Search Results (40)

Waste activated sludge (WAS), a byproduct of livestock wastewater treatment, poses significant disposal challenges due to its low biodegradability and potential environmental impact. Anaerobic digestion (AD) offers a sustainable approach for methane recovery and sludge stabilization. This study evaluates the biomethane potential (BMP) of WAS and its co-digestion with swine slurry (SS), water lily (Nymphaea spp.), and lotus (Nelumbo nucifera) shoot biomass to enhance methane yield. Batch BMP assays were conducted at substrate-to-inoculum (S/I) ratios of 1.0 and 0.5, with methane production kinetics analyzed using the modified Gompertz model. Mono-digestion of WAS yielded 259.35–460.88 NmL CH₄/g VS_added, while co-digestion with SS, water lily, and lotus increased yields by 14.89%, 10.97%, and 16.89%, respectively, surpassing 500 NmL CH₄/g VS_added. All co-digestion combinations exhibited synergistic effects (α > 1), enhancing methane production beyond individual substrate contributions. Lower S/I ratios improved methane yields and biodegradability, highlighting the role of inoculum availability. Co-digestion reduced the lag phase limitations of WAS and plant biomass, improving process efficiency. These findings demonstrate that co-digesting WAS with nutrient-rich co-substrates optimizes biogas production, supporting sustainable sludge management and renewable energy recovery in livestock wastewater treatment systems. Full article

Anaerobic digestion (AD) is a sustainable and widely adopted technology for the treatment of organic solid wastes (OSWs). However, AD efficiency varies significantly across different substrates, primarily due to differences in the microbial community and metabolic pathways. This review provides a comprehensive summary of the AD processes for four types of typical OSWs (i.e., sewage sludge, food waste, livestock manure, and straw), with an emphasis on their universal characteristics across global contexts, focusing mainly on the electron transfer mechanisms, essential microbial communities, and key metabolic pathways. Special attention was given to the mechanisms by which substrate-specific structural differences influence anaerobic digestion efficiency, with a focused analysis and discussion on how different components affect microbial communities and metabolic pathways. This study concluded that the hydrogenotrophic methanogenesis pathway, TCA cycle, and the Wood–Ljungdahl pathway serve as critical breakthrough points for enhancing methane production potential. This research not only provides a theoretical foundation for optimizing AD efficiency, but also offers crucial scientific insights for resource recovery and energy utilization of OSWs, making significant contributions to advancing sustainable waste management practices. Full article

Sulfamethazine (SMT) is an antibiotic with good antimicrobial effect and is widely used to treat human and livestock diseases. Though the degradation of SMT by the conventional Fenton and electro-Fenton (EF) processes is efficient, it is limited by a narrow pH and iron sludge generation. Herein, we constructed a cost-effective EF system with the synergistic effect of zero-valent iron (Fe⁰) and sulfite (Fe⁰-EF/Sulfite), and key parameters such as applied current, catalyst dosing, sulfite dosage, and initial pH were optimized. Under the optimal conditions (Fe⁰ dosing of 50 mg/L, sulfite dosage of 1.5 mM, current of 40 mA, and pH of 3), the removal efficiency of 10 mg/L SMT reached 100% within 30 min, and the degradation rate constant reached 0.194 min⁻¹. Electron paramagnetic resonance (EPR) analysis and quenching experiments confirmed the generation of various reactive oxygen species (ROS), such as ^•OH, SO₄⁻, O₂⁻, and ¹O₂, which significantly improved the pollutant removal efficiency. Sulfite accelerated iron cycling and inhibited the formation of iron sludge, thus broadening the pH range of the reaction from three to eight and overcoming the limitations of the conventional EF process. The Fe⁰-EF/Sulfite system performs cost-effectively at a wide pH range, providing an efficient and low-carbon solution for environmental pollution remediation with broad application prospects. Full article

