Life cycle assessment of composite materials made of recycled thermoplastics combined with rice husks and cotton linters

Background, aim, and scope The goal of this study is to analyze the environmental impact of new composite materials obtained from the combination of recycled thermoplastics (polypropylene [PP] and high-density polyethylene [HDPE]) and biodegradable waste of little economic value, namely, rice husks and recycled cotton. The environmental impact of these materials is compared to the impact of virgin PP and HDPE using life cycle assessment. Materials and methods From-cradle-to-grave life cycle inventory studies were performed for 1 kg of each of the three new composites: PP+cotton linters, PP+rice husks, and HDPE+cotton linters. Inventory data for the recycling of thermoplastics and cotton were obtained from a number of recycling firms in Spain, while environmental data concerning rice husks were obtained mainly from one rice-processing company located in Spain. Life cycle inventory data for virgin thermoplastics were acquired from PlasticsEurope. Two different scenarios—incineration and landfilling—were considered for the assessment of disposal phase. A quantitative impact assessment was performed for four impact categories: global warming over a hundred years, nonrenewable energy depletion, acidification, and eutrophication. Results The composites subject to analysis exhibited a significantly reduced environmental impact during the materials acquisition and processing phases compared to conventional virgin thermoplastics in all of the impact categories considered. The use of fertilizers for rice cultivation, however, impaired the results of the rice husk composite in the eutrophication category where it nevertheless outperformed its conventional counterparts. The compounding phase fundamentally implies an electric consumption. The disposal phase was analyzed with regard to emissions in the global warming category. Discussion Composites obtained from renewable sources are still in an incipient state of development in comparison with petroleum-derived plastics. In the future, as mass production of these plastics becomes more widespread, their environmental impact can be expected to reach lower levels than those obtained in our study. The new materials exhibited adequate mechanical performance for the application analyzed (structures used in aquaculture). Conclusions The composites subject to analysis exhibited a significantly reduced environmental impact compared to conventional virgin thermoplastics using 1 kg of material as a functional unit. Recommendation