Semi-Transparent Luminescent Solar Concentrators Based on Intramolecular Energy Transfer in Polyurethane Matrices.

Luminescent solar concentrators (LSCs) are spectral conversion devices offering interesting opportunities for the integration of photovoltaics into the built environment and portable systems. The Förster-resonance energy transfer (FRET) process can boost the optical response of LSCs by reducing energy losses typically associated to non-radiative processes occurring within the device under operation. In this work, a new class of FRET-based thin-film LSC devices is presented, in which the synthetic versatility of linear polyurethanes (PU) is exploited to control the photophysical properties and the device performance of the resulting LSCs. A series of luminescent linear PUs are synthesized in the presence of two novel bis-hydroxyl-functionalized luminophores of suitable optical properties, used as chain extenders during the step-growth polyaddition reaction for the formation of the linear macromolecular network. By synthetically tuning their composition, the obtained luminescent PUs can achieve a high energy transfer efficiency (≈90%) between the covalently linked luminophores. The corresponding LSC devices exhibit excellent photonic response, with external and internal photon efficiencies as high as ≈4% and ≈37%, respectively. Furthermore, their optimized power conversion efficiency combined with their enhanced average visible-light transmittance highlight their suitability for potential use as transparent solar energy devices.

Crosslinked Polyesters as Fully Biobased Coatings with Cutin Monomer from Tomato Peel Wastes.

Cutin, one of the main structural components of tomato peels, is a waxy biopolymer rich in hydroxylated fatty acids. In this study, 10,16-dihydroxyhexadecanoic acid (10,16-diHHDA) was extracted and isolated from tomato peels and exploited to develop fully crosslinked polyesters as potential candidates for replacing fossil-based metal protective coatings. A preliminary screening was conducted to select the base formulation, and then a design of experiments (DoE) was used as a methodology to identify the optimal composition to develop a suitable coating material. Different formulations containing 10,16-diHHDA and other biorefinery monomers, including 2,5-furandicarboxylic acid, were considered. To this end, all polyesters were characterized through differential scanning calorimetry (DSC) and gel content measurements to determine their Tg value and crosslinking efficiency. Compositions exhibiting the best trade-off between Tg value, chemical resistance, and sufficiently high 10,16-diHHDA content between 39 and 48 wt.% were used to prepare model coatings that were characterized for assessing their wettability, scratch hardness, chemical resistance, and adhesion to metal substrates. These polyester coatings showed a Tg in the range of 45-55 °C, a hydrophobic behavior with a water contact angle of around 100°, a good solvent resistance (>100 MEK double rubs), and an adhesion strength to steel higher than 2 MPa. The results obtained confirmed the potential of cutin-based resins as coatings for metal protection, meeting the requirements for ensuring physicochemical properties of the final product, as well as for optimizing the valorization of such an abundant agri-food waste as tomato peels.

Elucidating the Role of Lignin Type and Functionality in the Development of High-Performance Biobased Phenolic Thermoset Resins.

In this work, a series of biobased phenolic resins were developed starting from kraft and soda lignin, suitably functionalized through esterification by means of succinic anhydride. As a result of an extensive optimization study of the functionalization and curing reactions, clear correlations between lignin type and chemical-physical characteristics and the properties of the resulting phenolic resin systems were described. In particular, the esterification reaction through succinic anhydride was found to play a key role in enhancing the chemical reactivity and in facilitating the successful incorporation of lignin into the resin formulations. The obtained high-lignin-content thermoset materials were shown to exhibit tunable chemical (functionality, gel content, and cross-linking density), thermal (glass transition temperature and thermo-oxidative stability), and mechanical (surface hardness, indentation modulus, and creep behavior) characteristics, which could outperform those of fully oil-based reference phenolic resins by judicious control of lignin concentration and chemical characteristics. In particular, succinylated kraft lignin was found to enable more efficient incorporation into the cured systems. This work provides the first demonstration of the incorporation of succinic-anhydride-modified-lignin in the formulation of high-performance phenolic resins, ultimately contributing to the definition of structure-property-performance correlations for rational biobased material design in the context of advanced and sustainable manufacturing.

Tuning the Properties of Biobased PU Coatings via Selective Lignin Fractionation and Partial Depolymerization.

