Search Results (440)

Mathematical modeling is a key tool for describing and predicting the dynamic behavior of anaerobic digestion. Studies combining the co-digestion of aquaponics effluent (AE) and cattle manure (CM) with kinetic modeling remain scarce, particularly regarding the estimation of the apparent kinetic constant of hydrolysis constants and energy conversion indicators. Accordingly, this study aimed to evaluate the bioenergy potential of co-digesting aquaponics effluent (AE) and cattle manure (CM), with an emphasis on kinetic modeling and energy conversion. The experiments were carried out in a bench-scale Indian-type anaerobic biodigester. Different AE, CM, and water (W) (0:1, 1:0, 1:1, 1:3, 3:1 W:CM, and 1:1, 1:3, and 3:1 AE:CM) ratios were tested to identify the most efficient substrate combination for biogas production. The 1:3 AE:CM ratio achieved the best performance, with the Gompertz model providing the best fit for cumulative production and the first-order model accurately estimating k. This ratio yielded the highest cumulative biogas production (72.2 L kg⁻¹ substrate), shorter lag phase, higher production rate, and greater energy conversion efficiency. Comparative analysis revealed that 1:3 AE:CM outperformed both 1:3 A:CM and CM alone, highlighting the positive influence of aquaponics effluent on microbial activity and process stability. These results demonstrate that anaerobic co-digestion of AE and CM, particularly at the 1:3 ratio, is a viable and efficient strategy for renewable energy generation in rural areas, while promoting waste valorization and enhancing environmental and energy sustainability. Full article

Annual greenhouse gas emissions from livestock (CO₂ equivalent) are estimated at approximately 7.1 billion tons, accounting for 14.5% of global emissions, with beef and dairy cattle production contributing 41% and 20% of total emissions, respectively. Greenhouse gases released by ruminants not only lead to feed energy loss but also result in environmental degradation. Therefore, reducing greenhouse gas emissions from ruminants is crucial for the sustainable development of the ruminant industry. The primary greenhouse gases produced by ruminants include nitrous oxide from ruminant manure storage and methane generated in the rumen via the action of methanogenic archaea. Tannins, a class of polyphenolic compounds present in many plants, play a significant role in animal feed. Recent studies have shown that incorporating certain tannins and their metabolic products into diets can modulate protein metabolism and the ruminal microbiome, thereby regulating greenhouse gas emissions from ruminants. This review summarizes the types and properties of dietary tannins, as well as the latest advancements in understanding the impacts of tannins and their metabolites on cattle nutrient digestion and greenhouse gas emissions, concluding that dietary tannin supplementation can reduce greenhouse gas emissions from ruminants. Future research should focus on identifying the optimal concentrations of different tannins and their metabolites in diets to minimize ruminant greenhouse gas production while maintaining animal performance and health. Full article

Olive mill wastewater is a polluting residue generated from the olive oil industry and is one which constitutes an environmental concern in Mediterranean countries. Composting has been reported as a viable valorization alternative, as it reduces the volume and the phytotoxic characteristics of OMW. In this study, several composts derived from OMW were evaluated under controlled conditions over two growing season pot experiments using Lactuca sativa as a test crop. The analysis focused on soil quality changes, crop yield, and plant development. Additionally, potential phytotoxicity was also evaluated through a direct acute toxicity plant growth test. Application of OMW composts improved soil fertility indicators, including oxidizable carbon, Kjeldahl total nitrogen, Olsen phosphorous, and plant availability. Crop yields were comparable to those obtained with other organic amendments such as vermicompost and fresh cattle manure in both growing seasons and plant development (in terms of chlorophyll content and canopy cover) was not negatively affected. Nutrient uptake (NPK) was consistent during both growing seasons, with similar nitrogen use efficiency to that achieved in other organic treatments. Regarding the potential toxic effect, the OMW composts tested enhanced seed germination when mixed with coconut fiber at weight ratios below 29.2%. No half-maximal effective concentration (EC50) values were detected, even at 100% compost concentration, while half-maximal inhibitory concentration (LC50) values ranged between 65–75%. These results indicate that OMW composts can serve as an effective short-term source of plant-available nitrogen and a medium-term source of phosphorus, without risk of finding inhibitory or phytotoxic effects on crops. Full article

