Degradation Of Organic Matter Research Articles

Investigating fungal community characteristics in co-composted cotton stalk and various livestock manure products.

Agricultural wastes, comprising cotton straw and livestock manure, can be effectively managed through aerobic co-composting. Nevertheless, the quality and microbial characteristics of co-composting products from different sources remain unclear. Therefore, this study utilized livestock manure from various sources in Xinjiang, China, including herbivorous sheep manure (G), omnivorous pigeon manure (Y), and pigeon-sheep mixture (GY) alongside cotton stalks, for a 40-day co-composting process. We monitored physicochemical changes, assessed compost characteristics, and investigated fungal community. The results indicate that all three composts met established composting criteria, with compost G exhibiting the fastest microbial growth and achieving the highest quality. Ascomycota emerged as the predominant taxon in three compost products. Remarkably, at the genus level, the biomarker species for G, Y, and GY are Petromyces and Cordyceps, Neurospora, and Neosartorya, respectively. Microorganisms play a pivotal role in organic matter degradation, impacting nutrient composition, demonstrating significant potential for the decomposition and transformation of compost components. Redundancy analysis indicates that potassium, total organic carbon, and C:N are key factors influencing fungal communities. This study elucidates organic matter degradation in co-composting straw and livestock manure diverse sources, optimizing treatment for efficient agricultural waste utilization and sustainable practices.

Metal mobility after resuspension of contaminated sediments from a tropical urban bay

Dredging activities are recurrent in coastal cities, however, they can cause the remobilization of contaminants, increasing the risk to the biota. Guanabara Bay is a complex eutrophic estuary that undergoes dredging in several areas during the year. The Meriti River estuary is silted up and highly contaminated by metals, such as Cr, Cu, and Zn, due to the discharge of untreated sewage. In this sense, the present study aims to evaluate the remobilization of metals in the sediment (Cr, Cu, Fe, Mn, Ni, Pb, and Zn) and bioavailability after resuspension. Twelve sampling points were collected along 4 transects. The resuspension experiments were performed at two intervals: 1 h (T1) and 24 h (T2) and followed protocols from previous studies. In general, all metals are remobilized after resuspension. - In addition, the bioavailability change (BC) index was applied., which showed 54% remobilization of Cr after T2. The transects closer to the river showed less remobilization after resuspension, which may be related to the saline gradient. Zn was the only metal that exceeded CONAMA Resolution 454/12 level 2 after resuspension, indicating a significant anthropogenic input to the area. Although organic matter (OM) is one of the main regulators of bioavailability in this study, the results suggest that there is an interference of bacterial activity in the dynamics of OM degradation, which directly impacts the bioavailability of metals after resuspension.

Review of bacterial sulfate reduction in lacustrine deposition and its identification in the Jimsar Sag, Junggar Basin

Bacterial sulfate reduction (BSR) is the interaction between sulfates and organic matter that bacteria participate in during the early diagenetic stage. It is one of the important biogeochemical processes that affect the formation of sulfides and sulfur cycling. Due to the lack of sulfate in the lakes, there is relatively little research on lacustrine bacterial sulfate reduction (LBSR), and related research mainly focuses on marine sedimentation. Marine incursion and volcanic ash may bring sulfate to lakes, providing a possibility for the occurrence of LBSR. The process, main influencing factors, and identification methods of BSR are summarized systematically. Through comprehensive analysis, it is believed that the occurrence depth of LBSR is relatively shallow (about 10 cm). Sulfate concentration, total organic matter, and sulfate reducing bacteria activity are the main controlling factors of BSR. The petrological and geochemical characteristics of the product are commonly used indicators to determine whether BSR occurs. The Jimsar Sag is one of the important shale oil rich areas in China. Taking Jimsar Sag as an example, the identification of LBSR was attempted. Based on the characteristics of framboidal pyrite, columnar calcite, and fine-grained dolomite, comprehensive analysis suggests that LBSR has occurred in the Lucaogou Formation of the Jimsar Sag. BSR has a significant effect on the degradation of organic matter, and TOC is usually lower in areas with higher intensity. Therefore, BSR has impact on the enrichment of organic matter in shale. The relevant research may have reference significance for the enrichment of lacustrine organic matter and shale oil exploration.

