Search Results (67)

This critical review examines the evolution of mathematical modeling approaches for aerobic digestion processes in food industry waste management, highlighting their role in operational optimization and dynamic prediction. In recent years, increasing pressure for sustainable waste management, circular bioeconomy strategies, and process intensification in the food industry has accelerated the development of mathematical tools for describing complex biological treatment systems, making a critical synthesis of available modeling approaches particularly timely. Starting from mass conservation principles, simple kinetic models such as first-order and Monod models are analyzed. These models assume homogeneity and perfect mixing but fail to capture the heterogeneity of effluents rich in variable carbohydrates, proteins, and lipids. Structural limitations, including numerical rigidity, parametric non-identifiability, and idealized assumptions that underestimate spatial gradients and stochastic fluctuations, are examined. In continuous systems, coupled substrate–biomass–oxygen dynamics, washout phenomena, and extensions toward partial differential equations for representing real heterogeneity are explored. Structured models such as Activated Sludge Models (ASMs) incorporate multicomponent fractions but face parameterization challenges exacerbated by limited industrial data availability, as less than 25% of treatment plants currently employ formal modeling frameworks. Emerging paradigms include hybrid mechanistic–machine learning approaches for prediction under perturbations, multiscale modeling, and spatially explicit modeling. Unlike previous reviews that focus primarily on technological aspects of waste treatment, this study provides a critical comparison of modeling frameworks and their applicability to different food waste matrices. A classification table distributes approaches by food matrix, revealing the dominance of simple kinetics in composting and ASMs in activated sludge systems. Finally, a progressive model selection framework based on operational objectives is proposed, balancing model complexity with predictive robustness and experimental validation to support sustainable industrial adoption. Full article

This study aimed to evaluate the effects of adding sludge generated in water treatment plants on the composting of sewage sludge, urban organic waste, and agroindustrial waste. Four treatments were conducted with different proportions of water treatment plant sludge (WTS). Four treatments were conducted with 0%, 10%, 20%, and 30% proportions of WTS. The different proportions allowed for the evaluation of the effects of WTS addition on composting. The study was carried out in composting reactors. Kinetic models were applied to study the degradation of organic matter. Physicochemical and microbiological parameters were analyzed. During the process, temperature variation and basal respiration exhibited similar patterns. Principal component analysis showed that the 30WTS (32.2% water treatment sludge) treatment presented higher values of cation exchange capacity (CEC)/total organic carbon (TOC) ratio (3.83), and germination index (94.35%), and lower values of TOC (23.67%) and C/N (carbon/nitrogen) ratio (14.45). The composts produced in all treatments complied with Brazilian regulations for the environmental and agronomic quality of organic composts. It was concluded that the inclusion of up to 30% of WTS in composting did not negatively affect the composting process and did not compromise the environmental or agronomic quality of the final organic composts. Full article

The prolonged low temperature in cold regions significantly inhibits the initiation of straw composting and lignocellulose degradation, thereby restricting straw resource utilization. In this study, 24 cellulose-degrading strains capable of stable growth under low-temperature conditions were screened. Based on multiple indicators, including carboxymethyl cellulase (CMCase) activity, strain LDT1 was identified as the best-performing isolate under low-temperature conditions and as Paenarthrobacter nitroguajacolicus. Subsequently, an efficient mutant strain, LDT1-8, was obtained through atmospheric and room-temperature plasma mutagenesis. The CMCase activity of LDT1-8 at 10 °C increased to 74.25 U/mL, representing a 21.72% increase compared to the wild-type strain. In a straw degradation system at 10 °C, LDT1-8 significantly accelerated early-stage degradation kinetics, with straw degradation rates at 3 and 6 d being 72.72% and 38.15% higher than those of the wild-type strain, respectively. Multi-enzyme profiling further indicated enhanced activities of multiple lignocellulose-degrading enzymes at low temperatures, accompanied by a partial shift in the optimal temperature of some enzymes (e.g., laccase) toward lower temperatures. Whole-genome sequencing revealed increased gene numbers related to energy, amino acid, and lipid metabolism in LDT1-8. Comparative genomic analysis suggested that mutations were mainly enriched in regulatory regions, accompanied by local structural variations. Transcriptional analyses further verified the coordinated upregulation of genes involved in cellulose and hemicellulose degradation, cold adaptation, and transcriptional and protein homeostasis processes in LDT1-8. Overall, this study provides an efficient microbial resource and a mechanistic basis for straw bioconversion in cold regions. Full article