Polyurethane (PU) coatings with high lignin content and tunable properties were made using a combination of fractionation and partial catalytic depolymerization as a novel strategy to tailor lignin molar mass and hydroxyl group reactivity, the key parameters for use in PU coatings. Acetone organosolv lignin obtained from pilot-scale fractionation of beech wood chips was processed at the kilogram scale to produce lignin fractions with specific molar mass ranges (Mw 1000-6000 g/mol) and reduced polydispersity. Aliphatic hydroxyl groups were distributed relatively evenly over the lignin fractions, allowing detailed study of the correlation between lignin molar mass and hydroxyl group reactivity using an aliphatic polyisocyanate linker. As expected, the high molar mass fractions exhibited low cross-linking reactivity, yielding rigid coatings with a high glass transition temperature (Tg). The lower Mw fractions showed increased lignin reactivity, extent of cross-linking, and gave coatings with enhanced flexibility and lower Tg. Lignin properties could be further tailored by lignin partial depolymerization by reduction (PDR) of the beech wood lignin and its high molar mass fractions; excellent translation of the PDR process was observed from laboratory to the pilot scale necessary for coating applications in prospective industrial scenarios. Lignin depolymerization significantly improved lignin reactivity, and coatings produced from PDR lignin showed the lowest Tg values and highest coating flexibility. Overall, this study provides a powerful strategy for the production of PU coatings with tailored properties and high (>90%) biomass content, paving the path to the development of fully green and circular PU materials.

Unveiling the Hidden Properties of Tomato Peels: Cutin Ester Derivatives as Bio-Based Plasticizers for Polylactic Acid.

Polylactic acid (PLA) is one of the most important biopolymers employed on the market due to its good mechanical strength and barrier properties. On the other hand, this material presents a rather low flexibility, limiting its employment. The valorization of bio-based agro-food waste for the modification of bioplastics is a highly appealing approach for the replacement of petrol-based materials. The aim of this work is to employ cutin fatty acids derived from a biopolymer (i.e., cutin), present in waste tomato peels and its bio-based derivatives as new plasticizers to enhance PLA flexibility. In particular, pure 10,16-dihydroxy hexadecanoic acid was extracted and isolated from tomato peels and then functionalized to give the desired compounds. All the molecules developed in this study were characterized by NMR and ESI-MS. Blends at different concentrations (10, 20, 30, and 40% w/w) the flexibility (Tg measurements with differential scanning calorimetry-DSC) of the final material. Furthermore, the physical behavior of two blends obtained by mechanical mixing of PLA and 16-methoxy,16-oxohexadecane-1,7-diyl diacetate was investigated through thermal and tensile tests. The data collected by DSC show a lowering in the Tg of all the blends of PLA with functionalized fatty acids, in comparison with pure PLA. Lastly, the tensile tests highlighted how PLA blended with 16-methoxy,16-oxohexadecane-1,7-diyl diacetate (20% w/w) can efficiently enhance its flexibility.

Bio-Based Vitrimers from 2,5-Furandicarboxylic Acid as Repairable, Reusable, and Recyclable Epoxy Systems.

In this work, a series of bio-based epoxy vitrimers were developed by reacting diglycidyl ether of bisphenol A (DGEBA) and bio-based 2,5-furandicarboxylic acid (FDCA) at different molar ratios. Triazabicyclodecene was used as a transesterification catalyst to promote thermally induced exchange reactions. Differential scanning calorimetry, gel content measurements, and Fourier transform infrared spectroscopy were used to study the FDCA-DGEBA crosslinking reaction. The transesterification exchange reaction kinetics of such crosslinked systems was characterized via stress relaxation tests, evidencing an Arrhenius-type dependence of the relaxation time on temperature, and an activation energy of the dynamic rearrangement depending on the molar composition. In addition, self-healing, thermoformability, and mechanical recycling were demonstrated for the composition showing the faster topology rearrangement, namely, the FDCA/DGEBA molar ratio equal to 0.6. This work provides the first example of bio-based epoxy vitrimers incorporating FDCA, making these systems of primary importance in the field of reversible, high-performance epoxy materials for future circular economy scenarios.

Fractionation of Raw and Parboiled Rice Husks with Deep Eutectic Solvents and Characterization of the Extracted Lignins towards a Circular Economy Perspective.