Spatial heterogeneity of sedimentary organic matter sources in the Yangtze River estuary: Implications from fatty acid biomarkers

This study investigated the sources of sedimentary organic matter (OM) in the Yangtze River estuary (YRE), using multiple biomarkers. The results of stable carbon isotope (δ13C) and total organic carbon to nitrogen ratio (TOC/TN) suggests the contribution of marine-derived OM significantly increased seawards, while fatty acid (FA) composition provides more specific information on OM sources. In total, 30 components of FAs were identified at the studied 17 sites, which mainly composed of phytoplankton FA, followed by ubiquitous FA and bacterial FA, while terrestrial FA contributed less to the total FAs. Under the strong impacts of the large physicochemical gradients in the YRE, TOC, TN and FA components showed higher concentrations in the estuary mixing zone (especially within the turbidity maximum zone), attributing to their strong binding with OM-enriched fine particles. The spatial heterogeneity of sedimentary OM sources was highly impacted by salinity and Chl-a, as well as bacteria-mediated OM degradation.

Soil organic matter degradation and methylmercury dynamics in Hg-contaminated soils: Relationships and driving factors

Biodegradation of soil organic matter (SOM), which involves greenhouse gas (GHG) emissions, plays an essential role in the global carbon cycle. Over the past few decades, this has become an important research focus, particularly in natural ecosystems. SOM biodegradation significantly affects contaminants in the environment, such as mercury (Hg) methylation, producing highly toxic methylmercury (MeHg). However, the potential link between GHG production from SOM turnover in contaminated soils and biogeochemical processes involving contaminants remains unclear. In this study, we investigated the dynamics of GHG, MeHg production, and the relationship between biogeochemical processes in soils from two typical Hg mining sites. The two contaminated soils have different pathways, explaining the significant variations in GHG and MeHg production. The divergence of the microbial communities in these two biogeochemical processes is essential. In addition to the microbial role, abiotic factors such as Hg species can significantly affect MeHg production. On the other hand, we found an inverse relationship between CH4 and MeHg, suggesting that carbon emission reduction policies and management could inadvertently increase the MeHg levels. This highlights the need for an eclectic approach to organic carbon sequestration and contaminant containment. These findings suggest that it is difficult to establish a general pattern to describe and explain the SOM degradation and MeHg production in contaminated soils within the specific scenarios. However, this study provides a case study and helpful insights for further understanding the links between environmental risks and carbon turnover in Hg mining areas.

The Advantage of Citrus Residues as Feedstock for Biogas Production: A Two-Stage Anaerobic Digestion System

Anaerobic digestion (AD) is an important step in waste recovery. In Colombia, the production of citrus food significantly contributes to environmental impact via waste generation. In 2021, the waste produced, specifically citrus rind, amounted to 725,035 tons/year. During degradation, wastes generate leachate and greenhouse gases (GHGs), which negatively impact water sources (leachate), soil, and human and animal health. This article describes the design of a two-phase biodigestion system for the degradation of organic matter and biogas production. The system uses citrus waste to produce biogas with neutral emissions. The biodigestion process begins with the stabilization of the methanogenesis reactor (UASB), which takes approximately 19 days. During this period, the biogas produced contains approximately 60% methane by volume. Subsequently, the packed bed reactor operates for 7 days, where hydrolytic and acetogenic bacteria decompose the citrus waste, leading to the production and accumulation of volatile fatty acids. The final step involves combining the two phases for 5 days, resulting in a daily biogas production ranging from 700 to 1100 mL. Of this biogas, 54.90% is methane (CH4) with a yield of 0.51 LCH4gSV−1. This study assesses the methane production capacity of citrus waste, with the process benefiting from the pH value of the leachate, enhancing its degradability. Consequently, this approach leads to a notable 27.30% reduction in solids within the digestion system. The two-phase anaerobic biodigestion system described in this article demonstrates a promising method to mitigate the environmental impact of citrus waste while concurrently producing a renewable source of energy.

