Alternative Use of Biological Resources

1. Introduction

Over the last few decades, the use of materials of biological origin has garnered significant attention due to their favorable substitutional or complementary benefits [1,2,3]. Several authors have identified this field as a major contributor to recent sustainability initiatives and a sound transition toward circular economy frameworks [4,5,6]. This Special Issue of Resources presents recent innovations and challenges in the use of such materials as alternatives for non-food and non-conventional purposes. The 13 papers included in this Special Issue highlight substantial advancements in the field based on in-depth, high-standard experiments and extensive reviews of the most relevant literature.

2. Overview of the Published Articles

In their study, Khan et al. [7] demonstrated that cotton fabrics dyed with Ficus carica and Eucalyptus leaf extracts, combined with Aloe barbadensis Miller as a bio-mordant, achieved enhanced color strength (K/S value up to 5.85), excellent crocking fastness (4–5), and good washing fastness (3–4), resulting in deep, earthy shades such as green, yellow–green, and yellowish brown. Additionally, the treated fabrics exhibited up to 70% mosquito repellency, over 80% antibacterial activity against E. coli, and a 57% dye removal efficiency when adsorbed onto graphene oxide, highlighting the multifunctional benefits of this sustainable dyeing approach [7].

Manterola-Barroso et al. [8] evaluated walnut and hazelnut shells from Southern Chile over three seasons, revealing that walnut shells exhibited higher antioxidant capacity (ORAC) and total phenolic content (TPC) compared to hazelnut shells, with walnut showing greater seasonal variability. Additionally, the morphological and structural features of the shells, including cellulose and lignin distribution, were examined using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), providing insights into their potential as sustainable by-products for various applications [8,9].

Another research paper focusing on shell materials was published by Lejano et al. [10], who reported that replacing 10% of the cement with green mussel shell powder and adding 0.25% chitosan to the mortar increased its 28-day compressive strength by approximately 38.74% compared to the control. However, high levels of mussel shell (especially without impurity removal) reduced both workability and stability. However, in concrete mixes, using 10% mussel shell replacement (with or without chitosan) significantly decreased the compressive strength (by up to ~47%, depending on the water-to-cement ratio), a drop mainly attributed to magnesium impurities in the mussel shells [10,11].

A comprehensive evaluation underlined that both alkaline (1.5% NaOH) and hydrothermal (120 °C for 45 min) pretreatments significantly improve conversion of cellulose and hemicellulose in rice husk into fermentable sugars: alkaline pretreatment yielded ~81.7% glucose from cellulose and ~96.3% xylose from hemicellulose, while the best hydrothermal treatment gave ~93% glucose but somewhat lower xylose conversion (~83.35%). After fermentation with Saccharomyces cerevisiae, the pretreated hydrolysates produced ethanol yields of ~13 g/L (conversion factor of ~0.43), with alkaline pretreatment slightly outperforming hydrothermal pretreatment in overall sugar production. However, hydrothermal pretreatment allowed somewhat faster sugar consumption in some cases [12,13].

Pertiwi et al. [14] found that soil blocks made using Rawapening Lake sediment (mixed with cocopeat, manure, etc.) reduce Global Warming Potential by ~48% compared to conventional polybag seedling media, improve nutrient content (especially phosphorus and organic matter), increase productivity by ~90%, and offer a higher revenue-cost ratio and overall economic efficiency. Additionally, the sustainability evaluation across environmental, technological, economic, social, and institutional dimensions classifies the innovation as moderately sustainable, with institutional support identified as the weakest dimension and a key barrier to scaling up [14].

Another paper revealed that corrosion inhibitors synthesized from distilled higher fatty acids of beef fat (DHFAs) or vegetable oils (VO), when reacted with amines like diethanolamine or diaminoethyl, achieves protective effects (on St20 steel in saline/jet-fuel solutions at 50 °C) ranging from ~75% up to ~95%, depending on composition, and with the best formulation reaching 99.2% inhibition which compares favorably to standard industrial inhibitors (91.6–99.5%) [15].

