounted for, methodologies chosen, and the results obtained. Methods Studies related to the impact assessment of bioplastics and published between 2007 and 2018 were gathered. Five keyword strings were used to perform a wide search and select relevant LCA studies. The study aimed to analyze critical methodological aspects in LCA, in order to determine the most common choices made during biobased material analyses, as well as major limitations. Three filters were applied to select comparable studies, ending with a final number of 17 papers. Recommendations were obtained by comparing common practices performed by different authors with suggested best available practices mentioned in handbooks and guidelines. Interestingly, LUC metrics and impacts were, most of the time, neglected. Thus, a specific assessment and discussion was performed regarding the methods used to quantify LUC impacts, considering its importance during the production of biobased materials. Results and discussion The study discussed the main environmental problems linked to the development of new biomaterials. LCA of agricultural products or systems, when compared with fossil-based counterparts, is expected to show higher environmental impacts in categories directly affected by fertilizer use, occupied and transformed land, among others. Thus, studies that included additional impact categories besides global warming (e.g., eutrophication or acidification) concluded that biobased materials present higher impacts, recommending improvements in farming practices to improve their overall environmental profile. Moreover, this review gathered methodologies used to account for LUC impacts and the results obtained. The main constraint of including LUC impacts was the lack of a standardized methodology, as well as large uncertainties in existing methodologies. Conclusions Most studies concluded that improvements in farming practices might reduce the attributed environmental impacts with the reduction of the amount of land, fertilizer, pesticides, and water used. Studies computing LUC impacts agreed on the importance of including these impacts and concluded that greenhouse gas emissions of bioplastic production would increase, but in most cases would still be lower than the impact of their fossil-based counterparts. However, challenges remain when computing LUC impacts that need to be tackled when working with the available methodologies, including the collection of reliable inventory data (site-specific or regional data) and regionalized characterization factors.