Search Results (69)

This study, conducted in Mexico, evaluates the agricultural potential of three compost formulations BFS1, BFS2, and BFS3 produced from mining tailings and thermophilic microbial mats and collected from geothermal environments. The physicochemical characterization included pH, electrical conductivity (EC), macronutrients (N, P, K, Ca, Mg, and S), micronutrients (Fe, Zn, B, Cu, Mn, Mo, and Ni), organic matter (OM), and the carbon-to-nitrogen (C/N) ratio. All composts exhibited neutral pH values (7.38–7.52), high OM content (38.5–48.4%), and optimal C/N ratios (10.5–13.9), indicating maturity and chemical stability. Nitrogen ranged from 19 to 21 kg·t⁻¹, while potassium and calcium were present in concentrations beneficial for crop development. However, EC values (3.43–3.66 dS/m) and boron levels (>160 ppm) were moderately high, requiring caution in saline soils or with boron-sensitive crops. A semi-quantitative Compost Quality Index (CQI) ranked BFS3 highest due to elevated OM and potassium content, followed by BFS1. BFS2, while rich in nitrogen, scored lower due to excessive boron. One-way ANOVA revealed no significant difference in nitrogen (p > 0.05), but it did reveal significant differences in potassium (p < 0.01) and boron (p < 0.001) among formulations. These results confirm the potential of mining tailings—microbial mat composts are low-cost, nutrient-rich biofertilizers. They are suitable for field crops or as components in nursery substrates, particularly when EC and boron are managed through dilution. This study promotes the circular reuse of geothermal and industrial residues and contributes to sustainable soil restoration practices in mining-affected regions through innovative composting strategies. Full article

Electrolytic manganese residue (EMR) is a byproduct of electrolytic manganese production, rich in soluble pollutants such as manganese and ammonia nitrogen. Traditional stockpiling methods result in contaminant leaching and water pollution, threatening ecosystems. Meanwhile, EMR has significant resource-recovery potential. This paper systematically reviews the harmless process and resource technology of EMR, efficiency bottlenecks, and the current status of industrial applications. The mechanisms of chemical leaching, precipitation, solidification, roasting, electrochemistry, and microorganisms were analyzed. Among these, electrochemical purification stands out for its efficiency and environmental benefits, positioning it as a promising option for broad industrial use. The mechanisms of chemical leaching, precipitation, solidification, roasting, electrochemistry, and microorganisms were analyzed, revealing the complementarity between building materials and chemical materials (microcrystalline glass) in scale and high-value-added production. But the lack of impurity separation accuracy and market standards restricts its promotion. Finally, it proposes future directions for EMR resource utilization based on practical and economic considerations. Full article

Industrial munition facilities are increasingly manufacturing insensitive high explosives (IHEs) to improve safety. The explosive residues in wastewater from these facilities are treated to meet regulatory standards. However, the resulting effluent contains elevated levels of mineralized nitrogen species. This study evaluated the potential of vetiver grass (Chrysopogon zizanioides), a non-invasive perennial species, to remove high concentrations of nitrate, nitrite, and ammonium from munition plant wastewater. Vetiver was grown hydroponically in synthetic wastewater containing high levels of nitrogen compounds simulating munitions plant effluents. Vetiver plants were treated with one nitrogen species at a time, with concentrations ranging from 165 to 24,700 mg N/L of nitrate, 100 to 4000 mg N/L of nitrite, and 260 to 39,000 mg N/L of ammonium. Nitrogen concentrations in the media and plant responses were monitored over time. The results showed significant nitrogen removal at lower concentration ranges. When concentrations exceeded 3800 mg N/L of nitrate, 800 mg N/L of nitrite, and 2600 mg N/L of ammonium, the removal rates declined after 7 days. At higher nitrogen levels, vetiver exhibited stress symptoms such as chlorosis and elevated antioxidant enzyme activity. Our study demonstrates the potential of vetiver grass in treating nitrogen-rich wastewater from the munition industry and provides a baseline for future large-scale studies to optimize the technology. Full article