A study by Shabbir et al. [16] demonstrated that textile packaging coated with natural bioactive extracts from red, green, and brown algae significantly reduced weight loss and preserved firmness and juice content of tomatoes and apples over 21 days, with the blend of all three algae types performing the best (weight loss ~4.2% for tomatoes, ~3.8% for apples) compared to ~10–11% loss in uncoated packaging. The authors highlight that the algae coatings —particularly those based on red algae and the mixed-algae treatment—maintain fruit quality by limiting moisture loss and preserving texture, offering a biodegradable and more sustainable alternative to conventional plastic packaging [16].

Henao et al. [17] used the Analytic Hierarchy Process (AHP) to evaluate several alternatives for using rice chain residues in construction materials in Tolima, Colombia, with criteria including ease of implementation, treatment required, reproducibility, and marketability. The authors found that cement bricks incorporating rice husk ash (RHA) were the highest-ranked option overall due to low costs and simpler pretreatment. Additionally, RHA-based pavers achieved sufficient compressive strength for light traffic applications under low abrasion conditions, particularly when replacing up to ~20% of the cement, although higher replacement rates led to decreased mechanical performance [17].

It was also pointed out in an experiment-based evaluation that using cold carbonated water with 0.6% NaCl in the first wash cycle followed by two washes with cold tap water yields surimi from tropical mackerel with much better gel strength (~965 g·mm), improved water holding capacity (~65%), and significantly reduced levels of lipid (~80%), myoglobin (~65%), non-heme iron (~94%), and off-flavor components compared to unwashed mince or conventional washing. This washing strategy also enhances whiteness (approximately 45% improvement), reduces lipid oxidation (TBARS < 0.5 mg MDA/kg), and provides a viable and straightforward method for producing high-quality surimi from dark-fleshed fish, thereby supporting a more sustainable use of such fish resources [18,19,20].

In-depth research revealed that Hungarian propolis ethanolic extracts effectively inhibited the growth of Gram-positive bacteria (Staphylococcus spp., Enterococcus spp.), Candida albicans, and the protozoan Trichomonas gallinae, with minimum inhibitory concentrations (MICs) ranging from 1.56 to 400 µg/mL, while showing limited activity against Gram-negative bacteria (Escherichia coli and Salmonella enterica). These findings suggest that propolis could serve as a potential alternative to traditional antibiotics, particularly for treating infections in pigeons, though its efficacy against Gram-negative bacteria remains limited [21,22].

A study published based on 453 literature sources examined the relevance of plant-based building materials in the construction industry, revealing a steady increase in research output over time. Most articles focused on engineering disciplines and were aligned with the Sustainable Development Goals (SDGs). The analysis identified key plant-based materials, such as hemp, bamboo, and flax, which are extensively studied for their potential to enhance the mechanical properties of conventional materials and serve as sustainable alternatives in construction applications [23,24].

A review paper emphasized the potential of converting food waste into valuable resources through strategies like composting, bioconversion, and innovative recycling technologies, which can transform biowastes into fertilizers, animal feed, and even new food products, thereby closing the loop in the food system. This approach not only addresses environmental issues associated with food waste but also creates economic opportunities, contributing to sustainable solutions for waste valorization and enhancing food security [25,26,27].

Another extensive review highlighted the use of plant-based extracts—such as those from fruits, seeds, leaves, stems, and roots—as eco-friendly agents in the green synthesis of various inorganic nanoparticles, including gold, silver, zinc oxide, and iron. These plant-derived compounds, rich in bioactive molecules such as polyphenols and flavonoids, not only chelate metal ions but also cap and stabilize nanoparticles, leading to materials with diverse biological activities, including antioxidant, antimicrobial, and plant-growth-promoting effects [28,29,30,31].

3. Conclusions

This Special Issue emphasizes the importance and versatility of biological resources within their alternative application schemes. The included studies highlight some of the most impactful approaches of secondary utilization pathways. This contribution from the scientific community can support future research perspectives, while it can also trigger practical, high-scale utilization to reduce the dependency on conventional materials having relatively more adverse environmental impact through their life cycle.