Anaerobic digestion (AD) technology is universally acknowledged as the most economically viable and efficient approach for energy recovery from livestock manure. To validate the efficacy of riboflavin-functionalized carbon-based conductive materials (CCM-RF) in enhancing methane production at pilot scale, three pilot-scale upflow anaerobic sludge blanket (UASB) reactors were constructed and separately supplemented with carbon cloth (CC), granular activated carbon (GAC), and a combination of CC and GAC. During reactor initialization, riboflavin and a concentrated inoculum of Methanosarcina barkeri (M. barkeri) were introduced to investigate the mechanistic role of CCM-RF in promoting direct interspecies electron transfer (DIET) and optimizing treatment efficiency during anaerobic digestion of cattle manure wastewater. The results showed that all reactors improved AD performance and maintained stable operation at the OLR of 15.66 ± 1.95 kg COD/(m³·d), with a maximum OLR of 20 kg COD/(m³·d) and the HRT as short as 5 days. Among the configurations, the CC reactor outperformed the others, achieving a methane volumetric yield of 6.42 m³/(m³·d), which represents an eight-fold increase compared to conventional AD systems. Microbial community analysis revealed that, although M. barkeri was initially inoculated in large quantities, Methanothrix—a methanogen with DIET capability—eventually became the dominant species. The enrichment of Methanothrix and the simultaneous enhancement in sludge conductivity collectively verified the mechanistic role of CCM-RF in promoting CO₂-reductive methanogenesis through strengthened DIET pathways. Notably, M. barkeri showed progressive proliferation under conditions of high organic loading rates (OLR) and short hydraulic retention time (HRT). This phenomenon provides a critical theoretical basis for the development of future strategies aimed at the targeted enrichment of Methanosarcina-dominant microbial consortia. Full article

Fig tree growth and development are highly susceptible to variations influenced by abiotic factors and management practices, including fertilization and training systems. This study aimed to evaluate the effect of organic and mineral fertilization on the photosynthetic, nutritional, and productive efficiency of fig trees subjected to different training systems in semi-arid regions. The experimental design was randomized blocks in a 5 × 4 factorial scheme, with three blocks and three plants per plot. The treatments consisted of five fertilizer sources (mineral fertilizer (NPK) applied at a dose of 126 g N, 90 g P, and 90 g K per plant (M); and four organic sources—cattle manure (CM), organic compost (OC), chicken litter (CL), and sheep manure (SM), all applied at a dose of 10 kg per plant); and four types of training systems (plants with two branches (2B), three branches (3B), four branches (4B), and espalier). Our results demonstrated that the mineral fertilizer (M) and chicken litter (CL) treatments yielded the highest results, particularly in photosynthetic performance. Fig trees fertilized with mineral fertilizer and subjected to the 3B system showed enhanced net photosynthesis (36.96 µmol m⁻² s⁻¹) and, consequently, higher productivity of 21.28 t ha⁻¹. Similarly, plants fertilized with chicken litter (CL) under the 4B system produced comparable results. These findings demonstrate that the use of mineral and organic fertilizers, combined with an appropriate training system, is a viable strategy for optimizing fig productivity and profitability in semi-arid conditions. Full article