Grape Skin Composting Process to Recycle Food Waste: Kinetics and Optimization.

Within the various approaches to organic waste handling, composting has been recognized as an acceptable method to valorize organic waste. Composting is an aerobic technique of microbial disruption of organic matter which results with compost as a final product. To guarantee the quality of the compost, key process factors (like the moisture content, temperature, pH, and carbon-to-nitrogen ratio) must be maintained. In order to optimize the process, nine composting trials using grape skins were conducted in the present study under various initial moisture content and air flow rate conditions over the course of 30 days. The processes were monitored through physicochemical variables and microbiological activity. Also, the kinetics of the organic matter degradation and microbial growth were investigated. Although the thermophile phase was only achieved in experiments 3 and 8, the important variables proved the efficiency of all nine composting processes. The organic carbon content and C/N ratio decreased after the 30 days of composting processes and a great color change was noticed too. The values for the germination index for all experiments were above 80%, which means that the final products are non-toxic for plants. Also, the greatest change in organic carbon content in was evident in experiment 3; it decreased from 71.57 to 57.31%. And consequently, the rate of degradation for that experiment was the highest, at 0.0093 1/day. Furthermore, the response surface methodology was used to identify optimal operating conditions for grape skin composting and the obtained conditions were 58.15% for the initial moisture content and 1.0625 L/min for the air flow rate.

Synergy of phosphate and hyperthermophilic bio-drying reduces pollution of sludge bio-drying: Reducing ammonia emissions and heavy metal migration risk

Hyperthermophilic bio-drying has stronger organic matter degradation and drying ability than the conventional bio-drying. However, ammonia emissions during the hyperthermophilic bio-drying are significantly higher than those during the conventional bio-drying process due to the higher temperature and pH value. Phosphate has been reported to reduce ammonia emissions during composting. Meanwhile, both the degradation of organic matter and the addition of phosphate buffer can promote the formation of EPS. EPS exhibits strong passivation and adsorption properties for heavy metals and organic pollutants, thus positively impacting the control of pollution in bio-drying products. Furthermore, the formation of EPS and the risk of the migration of heavy metals during hyperthermophilic bio-drying have not been reported. According to the results, compared to conventional bio-drying, the hyperthermophilic bio-drying significantly increased the yield of EPS and generated more active groups, reducing the migration risk of Cu, Zn, Cr, Pb, Cd, As, and Ni. The comprehensive potential ecological risk was reduced by 29.71%, which was higher than the reduction achieved by conventional bio-drying (13.81%). The addition of phosphate significantly reduced the ammonia emissions from the hyperthermophilic bio-drying and retained more nitrogen. Meanwhile, it promoted the formation of EPS and the enrichment of active groups, further reducing the migration risk of heavy metals. Moreover, the addition of phosphate buffer further reduced the comprehensive potential ecological risk of the products obtained from.

Abrupt intensification of AMOC and monsoonal winds during mid-MIS4 (Heinrich Event 6) in the western Arabian Sea

In the Arabian Sea (AS), higher organic matter preservation and biological productivity are observed during the summer due to strong southwest monsoonal winds. Centennial and millennial-scale fluctuation in the geochemical and relative abundance of foraminifera species are widely used to study the past preservation and productivity variation reconstruction in the Western Arabian Sea (WAS). The sediment records from the AS also show similarities with the North Atlantic and Greenland mainly during Heinrich events (HEs) which is related to the atmospheric and oceanic teleconnections of the AS with the higher latitude climate perturbations. In this context, we used a sediment core VM3504-PC from the WAS to understand the long-term changes in productivity and organic matter preservation using Globigerina bulloides (G. bulloides) relative abundance, total organic carbon (TOC) content, and calcium carbonate (CaCO3) wt%. The TOC and G. bulloides shows a positive correlation, while significantly negative correlation is recorded in the TOC % and CaCO3 wt% datasets during interglacial periods (MIS5e-b, MIS3, and MIS1). Our results show evidence of CaCO3 dissolution and intense summer monsoon induced upwelling related productivity in core location during interglacial periods (MIS5e), based on higher relative abundance of G. bulloides (%), higher TOC content, and lower CaCO3 wt%. Interestingly, higher preservation of organic matter and increased productivity/nutrient concentration during mid-MIS4 suggesting stronger upwelling/winter convective mixing together with higher aeolian transport from adjacent landmasses. The abrupt weakening in the Atlantic Meridional Overturning Circulation (AMOC) synchronized with low productivity due to weak monsoon during HEs except for H6 and H4 in the tropical Indian Ocean. The H6 coincides with mid-MIS4 is showing abnormal preservation. Thus, AMOC and the summer monsoon significantly regulate primary productivity in the WAS. It is interesting to note that possibly well‑oxygenated deep-water masses do not penetrate up to surface water and/or ballistic effect (indicated by moderate sedimentation rate), preventing organic matter degradation on the seafloor during mid-MIS4.

