Bio-Epoxy Composites Formulation Using Bio-Oils from Walnut and Almond Shell Pyrolysis: Influence of Temperature on Chemical Composition and Curing Behavior
In this study, we develop bio-epoxy composites incorporating bio-oils obtained from the pyrolysis of almond and walnut shells at 400 °C and 600 °C, with the aim of evaluating their potential as renewable precursors for epoxy resin modification. The influence of pyrolysis temperature on bio-oil yield and chemical composition is examined to identify phenolic-rich fractions relevant to epoxy curing. Bio-oil production increased with temperature, reaching 40.46% for walnut shells and 36.84% for almond shells at 600 °C. Chemical analysis revealed that aromatic compounds, particularly phenolics, were the major constituents associated with epoxy curing reactivity. For walnut hulls, the total aromatic fraction increased from 30.4% at 400 °C to 35.2% at 600 °C, while almond hulls showed an increase from 23.8% to 26.1% over the same temperature range. Incorporation of bio-oil into the epoxy matrix promoted three-dimensional network formation through reactions between epoxy groups and the functional moieties present in the bio-oil, resulting in a higher cross-linking degree, Young’s modulus, and tensile strength. However, compared to neat epoxy, the bio-oil-modified systems exhibited reduced storage modulus (E′) and glass transition temperature (Tg), attributed to the plasticizing effect of lighter oxygenated species. Overall, although bio-oil incorporation decreases Tg and cross-linking degree, it still provides a viable pathway toward partially bio-based epoxy resins with enhanced stiffness and competitive mechanical performance.
https://doi.org/10.3390/su18042083
Improved Straw Decomposition Products Promote Peanut Growth by Changing Soil Chemical Properties and Microbial Diversity
The ameliorative effects of straw decomposition products on soil acidification have been extensively studied. However, the impact of chemically treated straw decomposition products on crop productivity and the underlying microbial mechanisms remain unclear. This study aimed to investigate the effects of two dosages of Ca(OH)2-treated straw decomposition products of peanuts on red soil acidity, fertility, and bacterial and fungal diversity through a pot experiment. The pot experiment included four treatments: chemical nitrogen, phosphorus, and potassium (NPK) fertilization alone (CK), NPK chemical fertilization combined with peanut straw decomposition products (PS), NPK chemical fertilization combined with 4% Ca(OH)2-treated peanut straw decomposition products (PS4Ca), and NPK chemical fertilization combined with 8% Ca(OH)2-treated straw decomposition products (PS8Ca). High-throughput sequencing was performed to investigate the effects of these treatments on soil microbial diversity. The treatments with PS, PS4Ca, and PS8Ca significantly increased soil pH, exchangeable base cations, and nutrient content, whereas they decreased the exchangeable acid, especially exchangeable aluminum. The peanut growth improved substantially with the application of straw decomposition products. Specifically, PS4Ca significantly increased the Shannon and Richness indices of fungi. The principal coordinate analysis showed that the soil microbial communities in the straw decomposition product treatments were significantly different from CK. Linear discriminant analysis effect size identified unique bacteria and fungi between treatments. The Mantel test indicated that exchangeable base cations and pH were significantly positively correlated with bacterial communities, whereas available potassium was positively correlated with fungal communities. The partial least squares path modeling revealed that the bacterial communities positively and directly affected all peanut agronomic traits. In contrast, the fungal communities had a negative and direct effect only on peanut 100-pod weight. Therefore, adding Ca(OH)2-treated straw decomposition products could effectively improve crop productivity by alleviating soil acidification, increasing soil nutrients, and subsequently changing microorganisms.
https://doi.org/10.3390/su16167096
An Eco-Friendly Modification of a Walnut Shell Biosorbent for Increased Efficiency in Wastewater Treatment
Herein, we report the performance of some low-cost biosorbents developed by environment-friendly modification of walnut shells. Two types of biosorbents were prepared by ecological modification of walnut shell surfaces: (1) biosorbents obtained by hot water treatment (WSH2O) and (2) biosorbents produced by mercerization (WSNaOH). Different techniques were used to evaluate the morphological, elemental, and structural modification of the biosorbents, by comparison with raw materials. These characterization techniques involved scanning electron microscopy (SEM) coupled with energy-dispersive X-ray analysis, and Fourier-transform infrared spectroscopy (FTIR). The biosorbents were employed for the removal of methylene blue (MB) and crystal violet (CV) cationic dyes (as model organic pollutants) from aqueous solutions. The kinetic adsorption data mainly followed the pseudo-first-order model. The maximum adsorption capacities of the produced biosorbents ranged from 102 to 110 mg/g and were observed at 330 K. Equilibrium data for adsorption were fitted to Langmuir and Freundlich isotherm models. The calculated values of thermodynamic parameters suggested that the investigated adsorption processes were exergonic (ΔG < 0) and exothermic (ΔH < 0). In addition, a possible valorization of the cost-effective and eco-friendly spent biosorbents was tested by performing secondary adsorption of the anionic dyes.
http://dx.doi.org/10.3390/su15032704
Macadamia Breeding for Reduced Plant Vigor: Progress and Prospects for Profitable and Sustainable Orchard Systems
Vigor control in tree crops plays an important role in increasing orchard efficiency and sustainability. It has enabled high-density plantations to maximize yield efficiency while reducing production costs. Although traditional methods such as frequent hedging and pruning are still used, dwarfing rootstocks and low-vigor cultivars are the most effective and sustainable means of vigor control, as these methods reduce labor and management costs while maintaining yield efficiency. Considerable variation among cultivars and rootstocks for vigor has been identified; however, mechanisms by which rootstocks affect scion vigor in slow-maturing tree crops remain unclear. With the lack of adequate information required for early and rapid selection, breeding programs in tree crops such as macadamia still utilize manual phenotyping, which is laborious, time-consuming, and expensive. Providing insights on emerging technologies that enhance breeding programs via rapid selection, this review summarizes the current state of vigor management and underlying mechanisms of vigor control in tree crops. It provides further understanding of the prospects of applying those techniques in rootstock and scion breeding for low-vigor and yield-efficient cultivars in tree crops, with specific reference to macadamia.
http://dx.doi.org/10.3390/su151914506