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Item type:Publication, Reviewing environmental life cycle impacts of biobased polymers: current trends and methodological challenges(Springer, 2020-11-01)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. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Life cycle assessment of bagasse fiber reinforced biocomposites(Elsevier, 2020-06-10)This study aims to evaluate the life cycle environmental implications of producing fiber-reinforced biocomposite pellets, compared with sugarcane- and petroleum-based polyethylene (PE) pellets. Life Cycle Assessment (LCA) methodology is used to evaluate the production of four types of pellets. LCA allows the evaluation of the benefits of improving the production of biobased materials by replacing part of the sugarcane bioPE with bagasse fibers. The functional unit selected was the production of 1 kg of plastic pellets. Primary data were collected from laboratory tests designed to obtain pulp fibers from bagasse and mix them with sugarcane bioPE. Two processes were studied to obtain fibers from bagasse: soda fractionation and hot water-soda fractionation. The results from the LCA show environmental improvements when reducing the amount of bioPE by replacing it with bagasse fibers in the categories of global warming, ozone formation, terrestrial acidification and fossil resource scarcity, when comparing to 100% sugarcane bioPE, and a reduction in global warming and fossil resource scarcity when compared to fossil-based PE. In contrast, results also indicate that there could be higher impacts in terms of ozone formation, freshwater eutrophication, and terrestrial acidification. Even though biocomposites result as a preferred option to bioPE, several challenges need to be overcome before a final recommendation is placed. The sensitivity analysis showed the importance of the energy source on the impacts of the processing of fibers. Thus, using clean energy to produce biobased materials may reduce the impacts related to the production stage. These results are intended to increase the attention of the revalorization of these residues and their application to generate more advanced materials. Further outlook should also consider a deeper evaluation of the impacts during the production of a plastic object and possible effects of the biobased materials during final disposal. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A simple approach to produce tailor-made chitosans with specific degrees of acetylation and molecular weights(MDPI AG, 2021-08-01)Chitin is a structural polysaccharide that is found in crustaceans, insects, fungi and some yeasts. Chitin deacetylation produces chitosan, a well-studied biopolymer with reported chemical and biological properties for diverse potential applications for drug delivery, metal ion absorption, scaffolds and tissue engineering. Most known properties of chitosan have been determined from samples obtained from a variety of sources and in different conditions, this is, from chitosans with a wide range of degrees of N-acetylation (DA) and molecular weight (MW). However, as for any copolymer, the physicochemical and mechanical characteristics of chitosan highly depend on their monomer composition (DA) and chain size (MW). This work presents a simple methodology to produce chitosans with specific and predictive DA and MW. Reaction with acetic anhydride proved to be an efficient method to control the acetylation of chitosan, DAs between 10.6% and 50.6% were reproducibly obtained. In addition to this, MWs of chitosan chains were reduced in a controlled manner in two ways, by ultrasound and by acidic hydrolysis at different temperatures, samples with MWs between 130 kDa and 1300 kDa were obtained. DAs were determined by 1H-NMR and MWs by gel permeation chromatography. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Additive construction using enhanced earthen-based composites: Improvement of the mechanical strength and water durability using chitosan and agave fibers(Elsevier Ltd, 2024-01-12)3D printing has emerged as a revolutionary technology with potential applications in the construction industry. However, the prevalent use of ordinary cement in most 3D printing formulations results in significant greenhouse gas emissions during 3D printing construction. In contrast, earthen-based composites are an eco-friendly alternative for building materials. However, as a construction material, earth presents poor mechanical strength and low durability against water erosion. This study aims to obtain earthen-based composites with suitable mechanical and durability properties to investigate their extrudability and buildability in tests. It also explores the effects of incorporating short sisal fibers (l/d ratio = 138.7) and chitosan (DD = 91%, Mw = 598 kDa) to improve strength and water durability in earthen-based composites for 3D printing purposes. Chitosan is a natural macromolecule derived from a waste product from the food industry, whereas sisal fibers are obtained from the Agave sisalana plant. The change in compressive strength was analyzed through uniaxial compression. Water durability was evaluated by measuring the water contact angle, total and capillary water absorption, and accelerated erosion tests. The results indicate that the use of 3.0% (w/v) aqueous solution of chitosan and 1.0% (w/w) of sisal fibers have an important effect on the hardening and water durability properties of earthen-based composites. This study suggests that these materials could serve as natural additives to enhance the mechanical properties and water durability of new eco-friendly construction materials for 3D printing. In conclusion, this study demonstrates that appropriate formulations with natural and eco-friendly additives can lead to stabilized earthen-based composites with suitable printing, mechanical and durability properties for 3D printing applications in construction materials. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A Review on the Development of Biopolymer Nanocomposite-Based Triboelectric Nanogenerators (Bio-TENGs)(American Chemical Society, 2023-07-25)Triboelectric nanogenerators (TENGs) are electronic devices capable of harvesting low-frequency mechanical motions to produce electrical energy through the triboelectrification effect. A great number of electronic devices, such as wearable devices, implantable medical devices, and monitoring sensors, among others, use conventional power sources such as batteries and capacitors. They are usually toxic, nondegradable, and hard to recycle, representing human and environmental hazards. In addition, conventional batteries and capacitors are usually rigid, heavy, and not suitable for the fabrication of portable and flexible devices. TENGs appear as a promising option to be used in the development of light, portable, and self-powered electronic devices. TENGs were first developed using synthetic polymers such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), polydimethylsiloxane (PDMS), and polyimide (Kapton) for the fabrication of the active surfaces that store charge. Bio-TENGs have been fabricated using biopolymers such as cellulose, silk, and chitosan. These Bio-TENGs take advantage of the inherent biodegradability and biocompatibility of biopolymers. In order to improve the capability of biopolymer-based surfaces to store electrostatic charge, several treatments are reported, including the incorporation of nanoparticles and surface treatments. These biopolymer-based active surfaces with improved properties allow Bio-TENGs to achieve output performances similar to those reported for synthetic TENGs. Bio-TENGs have been used in a wide range of applications, such as human monitoring systems, tissue engineering, electronic devices, and industrial-level flooring, among others. This review is focused on the development of Bio-TENGs. The different types of biopolymers used for the fabrication of active surfaces are described and classified as protein-based, polysaccharide-based, and synthetic-based biopolymers. The different strategies used for improving the triboelectric properties of biopolymer-based surfaces are presented, along with the resulting output performance of Bio-TENGs. The reported applications for these Bio-TENGs are also discussed.