Historical application of wastewater treatment sludge (biosolids) has introduced per- and polyfluoroalkyl substances (PFAS) into agricultural systems and led to contamination of crops and livestock. Previous work validated a dynamic exposure and population toxicokinetic (DE_PopTK) modeling approach for estimating perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS) concentrations in cattle tissues at sites primarily dominated by water contamination. This work expands the efforts to validate the DE_PopTK model at a self-contained beef farm in Maine with PFAS exposures from feed grown on site where soil is contaminated from historical biosolids applications. The model is also extended to estimate perfluorodecanoic acid (PFDA) exposure and tissue levels. Farm-specific data were obtained to consider farm management practices, spatial variation of PFAS in soil, animal growth, and seasonal and annual variability in estimating daily exposures based on water, feed, and soil intake. A dynamic exposure pattern was observed as cattle accumulated PFAS while consuming feed grown on contaminated land and eliminated it while grazing on non-contaminated pastures. Model-estimated PFOS and PFDA levels in serum and muscle were in good agreement with biomonitoring data collected at the farm over a four-year period to reflect periods of accumulation and depuration, with the percentage error ranging from 16% to 73% when comparing modeled and measured data. Our findings demonstrated that understanding farm exposures and collecting site-specific data were integral to model performance. The model was applied to simulate management strategies and complement economic analyses to demonstrate that, with modifications to management practices, it is feasible for the farm to achieve lower PFOS and PFDA levels in beef and maintain economic viability despite elevated PFAS soil levels. Full article

This study evaluates Spain’s biomethane production potential for 2030 and 2050, focusing on agricultural residues, livestock manure, municipal solid waste (MSW), and wastewater treatment plant (WWTP) sludge. The research aims to provide a regional analysis based on historical data on livestock populations, cultivated land, waste availability, and demographic projections. Using utilization coefficients and technological assumptions derived from existing biogas infrastructure, the study estimates that Spain could generate 9.71 TWh of biomethane by 2030, slightly below the national target of 10.41 TWh. By 2050, agricultural and livestock residues are expected to contribute 30.04 TWh, accounting for nearly 80% of total biomethane production, while the relative share of MSW and WWTP sludge will decrease. Andalusia, Castilla-La Mancha, and Castilla y León emerge as key contributors due to their extensive agricultural and livestock sectors. Catalonia and Madrid maintain significant roles driven by urban waste generation. The findings underscore the need for infrastructure expansion, particularly enhancing biomethane injection facilities into the natural gas grid, alongside financial incentives to support industry growth. This study highlights the role of biomethane in Spain’s renewable energy sector, emphasizing its potential to reduce greenhouse gas emissions, optimize organic waste utilization, and contribute to a sustainable energy transition. Full article

This study aims to develop a novel use of baker’s yeast in biosorption as a sustainable metal recovery process for cost-effective and practical applications in recovering copper and zinc from waste gravity-thickened sludge generated at livestock wastewater treatment facilities. The supernatant of the acid-extracted product was separated from the residues through centrifugation. To ensure cost efficiency, the supernatant was treated with 2N acetic acid for 24 h, with the addition of hydrogen peroxide, and used for the biosorption experiments. The filtrated supernatant was adjusted to various pH values (4.5, 5.0, and 5.5) to explore the effects of acidity on the subsequent biosorption of extracted zinc and copper by baker’s yeast. A diluted molasses solution was added to the filtrate as a carbon source to support yeast growth during the 4 h biosorption experiments. The results revealed that the removal efficiency of zinc from the filtrate by baker’s yeast was 97.3%, while the removal efficiency for copper was about 48.8% at pH 5.5 with a reaction time of 4 h. In summary, this combined approach is expected to reduce and recycle heavy metals in livestock sludge. Acetic acid with hydrogen peroxide can extract copper and zinc from the sludge, and baker’s yeast can absorb both metals from the filtrate at pH 5.5 in a 4 h reaction time. This technological innovation has the potential to transform waste management practices in the livestock industry, contributing to resource recovery and environmental sustainability. Full article

