Within developing countries, there is an appeal to use waste biomass for energy generation in the form of bio-briquettes. This study investigated the potential use of bio-briquettes that are produced from the waste biomass of the following tropical fruits: durian (Durio zibethinus), coconut (Cocos nucifera), coffee (Coffea arabica), cacao (Theobroma cacao), banana (Musa acuminata) and rambutan (Nephelium lappaceum). All fruit waste biomass samples exhibited an extremely high level of initial moisture content (78.22% in average). Fruit samples with the highest proportion of fruit waste biomass (of total unprocessed fruit mass) were represented by cacao (83.82%), durian (62.56%) and coconut (56.83%). Highest energy potentials (calorific value) of fruit waste biomass were observed in case of coconut (18.22 MJ·kg −1 ), banana (17.79 MJ·kg −1 ) and durian (17.60 MJ·kg −1 ) fruit samples, whereas fruit waste biomass with the lowest level of ash content originated from the rambutan (3.67%), coconut (4.52%), and durian (5.05%) fruit samples. When investigating the energy demands to produce bio-briquettes from such feedstock materials, the best results (lowest amount of required deformation energy in combination with highest level of bio-briquette bulk density) were achieved by the rambutan, durian and banana fruit waste biomass samples. Finally, all investigated bio-briquette samples presented satisfactory levels of bulk density (>1050 kg·m −3 ). In conclusion, our results indicated the practicability and viability of such bio-briquette fuel production, as well as supporting the fact that bio-briquettes from tropical fruit waste biomass can offer a potentially attractive energy source with many benefits, especially in rural areas.

The deformation curve characteristics of rapeseeds and sunflower seeds compressed using the equipment ZDM 50-2313/56/18 and varying vessel diameters (40, 60, 80, and 100 mm) were investigated. Maximum compressive force of 100 kN was applied on bulk oilseeds of rape and sunflower of measured height 20-80 mm and deformed at a speed of 60 mm∙min-1. The compression test using the vessel diameters of 40 and 60 mm showed a serration effect while the vessel diameters of 80 and 100 mm indicated an increasing function effect on the force-deformation characteristic curves. Clearly, the increasing function effect described the region with oil flow and that of serration effect described the region without any oil flow. However, it was observed that the serration effect could be due to the higher compressive stress inside the smaller vessel diameters (40 and 60 mm) compared to those with bigger vessel diameters (80 and 100 mm). Parameters such as deformation, deformation energy, and energy density were determined from the force-deformation curves dependency showing both increasing function and serration effect. The findings of the study provide useful information for the determination of specific compressive force and energy requirements for extracting maximum oil from oilseed crops such as rape and sunflower.

Composite materials with natural fillers have been increasingly used as an alternative to synthetically produced materials. This trend is visible from a representation of polymeric composites with natural cellulose fibers in the automotive industry of the European Union. This trend is entirely logical, owing to a preference for renewable resources. The experimental program itself follows pronounced hypotheses and focuses on a description of the mechanical properties of untreated and alkali-treated natural vegetable fibers, coconut and abaca fibers. These fibers have great potential for use in composite materials. The results and discussion sections contribute to an introduction of an individual methodology for mechanical property assessment of cellulose fibers, and allows for a clear definition of an optimal process of alkalization dependent on the content of hemicellulose and lignin in vegetable fibers. The aim of this research was to investigate the influence of alkali treatment on the surface microstructure and tensile properties of coir and abaca fibers. These fibers were immersed into a 5% solution of NaOH at laboratory temperature for a time interval of 30 min, 1 h, 2 h, 3 h, 6 h, 12 h, 24 h, and 48 h, rinsed and dried. The fiber surface microstructures before and after the alkali treatment were evaluated by SEM (scanning electron microscopy). SEM analysis showed that the alkali treatment in the NaOH solution led to a gradual connective material removal from the fiber surface. The effect of the alkali is evident from the visible changes on the surface of the fibers.

Additive production is currently perceived as an advanced technology, where intensive research is carried out in two basic directions—modifications of existing printing materials and the evaluation of mechanical properties depending on individual production parameters and the technology used. The current research is focused on the evaluation of the fatigue behavior of 3D-printed test specimens made of pure PLA and PLA reinforced with filler based on pinewood, bamboo, and cork using FDM (fused deposition modeling) technology. This research was carried out in response to the growing demand for filaments from biodegradable materials. This article describes the results of tensile fatigue tests and image analysis of the fracture surface determined by the SEM method. Biodegradable PLA-based materials have their limitations that influence their applicability in practice. One of these limitations is fatigue life, which is the cyclic load interval exceeding 50% of the tensile strength determined in a static test. Comparison of the cyclic fatigue test results for pure PLA and PLA reinforced with natural reinforcement, e.g., pinewood, bamboo, and cork, showed that, under the same loading conditions, the fatigue life of the 3D-printed specimens was similar, i.e., the filler did not reduce the material’s ability to respond to low-cycle fatigue. Cyclic testing did not have a significant effect on the change in tensile strength and associated durability during this loading interval for PLA-based materials reinforced with biological filler. Under cyclic loading, the visco-elastic behavior of the tested materials was found to increase with increasing values of cyclic loading of 30%, 50% and 70%, and the permanent deformation of the tested materials, i.e., viscoelastic behavior (creep), also increased. SEM analysis showed the presence of porosity, interlayer disturbances, and at the same time good interfacial compatibility of PLA with the biological filler.

This paper deals with a research focused on utilization of microparticle and short-fiber filler based on cotton post-harvest line residues in an area of polymeric composites. Two different fractions of the biological filler (FCR—reinforced cotton filler) of 20 and 100 µm and the filler with short fibers of a length of 700 µm were used in the research. The aim of the research was to evaluate mechanical characteristics of composites and adhesive bonds for the purpose of gaining new pieces of knowledge which will be applicable in the area of material engineering and assessing application possibilities of residues coming into being from agricultural products processing. Mechanical properties of the composite material produced by a vacuum infusion and tested at temperatures 20, 40, and 60 °C and adhesive bonds which were exposed to a low-cyclic loading, i.e., 1000 cycles at 30% to 70% from reference value of the maximum strength, were evaluated. Composite systems with the FCR adjusted in 5% water solution of NaOH showed higher strength values on average compared to untreated FCR. Unsuitable size of the FCR led to a deterioration of the strength. The filler in the form of 700 FCR microfibers showed itself in a positive way to composite materials, and the particle in the form of 20 FCR did the same to adhesive bonds. Results of adhesive bond cyclic tests at higher stress values (70%) demonstrated viscoelastic behavior of the adhesive layer.