This research explores the potential and significance of 3D printing natural fiber composite (NFC) materials. The primary objective is to investigate the mechanical, thermal, and environmental properties of NFC filaments, mainly focusing on biodegradable, renewable fibers such as jute, hemp, flax, and kenaf. In addition to studying the properties of NFCs, our research delves into the challenges associated with processing, including moisture absorption and fiber-matrix interfacial bonding. The novelty of this work lies in the convergence of traditional composite materials with the versatility of 3D printing technology. NFC filaments offer unique advantages in terms of sustainability, and we examine their potential contributions to the circular economy. By using eco-friendly NFC materials in 3D printing, we aim to present a viable, environmentally responsible alternative to conventional synthetic composites. The importance of 3D printing NFCs stems from the ways their use can align with sustainability goals. These materials provide the advantages of renewability, reduced carbon impact, and in some cases, biodegradability. Their applications extend to various industries, such as automotive, construction, and packaging, where eco-friendly materials are increasingly sought. Such applications showcase the ways in which NFC-based 3D printing can contribute to a more environmentally responsible and sustainable future. This research explores the mechanical, thermal, and environmental properties of NFC materials, highlighting their unique advantages for 3D printing and the potential to have eco-friendly applications in diverse industries.

Biomass-derived coal or “biocoal” produced using a torrefaction process presents a carbon-neutral option of coal for power generation. While torrefaction delivers a carbon content and hydrophobicity comparable to coal, it lowers its density and creates material handling, storage, and transportation challenges. Densification into briquettes would help mitigate these challenges. However, the torrefied biomass is difficult to densify and may require the use of binders, which are expensive and can be incompatible with respect to material and emissions. A cost-effective approach to utilize lignin in-situ of the biomass to promote binding during densification was demonstrated using a pilot-scale briquetter unit during this study. Lignin, a cross-linked polymer, tends to break down and lose its binding ability under high-temperature conditions of torrefaction. In this paper, we investigated the use of a lightly torrefied material as a binder―LTM (biomass torrefied in the transition region of non-reactive and reactive temperature ranges of torrefaction). When mixed with torrefied biomass and densified together under suitable moisture and temperature conditions, the lignin is shown to mobilize and provide binding to the briquettes. The results showed that briquettes produced using LTM as binder and 10% to 11% moisture provided in-situ binding, improved density and durability, and produced hydrophobic briquettes.

This article explores using biomass, namely rice husks, as a reinforcement material in thermoplastic copolyester (TPC) composites. Rice husks were subjected to three chemical pretreatments: single-stage sulfuric acid hydrolysis, first-stage sulfuric acid hydrolysis followed by a second-stage methanesulfonic acid (MSA) treatment, and first-stage sulfuric acid hydrolysis followed by a second-stage sodium hydroxide alkali treatment. We studied the effects of these treatments on the rheological, thermal, interfacial, and mechanical properties of composites. The fibers were mixed with polymers at high shear rates and temperatures, and 3D-printed filaments were produced using a desktop 3D printer. The printed parts were analyzed using tensile tests, torque and viscosity measurements, and thermogravimetric analysis to obtain their mechanical, rheological, and thermal properties. SEM imaging was performed to understand the fiber–polymer interface and how it affects the other properties. The results showed that first-stage sulfuric acid hydrolysis followed by a second-stage pretreatment of the fibers with MSA showed better fiber–polymer adhesion and a 20.4% increase in stress at 5% strain, a 30% increase in stress at 50% strain, and a 22.6% increase in the elastic modulus as compared to untreated rice husk composites. These findings indicate that readily available and inexpensive rice husks have significant potential for use in natural fiber-reinforced composites when pretreated using dilute sulfuric acid followed by methane sulfonic acid hydrolysis.