112 In situ evaluation of multiple edible insects as feed for cattle

Abstract Livestock production is growing and intensifying in response to a growing population and associated food demands. Commercially reared insects have been positioned as a potential protein source for livestock due to their nutritional value and decreased environmental footprint as compared with conventional protein feeds. The American Association of Feed Officials (AAFCO) has issued a definition for black soldier fly larvae (BSFL) as feed for certain livestock but has not yet authorized feeding BSFL to ruminants. Further, AAFCO has not provided a feed definition for other edible insects [e.g., mealworm larvae (MWL)], likely due to a lack of research evaluating the value of insects as feed. The objective of this study was to evaluate edible insect species as feed for cattle by determining in situ characteristics of multiple commercially reared species. This research was approved by Texas State University IACUC (#8693). Samples (n = 14) included five insect species [i.e., black soldier fly larvae (BSFL)], mealworm larvae (MWL), house cricket, grasshopper, and banded cricket] that were commercially reared on different feed inputs and with various processing parameters and BSFL frass, which is insect excreta. There were 6 samples of BSFL, two of MWL, and three of house crickets. Three ruminally cannulated steers were used and provided ad libitum hay and water. A 6-d trial period was performed including a 3-d adaptation and 3-d experimental incubation period. Samples incubated in the rumen at 7 timepoints in reverse order (0, 4, 6, 12, 14, 48, and 72 h). After incubation, residues were analyzed for partial dry matter (PDM), dry matter (DM), and organic matter (OM). Dry matter and OM were separated into immediately soluble (IS), potentially soluble (PS), and not soluble (NS) fractions. For DM, the average NS fraction was 6.2% with a range from 3.0 to 10.4%. The sample with the greatest NS fraction was grasshopper. Across samples, the average PS fraction was 74.5% with a range from 69.3 to 79.1%. The sample with the smallest PS fraction was BSFL frass whereas the sample with the greatest was BSFL. Multiple samples had a DM degradability >85%. However, MWL and BSFL had fluctuating DM degradability across samples, likely due to variability among processing parameters. For OM fractionation, the average NS fraction was 5.7% with a range of 2.8 to 10.4%. Grasshopper had the greatest NS fraction. The average PS fraction was 74.9%; BSFL had the greatest PS fraction while frass had the least. Many samples had an OM degradability >85% and frass had the greatest degradability (90.0%). There was great variability in OM degradability across house cricket samples, likely related to rearing diet. These findings indicate that BSFL and MWL have potential value as feed for cattle but there would be challenges associated with feeding crickets.