Sustainable agriculture is increasingly reliant on reducing anthropogenic inputs and recycling organic waste while protecting ecosystems. In this context, this study investigated the agro-environmental properties of biosulfate, focusing on its interaction with herbicides and its effects on soil fungi and horticultural plants. Two biosulfate samples obtained from urban sewage sludge from the Barletta (BIO-BA) and Foggia (BIO-FO) treatment plants were characterized by Fourier transform infrared–attenuated total reflectance (FTIR-ATR) spectroscopy and scanning electron microscopy (SEM). The adsorption/desorption of the herbicides metribuzin (MET), S-metolachlor (S-ME) and cycloxydim (CYC) on biosulfates was evaluated by studying adsorption kinetics and isotherms. All herbicides reached adsorption equilibrium within a few hours, according to pseudo-second-order kinetics, indicating a predominant chemical interaction between biosulfate and the molecules. Considering the organic C content of BIO-BA (~21%) and BIO-FO (~17%), which was less than half that commonly measured for other organic fertilizers, such as compost and digestate, their adsorption capacity was high, with Freundlich adsorption constants ranging from 772 µg g⁻¹ (S-ME on BIO-BA) to 1464 µg g⁻¹ (CYC on BIO-FO). A low hysteresis coefficient indicated a rather slow and incomplete release of the molecules from the biosulfate. Exposure of the fungi Pleurotus ostreatus and Pleurotus eryngii to 1, 2, 3, and 4% BIO-BA and BIO-FO stimulated mycelium growth, indicating that responses depended on fungal species and biosulfate dose. Finally, germination and early growth of lettuce and basil were generally unaffected by either biosulfate, as parameters such as germination percentage, root and shoot length, and fresh and dry biomass were not statistically different from the control. Some growth stimulation was observed in basil. Overall, biosulfate appears to be a promising soil fertilizer, as it can contribute to soil organic matter, retain xenobiotics, and exert biostimulatory effects under controlled conditions. Full article

Carbon monoxide (CO) is a key component of syngas and an important intermediate in the chemical, metallurgical, heavy, and food industries. Although mainly associated with thermochemical processes, CO can also be generated during composting, offering an environmentally friendly biological alternative. This study assessed the potential for CO production during laboratory-scale composting of seven selected organic waste fractions: coffee grounds, green tea leaves/grounds, wheat straw, grass cuttings, branches, food waste, and a biowaste mixture with an optimal C/N ratio. Composting was carried out under laboratory conditions at 45 °C for 14 days, with daily passive aeration and monitoring of CO, CO₂, and O₂ concentrations in the reactor headspace. CO production kinetics were calculated for each substrate, and the CO mass yield was determined in each bioreactor. The study confirmed the CO generation potential of the analyzed organic waste fractions. The highest CO production was observed for grass cuttings (max. 2000 ppm, 1.21 mg), biowaste mix (2000 ppm, 0.82 mg), and wheat straw (1180 ppm, 0.24 mg). Grass cuttings exhibited the highest average reaction rate (3991.1 ppm·d⁻¹) and the most rapid process (2.920 d⁻¹). Fungal colonization was visibly present in the most CO-productive reactors, suggesting a role of fungal metabolism in CO formation. Full article

Carbonaceous amendments are widely proposed to sequester hydrophobic organic contaminants in sediments, yet their effectiveness for alkylphenolic endocrine disruptors in organic-rich freshwater systems—and its time dependence—remains poorly constrained. Here, we compared activated carbon (AC), biochar (BC), and humic compost (HC) for reducing desorption and maize phytoexposure to 4-octylphenol (4-OP) and 4-nonylphenol (4-NP) in canal sediment from the Jegrička River. Sediment was spiked (~1.1 mg kg⁻¹ 4-OP; 1.2 mg kg⁻¹ 4-NP), amended with 0.5–10% (w/w) AC, BC, or HC, and aged for up to 180 days prior to multi-step XAD-4 desorption tests. A two-compartment first-order model resolved fast- and slow-desorbing pools, while a 10-day maize (Zea mays L.) pot experiment quantified early phytoextraction and sediment–plant–loss mass balances for AC and HC treatments. The unamended sediment exhibited high operational bioavailability: ~98% of both alkylphenols were XAD-4-extractable, and 83–89% of the desorbable pool was released within 24 h. AC produced the most rapid immobilization; at 0.5–1%, it halved XAD-4-extractable fractions within weeks and reduced them to near-zero within months, whereas BC and HC achieved comparable reductions only after longer aging. Plant uptake was a minor sink: in the control, shoots accumulated ~21 µg kg⁻¹ sediment of 4-OP and 65 µg kg⁻¹ sediment of 4-NP (≈2% and 5% of the initial inventory). HC generally lowered uptake, and high AC doses kept plant burdens consistently low. Overall, amendment-enhanced sorption and sequestration dominated attenuation, with AC delivering the fastest risk reduction and HC representing a more plant-compatible amendment option. Full article

