Search Results (898)

Anaerobic co-digestion (AcoD) is increasingly applied in sewage-sludge management and organic-waste treatment because it can improve methane recovery, stabilize mixed substrates, and reduce life-cycle greenhouse-gas emissions under appropriate feedstock and operating conditions. However, existing reviews still focus mainly on feedstock types or isolated enhancement measures and less often connect synergistic mechanisms with engineering implementation and carbon outcomes. The specific novelty of this review is to connect functional feedstock classification, mechanism boundaries, engineering controls, and carbon-performance evaluation within one sludge-centered AcoD framework. This review synthesizes recent progress in AcoD of sewage sludge, food waste, livestock manure, crop residues, and industrial organic streams through a chain from feedstock traits to substrate interactions, microbial responses, engineering performance, and carbon benefits. Feedstocks are reorganized by function rather than by waste name, highlighting how carbon-to-nitrogen contrast, buffering capacity, hydrolysis recalcitrance, and inhibitor profiles jointly define synergy potential. Key mechanisms, including C/N balancing, hydrolysis complementarity, inhibitor mitigation, and direct interspecies electron transfer (DIET), are discussed together with their applicability limits. Representative evidence shows methane-yield or methane-production increases of about 41–55% for selected food-waste–manure blends, approximately 45% for rice–straw–pig manure systems after cellulolytic pretreatment, and approximately 16–55% for selected additive strategies; these values are illustrative rather than directly comparable because the underlying studies differ in substrates, baselines, reactor configurations, pretreatment conditions, and operating parameters. The review then translates mechanism into practice through pretreatment, reactor-selection templates, operating windows, additive reinforcement, and artificial-intelligence-assisted monitoring. Representative cases and life-cycle evidence indicate that AcoD can improve methane productivity while lowering greenhouse-gas emissions relative to landfill or mono-digestion pathways when energy substitution and nutrient recycling are credibly counted. Remaining bottlenecks include incomplete kinetic integration, limited DIET quantification, insufficient reporting of quantitative operating ranges and additive dosages, and weak coupling of carbon, economics, and regional feedstock dynamics. The revised review therefore treats AcoD as a sludge-centered mechanism-to-engineering framework and highlights two transferability gaps that require stronger standardization: biodegradation/toxicity testing and local co-substrate logistics. Full article

This study investigates the synergistic regulation mechanism of water–heat–salt transport in the black soil of cold regions in Northeast China by combining field monitoring with HYDRUS-2D simulations. Four tillage treatments were evaluated: control group (CK), no-tillage with flat straw mulching (NM), ridge tillage with flat straw mulching (RM), and straw return with rotary tillage (RR). Monitoring data indicated that all straw incorporation treatments significantly improved soil moisture retention capacity. Compared with CK, soil water content under RM increased by 63.93% correspondingly; soil salinity in CK was 5.75–13.68% higher than that in straw-amended treatments. In addition, RM exerted a more prominent regulatory effect on soil temperature fluctuations relative to CK. Simulation results reveal that straw incorporation effectively reduces surface runoff, thereby substantially weakening the driving force for upward salt migration. Structural equation modeling (SEM) quantified path coefficients, revealing that straw incorporation optimizes the soil microenvironment. This integrated approach provides a mechanistic basis for black soil conservation in seasonally frozen regions, identifying RM as the optimal management practice to balance water retention and salt inhibition. Full article