116 In-situ degradability of hemp (Cannabis sativa L.) plant components in cattle

Abstract The 2014 and 2018 Farm Bills defined hemp (Cannabis sativa L.) as an agricultural commodity and removed it from the controlled substances list, developing a pathway for commercialization and increasing interest in cultivating hemp in the United States. Demand for therapeutic, cannabinoid-based hemp products is increasing, and, as not all of the plant components are utilized for these products, there will likely be significant quantities of hemp by-products created. As these by-products are cellulosic, they may be marketed as livestock feed, especially for ruminant animals. There have been limited studies into hemp as cattle feed. Accordingly, the objective of this study was to determine the in-situ degradability of different hemp components in beef cattle. We conducted an in-situ trial with three ruminally cannulated steers (IACUC #8497) and 16 unique hemp samples: leaves, flower, stalk, or whole plant cultivated with four different seed inoculants. Samples were incubated in the rumen for 0, 4, 6, 12, 24, 48, and 72 h and replicated across each steer. After samples were removed, they were rinsed and analyzed for partial dry matter (DM), DM, organic matter (OM), and crude protein (CP). Solubility fractions [immediately soluble (IS), potentially soluble (PS), and not soluble (NS)], rate of degradation (kd), and rumen degradability was determined for OM and CP. Rate of passage (kp) was set at 4.7%. As there were not differences across seed inoculant method, data were combined across plant components. For OM, the NS fraction was greatest for hemp stalks (12%) and least for leaves (7%). The PS fraction ranged 72-75% across plant components with the least value for stalks and greatest for leaves. Of the PS fraction, ruminal OM degradability was least for stalks (51%) and greatest for leaves (72%). For CP, the NS fraction of hemp stalks (16%) was greater than other fractions, which ranged from 6-8%. The PS fraction was approximately 76% for both whole plant and leaves, a vast majority of which (71-73%) was degradable, indicating these plant components provide a good source of rumen degradable protein. The IS fraction was greatest (20%) for hemp flower. Although hemp flower may be easily digested by ruminants, it does not have practical value because this plant component competes in the human market as the flower contains a high percentage of cannabinoids which have therapeutic properties. Ultimately, our data indicate that hemp leaves have nutritional and practical value as feed for beef cattle and that hemp stalks would likely not be well-utilized as a forage source. Before hemp can be integrated into the beef cattle industry as feed, additional research is required to determine the effects of feeding hemp on animal performance and evaluate uptake and retention of cannabinoids in body tissues.

156 In-situ degradability of hemp (Cannabis sativa L.) plant components in cattle

Abstract The 2014 and 2018 Farm Bills defined hemp (Cannabis sativa L.) as an agricultural commodity and removed it from the controlled substances list, developing a pathway for commercialization and increasing interest in cultivating hemp in the United States. Demand for therapeutic, cannabinoid-based hemp products is increasing, and, as not all of the plant components are utilized for these products, there will likely be significant quantities of hemp by-products created. As these by-products are cellulosic, they may be marketed as livestock feed, especially for ruminant animals. There have been limited studies into hemp as cattle feed. Accordingly, the objective of this study was to determine the in-situ degradability of different hemp components in beef cattle. We conducted an in-situ trial with three ruminally cannulated steers (IACUC #8497) and 16 unique hemp samples: leaves, flower, stalk, or whole plant cultivated with four different seed inoculants. Samples were incubated in the rumen for 0, 4, 6, 12, 24, 48, and 72 h and replicated across each steer. After samples were removed, they were rinsed and analyzed for partial dry matter (DM), DM, organic matter (OM), and crude protein (CP). Solubility fractions [immediately soluble (IS), potentially soluble (PS), and not soluble [NS]), rate of degradation (kd), and rumen degradability was determined for OM and CP. Rate of passage (kp) was set at 4.7%. As there were not differences across seed inoculant method, data were combined across plant components. For OM, the NS fraction was greatest for hemp stalks (12%) and least for leaves (7%). The PS fraction ranged 72-75% across plant components with the least value for stalks and greatest for leaves. Of the PS fraction, ruminal OM degradability was lowest for stalks (51%) and highest for leaves (72%). For CP, the NS fraction of hemp stalks (16%) was greater than other fractions, which ranged from 6-8%. The PS fraction was approximately 76% for both whole plant and leaves, a vast majority of which (71-73%) was degradable, indicating these plant components provide a good source of rumen degradable protein. The IS fraction was largest (20%) for hemp flower. Although hemp flower may be easily digested by ruminants, it does not have practical value because this plant component competes in the human market as the flower contains an increased percentage of cannabinoids which have therapeutic properties. Ultimately, our data indicate that hemp leaves have nutritional and practical value as feed for beef cattle and that hemp stalks would likely not be well-utilized as a forage source. Before hemp can be integrated into the beef cattle industry as feed, additional research is required to determine the effects of feeding hemp on animal performance and evaluate uptake and retention of cannabinoids in body tissues.

