Manure Slurry Research Articles

Solid–Liquid Separation of Dairy Barn by Electrocoagulation with Cationic Polymer Coagulant

High–molecular-weight polymer coagulants are widely used in wastewater treatment combined with traditional inorganic coagulants to improve the solid–liquid separation efficiency. However, it is desirable to keep chemicals used in treatments at minimum levels for economic and safety reasons. This study aimed to increase the efficiency of two-stage electro- and chemical-coagulation treatment with a minimum chemical dosage for the separation of solids and liquid in dairy manure slurry for the safe composting of solids and safe discharge of wastewater. Accordingly, dairy manure slurry was treated with aluminum (Al) coagulants, such as polyaluminum chloride (PAC), aluminum chloride (AlCl3), and aluminum sulfate (Al2(SO4)3), PAC combined with the cationic polyacrylamide (CPAM), and PAC and CPAM combined with electrocoagulation (EC). Results revealed that PAC was the best among the Al coagulants evaluated for the reduction in turbidity in the liquid fraction at a dosage of 100 mg/L. PAC dosage was reduced to 40 mg/L when the treatments were combined with CPAM at a dosage of 40 mg/L, which was further reduced to 30 mg/L when treatments were combined with 5 min EC and 20 mg/L of CPAM dosage.

DETERMINATION OF EVALUATION INDICATORS FOR PRE-ABANDONED PROJECT BASED ON SUSTAINABLE GOAL DEVELOPMENT ASPIRATION

Every project management will strive to ensure that one project can operate without any problems. Unfortunately, some projects are still abandoned due to certain reasons. If the abandonment occurs, the requirement to submit an abandonment plan is stipulated on the Environmental Impact Assessment (EIA) Guideline in Malaysia, 2016. Unfortunately, still lack of resources on pre-project abandonment guidelines which will lead to poor project abandonment report preparation and assessment. Thus, this study aims to determine crucial indicators for assessing the pre-abandoned project, proposing a framework of Malaysia Guidelines for Pre- Project Abandonment Plan (PAP), and validating the draft of the Malaysia Guidelines Framework for PAP. The collected data was compiled from various sources, including document review, survey, and Delphi Method (focus group discussion). The survey conducted proved that the most crucial indicators for the assessment of pre-abandoned project were (i) waste management, (ii) allocation of environmental budgeting, (iii) inventory of scheduled waste, (iv) slurry management, (v) method of demolished, (vi) safety and health of workers, (vii)drainage management system, (viii) site management, (ix) type of treatment plant, and (x) site housekeeping. This framework will assist both report preparer and policymakers on project abandonment report preparation and evaluation, respectively. The development of this framework was strengthened by comprising related legislations, and each indicator synchronized towards Sustainable Development Goal (SDG) 2030.

Production and Application of High-nitrogen Compost Extract as Liquid Fertilizer for Leafy Vegetable and Microalgae

This study aimed to produce high-nitrogen compost extract and applicate it to land plants and microalgae, a candidate crop for biofuel and high value-added material production, as a part of low-salinity compost production system. For this purpose, we selected komatsuna, a leafy vegetable, and Botryococcus braunii, a microalga, as the test species. Nitrogen-added compost, which was used as a deodorizing material for ammonia released from composting, had a higher amount of inorganic nitrogen than potassium, unlike general dairy cattle manure compost. The extraction efficiency of the fertilizer elements from nitrogen-added compost did not increase by extending the extraction time (5 min) or increasing the solvent ratio to 4, except for phosphoric acid. That of phosphoric acid increased with the solvent ratio up to 100. The moisture content discharged from screw press tended to be lower than that of the dairy manure slurry. In the culture of komatsuna, compost extract could be used as an alternative to chemical fertilizers by supplementing the deficient of phosphoric acid. In the microalgae, compost extracts could be also used as an alternative to chemical fertilizers although phosphorus deficiency was observed in the late stage.