Soil salinization is a major threat to agriculture and food security globally. The effectiveness of amendments on soil quality and crop production is management-dependent, and low-cost management practices are essential for developing countries. In this 3-year field study, the effects of cattle manure and gypsum amendments on the physicochemical properties of saline–alkali soil were evaluated. We found that both single gypsum and mixed amendments significantly reduced soil hardness, bulk density, pH, and soil salt content in 20–40 cm in 2015 and 2017. A more significant decrease in soil EC and density was observed with the mixed amendments compared to single gypsum after three years of reclamation. Specifically, applying mixed amendments (M-G15) led to a significant increase in Hordeum yield by 60.94%, whereas the application of single gypsum increased Hordeum yield by 25.20–53.14%. This indicated that co-application of cattle manure can reduce the amount of gypsum needed to achieve similar improvements in soil properties and Hordeum yield, with a long-term cumulative effect. Na⁺/(Ca²⁺ + Mg²⁺) showed the largest negative contribution to Hordeum yield under amendments, while soil bulk density showed the second largest number of negative effects on Hordeum yield under mixed amendments. Single gypsum improved the soil’s physical quality during the early stage of saline–alkali soil remediation, and mixed amendments improved the soil’s physicochemical properties and Hordeum yield during the late stage of remediation. Na⁺/(Ca²⁺ + Mg²⁺) in topsoil was confirmed to be the dominant factor under the mixed amendments affecting Hordeum yield, followed by the soil bulk density. These results confirm that the co-application with cattle manure achieves a similar reclamation effect with a reduced gypsum dosage, thereby lowering the reclamation costs of saline–alkali land in semi-arid areas. Full article

Optimizing organic fertilizer substitution is essential for enhancing the sustainability of agriculture and achieving a balance between crop productivity, nutritional quality, and environmental safety. Here, we conducted an 11-year field experiment to evaluate the effects of substituting 50% of mineral fertilizers with pig manure (PM) or cattle manure (CM) on the nutritional quality of wheat grain, heavy metal (HM) accumulation, and associated human health risks. The yield and protein content were highest in the mineral fertilizer (MF) treatment, and grain micronutrients (Fe, Mn, Cu, Zn) were 6.7–13.8% higher under organic substitution (PM/CM) than in the MF treatment. The Ni, Pb, and As contents were 35.4–43.0% higher in the PM treatment than in the MF treatment, which stems from the higher HM content in pig manure. Health risk assessments indicated that the Hazard Index (HI) for children exceeded 1 in the PM treatment, primarily due to As, which accounted for 69.6% of the HI. All treatments remained within safe thresholds, although As and Pb posed detectable carcinogenic health risks. The higher levels of Ni and As in pig manure likewise led to a significant increase in the health risk associated with the PM treatment compared to the MF treatment. We developed a novel Grain Quality Index (GQI) that combined nutrient and HM data, which indicated that the nutritional quality of wheat grain was similar in the CM and MF treatments. The GQI was 9.1% lower in the PM treatment than in the MF treatment. These findings suggest that the substitution of mineral fertilizer with cow manure can help achieve a balance between yield, nutrition, and safety, and more stringent regulation of HMs is required for the use of pig manure. Our findings provide actionable insights with implications for sustainable wheat production policies. Full article

As cattle are criticized for contributing to environmental problems by emitting pollutants, it is expected that environmental regulations on livestock will be strengthened. This will lead to an increase in the costs and benefits associated with these regulations. This paper develops a model that clearly shows the effects of environmental regulations on the production costs for cattle-breeding farmers and the changes in social welfare, as well as environmental benefits. The benefits associated with the regulation are measured by evaluating reductions in both greenhouse gas (GHG) and ammonia emissions. These benefits are then compared to the reduction in social welfare. According to the analysis, the reduction in social welfare, in terms of consumer and producer surplus, outweighs the environmental benefits. These results suggest that, in designing environmental regulations, policy measures are needed to alleviate producers’ economic burdens and minimize reductions in social welfare through byproduct utilization and technical support. Furthermore, this study contributes to laying the institutional foundation for the sustainable development of the livestock industry and the reduction in management costs associated with manure treatment. Full article

Given the demand for sustainable and cost-effective manure management in livestock systems, this study evaluated the economic feasibility of cattle manure treatment via composting and anaerobic digestion (AD) under different configurations. Five scenarios were compared: composting without solid–liquid separation, AD without separation at 20- and 30-day hydraulic retention times (HRTs), and combined systems with separation, composting the solid fraction and digesting the liquid. The analysis was based on a 200-cow herd and experimental data, with 15-year projected cash flows. Economic indicators included net present value (NPV), internal rate of return (IRR), discounted payback period (DPP), benefit–cost ratio (B/C), modified internal rate of return (MIRR), uniform annual equivalent (UAE), and profitability index (PI), supported by sensitivity analysis and Monte Carlo simulation. All scenarios were viable and posed low risk. Energy and fertilizer value were key drivers. The scenario 30-day HRT without separation had the best financial performance (NPV = 53,407.15 USD; IRR = 15.54%; DPP = 7.33 years; B/C = 1.57; MIRR = 9.28%; UAE = 5654.48 USD; PI = 1.66) and is recommended for capitalized farms seeking higher returns. Composting had lower returns (NPV = 9832.06 USD) but required the lowest investment, remaining a cost-effective alternative for smallholders. Full article