Combination effects of phytonutrient pellet and lemongrass (Cymbopogon citratus) powder on rumen fermentation efficiency and nutrient degradability using in vitro technique.

Phytonutrients (PTN) namely saponins (SP) and condensed tannins (CT) have been demonstrated to assess the effect of rumen fermentation and methane mitigation. Phytonutrient pellet containing mangosteen, rambutan, and banana flower (MARABAC) and lemongrass including PTN, hence these plant-phytonutrients supplementation could be an alternative plant with a positive effect on rumen fermentation. The aim of this experiment was to evaluate the effect of supplementation of MARABAC and lemongrass (Cymbopogon citratus) powder on in vitro fermentation modulation and the ability to mitigate methane production. The treatments were arranged according to a 3 × 3 Factorial arrangement in a completely randomized design. The two experimental factors consisted of MARABAC pellet levels (0%, 1%, and 2% of the total substrate) and lemongrass supplementation levels (0%, 1%, and 2% of the total substrate). The results of this study revealed that supplementation with MARABAC pellet and lemongrass powder significantly improved gas production kinetics (P < 0.01) and rumen fermentation end-products especially the propionate production (P < 0.01). While rumen methane production was subsequently reduced by both factors. Additionally, the in vitro dry matter degradability (IVDMD) and organic matter degradability (IVOMD) were greatly improved (P < 0.05) by the respective treatments. MARABAC pellet and lemongrass powder combination showed effective methane mitigation by enhancing rumen fermentation end-products especially the propionate concentration and both the IVDMD and IVOMD, while mitigated methane production. The combined level of both sources at 2% MARABAC pellet and 2% lemongrass powder of total substrates offered the best results. Therefore, MARABAC pellet and lemongrass powder supplementation could be used as an alternative source of phytonutrient in dietary ruminant.

Microbial Assemblages and Metabolic Activity in Organic‐Rich Subterranean Estuaries: Impact of Climate and Land Use Changes

AbstractMicrobial communities in subterranean estuaries mediate biogeochemical reactions of coastal groundwater discharging into the oceans; however, studies on their response to abrupt environmental changes caused by climate and land use alterations are still limited. In this study, we conducted a controlled laboratory study using combined geochemical and metagenomic approaches to investigate microbial structures and their metabolic pathways under a wide range of nitrate () inputs, saline solutions, and incubation times. These factors served as proxies for land use, salinization of the shallow aquifer, and climate changes. We found a highly reducing habitat and an amplification of genes related to denitrification, sulfate reduction, and methanogenesis processes. Core communities consisting of Clostridia, Bacilli, Alphaproteobacteria, Gammaproteobacteria, and Desulfobaccia were observed across all treatments. The metabolic prediction of plant‐derived organic matter (i.e., tannin and lignin) degradation was not affected by inputs or salinity because of it being implemented by core communities and the abundance of electron donors and acceptors. Quantification of denitrification genes shows that they are susceptible to inputs and seawater ions. Long‐term incubation allowed sufficient time for microbes to degrade less labile DOM, promoting the re‐release of buried solid phase organic matter into the active carbon cycle and increasing the relative abundance of biofilm or spore‐forming taxa while decreasing that of rare taxa. Our results illustrate the sensitivity of microbial assemblages to environmental changes and their capacity to altering the C and N cycles in coastal areas, further affecting coastal water quality and ecosystem‐scale biogeochemistry.

Annual recurrence of prokaryotic climax communities in shallow waters of the North Mediterranean.