The use of crop residues is increasing across farming systems as part of climate change mitigation efforts and agricultural management practices to improve soil health. Hemp residues offer valuable potential in these efforts due to their rich nutrient composition. However, the complex chemical composition of hemp residue could pose a significant challenge by slowing the decomposition rate if not adequately managed. The aim of this study is to evaluate the influence of different timings of hemp residue incorporation, soil tillage practices, and mode of application on the rate of mineralization and soil chemical parameters. A complete randomized design field trial was conducted on hemp (Cannabis sativa L.) residue incorporation across different seasonal periods and modes of application. The results showed that the fastest mineralization occurred when hemp residue was incorporated in autumn, while the slowest mineralization was observed when the residue was left on the surface of the soil as mulch. The application of hemp residues over three years led to a slight increase in soil pH from an initial value of 4.9; however, this change was not statistically significant. Similarly, nitrogen content did not change significantly between the different periods after applying hemp residues. In contrast, hemp residues contributed to an increase in soil carbon content. Overall, this study emphasizes the need to optimize hemp residue management to maximize its benefits for enhancing soil chemical properties and promoting sustainable agriculture. Full article

The use of agro-industrial by-products and processing residues, which are rich in carbohydrates, proteins, and lipids, in the production of lipases allows the sustainable use of these residues, reducing environmental impacts. In this study, the immersion water of lentils, soybeans, and textured soy protein was evaluated as carbon and nitrogen sources in the production of whole-cell lipases, and the resulting biomass was used in the hydrolysis of residual soybean oil with conventional heating and ultrasound. The results showed that the best culture medium was the one with 50% textured soybean protein, reaching values of 149.04 U/g of hydrolytic activity, 12.92 g/L of biomass concentration, 144.17 U of total biomass activity, and specific and volumetric productivities of 2.07 U/g·h and 20.02 U/L·h, respectively. The positive effect of adding soybean frying oil to the crop was observed, which increased cell production and hydrolytic activity. The biomass obtained showed potential for the ultrasound-assisted hydrolysis of vegetable oils, reaching approximately 43.36% hydrolysis in 7 h of reaction, with an initial rate of 31.03 mmol/h. It is concluded that soybean protein processing water is a viable candidate to replace traditional nitrogen sources, being an economically attractive alternative due to its wide generation in restaurants. Full article

Citrus fruit production generates substantial by-products, primarily from juice processing, which represent significant environmental and economic challenges. However, these residues, rich in polysaccharides, flavonoids, essential oils, and enzymes, offer an untapped resource for biotechnological applications. This review explores the potential of citrus by-products as substrates for enzyme production, focusing on key industrial enzymes such as cellulases, pectinases, xylanases, ligninases, lipases, and proteases. Various microbial strains have demonstrated the ability to convert citrus residues into high-value enzymes through solid-state and submerged fermentation. The optimization of fermentation conditions—including temperature, pH, moisture content, and the carbon-to-nitrogen ratio—further enhances enzymatic yields. The valorization of citrus waste aligns with circular economy principles, reducing environmental impacts while supporting sustainable bioproduct development for the food, biofuel, pharmaceutical, and textile industries. Future research should focus on scaling up enzyme production using citrus waste to improve economic feasibility and advance industrial biorefineries. Full article

The pyrolysis process of residues has emerged as a sustainable method for managing organic waste, producing biochars that offer significant benefits for agriculture and the environment. These benefits depend on the properties of the raw biomass and the pyrolysis conditions, such as washing and drying. This study investigated biochar production through slow pyrolysis at 300 °C, using eight biomass types, four being plant residues (PBR)—sugarcane bagasse, filter cake, sawdust, and stranded algae—and four non-plant-based residues (NPBR)—poultry litter, sheep manure, layer chicken manure, and sewage sludge. The physicochemical properties assessed included yield, carbon (C) and nitrogen (N) content, electrical conductivity, pH, macro- and micronutrients, and potentially toxic metals. Pyrolysis generally increased pH and concentrated C, N, phosphorus (P), and other nutrients while reducing electrical conductivity, C/N ratio, potassium (K), and sulfur (S) contents. The increases in the pH of the biochars in relation to the respective biomasses were between 0.3 and 1.9, with the greatest differences observed for the NPBR biochars. Biochars from sugarcane bagasse and sawdust exhibited high C content (74.57–77.67%), highlighting their potential use for C sequestration. Filter cake biochar excelled in P (14.28 g kg⁻¹) and micronutrients, while algae biochar showed elevated N, calcium (Ca), and boron (B) levels. NPBR biochars were rich in N (2.28–3.67%) and P (20.7–43.4 g kg⁻¹), making them ideal fertilizers. Although sewage sludge biochar contained higher levels of potentially toxic metals, these remained within regulatory limits. This research highlights variations in the composition of biochars depending on the characteristics of the original biomass and the pyrolysis process, to contribute to the production of customized biochars for the purposes of their application in the soil. Biochars derived from exclusively plant biomasses showed important aspects related to the recovery of carbon from biomass and can be preferred as biochar used to sequester carbon in the soil. On the other hand, biochars obtained from residues with some animal contributions are more enriched in nutrients and should be directed to the management of soil fertility. Full article