The increasing generation of natural fiber textile waste highlights the urgent need for sustainable management strategies. This study investigated the biodegradation of textiles made from viscose, cotton, and linen under controlled composting and vermicomposting conditions in a four-month cycle to assess their decomposition dynamics and the quality of the resulting products. Composting was performed by an outdoor method and under controlled conditions, while vermicomposting included outdoor and home-scale variants using Eisenia andrei. Textile biodegradability and quality of the final product were quantified by weight loss, microscopic evaluation, and changes in pH, electrical conductivity, volatile solids, the carbon-to-nitrogen ratio (C/N), macroelement content, and levels of potentially toxic compounds. By month 2, textiles reached complete (100%) degradation in outdoor composting and in both vermicomposting systems; controlled composting achieved 87% degradability at month 2, 94% at month 3, and 99% at month 4. Across all systems, the C/N ratio stabilized around 11, and the resulting compost and vermicompost met quality standards for nutrients and safety criteria for toxicity. The findings confirm that both composting and vermicomposting are suitable methods for processing natural fiber textile waste, yielding environmentally safe and agronomically valuable products that support circular waste management in the textile sector. Full article

Compost amendments are widely recognized as an effective strategy for improving soil quality, modulating enzyme activities, and enhancing nitrogen cycling. Urease, a key enzyme in nitrogen transformation, is characterized by kinetic parameters such as the maximum reaction rate (V_max) and Michaelis constant (K_m), as well as thermodynamic attributes including temperature sensitivity (Q₁₀), activation energy (E_a), enthalpy change (ΔH), Gibbs free energy change (ΔG), and entropy change (ΔS). However, how different compost sources regulate urease kinetics, thermodynamics, and nitrogen availability remains poorly understood. In this study, we evaluated the effects of three compost amendments—mushroom residue (MR), mushroom residue–straw mixture (MSM), and leaf litter (LL)—on urease kinetics and thermodynamics in a temperate agroecosystem. The MSM treatment significantly enhanced urea hydrolysis capacity and catalytic efficiency. In contrast, LL treatment resulted in the highest Km value, indicating a substantially lower enzyme-substrate affinity. Furthermore, MSM reduced the E_a and increased the thermal stability of urease, thereby supporting enzymatic performance under fluctuating temperatures. Collectively, our findings highlight that compost composition is a critical determinant of urease function and nitrogen turnover. By elucidating the coupled kinetic and thermodynamic responses of urease to compost inputs, this study provides mechanistic insights to guide optimized soil management and sustainable nitrogen utilization in temperate agricultural systems. Full article

New compostable materials have been developed to replace single-use soft materials such as polyurethane foams (PUR). To this end, eco-friendly systems have been formulated on the basis of agar gels prepared in mixed solvent (glycerol/water) to meet specifications, i.e., stiffness of several hundred kPa, reasonable extensibility, and good stability when exposed to open air. While the addition of glycerol slows down gelation kinetics, mechanical properties are improved up to a glycerol content of 80 wt%, with enhanced extensibility of the gels while maintaining high Young’s moduli. Swelling analyses of mixed gels, in water or pure glycerol, demonstrate the preservation of an energetic network, with no change in volume, in pure water and the transition towards an entropic network in glycerol related to the partial dissociation of helix bundles. Dimensional and mechanical analysis of gels aged in an open atmosphere at room temperature shows that the hygroscopic character of glycerol enables sufficient water retention to maintain the physical network, with antagonistic effects linked to relative increases in glycerol, which tends to weaken the network, and agar, which on the contrary strengthens it. Complementary analyses carried out on aged agar gels formulated with an initial glycerol/water mass composition of 60/40, the most suitable for the targeted development, enabled the comparison of the properties of agar gels favorably with those of PURs and verified their stability during long-term storage, as well as their non-toxicity and compostability. Full article