The paper presents an analysis of methods for utilizing digestate for energy purposes from two different biogas plants using different technologies. Biogas plant A used only cattle manure and corn silage as substrates, while biogas plant B used technology based on the utilization of food production waste. The analysis showed differences in the chemical, elemental, and thermogravimetric composition of both types of digestate. An analysis of the energy inputs required to produce fuel from digestate was also performed, along with energy balance calculations. The research and analysis led to the conclusion that both types of digestate are suitable for energy recovery. The possibilities of optimizing the process using excess heat from the biogas plant were also analyzed. In the case of digestate A, the combustion heat of digestate B was 17.20 MJ·kg⁻¹, while for digestate A, it was 14.80 MJ·kg⁻¹. The calorific value of digestate A at 8.79% moisture content was 13.40 MJ·kg⁻¹, while for digestate B at 6.03% moisture content, it was 15.80 MJ·kg⁻¹, respectively. Full article

One of the most interesting applications of crude glycerol (CG) is its use for biogas production via the anaerobic co-digestion (AcoD) process. The main aim of the current study was to provide a comprehensive review on the performance of the AcoD of CG mixed with various substrates. For this purpose, analyses were performed for studies available in the literature wherein one-stage experiments were conducted. To the best of the authors’ knowledge, the present study is the first one which demonstrates an analysis of the main parameters of CG and substrates (e.g., animal manure, sewage sludge, cattle manure and food waste) used for AcoD. Moreover, a detailed analysis of the impact of selected parameters on AcoD performance was carried out. It is demonstrated that the values of key parameters characterizing the CG used for AcoD were within wide ranges. This can be explained by the fact that the composition of CG depends on many factors; for instance, these include the source of oil used for biodiesel production, processing technology, the ratio of reactants, the type of catalyst and the procedure applied. Moreover, performing a literature review allowed us to demonstrate that adding CG to feedstock caused the enhancement of process performance compared to results obtained for mono-digestion. Additionally, it was shown that, in general, increasing the concentration of CG in feedstock led to improvement of the biogas yield; however, a potential inhibitory effect should be considered. Analysis of data available in the literature allowed us to indicate that for most of the experiments performed, a methane (CH₄) content in biogas higher than 60% was obtained for CG content in feedstock up to 8% v/v. In addition, it is demonstrated that in order to evaluate the performance of AcoD performed under thermophilic conditions, more studies are required. Finally, it should be pointed out that the present study provides considerable insight into the management of CG. Full article

This study investigates the economic viability of a new composting station dedicated to the recycling of date palm by-products. A field experiential analysis was performed in the Figuig Oasis (Morocco), providing the first evidence on the agronomic quality of the compost. The compost produced from date palm by-product was compared to cattle manure and unamended soil and can be considered as a good-quality amendment, demonstrating its ability to enhance soil fertility. Second, a socio-economic survey was conducted to explore farmers’ perceptions and adoption of sustainable agricultural practices. A total of 201 farmers out of 450 farmers registered in Figuig’s municipal administration were surveyed. In terms of fertilisation, farmers preferred locally produced organic fertiliser when available in order to improve soil organic matter content and reduce dependence on chemical inputs. The selling price for the compost was set at 0.14 EUR/kg to reflect the current market price for compost and the willingness of about 38% of the farmers surveyed to buy it. Third, a detailed cost/benefit analysis was performed, with a breakdown of the station’s operational and investment expenses. This illustrates the minimum scale needed to generate a viable business model. Financial projections show that increasing production capacity from 350 tonnes/year to 3500 tonnes/year reduces unit production costs while increasing profits. As illustrated by the application of the Ecocanvas framework, the socio-economic analysis reveals the potential to generate positive environmental, economic, and social impacts, as the circular approach could be replicable and scalable in similar oases agro ecosystems. Full article