In the present work, rice husks (RHs), which, worldwide, represent one of the most abundant agricultural wastes in terms of their quantity, have been treated and fractionated in order to allow for their complete valorization. RHs coming from the raw and parboiled rice production have been submitted at first to a hydrothermal pretreatment followed by a deep eutectic solvent fractionation, allowing for the separation of the different components by means of an environmentally friendly process. The lignins obtained from raw and parboiled RHs have been thoroughly characterized and showed similar physico-chemical characteristics, indicating that the parboiling process does not introduce obvious lignin alterations. In addition, a preliminary evaluation of the potentiality of such lignin fractions as precursors of cement water reducers has provided encouraging results. A fermentation-based optional preprocess has also been investigated. However, both raw and parboiled RHs demonstrated a poor performance as a microbiological growth substrate, even in submerged fermentation using cellulose-degrading fungi. The described methodology appears to be a promising strategy for the valorization of these important waste biomasses coming from the rice industry towards a circular economy perspective.

Metallization of Recycled Glass Fiber-Reinforced Polymers Processed by UV-Assisted 3D Printing.

An ever-growing amount of composite waste will be generated in the upcoming years. New circular strategies based on 3D printing technologies are emerging as potential solutions although 3D-printed products made of recycled composites may require post-processing. Metallization represents a viable way to foster their exploitation for new applications. This paper shows the use of physical vapor deposition sputtering for the metallization of recycled glass fiber-reinforced polymers processed by UV-assisted 3D printing. Different batches of 3D-printed samples were produced, post-processed, and coated with a chromium metallization layer to compare the results before and after the metallization process and to evaluate the quality of the finishing from a qualitative and quantitative point of view. The analysis was conducted by measuring the surface gloss and roughness, analyzing the coating morphology and thickness through the Scanning Electron Microscopy (SEM) micrographs of the cross-sections, and assessing its adhesion with cross-cut tests. The metallization was successfully performed on the different 3D-printed samples, achieving a good homogeneity of the coating surface. Despite the influence of the staircase effect, these results may foster the investigation of new fields of application, as well as the use of different polymer-based composites from end-of-life products, i.e., carbon fiber-reinforced polymers.

Cardanol-Derived Epoxy Resins as Biobased Gel Polymer Electrolytes for Potassium-Ion Conduction.

In this study, biobased gel polymer electrolyte (GPE) membranes were developed via the esterification reaction of a cardanol-based epoxy resin with glutaric anhydride, succinic anhydride, and hexahydro-4-methylphthalic anhydride. Nonisothermal differential scanning calorimetry was used to assess the optimal curing time and temperature of the formulations, evidencing a process activation energy of ∼65-70 kJ mol-1. A rubbery plateau modulus of 0.65-0.78 MPa and a crosslinking density of 2 × 10-4 mol cm-3 were found through dynamic mechanical analysis. Based on these characteristics, such biobased membranes were tested for applicability as GPEs for potassium-ion batteries (KIBs), showing an excellent electrochemical stability toward potassium metal in the -0.2-5 V voltage range and suitable ionic conductivity (10-3 S cm-1) at room temperature. This study demonstrates the practical viability of these biobased materials as efficient GPEs for the fabrication of KIBs, paving the path to increased sustainability in the field of next-generation battery technologies.

Lignin as Polymer Electrolyte Precursor for Stable and Sustainable Potassium Batteries.

Potassium batteries show interesting peculiarities as large-scale energy storage systems and, in this scenario, the formulation of polymer electrolytes obtained from sustainable resources or waste-derived products represents a milestone activity. In this study, a lignin-based membrane is designed by crosslinking a pre-oxidized Kraft lignin matrix with an ethoxylated difunctional oligomer, leading to self-standing membranes that are able to incorporate solvated potassium salts. The in-depth electrochemical characterization highlights a wide stability window (up to 4 V) and an ionic conductivity exceeding 10-3  S cm-1 at ambient temperature. When potassium metal cell prototypes are assembled, the lignin-based electrolyte attains significant electrochemical performances, with an initial specific capacity of 168 mAh g-1 at 0.05 A g-1 and an excellent operation for more than 200 cycles, which is an unprecedented outcome for biosourced systems in potassium batteries.

Evaluation of the anaerobic degradation of food waste collection bags made of paper or bioplastic.