Poultry litter waste management poses a significant global challenge, attributed to its characteristics (odorous, organic, pathogenic, attracting flies). Conventional approaches to managing poultry litter involve composting, biogas generation, or direct field application. Recently, there has been a surge of interest in a novel technology that involves the bioconversion of organic waste utilizing insects (known as entomoremediation), particularly focusing on black soldier fly larvae (BSFL), and has demonstrated successful transformation of various organic waste materials into insect meal and frass (referred to as organic frasstilizer). Black soldier flies have the capacity to consume any organic waste material (ranging from livestock litter, food scraps, fruit and vegetable residues, sewage, sludge, municipal solid waste, carcasses, and defatted seed meal) and convert it into valuable BSFL insect meal (suitable for animal feed) and frass (serving as an organic fertilizer). The bioconversion of poultry litter by black soldier flies offers numerous advantages over traditional methods, notably in terms of reduced land and water requirements, lower emissions, cost-effectiveness, swift processing, and the production of both animal feeds and organic fertilizers. This review focuses on the existing knowledge of BSFL, their potential in bioconverting poultry litter into BSFL meal and frass, and the utilization of BSFL in poultry nutrition, emphasizing the necessity for further innovation to enhance this sustainable circular economy approach. Full article

Microalgae demonstrate significant efficacy in wastewater treatment. Anaerobic digestion effluent (ADE) is regarded as an underutilized resource, abundant in carbon, nitrogen, phosphorus, and other nutrients; however, the presence of inhibitory factors restricts microalgal growth, thereby preventing its direct treatment via microalgae. The purpose of this study was to dilute ADE using various dilution media and subsequently cultivate Chlorella sp. to identify optimal culture conditions that enhance microalgal biomass and water quality. The effects of various dilution conditions were assessed by evaluating the biomass, sedimentation properties, and nutrient removal efficiencies of microalgae. The results demonstrate that microalgal biomass increases as the dilution ratio increased. The microalgae biomass in the treatments diluted with simulated wastewater was significantly higher than that with deionized water, but their effluent quality failed to meet discharge standards. The treatment diluted with deionized water for 10 times exhibited abundant microbial biomass with strong antioxidant properties. The corresponding total phosphorus concentration in the effluent (6.96 mg/L) adhered to emission limits under the Livestock and Poultry Industry Pollutant Emission Standards (8 mg/L), while ammonia nitrogen concentration (90 mg/L) was near compliance (80 mg/L). The corresponding microbial biomass, with a sludge volume index (SVI₃₀) of 72.72 mL/g, can be recovered economically and efficiently by simple precipitation. Its high protein (52.07%) and carbohydrate (27.05%) content, coupled with low ash (10.75%), makes it a promising candidate for animal feed and fermentation. This study will aid in understanding microalgal growth in unsterilized ADE and establish a theoretical foundation for cost-effective ADE purification and microalgal biomass production. Full article

The pandemic crisis has created significant challenges for small farms, leading to increased energy costs, higher prices for feed and nutrients, unreliable supplies of chemical fertilizers, and disruptions in product sales markets. These factors have collectively compromised the operational viability and economic sustainability of small-scale agricultural enterprises. To address these challenges, this paper explores the concept of a self-sufficient farming system, focusing on locally producing most of the resources needed to sustain operations and reduce dependence on external sources. A self-sufficient integrated pisciculture farming system is proposed and evaluated, promoting an autonomous circular model that prioritizes environmental sustainability. This system incorporates the integration of local livestock into fish diets, production of renewable energy sources, and efficient water and sludge management to reduce reliance on external resources. The detailed methodology used to evaluate sustainability indicators objectively demonstrates that the proposed system can be self-sustainable and autonomous; however, it requires considerable initial investments that can be recovered within at least six years. Optimizing the energy management plan can reduce daily power consumption by up to 25%. However, local conditions may challenge the efficiency of photovoltaic–hybrid energy production, requiring slight oversizing of the system. The research indicated that rearing carp with cereal-based feed mixtures produces growth results comparable to those achieved with commercially purchased feed. The indicators of resource efficiency, reliability, flexibility, productivity, environmental impact, and social impact were met as expected. The weakest indicator was the technology’s potential for scalability, due to its strong dependence on various regional factors. Full article