Soil carbon is a crucial component of the global carbon cycle, and carbon mineralization is influenced by various factors. However, there is a lack of systematic analyses on the responses of carbon mineralization in different soil types to the addition of exogenous organic matter. This study investigates the effects of compost addition on the mineralization and kinetic characteristics of soil carbon across three typical agricultural soils: paddy soil, black soil, and cinnamon soil. A 210-day incubation study was conducted with four treatments: Control (un-amended soil), R (soil + straw), R1M (soil + straw + low compost application rate), R2M (soil + straw + high compost application rate). The results showed that the CO₂ emission rates of the three soils were higher during the early stage (1–37 days) and decreased afterward. The CO₂ emission rates of the paddy soil and the black soil were significantly higher than those of the cinnamon soil. The addition of compost significantly increased both the CO₂ emission rate and the cumulative release of CO₂, especially in the R2M treatment. At the end of the incubation, the SOC contents were higher in the R2M treatment than in the Control for all three soils (p < 0.05), with the most notable increase in the cinnamon soil (60.93%). Compost addition significantly enhanced the active carbon pool (C_a), slow carbon pool (C_s), and potentially mineralizable carbon pool (C_p), while decreasing the mineralization rate (k_a) of the C_a, but the effect on the mineralization rate (k_s) of the C_s and mineralization entropy (C_m) varied by soil types. The k_s of the paddy soil was significantly reduced by 23.08% under the R1M and R2M treatments compared with the Control and R treatment. The k_s of the black soil was significantly increased by 59.52% under the R2M treatment compared with the Control. The k_s of the cinnamon soil was elevated considerably by 79.31% under the R2M treatment compared with the Control, R, and R1M treatments (averaging 0.29 × 10⁻² d), and the k_s of the paddy soil and black soil were significantly higher than those of the cinnamon soil under the R2M treatment. The C_m was significantly higher in the organic material added treatments than in the Control for the black soil and the paddy soil, but showed a higher value in the R treatment than in the R2M and Control for the cinnamon soil. In conclusion, compost addition stimulated soil carbon mineralization and improved the SOC content, especially in the cinnamon soil, while reducing the mineralization rate of the active carbon pool across the three soils. The mineralization rate of the slow carbon pool and the changes in mineralization entropy were dependent on soil types, primarily related to the initial soil nutrient contents, pH, and particle compositions. These findings offer valuable insights for managing the soil carbon pool in agricultural ecosystems. Full article

Conventional horticultural fertilization frequently leads to nutrient loss and environmental contamination, driving interest in biodegradable controlled-release systems. This work developed soy protein isolate (SPI) matrices containing 5 wt.% FeSO₄·7H₂O using injection. The matrices were evaluated for crosslinking, mechanical properties, water uptake (WUC), soluble matter loss (SML), iron-release kinetics in water and soil, and biodegradability under composting conditions. Injection-molded samples achieved very high crosslinking with moderate rigidity and water absorption and delivered iron rapidly in water, while compression-molded samples exhibited slightly lower crosslinking but greater stiffness, higher WUC, minimal SML, and sustained iron release. Notably, both processing methods yielded comparable iron-release profiles in soil and complete biodegradation within 71 days. Overall, compression molding produces SPI-based matrices with superior mechanical strength and water retention, positioning them as an ideal solution for long-lasting, sustainable nutrient delivery in horticulture. Full article

The viability of anaerobic degradation treatment as an end-of-life option for commercial disposable bioplastic tableware, typically certified as compostable, was assessed. Two types of polylactic acid-based items were selected and tested under mesophilic conditions (38 °C) for 155 days, until reaching a plateau. Advanced chemical characterization of the products was performed with a combination of analytical techniques, i.e., microscopy, spectroscopy, and thermogravimetry. Two methods for calculating the biodegradation degree of the products were discussed and compared, using the biogas generated in the test and the total organic carbon (TOC) removal, respectively. The method based on TOC removal, resulting in a biodegradation degree ranging from 80.5% to 88.9%, was considered to more accurately describe the process. Given the complexity of assessing the biodegradation of a bioplastic product, an effort was made to derive correlations among the chemical–physical composition of the product, the biodegradation conditions, and the biodegradation yields/kinetics, with an aim to describe the process comprehensively. Statistical tools were also applied to derive additional considerations regarding the influence of the polymeric blend and digestion parameters on the biodegradation of bioplastic products. The identified data clusters, which were found to be grouped by the digestion temperature and the type of bioplastic, indicated specific biodegradation features of the investigated materials. Full article