The amount of compostable bioplastics collected with the food waste is constantly growing, particularly due to the bags used for collection. According to the Italian legislation, compostable bioplastics must be accepted by all biological treatment plants, including aerobic and anaerobic facilities. Anyway, the compostability standard requires only the assessment of the aerobic degradability, while it is generally not required to test the behaviour under anaerobic conditions. This aspect is evaluated in the paper, where the anaerobic degradability of bioplastic bags used for the food waste collection is assessed. First, Biochemical Methane Potential (BMP) tests were performed on four commercial types of bioplastic bags, including those designed only for the collection of food waste and the shoppers, that can be reused for the same purpose. Subsequently, an innovative approach for this kind of substrate was applied, subjecting two bags to semi-continuous co-digestion tests together with the food waste. Both tests were performed by comparing the behaviour of bioplastic bags with that of an alternative collection paper bag. Finally, tests to evaluate the influence of physical phenomena on the degradation of bioplastics were performed to better understand the results of biological tests. BMP tests indicated a good degradability (>71%) of bioplastic bags, while semi-continuous tests showed a much lower degradability (<27%), confirmed by the observation of the undigested bag pieces. On the contrary, the paper bag presents interesting characteristics, because its degradability in the semi-continuous tests (82%) resulted even higher than that observed in the BMP tests (74%). These results highlight an important difference between the bags mono-digestion by means of BMP tests and the semi-continuous co-digestion tests with food waste, which better simulate the full-scale operational conditions.

Lignin-Based Polymer Electrolyte Membranes for Sustainable Aqueous Dye-Sensitized Solar Cells.

In the quest for sustainable materials for quasi-solid-state (QS) electrolytes in aqueous dye-sensitized solar cells (DSSCs), novel bioderived polymeric membranes were prepared in this work by reaction of preoxidized kraft lignin with poly(ethylene glycol)diglycidylether (PEGDGE). The effect of the PEGDGE/lignin relative proportions on the characteristics of the obtained membranes was thoroughly investigated, and clear structure-property correlations were highlighted. In particular, the glass transition temperature of the materials was found to decrease by increasing the amount of PEGDGE in the formulation, indicating that polyethylene glycol chains act as flexible segments that increase the molecular mobility of the three-dimensional polymeric network. Concurrently, their swelling ability in liquid electrolyte was found to increase with the concentration of PEGDGE, which was also shown to influence the ionic transport efficiency within the membrane. The incorporation of these lignin-based cross-linked systems as QS electrolyte frameworks in aqueous DSSCs allowed the preparation of devices with excellent long-term stability under UV-vis light, which were found to be superior to benchmark QS-DSSCs incorporating state-of-the-art carboxymethylcellulose membranes. This study provides the first demonstration of lignin-based QS electrolytes for stable aqueous DSSCs, establishing a straightforward strategy to exploit the potential of lignin as a functional polymer precursor for the field of sustainable photovoltaic devices.

UV-Assisted 3D Printing of Polymer Composites from Thermally and Mechanically Recycled Carbon Fibers.

Despite the growing global interest in 3D printed carbon fiber reinforced polymers, most of the applications are still limited to high-performance sectors due to the low effectiveness-cost ratio of virgin carbon fibers. However, the use of recycled carbon fibers in 3D printing is almost unexplored, especially for thermoset-based composites. This paper aims to demonstrate the feasibility of recycled carbon fibers 3D printing via UV-assisted direct ink writing. Pyrolyzed recycled carbon fibers with a sizing treatment were firstly shredded to be used as a reinforcement of a thermally and photo-curable acrylic resin. UV-differential scanning calorimetry analyses were then performed to define the material crosslinking of the 3D printable ink. Because of the poor UV reactivity of the resin loaded with carbon fibers, a rheology modifier was added to guarantee shape retention after 3D printing. Thanks to a customized 3D printer based on a commercial apparatus, a batch of specimens was successfully 3D printed. According to the tensile tests and Scanning Electron Microscopy analysis, the material shows good mechanical properties and the absence of layer marks related to the 3D printing. These results will, therefore, pave the way for the use of 3D printed recycled carbon fiber reinforced polymers in new fields of application.

Poly(vinylidenefluoride) polymers and copolymers as versatile hosts for luminescent solar concentrators: compositional tuning for enhanced performance.