Residual organic sludge generated from bioenergy facilities (BF-rOS) is often disposed instead of recycled, thus contributing to further environmental pollution. This study explored the resource utilization of BF-rOS using Hermetia illucens larvae (BSFL). When BF-rOS was fed to BSFL for two weeks, the dry weight per individual BSFL was approximately 15% of that of BSFL that were fed food waste (FW). However, the dry weight increased by approximately two-fold in BSFL that were fed effective microorganism (EM)-supplemented BF-rOS containing 60% moisture. However, under both conditions, the BSFL did not mature into pupae. In contrast, the highest dry weight per BSFL was observed with the BF-rOS/FW (50%:50%) mixture, regardless of EM supplementation. Furthermore, the highest bioconversion rate was observed when the BSFL were fed the BF-rOS/FW (50%:50%) mixture, and the frass produced by the BSFL contained fertilizer-appropriate components. In addition, the nutritional components of the BSFL exhibited a nutrient profile suitable for animal feed, except for those fed BF-rOS only. In conclusion, this investigation demonstrates that BF-rOS should be recycled for fertilizer production by mixing it with FW as a BSFL feed, which generates the valuable insect biomass as potential nutrition for animal feeding. Full article

Antibiotics in animal production are widely used around the world for therapeutic and preventive purposes, and in some countries, they still serve as antibiotic growth stimulants. Regardless of the purpose of using antibiotics in livestock, they may be present in animal tissues and organs as well as in body fluids and excretions (feces and urine). Farm animal excrement in unprocessed form (natural fertilizers) or processed form (organic fertilizers) is applied to agricultural fields because it improves soil fertility. Antibiotics present in fertilizers may therefore contaminate the soil, surface, groundwater, and plants, which may pose a threat to the environment, animals, and humans. Therefore, it is important to develop analytical methods that will allow for the control of the presence of antibacterial substances in natural and organic fertilizers. Therefore, in this study, an LC-MS/MS method was developed and validated for the determination of 21 antibacterial substances in natural and organic liquid fertilizers. The developed method was used to analyze 62 samples of natural and organic liquid fertilizers, showing that over 24% of the tested samples were contaminated with antibiotics, mainly from the group of tetracyclines and fluoroquinolones. Studies of post-fermentation sludge from biogas plants have shown that the processes of anaerobic methane fermentation, pH, and temperature changes taking place in bioreactors do not lead to the complete degradation of antibiotics present in the material used for biogas production. For this reason, monitoring studies of natural and organic fertilizers should be undertaken to limit the introduction of antibiotics into the natural environment. Full article

Pig farmers in Taiwan tend to overdose copper (Cu) and zinc (Zn) in animal feeds to ensure pig health. The application of Cu- or Zn-rich livestock compost to fields can result in high Cu/Zn residues in surface soil and violate limitations for zinc and copper in land applications. This study aims to extract Cu and Zn from sludge using organic acid or H₂O₂/organic acids. The livestock bio-sludge was dried and treated with different concentrations of acetic acid (1N, 2N, and 4N). The acid-extracted sludge was then treated with or without adding H₂O₂ during different periods (4, 24, and 48 h) to investigate the efficiency of acid extraction of Cu and Zn. The supernatant of the acid-extracted product was separated from the residues through centrifugation. Experimental results showed that the treatment set of dried bio-sludge with 2% H₂O₂ significantly promoted the removal efficiency of Cu and Zn from the bio-sludge (p < 0.01). The best removal efficiency of Cu and Zn from the bio-sludge was 40% and 70%, respectively, using 4N acetic acid in the 48 h group. The study shows a green method for extracting Cu and Zn from livestock sludge, enhancing the sustainability of intensive livestock farming. Full article