This study investigated the mechanism underlying how the integration of chemical fertilizer and maize straw-derived organic amendments affects different potassium (K) pools, K saturation, K fixation characteristics, and non-exchangeable potassium (NEK) release kinetics in black soil. A field experiment involving five treatments was conducted: no fertilizer (CK), chemical fertilizer alone (NPK), chemical fertilizer plus maize straw (NPK+ST), chemical fertilizer plus straw compost (NPK+CP), and chemical fertilizer plus straw biochar (NPK+BR). The findings demonstrated remarkably increased contents of different K pools and K saturation in the black soil following the combined application of straw-derived organic amendments, with NPK+CP exhibiting the most significant effect. Exogenous K fixation simulation tests indicated that the amount of K fixation in the black soil increased with the incorporation of exogenous K, while the fixation rate showed the opposite trend. The quadratic regression model well fitted the relationship between the amount of K fixation and the addition of exogenous K; the treatments were ranked according to the soil K fixation capacity as follows: CK > NPK > NPK+BR > NPK+ST > NPK+CP. The simplified Elovich model well fitted the NEK release process in the black soil under different treatments. Significant differences in total cumulative NEK release and apparent release rate coefficients were observed among the treatments, which showed an identical trend: NPK+CP > NPK+BR > NPK+ST > NPK > CK. The application of straw-derived organic amendments could effectively reduce the K fixation capacity of black soil and promote NEK release. In this study, chemical fertilizer combined with straw compost was the optimal measure for improving black soil’s potassium availability. Full article

In the present study, Fe₃O₄@hydrothermal carbon was prepared successfully using rice straw waste. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis confirmed that the material had rich and strong redox-active centers on its surface, indicating that it has potential to be used as a redox mediator for electron transfer. Fe₃O₄@hydrothermal carbon was added into the anaerobic sludge treatment system for the collaboration of dye decolorization. The results showed that azo dye decolorization efficiency reached the maximum value (98.3%) with the presence of Fe₃O₄@hydrothermal carbon, which was 16.6% higher than control reactor (without Fe₃O₄@hydrothermal carbon added). In addition, Fe₃O₄@hydrothermal carbon exhibits good reusability and the dye decolorization rates in the “anaerobic sludge–material” combining system were significantly higher than that in the “sludge-alone” system during the semi-continuous wastewater treatment process. Mechanistic investigations revealed that the enhanced decolorization is driven by a synergistically constructed interspecies electron transfer pathway. Specifically, the addition of Fe₃O₄@hydrothermal carbon improved the formation of the extracellular polymeric substance (EPS), which had positive effects on sludge stability and its interaction with the material. CV and electron transport system (ETS) activity analysis showed that the sludge exhibited high electrochemical activities with the support of the material, which led to a high electron transfer efficiency between the electron-donating and accepting microbial pairs in the treatment system. The high-throughput sequencing analysis showed that the structure of the microbial community changed during the semi-continuous treatment process; Megasphaera and Clostridium accounted for more than 87.5% of the total abundance of the bacterial community in the anaerobic sludge with material addition. Driven by the material-mediated process, these enriched functional taxa exhibited a high electron transfer efficiency between electron-donating and accepting pairs, accelerating the catalytic cleavage of azo bonds and ultimately improving the overall anaerobic treatment performance. Full article

Crop residue management strongly influences soil microbial communities, yet the mechanisms by which it regulates microbial co-occurrence network assembly across soil profiles remain poorly understood. Here, we investigated the effects of three straw management practices—no straw return (CK), straw burning (BS), and deep plowing with straw incorporation (DPS)—on soil physicochemical properties, microbial diversity, and co-occurrence network structure across multiple soil depths in a Mollisol of Northeast China. By integrating high-throughput sequencing, network analysis, and structural equation modeling (SEM), we explored the correlative relationships associated with microbial network assembly. DPS significantly correlates with higher soil organic carbon content, nutrient availability, and moisture content, particularly in subsoil layers. Under DPS, we obtained more complex and robust microbial networks characterized by higher connectivity and clustering. In contrast, under BS, we found reduced network complexity and stability. SEM may suggest the presence of distinct assembly mechanisms between microbial groups: bacterial network structure models responded to soil physicochemical properties, suggesting strong environmental filtering, whereas shifts in fungal network structures correlate with alpha diversity, highlighting the importance of biotic regulation. Notably, under the evaluated conditions, beta diversity was positively associated with network structural attributes across both groups, indicating potential links between community compositional variation and microbial co-occurrence patterns. These findings suggest that straw incorporation may be associated with shifts in microbial co-occurrence network attributes under the evaluated field conditions. However, the observed relationships are primarily correlative and based on statistical modeling approaches. The underlying ecological mechanisms linking soil properties, microbial diversity, and network structure require further validation through controlled biochemical, physiological, and experimental studies. This study provides additional ecological insights into soil microbial responses to residue management and highlights the potential role of residue management in shaping microbial network stability under the evaluated field conditions. Full article