Albania, situated in southeastern Europe, enjoys a Mediterranean climate that is well-suited for grape cultivation. The vineyard area totals 7.202 million hectares. Since the 1990s, the country has experienced a resurgence in its rich winemaking traditions, which have gained considerable attention over the last decade. Alongside its significant wine production, large amounts of vine pruning waste and fermentation by-products are generated, estimated at over 50,000 t of prunings and 35,900 t of grape pomace annually. This waste is often burned, and the ash is used as fertilizer, releasing considerable CO₂ emissions, and contributing to greenhouse gas levels. However, recycling these prunings into fertilizer by chipping and grinding them in the vineyard presents a sustainable choice, providing key minerals, nitrogen, phosphorus, and various micronutrients, thereby reducing the dependence on synthetic fertilizers in farming. Characterized by small plantations, the vine pruning issue needs site-specific, economically feasible solutions for the farmer. Additionally, there is unexplored potential for applying wine fermentation pressing residues as fertilizer for agricultural land or vineyards. The Albanian wine sector has significant untapped opportunities, such as employing vine pruning ash as a mineral fertilizer to help achieve sustainability goals. Full article

This study explores the effects of a subcritical seawater treatment (SST) on buckwheat waste (BW), and the use of the hydrolysate as a liquid fertilizer to improve the growth of lettuce (Lactuca sativa L.). Three temperature treatments (110 °C, 170 °C, 230 °C) were used for the SST, and the ionic composition in the seawater achieved the depolymerization and degradation of BW. The X-ray diffraction of the residual solids showed that the structure of BW was destroyed. Compared with seawater, the hydrolysate contained higher amounts of elements beneficial to plant growth, such as N, P, K, and organic compounds such as phenolics and sugars, as a result of the degradation of BW caused by the SST. The hydrolysate was tested as a liquid fertilizer (treatments H_110°C, H_170°C, H_230°C) to irrigate lettuce. The content of proteins, phenolics, and chlorophyll, as well as the weight of the lettuce in the H_110°C and H_170°C treatments, were significantly higher than those in the seawater and the H_230°C irrigation treatments (p < 0.05). The hydrolysate from the SST of BW, being rich in various organic and inorganic nutrients, can act as a liquid fertilizer that promotes the growth of lettuce, whereas hydrolysate from higher SST temperatures might inhibit the growth of lettuce, because of the excessive total nitrogen and organic acid. Full article

Nitrogen inputs for sustainable crop production for a growing population require the enhancement of biological nitrogen fixation. Efforts to increase biological nitrogen fixation include bioprospecting for more effective nitrogen-fixing bacteria. As bacterial nitrogenases are extremely sensitive to oxygen, most primary isolation methods rely on the use of semisolid agar or broth to limit oxygen exposure. Without physical separation, only the most competitive strains are obtained. The distance between strains provided by plating on solid media in reduced oxygen environments has been found to increase the diversity of culturable potential diazotrophic bacteria. To obtain diverse nitrogen-fixing isolates from natural grasslands, we plated soil suspensions from 27 samples onto solid nitrogen-free agar and incubated them under atmospheric and oxygen-reducing conditions. Putative nitrogen fixers were confirmed by subculturing in liquid nitrogen-free media and PCR amplification of the nifH genes. Streaking of the 432 isolates on nitrogen-rich R2A revealed many cocultures. In most cases, only one community member then grew on NFA, indicating the coexistence of nonfixers in coculture with fixers when growing under nitrogen-limited conditions. To exclude isolates able to scavenge residual nitrogen, such as that from vitamins, we used a stringent nitrogen-free medium containing only 6.42 μmol/L total nitrogen and recultured them in a nitrogen-depleted atmosphere. Surprisingly, PCR amplification of nifH using various primer pairs yielded amplicons from only 17% of the 442 isolates. The majority of the nifH PCR-negative isolates were Bacillus and Streptomyces. It is unclear whether these isolates have highly effective uptake systems or nitrogen reduction systems that are not closely aligned with known nitrogenase families. We advise caution in determining the nitrogen fixation ability of plants from growth on nitrogen-free media, even where the total nitrogen is very limited. Full article