In temperate coastal environments, wide fluctuations of biotic and abiotic factors drive microbiome dynamics. To link recurrent ecological patterns with planktonic microbial communities, we analysed a monthly-sampled 3-year time series of 16S rRNA amplicon sequencing data, alongside environmental variables, collected at two stations in the northern Adriatic Sea. Time series multivariate analyses allowed us to identify three stable, mature communities (climaxes), whose recurrence was mainly driven by changes in photoperiod and temperature. Mixotrophs (e.g., Ca. Nitrosopumilus, SUP05 clade, and Marine Group II) thrived under oligotrophic, low-light conditions, whereas copiotrophs (e.g., NS4 and NS5 clades) bloomed at higher temperatures and substrate availability. The early spring climax was characterised by a more diverse set of amplicon sequence variants, including copiotrophs associated with phytoplankton-derived organic matter degradation, and photo-auto/heterotrophic organisms (e.g., Synechococcus sp., Roseobacter clade), whose rhythmicity was linked to photoperiod lengthening. Through the identification of recurrent climax assemblages, we begin to delineate a typology of ecosystem based on microbiome composition and functionality, allowing for the intercomparison of microbial assemblages among different biomes, a still underachieved goal in the omics era.

Dissolved carbon in effluent of wastewater treatment plants and its potential impacts in the receiving karst river

The dissolved carbon cycling in river system fueled by wastewater treatment plant effluent have been a research hotspot. However, the composition of dissolved carbon (DC) in wastewater effluents from karst regions remains poorly understood, resulting in a lack of clarity regarding its impact on the dynamics of dissolved carbon in karst rivers. To address this knowledge gap, this study investigated variations of dissolved inorganic (DIC) and organic C (DOC) components in effluent in karst regions and preliminarily discussed their influence on the DC cycling in karst rivers. The results showed that bicarbonate (HCO3–) in WWTP effluents makes more than 90% of the total dissolved inorganic carbon (DIC). The partial pressure of aqueous CO2 (pCO2) of the effluent reached 14450 ± 10084μtam, and pCO2 level declined with increasing river distance from the effluent discharge, effluent acted as a strong CO2 emitter to the atmosphere. Stable carbon isotope and water chemistry evidence revealed that organic matter degradation made important contributions to the high CO2 concentrations in effluent. PHREEQC mixing simulation together with filed samples data indicated that the DIC species can be changed, and pCO2 increased in receiving karst river water after mixed with effluent. The dissolved organic carbon (DOC) of effluent contained humic-like and protein-tryptophan-like, both of them appeared important and recent autochthonous, which could interfere the distinguish the sources of DOC in receiving karst river water. Thus, these findings highlight that the effluent can be an essential factor for the changes of the karst riverine DC pool, which advance our understanding on karst riverine DC evolution under anthropogenic activities. As more than 30% of the earth surface in China, northern America, and Europe are covered by carbonate rocks, this study has relevant implications for other karst regions as it underscores the influence of WWTP effluents on the carbon cycle in karst rivers. Such information and knowledge are valuable for monitoring and managing effluent-receiving river in other karst regions in the world.

Enhancing bioavailable carbon sources and minimizing ammonia emissions in distillery sludge and distiller's grains waste co-composting through deep eutectic solvent addition

This study introduced two deep eutectic solvents, ChCl/oxalic acid (CO) and ChCl/ethylene glycol (CE), into a 34-day co-composting process of distillery sludge and distiller's grains waste to address challenges related to NH3 emissions. The addition of DES increased dissolved organic carbon by 68% to 92%, offering more utilizable carbon for microorganisms. SYTO9/PI staining and enzyme activity tests showed the CE group had higher bacterial activity and metabolic levels during the thermophilic phase than the control. Bacterial community analysis revealed that early dominance of Lactobacillus and Lysinibacillus in CE accelerated the onset of the thermophilic phase, reduced pile pH, and significantly decreased urease production by reducing Ureibacillus. Consequently, CE treatment substantially dropped NH3 emissions by 73% and nitrogen loss by 54%. Besides, CE fostered a more abundant functional microbial community during the cooling and maturation phases, enhancing deep degradation and humification of organic matter.