Novel host matrices based on fluoropolymers blended with poly(methyl methacrylate) (PMMA) are presented in this work for application in efficient and photochemically stable thin-film luminescent solar concentrators (LSCs). These systems consist of blends of PMMA with three different partially fluorinated polymers in different proportions: polyvinylidenefluoride homopolymer, a copolymer of vinylidenefluoride and chloro-trifluoro-ethylene, and a terpolymer of vinylidenefluoride, hexafluoropropylene and hydroxyl-ethyl acetate. A detailed chemical, physical and structural characterization of the obtained materials allowed us to shed light on the structure-property relationships underlying the response of such blends as a LSC component, revealing the effect of the degree of crystallinity of the polymers on their functional characteristics. An optimization study of the optical and photovoltaic (PV) performance of these fluoropolymer-based LSC systems was carried out by investigating the effect of blend chemical composition, luminophore concentration and film thickness on LSC device output. LSCs featuring copolymer/PMMA blends as the host matrix were found to outperform their homopolymer- and terpolymer-based blend counterparts, attaining efficiencies comparable to those of reference PMMA-based LSC/PV assemblies. All optimized LSC systems were subjected to weathering tests for over 1000 h of continuous light exposure to evaluate the effect of the host matrix system on LSC performance decline and to correlate chemical composition with photochemical durability. It was found that all fluoropolymer/PMMA-based LSCs outperformed reference PMMA-based LSCs in terms of long-term operational lifetime. This work provides the first demonstration of thermoplastic fluoropolymer/PMMA blends for application as host matrices in efficient and stable LSCs and widens the scope of high-performance thermoplastic materials for the PV field.

Additive Re-Manufacturing of Mechanically Recycled End-of-Life Glass Fiber-Reinforced Polymers for Value-Added Circular Design.

Despite the large use of composites for industrial applications, their end-of-life management is still an open issue for manufacturing, especially in the wind energy sector. Additive manufacturing technology has been emerging as a solution, enhancing circular economy models, and using recycled composites for glass fiber-reinforced polymers is spreading as a new additive manufacturing trend. Nevertheless, their mechanical properties are still not comparable to pristine materials. The purpose of this paper is to examine the additive re-manufacturing of end-of-life glass fiber composites with mechanical performances that are comparable to virgin glass fiber-reinforced materials. Through a systematic characterization of the recyclate, requirements of the filler for the liquid deposition modeling process were identified. Printability and material surface quality of different formulations were analyzed using a low-cost modified 3D printer. Two hypothetical design concepts were also manufactured to validate the field of application. Furthermore, an understanding of the mechanical behavior was accomplished by means of tensile tests, and the results were compared with a benchmark formulation with virgin glass fibers. Mechanically recycled glass fibers show the capability to substitute pristine fillers, unlocking their use for new fields of application.

Tuning Lignin Characteristics by Fractionation: A Versatile Approach Based on Solvent Extraction and Membrane-Assisted Ultrafiltration.

Technical lignins, typically obtained from the biorefining of lignocellulosic raw materials, represent a highly abundant natural aromatic feedstock with high potential in a sustainable economy scenario, especially considering the huge primary production volumes and the inherently renewable nature of this resource. One of the main drawbacks in their full exploitation is their high variability and heterogeneity in terms of chemical composition and molecular weight distribution. Within this context, the availability of effective and robust fractionation processes represents a key requirement for the effective valorization of lignin. In the present work, a multistep fractionation of two different well known technical lignins obtained from two distinct delignification processes (soda vs. kraft pulping) was described. A comprehensive approach combining solvent extraction in organic or aqueous medium with membrane-assisted ultrafiltration was developed in order to maximize the process versatility. The obtained lignin fractions were thoroughly characterized in terms of their chemical, physical, thermal, and structural properties, highlighting the ability of the proposed approach to deliver consistent and reproducible fractions of well-controlled and predictable characteristics, irrespective of their biomass origin. The results of this study demonstrate the versatility and the reliability of this integrated multistep fractionation method, which can be easily adapted to different solvent media using the same ultrafiltration membrane set up, thereby enhancing the potential applicability of this approach in an industrial scale-up perspective for a large variety of starting raw lignins.

Two-Step Fractionation of a Model Technical Lignin by Combined Organic Solvent Extraction and Membrane Ultrafiltration.