Cadmium (Cd) and lead (Pb) are ubiquitous toxic heavy metals in farmland soils, posing a threat to agricultural product safety and human health through food chain transmission. Biochar is widely used for in situ immobilization of heavy metals; however, systematic comparisons of the immobilization performance of rice straw biochar (RSB) and sugarcane bagasse biochar (SCB) under single and combined Cd–Pb contamination remain limited. This study systematically evaluated their immobilization performance and mechanisms through pot and batch adsorption experiments. Without altering total soil Cd and Pb contents, both biochars significantly regulated heavy metal bioavailability in the soil–plant system. In batch adsorption, RSB exhibited maximum Cd and Pb adsorption capacities 2.1 and 3.0 times those of SCB, respectively, with chemisorption as the dominant mechanism. In pot experiments, RSB reduced Pb uptake in pakchoi by 60.0% and 81.0%, but increased Cd uptake. SCB increased Cd uptake under single Cd contamination, had no significant effect on Pb under single Pb contamination, yet reduced Cd and Pb uptake under co-contamination by 44.4% and 31.6%, respectively. These differential effects are attributed to distinct mechanisms: Pb was primarily immobilized via stable mineral precipitation, whereas Cd was bound through weakly reversible ion exchange. Both biochars improved soil fertility and maintained core bacterial ecological functions without posing additional ecological risks. This study clarifies the feedstock-dependency and metal-specificity of biochar in remediating Cd- and Pb-contaminated farmlands, guiding precise biochar selection under varying contamination scenarios. Full article

The world’s energy matrix faces challenges in replacing fossil fuels and reducing greenhouse gas emissions. Pellet production is effective for the correct disposal of agricultural waste through the production of biofuels. The objective of this work was to produce and characterize pellets from blends of pine and coffee straw residues, in addition to their compliance with ISO 17225-6/2021. The biomasses were subjected to analysis of dry and wet base moisture, bulk density, upper and lower calorific value (HCV and LCV dry), immediate, structural and elemental chemistry, chloride content, and thermogravimetric behavior. The pellets were produced in nine blends with the Amandus Kahl pellet mill, model 14-175, being submitted to analysis of productivity, moisture in dry and wet base, HCV and LCV dry, chloride, immediate chemistry, hardness, diameter and length, durability and percentage of fines, the analyses were compared by the Scott-knott test at the level of 95% probability. The blends that presented the best overall performance were 100% pine and a mixture of 87.5% pine and 12.5% coffee straws, especially for the higher calorific value (20.65 and 20.65 MJ/kg), moisture (8.98 and 9.17%), and ash (0.22 and 1%), but had limitations regarding mechanical durability (96.74 and 97.12%). The use of blends in pellet production is promising to promote the sustainable use of agricultural waste and the generation of clean energy. Full article