The brewing industry generates significant organic waste, much of which remains underutilized despite its potential for energy recovery. This study assesses the feasibility of anaerobic co-digestion (AcoD) using brewers’ spent grain (BSG) from the craft beer production process and cattle manure from feedlots. Thermogravimetric analysis confirmed similar volatile solids content in both substrates, validating BSG as a viable feedstock. AcoD trials were conducted in 20 L biodigesters under dry and ambient conditions over 40 days. Methane yields reached 25 mL CH₄ gVS⁻¹ at a 1:1 inoculum–substrate ratio fresh matter basis and 67.33 mL CH₄ gVS⁻¹ at 2.5:1, indicating that higher inoculum levels enhance methane production. Kinetic modeling using Modified Gompertz, Logistic, and other microbial growth-based models showed that the Logistic model best represented the methane production trends. The detection of hydrogen sulfide in the biogas emphasizes the need for effective filtration. Overall, this work highlights AcoD as a promising approach for organic waste valorization and renewable energy generation in the craft brewing sector, supporting circular economy practices and contributing to environmental and economic sustainability. Full article

Manure application may improve plant growth, yield, and ecological sustainability. This study investigates optimized organic fertilizer application methods for enhancing buckwheat (Fagopyrum esculentum) productivity in semi-arid conditions. Treatments include broadcasting (Br) and subsurface banding (Ba) of poultry (PM) and cattle (CM) manure and foliar spraying (S) of manure extracts (1:5 and 1:10 ratios), urea fertilizer (UF), and a control. Subsurface-banded poultry manure (BaPM) maximized chlorophyll b (4.0 µg/mL), carotenoids (2.30 µmol/mL), anthocyanin (0.02 µmol/mL), leaf area index (2.03), seed nitrogen (3.4%), and spikes per plant (17). BaPM achieved the highest seed yield (646 kg/ha), comparable to BrPM, BaCM, and SPM(1:5). The maximum seed phosphorus content (0.43%) was observed in the BaPM, BrPM, and SCM(1:10) treatments. Dry matter peaked under UF (4870 kg/ha) and BaPM (4641 kg/ha). Banding placement improved nutrient uptake by enhancing root zone retention, while foliar poultry extract (1:5) mitigated phosphorus deficiency. These findings demonstrate that integrating certain manure types with targeted application methods—particularly subsurface banding of poultry manure—optimizes nutrient use efficiency, crop performance, and environmental sustainability in buckwheat cultivation. Full article

Livestock-intensive regions in Europe face dual challenges: nutrient surpluses and a high dependency on import of high-protein feedstocks. This study proposes duckweed (Lemnaceae) as a potential solution by recovering nutrients from manure-derived waste streams while producing protein-rich biomass. This study evaluated the performance of duckweed treatment systems at a pig manure processing facility in Belgium. Three outdoor systems were monitored over a full growing season under temperate climate conditions. Duckweed cultivated on constructed wetland effluent showed die-off and low protein content, while systems supplied with diluted liquid fraction and nitrification–denitrification effluent achieved consistent growth, yielding 8 tonnes of dry biomass/ha/year and 2.8 tonnes of protein/ha/year. Average removal rates were 1.2 g N/m²/day and 0.13 g P/m²/day. Growth ceased after approximately 100–120 days, likely due to rising pH and electrical conductivity, suggesting ammonia toxicity and salt stress. Harvested duckweed had a high protein content and a total amino acid profile suitable for broilers, though potentially limiting in histidine and methionine for pigs or cattle. Additionally, promising energy and protein values for ruminants were measured. Although high ash and fibre contents may limit use in monogastric animals, duckweed remains suitable as part of a balanced feed. Its broad mineral profile further supports its use as a circular, locally sourced feed supplement. Full article