An improved carbon fixation management strategy into the crop–soil ecosystem by using biomass ash as the medium

Returning the carbonated biomass ash into the soil can enhance the carbon fixation capacity of crop–soil ecosystem, contributing to the achievement of ‘4 per mille Soils for Food Security and Climate’ goal launched at COP21. The CO 2 sequestration of crop–soil ecosystem induced by biomass ash, however, highly depended on the soil pH and crops growth, which have not​ been elucidated. Here, we explored the effects of different management strategies (watering, chemical fertilizer, and CO 2 -rich biogas slurry on the CO 2 fixation performance of tomato ecosystem (Tom-E) containing one tomato plant, biomass ash, and soil, and evaluated the impact of tomato cultivation concerning carbon fixation. Results showed that when burying biomass ash into the soil, biomass ash did not cause physiological stress on tomato growth, and even improved the tomato qualities. Furthermore, through sequestrating CO 2 from biomass ash, CO 2 fixation capacity of the tomato ecosystem reached about 8.8 ± 1.10, 13.7 ± 0.74, and 20.7 ± 0.53 mmol-CO 2 /Tom-E for watering, chemical fertilizer, and CO 2 -rich biogas slurry management strategies, respectively. However, due to the influence of fertilization management strategy, about 57.4% ± 0.09 and 27.3% ± 0.09 of CO 2 sequestrated in the biomass ash returned to the atmosphere ( i.e , CO 2 loss) for only watering treatment and conventional fertilization (chemical fertilizer) treatment, respectively. Comparatively, as a pH buffering fertilizer, CO 2 -rich biogas slurry application improved the bicarbonate assimilation environment of tomato, which contributed to reducing the CO 2 loss to only 12.5% ± 0.01. Clearly, adopting the carbonated biomass ash and CO 2 -rich biogas slurry as fertilizer provides a suitable and potential strategy for the enhancement of soil carbon sink. • Recycling the biomass ash into soil enhanced the carbon sink of tomato ecosystem. • CO 2 -rich biogas slurry application improved the carbon sink of tomato ecosystem. • DIC assimilation rate of tomato increased by recycling the biomass ash. • Different fertilization management strategies caused different CO 2 sequestration.

Impacts of slurry acidification and injection on fertilizer nitrogen fates in grassland

Low nitrogen (N) use efficiency of broadcast slurry application leads to nutrient losses, air and water pollution, greenhouse gas emissions and—in particular in a warming climate—to soil N mining. Here we test the alternative slurry acidification and injection techniques for their mitigation potential compared to broadcast spreading in montane grassland. We determined (1) the fate of 15N labelled slurry in the plant-soil-microbe system and soil-atmosphere exchange of greenhouse gases over one fertilization/harvest cycle and (2) assessed the longer-term contribution of fertilizer 15N to soil organic N formation by the end of the growing season. The isotope tracing approach was combined with a space for time climate change experiment. Simulated climate change increased productivity, ecosystem respiration, and net methane uptake irrespective of management, but the generally low N2O fluxes remained unchanged. Compared to the broadcast spreading, slurry acidification showed lowest N losses, thus increased productivity and fertilizer N use efficiency (38% 15N recovery in plant aboveground plant biomass). In contrast, slurry injection showed highest total fertilizer N losses, but increased fertilization-induced soil organic N formation by 9–12 kg N ha−1 season−1. Slurry management effects on N2O and CH4 fluxes remained negligible. In sum, our study shows that the tested alternative slurry application techniques can increase N use efficiency and/or promote soil organic N formation from applied fertilizer to a remarkable extent. However, this is still not sufficient to prevent soil N mining mostly resulting from large plant N exports that even exceed total fertilizer N inputs.