The European construction sector accounts for approximately 40% of EU final energy consumption and around 36% of lifecycle CO₂ emissions, creating structural demand for low-carbon alternatives consistent with the European Green Deal and the revised Energy Performance of Buildings Directive. This article presents a structured multi-criteria assessment of seven bio-based construction material categories producible within the EU—wood fibre/cellulose insulation, expanded cork agglomerates (insulation corkboard), mass timber (CLT and Glulam), hemp–lime composites (hempcrete), straw bale systems, mycelium-based composites, and cellulose aerogels—evaluated across twelve sub-criteria organised under three equally weighted pillars: environmental impact, economic opportunity, and social value. The analysis integrates durability maturity as a primary market-access variable, fire performance under Wildland–Urban Interface (WUI) exposure conditions, seismic risk compatibility, and EU regional demand heterogeneity. Composite scores are calculated by summing individual criterion scores, with pillar sub-totals shown explicitly. A sensitivity analysis under three alternative pillar-weighting scenarios, a single-criterion perturbation analysis, a Monte Carlo simulation, and a TOPSIS method comparison collectively test the robustness of rankings. Results indicate that wood fibre/cellulose insulation, expanded cork agglomerates, and hemp–lime composites constitute the highest-impact portfolio under baseline and environmental priority weighting; under economic priority weighting, mass timber displaces hemp–lime in the top 3. Under environmental priority weighting, cork achieves the highest composite score of any material, driven by its perfect environmental pillar sub-score and the regenerative carbon sequestration of the cork oak. All four robustness tests confirm that wood fibre, cork, and hemp–lime occupy the top 3 positions across all weighting scenarios—with cork rising to first and wood fibre dropping to third under environmental priority weighting—and that the additive scoring method produces rankings identical to those generated by the TOPSIS method. Full article

Aquaculture solid waste (ASW) from intensive farming poses significant environmental challenges, yet its potential as a composting feedstock remains insufficiently evaluated. This study systematically assessed the feasibility of aerobic composting for ASW valorization through integrated feedstock characterization, composting process monitoring, microbial community analysis, and pot experiment validation. ASW collected from intensive aquaculture facilities was characterized by high phosphorus (mean TP: 6.80 mg/g), potassium (TK generally >10 mg/g), and iron (mean Fe: 49,112 mg/kg) content but low organic matter (17.60%) and total nitrogen (0.72%). Composted with rice straw powder, meat and bone meal, and mineral amendments, ASW was successfully converted into mature compost, with the thermophilic phase (>50 °C) lasting only 4 days and the seed germination index exceeding the 80% safety threshold within 15 days. The composting process exhibited an organic matter degradation rate of approximately 20.82%, along with low electrical conductivity and stable pH in the final product. Microbial community analysis revealed that ASW addition significantly altered bacterial and fungal community structure, enriching functional taxa associated with organic matter decomposition and nutrient transformation. Pot experiments conducted under equal nutrient input conditions demonstrated that the ASW-derived compost supported satisfactory crop growth, with the fresh weight of Fast-growing Cabbage reaching 106.95 g per plant. The compost also improved soil properties, including reduced electrical conductivity (72.8% lower than urea), increased soil organic matter (17.8% increase over original soil), and enhanced available phosphorus (93.0% increase over original soil). These results indicate that aerobic composting is a technically viable pathway for converting ASW into a qualified organic fertilizer, providing a preliminary scientific basis for future waste management strategy for the sustainable development of the aquaculture industry. Full article

This review evaluates pretreatment strategies for blending the organic fraction of municipal solid waste (OFMSW) with agricultural residues to recover fermentable sugars. Three mechanistic benefits have been hypothesized for such blends: ash-mineral pH buffering, endogenous protein reduction of non-productive cellulase–lignin binding, and inhibitor dilution. These mechanisms are inferred from analogous lignocellulosic systems rather than measured directly in OFMSW–agricultural residue combinations, and their translation into saccharification gains remains substrate- and pretreatment-specific. A synergy index framework with a four-tier classification (true synergy, additive, substitution, and process complementarity) is applied to reclassify the available evidence, alongside an assessment of pretreatment chemistry, enzymatic hydrolysis outcomes, and techno-economic feasibility. Integrated sequential pretreatment, particularly acid-catalyzed steam explosion and deacetylation with mechanical refining, proved most robust for heterogeneous feeds. The strongest Tier I synergy is found for SO₂-catalyzed steam explosion of hybrid poplar–wheat straw (SI 1.29–1.33; 22% monomeric sugar gain). OFMSW combined with organosolv beechwood cellulose at 35–45% OFMSW reached 58–68% saccharification (44–46 g sugar L⁻¹), a Tier III–IV outcome. Matched-control saccharification data for OFMSW–agricultural residue blends specifically have not been reported. Co-processing corn stover with wet organic waste reduced CO₂ mitigation cost from $236 to $67 per ton CO₂-eq under bio-CNG upgrading. Formal synergy quantification, blend-specific inhibitor profiling, and high-solids process intensification are the central prerequisites for commercial translation. Full article