Stability and Effects of Protected Palmitic Acid on In Vitro Rumen Degradability and Fermentation in Lactating Goats

Few studies have evaluated the impact of a lipid-rich diet with palmitic acid (PA) in ruminal fermentation. The objective was to evaluate the in vitro bath culture of the protected PA on the ruminal fermentative variables. Four diets were used: (a) without protected PA (nPA) and (b) inclusion of protected PA at three levels: PA3 = 3%, PA6 = 6%, and PA9 = 9% dry matter (DM). The maximum gas production occurred without including protected PA and the low gas production given with the inclusion of protected PA9 (p ≤ 0.05). Meanwhile, the inclusion with 3 and 6% of protected PA showed a higher level of gas production kinetics than the other treatments (p ≤ 0.05). DM and organic matter degradation after 72 h of incubation linearly decreased (p ≤ 0.05) with a high level of protected PA. The level of C16:0 in the protected AP increased with the higher level of supplemented AP (p ≤ 0.05). The best efficiency in propionic acid, decrease in methane, and increase in biohydrogenation (79%) occurred with the inclusion of protected PA3 (p ≤ 0.05). In conclusion, supplements with protected PA at 3 and 6% increased PA availability. The results indicate good benefits of protected PA on fermentative variables, and these doses seem ideal for future research in lactating goats.

Catalyzing oxygen reduction by morphologically engineered ZIF-derived carbon composite catalysts in dual-chamber microbial fuel cells

From the past decades, microbial fuel cells (MFCs) have evolved as a green alternative to produce electrical energy from organic matter degradation. Cathode modification significantly enhances the overall MFC performance. In this work, we report on ZIF-8 and carbon nanotubes (CNTs) derived catalyst materials as cathode for MFC. The catalysts were prepared via high-temperature pyrolysis at 900 °C and were physically characterized by various analytical techniques. All the catalyst materials carry tubular arrangements of CNTs covering the ZIF-8 crystals and exhibit highly micro-mesoporous texture. The electrocatalytic activity for oxygen reduction reaction (ORR) was studied in 0.1 M phosphate buffer at a catalyst loading of 0.2 mg cm−2. The FeCo-N-C@900 catalyst showed the highest ORR activity with half-wave potential of 0.71 V vs RHE and limiting current density of −5.62 mA cm−2 at 1900 rpm. When tested in MFC, FeCo-N-C@900 coated cathode delivered the maximum power density of 1557 mW m−2 (comparable to Pt/C catalyst reaching Pmax of 1681 mW m−2) with chemical oxygen demand (COD) removal efficiency of 87.3%. The Next generation DNA sequencing analysis revealed the accumulation of various exoelectrogenic bacterial strains i.e., Bacillus, Desulfovibrio, Comamonadaceae sp. etc. commonly found in anaerobic biomass and showing the successful enrichment of the biofilm responsible for oxidizing organic matter at the anode. The present study illustrates the potential of transitional metal-doped ZIF-8 and CNTs composite electrocatalysts for enhancing the power output of MFC with generating promising power and current densities.

&lt;i&gt;In situ&lt;/i&gt; and &lt;i&gt;in vitro&lt;/i&gt; degradation parameters of elephant grass silage with sugarcane bagasse

The objective of this study was to evaluate the chemical composition and in situ degradability of elephant grass silage dry matter with increasing levels of sugarcane bagasse. A completely randomized design was adopted with five treatments: 0, 5, 10, 15, and 20% inclusion of sugarcane bagasse on an as-fed matter basis, with five replications, totalling 25 experimental units. The increasing proportion of sugarcane bagasse analysed was favourable only in increasing the concentration of dry matter and fibre of silages and in maintaining a considerable crude protein content. In the in situ degradation assay, the addition of sugarcane bagasse in silage decreased the ruminal degradability of dry matter, and as the passage rates increased, the effective degradability decreased. In the in vitro gas production assay, the total production of gases was decreased with the inclusion of sugarcane bagasse, as did the degradability of organic matter and neutral detergent fibre. The recommendation for the inclusion of sugarcane bagasse should be analysed according to the desired objective, emphasizing that values higher than 5% can greatly compromise the final nutritive value of elephant grass silage