A fractionation method for technical lignin was developed, combining organic solvent extraction and membrane ultrafiltration of the solvent soluble component. This method was validated on a commercial wheat straw/Sarkanda grass lignin (Protobind 1000) using 2-butanone (MEK) as the solvent for both the extraction and the ultrafiltration operations. The parent lignin and the different obtained fractions were fully characterized in terms of chemical composition and physicochemical properties by gel permeation chromatography, gas chromatography/mass spectrometry (GC/MS), pyrolysis-GC/MS, total phenol contents, 31P nuclear magnetic resonance (31P NMR), thermogravimetric analysis, differential scanning calorimetry analysis, and Fourier-transform infrared spectroscopy. The results show that the proposed process allows a straightforward recovery of the different lignin fractions as well as a selective control over their molecular mass distribution and related dependent properties. Moreover, the operating flexibility of the Soxhlet/ultrafiltration process allows the treatment of lignins from different feedstocks using the same installation just by modulating the choice of the solvent and the membrane porosity with the best characteristics. This is one of the most important features of the proposed strategy, which represents a new fractionation approach with the potential to improve lignin valorization for materials science and preparative organic chemistry applications.

Simultaneous Recovery of Matrix and Fiber in Carbon Reinforced Composites through a Diels-Alder Solvolysis Process.

Efficient and comprehensive recycling of fiber-reinforced thermosets is particularly challenging, since the irreversible degradation of the matrix component is necessary in order to separate the fiber component in high purity. In this work, a new approach to fully recyclable thermoset composites is presented, based on the thermal reversibility of an epoxy-based polymer network, crosslinked through Diels-Alder (DA) chemistry. Carbon fiber composites, fabricated by compression molding, were efficiently recycled through a simple solvolysis procedure in common solvents, under mild conditions, with no catalysts. Specifically, the purity of reclaimed fibers, assessed by thermogravimetric analysis and scanning electron microscopy, was very high (>95%) and allowed successful reprocessing into second generation composites. Moreover, the dissolved matrix residues were directly employed to prepare smart, thermally healable coatings. Overall, DA chemistry has been shown to provide a convenient strategy towards circular economy of thermoset composites.

Mechanical Reinforcement by Microalgal Biofiller in Novel Thermoplastic Biocompounds from Plasticized Gluten.

The aim of this work was to develop new bioplastic compounds from wheat gluten, biobased plasticizers (glycerol, octanoic acid and 1,4-butanediol), and microalgal biomass as a filler. The effects of the composition on tensile properties, thermal stability, and water sensitivity were investigated. Microalgal biomass was added with the selected quantities: 10, 20, and 30 per hundred parts (php). Mechanical mixing of the components, i.e., gluten, plasticizer, and microalgae, was followed by molding in a hot press. Microlgal filler improved mechanical properties of the plasticized gluten material: in samples plasticized with 1,4-butanediol, 30 php of biomass increased the tensile modulus by nearly one order of magnitude, from 36.5 MPa to 273.1 MPa, and it also increased the tensile strength from 3.3 MPa to 4.9 MPa. The introduction of microalgal biomass slightly increased the surface sensitivity against water: 30 php of biomass reduced the water contact angle from 41° to 22° in samples plasticized with glycerol, but the biomass lowered the overall water absorption kinetics for material with each plasticizer. Microalgal biomass proved therefore to be an interesting sustainable resource with which to develop materials based on gluten, in particular to increase the mechanical properties of the compounds without reducing thermal stability or water resistance.

Additive Manufacturing of Geopolymers Modified with Microalgal Biomass Biofiller from Wastewater Treatment Plants.

This paper deals with the additive manufacturing of metakaolin-based geopolymers and with the use of microalgal biomass from wastewater treatment plants as biofiller in this kind of cementitious material. The study was developed following the evolution stages of the material, which was prepared and printed as a soft paste and then hardened thanks to an inorganic polymerization reaction (geopolymerization). Thus, the characterization techniques adopted encompassed rheometry, mechanical tests performed on the hardened material, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and mercury intrusion porosimetry (MIP). Microalgal biomass addition, evaluated in this study at 1, 3 and 5 php with respect to the powder weight, affected both the properties of the fresh and of the hardened material. Regarding the former aspect, biomass reduced the yield stress of the pastes, improving the ease of the extrusion process, but potentially worsening the ability to build structures in height. When hardened, geopolymers containing microalgae showed mechanical properties comparable to the unfilled material and a microstructure characterized by smaller pores. Finally, a printing test was successfully performed with a larger printer to assess the feasibility of producing large-scale structures. Taking into account these results, this study demonstrates the possibility of using microalgal biomass as biofiller in geopolymers for additive manufacturing.