Hydrothermal carbonization (HTC) of wet biomass faces a fundamental tradeoff between higher heating value (HHV) and energy recovery (ER), where conditions that enhance carbon densification often reduce solid-phase energy retention. This study investigates whether co-biomass selection combined with citric acid (CA) catalysis can overcome this tradeoff in HTC of water hyacinth (WH), an invasive aquatic feedstock. WH was co-processed with wheat straw (WS), rice husk (RH), and chicken manure (CM) at 240–270 °C, with CA-assisted experiments performed at 240 °C. Individual feedstock HTC confirmed the HHV–ER tradeoff, and co-HTC without catalysis failed to resolve it. CA addition improved carbon densification but reduced ER when applied to WH alone. The WH–CM–CA system uniquely achieved a concurrent HHV of 21.3 MJ kg⁻¹ and ER of 95.8%, with synergistic effects of 50.0% and 29.7%, respectively. FTIR and elemental analysis indicated that Maillard-type condensation between WH-derived sugars and CM-derived amino acids drove preferential solid-phase carbon retention. These findings demonstrate that resolving the HHV–ER tradeoff requires coupling CA catalysis with biochemical complementarity between carbohydrate-rich and protein-rich feedstocks. This approach provides a practical route for hydrochar production with high energy density and recovery for waste-to-energy applications, supporting circular and low-carbon valorization of invasive aquatic biomass and livestock waste streams. Full article

Yaks (Bos grunniens) on the Qinghai–Tibetan Plateau face severe nutritional limitations during the dry season due to dependence on highly lignified, low-quality roughage. Identifying safe and effective rumen regulators capable of enhancing fiber utilization in this species is therefore of great practical importance. This study employed a two-pronged approach integrating in vitro mechanistic investigation and in vivo validation to evaluate the effects of the amphoteric surfactant cocamidopropyl betaine (CAPB) on rumen fermentation, the micro-spatial distribution of digestive enzymes, apparent total tract digestibility, and the macroscopic growth performance of yaks. In the in vitro fermentation trial (Experiment 1), a randomized block design was employed where a straw-based high-forage diet was used as the substrate and supplemented with 0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0% CAPB (based on substrate dry matter, DM) for a 48 h batch culture. The results showed that as the CAPB supplementation level increased, cumulative gas production, the degradation rates of DM and neutral detergent fiber (NDF), and the yields of total volatile fatty acids and microbial protein all exhibited significant quadratic responses (p < 0.05), peaking at the 0.5–1.0% supplementation levels. Concurrently, CAPB significantly promoted the transfer and release of carboxymethyl cellulase and xylanase into the free liquid phase (p < 0.01). In the in vivo validation trial (Experiment 2), 24 healthy growing male yaks (initial body weight 131.2 ± 8.4 kg) were allocated in a completely randomized design to four groups and fed a basal diet supplemented with 0, 0.5, 1.0, or 2.0% CAPB for 44 days. The results indicated that, while maintaining a stable DM intake, the addition of 0.5% CAPB significantly increased the average daily gain (ADG) of yaks (p < 0.05), improved the feed-to-gain ratio, and significantly enhanced the apparent total tract digestibility of NDF and ether extract (p < 0.05). However, when the supplementation dose exceeded the safety threshold (≥2.5% in vitro and ≥2.0% in vivo), both fermentation parameters and growth advantages declined. In conclusion, under the present experimental conditions, 0.5% CAPB improved roughage fermentation efficiency, putatively through an ‘enzyme elution’ mechanism, and was associated with macroscopic improvements in NDF and EE apparent digestibility and ADG in growing yaks. These findings identify 0.5% CAPB as a promising candidate rumen regulator for improving roughage utilization in growing yaks; broader generalization will require larger-scale and longer-duration trials. Full article