The rapid increase in fertilizer use has led to the degradation of soil quality, nutrient imbalances, reduced biodiversity, and soil compaction. To address these challenges, hybrid soybeans with efficient biological nitrogen fixation capabilities and broad environmental adaptability were selected as green manure to reduce fertilizer application, thereby improving soil fertility and structure. This study utilized the varieties “Forage Soybean S001” (S001), “Neinong S002 Forage Soybean” (S002), “Mengnong S003 Forage Soybean” (S003), “Mengnong S004 Forage Soybean” (S004), “Mengnong S005 Forage Soybean” (S005), and “Mengnong S006 Forage Soybean” (S006) as green manure materials. The clean tillage (CK) treatment served as the control, ensuring a residue-free soil surface while maintaining consistent practices in soil preparation, irrigation, and field management across all treatments. Field planting of green manure and subsequent crops was conducted at the M-Grass Ecology and Environment (Group) Company’s experimental site in Hohhot in early May of 2023 and 2024. The plots each measured 20 m², with three replications arranged in a randomized block design. A combination of field experiments and laboratory analyses was utilized to investigate the effects of incorporating various hybrid soybean varieties as green manure on soil nutrient levels, soil enzyme activity, soil microbial communities, and the subsequent growth of oats. The results indicated that incorporating various hybrid soybean varieties as green manure into the soil significantly improved soil nutrient levels and enzyme activity. The diversity and richness of soil bacterial communities increased significantly, accompanied by alterations in community structure and composition. These changes enhanced soil fertility and optimized the microbial community structure, promoting the growth of subsequent crops. Among all the treatments, S001 and S004 were particularly effective in enhancing the soil environment, indicating their potential as superior green manure resources for broader application. Full article

Crack-free Stellite-6 alloy was fabricated using the laser powder bed fusion technique equipped with a heating module as the first attempt. Single tracks were printed with a build plate heated to 400 °C to identify the processing window. Based on the melt pool dimensions, two combinations (sample A: 300 W/750 mm/s and sample B: 275 W/1000 mm/s) were identified to print the cubes. The as-printed microstructure comprised FCC-Co dendrites with M₇C₃ in the interdendritic region. W-rich M₆C particles were found in the overlapping regions between the melt pools, matching the Scheil simulations. However, gas pores were observed due to the higher nitrogen and oxygen content of the feedstock requiring hot isostatic pressing (HIP) at 1250 °C and 150 MPa for 2 h. Sample A was partially recrystallized with slightly coarsened M₇C₃, while sample B underwent complete recrystallization followed by grain growth along with higher coarsening of the M₇C₃ after HIP. The varying recrystallization behavior can be attributed to the difference in residual stresses and grain aspect ratio in the as-built condition dictated by laser power and scanning speed. The microhardness after HIP was slightly higher than its wrought counterpart, indicating no severe impact of post-processing on the properties of Stellite-6 alloy. Full article