This article examines the process of pressure agglomeration of garden waste compost mixed with sewage sludge ash (SSA) to produce granulated fertilizer material, using a flat die rotating compaction roller system. The study evaluated the effects of adding SSA at mass fractions of 0%, 10%, 20%, 30%, 40%, and 50% on the process of pelleting and the quality of pellets. Increasing the SSA content from 0% to 50% reduced the power demand of the pellet mill by 13.5% (from 4.92 kW to 4.25 kW), decreased the kinetic strength of the pellets by 0.7% (from 98.21% to 97.56%), and slightly increased the pellet density, by 2.6% (from 1641.17 kg·m⁻³ to 1684.09 kg·m⁻³). The high density of the pellets, i.e., over 1600 kg·m⁻³, indicates that they are of market quality. A chemical analysis revealed that SSA addition positively influenced fertilizer properties. A higher SSA content (up to 50%) decreased the nitrogen content (1.4% to 0.73%) but significantly increased the phosphorus content (0.32% to 2.67%). The potassium content remained stable, at approximately 1.3%. The process of co-pelleting also diluted the heavy metals present in SSA, reducing the final product’s lead and cadmium levels to meet the standards set for fertilizers. Although the SSA contained high levels of heavy metals (lead: 93.89 mg·kg_d.m.⁻¹, cadmium: 11.28 mg·kg_d.m.⁻¹), these elements were not detected in the compost. Co-pelleting of compost and SSA produces high-density, high-quality fertilizer pellets with favorable nutrient profiles and heavy metal contents, complying with regulatory standards. Moreover, by converting garden waste and SSA into valuable agricultural products, the process supports sustainable waste management. This study evaluated the impact of SSA additives on the composition and water absorption of the granulate, providing insights into its suitability as an eco-friendly fertilizer alternative and its potential implications for sustainable agricultural practices. Full article

The problems created by conventional polymers after their end use have driven research into new biodegradable polymeric materials. PLA is a compostable polymer obtained from renewable sources, but its main drawbacks are its fragility and slow crystallization kinetics. These drawbacks limit its use in different applications. In order to overcome fragility, in the current study, different compositions of PLA/PCL blends, rich in PLA content and without and with DGEBA, were prepared and characterized by means of different techniques, such as FTIR, DSC, DMA, and the mechanical properties. Some compositions show a certain improvement in the deformation capacity compared to the neat PLA at a low test speed. However, when the test speed increases, no improvement is observed in terms of deformation capacity. By SEM, the morphology of injection-molded specimens was observed. All blends showed a biphasic morphology where the PCL droplets are dispersed within the continuous PLA matrix. In the current study, an attempt has been made to improve the compatibility and adhesion between the phases by incorporating a diglycidyl bisphenol A compound. The results obtained indicate that the epoxy groups seem to react with the end groups of the PLA chain; however, the interactions that it creates with the PCL phase are weak, which is in agreement with the FTIR and DSC results obtained. Full article

To achieve the required recycling rates, organic recycling via composting should be widely introduced in Poland for selectively collected biowaste. However, this process not only produces compost but also leachate (L_CB), a nitrogen- and organics-rich liquid by-product. So far there has been limited information on the application of anaerobic digestion (AD) for treating L_CB, which has fermentative potential. However, for effective methane production (MP) via AD, the ratio of chemical oxygen demand to total Kjeldahl nitrogen (COD/TKN) and pH of L_CB are too low; thus, it should be co-digested with other organics-rich waste, e.g., glycerine (G). The present study tested the effect of G content in feedstock (in the range of 3–5% (v/v)) on the effectiveness of co-digestion with L_CB, based on MP and the removal of COD. MP was accessed by using an automatic methane potential test system (AMPTS). Regardless of the feedstock composition (L_CB, or L_CB with G), the efficiency of COD removal was over 91%. Co-digestion not only increased MP by 6–15%, but also the methane content in the biogas by 4–14% compared to L_CB only (353 NL/kg COD_added, 55%). MP and COD removal proceeded in two phases. During co-digestion in the 1st phase, volatile fatty acids (VFA) accumulated up to 2800 mg/L and the pH decreased below 6.8. The presence of G altered the shares of individual VFA and promoted the accumulation of propionic acid in contrast to L_CB only, where caproic acid predominated. An initial accumulation of propionic acid and acidification in the mixtures decreased the kinetic constants of MP (from 0.79 to 0.54 d⁻¹) and the rate of COD removal (from 2193 to 1603 mg/(L·d)). In the 2nd phase, the pH recovered, VFA concentrations decreased, and MP was no longer limited by these factors. However, it should be noted that excessive amounts of G, especially in reactors with constant feeding, may cause VFA accumulation to a greater extent and create a toxic environment for methanogens, inhibiting biogas production. In contrast, digestion of L_CB only may lead to ammonium buildup if the COD/TKN ratio of the feedstock is too low. Despite these limitations, the use of AD in the treatment of L_CB as a sustainable “closed-loop nutrient” technology closes the loop in composting of biowaste. Full article