There is much organic waste that comes from by-products of agriculture and product processing, solid waste from livestock, and municipal waste. Conventional methods that are widely used for the treatment and management of organic fractions of waste are landfilling, composting, anaerobic digestion, incineration, gasification, and pyrolysis. Among the above methods, pyrolysis is a relatively simple, robust, and scalable technology for transforming diverse organic waste feedstock into renewable energy products. Recently, the electrochemical conversion of biochar into electricity in direct carbon fuel cells (DCFC) has also been investigated and shown to be feasible and highly efficient. This paper focuses on the utilization of organic waste as a fuel and the investigation of their characteristics during electrochemical reactions in molten hydroxide direct carbon fuel cells (MH-DCFCs). Organic waste of different origins (the food-processing industry, urban and suburban areas, municipal solid organic waste, sewage sludge) with diversified characteristics was used as the main feedstock. The lowest power density was determined for sewage sludge (5.1 mW cm⁻²), and the best results were obtained for peanut shells (53.14 mW cm⁻²). This study concludes that higher elemental carbon, lower ash content and the presence of reactive surface oxygen functional groups in biochar obtained from organic waste might contribute to better cell performance. Moreover, the research establishes the potential of carbonized organic waste as a prospective alternative fuel source for power generation in an MH-DCFC. Full article

Birds are commonly used as bioindicators, and their feathers are considered suitable tissues for assessing the presence of contaminants, such as trace elements, in the environment. In agroecosystems, trace elements’ occurrence can be associated with both natural and anthropogenic processes, including vehicular traffic, traditional fertilizers, food feed additives for livestock, and the use of sewage sludge as fertilizer. Here, we evaluated the concentrations of twelve trace elements (Aluminium, Arsenic, Cadmium, Chromium, Copper, Iron, Mercury, Manganese, Nickel, Lead, Selenium, and Zinc) in the feathers of barn swallow (Hirundo rustica) nestlings. We then compared the concentrations of these elements between nestlings grown in areas amended or not amended with sewage sludge in 2019 and 2020 in a broad region of the Po Plain (Northern Italy). Multivariate analysis showed that the element content of the feathers significantly differed among years and areas, suggesting that the concentration of nestlings’ feathers may indicate the local level of contamination. However, univariate analyses did not show clear spatial differences, possibly due to co-occurring sources of trace elements other than sewage sludge. These results suggest that barn swallow nestlings can be a reliable sentinel for the monitoring of local variation of the environmental occurrence of trace elements. Full article

Heavy metals and metalloids (HMs) are environmental pollutants, most notably cadmium, lead, arsenic, mercury, and chromium. When HMs accumulate to toxic levels in agricultural soils, these non-biodegradable elements adversely affect crop health and productivity. The toxicity of HMs on crops depends upon factors including crop type, growth condition, and developmental stage; nature of toxicity of the specific elements involved; soil physical and chemical properties; occurrence and bioavailability of HM ions in the soil solution; and soil rhizosphere chemistry. HMs can disrupt the normal structure and function of cellular components and impede various metabolic and developmental processes. This review evaluates: (1) HM contamination in arable lands through agricultural practices, particularly due to chemical fertilizers, pesticides, livestock manures and compost, sewage-sludge-based biosolids, and irrigation; (2) factors affecting the bioavailability of HM elements in the soil solution, and their absorption, translocation, and bioaccumulation in crop plants; (3) mechanisms by which HM elements directly interfere with the physiological, biochemical, and molecular processes in plants, with particular emphasis on the generation of oxidative stress, the inhibition of photosynthetic phosphorylation, enzyme/protein inactivation, genetic modifications, and hormonal deregulation, and indirectly through the inhibition of soil microbial growth, proliferation, and diversity; and (4) visual symptoms of highly toxic non-essential HM elements in plants, with an emphasis on crop plants. Finally, suggestions and recommendations are made to minimize crop losses from suspected HM contamination in agricultural soils. Full article