Microbial cultures repurposing organic industrial residues for value-added metabolite production is pivotal for sustainable resource use. Highlighting polyunsaturated fatty acids (PUFAs), particularly gamma-linolenic acid (GLA), renowned for their nutritional and therapeutic value. Notably, Zygomycetes’ filamentous fungi harbor abundant GLA-rich lipid content, furthering their relevance in this approach. In this study, the strain C. elegans NRRL Y-1392 was evaluated for its capability to metabolize glycerol and produce lipids rich in GLA under different culture conditions. Various carbon-to-nitrogen ratios (C/N = 11.0, 110.0, and 220.0 mol/mol) were tested in batch-flask cultivations. The highest GLA production of 224.0 mg/L (productivity equal to 2.0 mg/L/h) was observed under nitrogen excess conditions, while low nitrogen content promoted lipid accumulation (0.59 g of lipids per g of dry biomass) without yielding more PUFAs and GLA. After improving the C/N ratio at 18.3 mol/mol, even higher PUFA (600 mg/L) and GLA (243 mg/L) production values were recorded. GLA content increased when the fungus was cultivated at 12 °C (15.5% w/w compared to 12.8% w/w at 28 °C), but productivity values decreased significantly due to prolonged cultivation duration. An attempt to improve productivity by increasing the initial spore population did not yield the expected results. The successful scale-up of fungal cultivations is evidenced by achieving consistent results (compared to flask experiments under corresponding conditions) in both laboratory-scale (Working Volume—Vw = 1.8 L; C/N = 18.3 mol/mol) and semi-pilot-scale (Vw = 15.0 L; C/N = 110.0 mol/mol) bioreactor experiments. To the best of our knowledge, cultivation of the fungus Cunninghamella elegans in glycerol-based substrates, especially in 20 L bioreactor experiments, has never been previously reported in the international literature. The successful scale-up of the process in a semi-pilot-scale bioreactor illustrates the potential for industrializing the bioprocess. Full article

With the growing world population, food demand has also increased, resulting in increased agricultural waste and livestock manure production. Wheat straw and cow dung are rich nutrient sources and, if not utilized properly, may lead to environmental pollution. Keeping in view the cultivation of Agaricus bisporus on straw/manure-based substrate, the current study aimed to optimize the conventional manure preparation technique to reduce nutrient losses and keep the quality of manure at its best. The treatments were considered as traditional and optimized schemes for mushroom substrate preparation. The results achieved herein indicated that the nutrient losses were low in the optimum scheme. For carbon (C), the loss was 43.55% at the substrate stage in the traditional scheme and reduced to 37.75% in the optimum scheme. In the case of nitrogen (N), the loss was 22.01% in the traditional scheme and was lower (18.49%) in the optimum scheme. The nutrient concentration in Agaricus bisporus was higher with the optimum scheme compared with the traditional scheme. It was 1.74% for C, 7.17% for N, 3.58% for phosphorus (P), and 4.92% for potassium (K). The optimum scheme also improved the Agaricus bisporus yield per unit area (84.55%) and the total yield (28.92%). The net income of the optimum scheme was 102.95% higher compared to the traditional scheme. The economic analysis also revealed that the benefit–cost ratio of the optimum scheme was high (48.86%) compared with the traditional scheme. This study concludes that the use of the optimum scheme can better utilize the wheat straw and cow manure waste for substrate preparation and reducing nutrient losses. In addition, the final mushroom residue can also be used as a leftover substrate for further utilization. Full article

Biological treatment processes at low or neutral pH are ineffective for gold mine wastewater treatment. The aim of this study was to develop a new cyanide-rich gold mine wastewater treatment system using alkaliphilic microbial consortia from the Ethiopian Rift Valley soda lake, Lake Chitu. The treatment setup incorporates aerobic and anoxic reactors connected in series and operated for about 200 treatment days. Simulated gold mine wastewater was formulated in the laboratory. Colorimetry was used to measure residual cyanide and reactive nitrogen molecules derived from cyanide biodegradation. Flocks and biofilms developed in the reactors during the acclimatization process. Using sodium cyanide at 200 mg/L as an initial concentration, the consortia degraded to 99.74 ± 0.08% of cyanide, with no significant variation (p > 0.05) occurring when the dose was increased to 800 mg/L. However, changes were observed (p < 0.05) at 1000 mg/L. Acetate was the preferred carbon source for the consortia. The established consortia effectively degraded cyanide to levels below the permissible discharge limit set by the International Cyanide Management Institute (ICMI). This study provides insights into the effectiveness of alkaliphilic microbial consortia derived from soda lakes for treating cyanide-polluted wastewater. Full article