Toxoplasma gondii and Neospora caninum are apicomplexan parasites infecting cattle, with implications for public health and livestock productivity, respectively. Since effective vaccines against these parasites are not currently available, identifying epidemiological factors associated with infection is important for improving control strategies. This study aimed to estimate the seroprevalence of both parasites and to identify factors associated with seropositivity in intensive dairy cattle in central Chile. A cross-sectional study was conducted using serum samples from 567 cattle, analyzed by ELISA. Epidemiological data were collected through semi-structured surveys, and associations with seropositivity were evaluated using multivariable logistic regression models, including mixed-effects models to account for farm-level clustering. Seroprevalence was 7.6% for T. gondii and 22.4% for N. caninum. For T. gondii, factors associated with seropositivity included older age categories (OR = 7.09; 11.25) and the presence of dogs in pens (OR = 6.07). For N. caninum, straw bedding use (OR = 5.13) and cat presence (OR = 6.32) were associated with higher odds of seropositivity. An additional association with lower N. caninum seropositivity was observed for BCG vaccination (OR = 0.24). These findings provide updated epidemiological data for dairy cattle in Chile. The association observed with BCG vaccination should be interpreted cautiously, as the study design does not permit causal inference. Full article

The transition towards circular agriculture requires sustainable fertilization strategies that maintain crop productivity, reducing environmental impacts associated with synthetic inputs. In this study, compost-derived biofertilizers produced from cattle manure, with and without structuring agents (wheat straw and almond pruning), were evaluated as alternatives to mineral fertilization for lettuce (Lactuca sativa L.) grown under controlled greenhouse conditions. A two-cycle pot experiment was conducted to increase total nitrogen, extractable phosphorus and exchangeable potassium, while slightly decreasing soil pH. Mineral fertilization produced the highest biomass in the first growing cycle, whereas compost treatments achieved comparable yields and showed clear residual effects in the second cycle. Multispectral sensing shows to be a useful non-destructive tool for monitoring crop development. Red-edge-based indices (NDRE) showed high sensitivity to variations in nutrient content dynamics. Generalized additive models (GAMs) enabled nutrient prediction, with strong performance for phosphorus (R² = 0.79) and selected micronutrients and moderate performance for nitrogen (R² = 0.62) and weaker performance for potassium (R² = 0.45). These results indicate that combining compost-based fertilization with multispectral sensing can improve nutrient use efficiency and support precision horticulture under circular agricultural frameworks. Full article

This study investigates the environmental and energy performance of rice straw-based energy pathways in Egypt, combining life cycle assessment (LCA) with supply chain optimization to improve system efficiency. The analysis covers thirteen governorates producing over 4.45 million tons of rice straw annually. It examines the whole supply chain from paddy farming, straw collection, and transport to electricity generation and ash disposal. Total energy consumption was 11,287 TJ, dominated by farming (5673 TJ) and transport (5490 TJ). Greenhouse gas (GHG) emissions were estimated at 12,007.5 million kg CO₂-eq, with significant contributions from farming (5158 million), combustion (3630 million), and natural gas use (3039 million). Gross electricity output was 5525 GWh, yielding a net of 4973 GWh, equivalent to 1116.5 kWh per ton of straw. Scenario analysis highlighted that the optimized multi-hub system, prioritizing Cluster 1 in the Nile Delta, which contributes over 92% of straw production and 4607 GWh of net electricity, achieved a reduction of more than 25% in transport distances and an 18% decrease in diesel consumption and related emissions. Sensitivity analysis further indicated that delivered electricity and GHG intensity are more sensitive to conversion efficiency and transmission and distribution losses than to moderate changes in transport assumptions. In addition to environmental improvements, the optimized scenario indicates potential social co-benefits, including rural employment generation, additional income opportunities for farmers, and improved air quality associated with reduced open-field burning. These outcomes are presented as indicative qualitative insights. Findings confirm rice straw as a strategic, scalable, and sustainable energy resource aligned with Egypt’s Vision 2030 and the UN Sustainable Development Goals (SDGs). Full article