Assessment of catalytic thermal hydrolysis of swine manure slurry as liquid fertilizer: Insights into nutrients and metals

The recovery of nutrients from livestock manure has generated a lot of interest in biosolids value-adding. There is now more research on manure with high solids content but less study on manure with lower solids content. This study used swine manure slurry as the research object and comprehensively examined the characteristics of organic matter conversion, nitrogen, phosphorus, and metals release during the catalytic-thermal hydrolysis (TH) process. It was found that ammonia nitrogen showed a continuous increase with increasing temperature while inorganic phosphorus showed a rising and then decreasing trend. The addition of HCl and H2O2 (TH-HCl-H2O2) promoted the hydrolysis of organic matter, showing the best nitrogen and phosphorus release performance, releasing 62.2% of inorganic phosphorus and 50.8% of nitrogen. The release characteristics of nutrients and metals from the TH process were significantly affected by the addition of HCl and H2O2, according to structural equation modelling study. The data analysis demonstrated that the liquid fertilizer produced by TH did not surpass the environmental risk associated with nutrients or the ecological risk associated with heavy metals. This study would offer theoretical justification for biowaste conversion for agricultural applications.

167 Monomodular and Multi-Functional Processive Endocellulases for Improving Fibre Utilization and Reducing Environmental Footprint in Pigs

Abstract Global emission of the major greenhouse gases (GHG) from food animal production accounts for 15% of the total human-induced GHG with pork production being a significant contributor. Poor efficiency of dietary fibre utilization not only limits global pork production profit margins but also adversely affects dietary crude protein and amino acid utilization; and these collectively lead to excessive manure fibre and nitrogenous compounds, resulting in anaerobic biogenesis and emission of the major GHG from swine manure slurry storage. Two unique glycosyl hydrolase family-5 (GH5) processive endoglucanases, referred to as GH5-tCel5A1 and GH5-, have been reported. The GH5-tCel5A1 was originally identified via targeted genome sequencing of the extremely thermophilic Thermotoga maritima while the GH5-p4818Cel5_2A was screened from the porcine hindgut microbial metagenomic expression library. Both GH5-tCel5A1 and GH5-p4818_2A have been characterized to be monomodular, act as processive β-1,4-endoglucanases and have multi-functionality towards hydrolyzing dietary natural crystalline cellulose and pre-treated cellulosic substrates as well as several hemicelluloses including β-glucans, xylan, xylogulcans, mannans, galactomannans and glucomannans. We have recently overexpressed both GH5-tCel5A1 and GH5-p4818Cel5_2A in the ClearColiBL21(DE3) cell and investigated the susceptibility of both these cellulases to auto-oxidation by air-borne O2. Furthermore, we have also examined these endoglucanases’ stability under the mimicked in vitro porcine gastric and the small intestinal pH and proteases’ conditions. Further pig nutrition and growth performance studies are being conducted to investigate the in vivo efficacy of these two processive endoglucanases as newly emerging potential exogenous fibre enzymes.

315 Recognizing and Balancing Sustainable Trade-Offs in the Swine Industry

Abstract Recognizing and balancing trade-offs that constitute sustainability, economics, and practical reality is essential for practice adoption. There are many situations where producers have aligned all three criteria. Advancement of in-barn practices such as water cups compared to nipple drinkers provides for improved water conservation and economics. Also, injection of manure slurry directly into the soil decreases atmospheric nitrogen losses, reduces phosphorus runoff, reduces or eliminates inorganic fertilizer applications, and improves soil health and fertility. The use of dietary synthetic amino acids to lower nitrogen excretion or feed additives such as phytase to lower phosphorus excretion are widely used and are economical sustainable practices. Increasing whole farm productivity through improved pig survivability is a means to achieve a win-win tradeoff. Improving pig survivability with advancements in-barn management practices, genetic selection, health and nutritional programs will directly impact the sustainability of pork producers. However, everyday examples are also present where these criteria conflict. The use of feed by-products in diets to reduce feed cost per pig are common. However, these types of dietary ingredients, in particular dried distiller grains with solubles (DDGS) is lower in protein digestibility then soybean meal and corn, thus increases nitrogen excretion. At a higher inclusion such as 30% of the diet, the nitrogen excretion level would be raised by approximately 15%. Also, as the value of corn oil has increased for other industries, ethanol plants are extracting more oil from DDGS, in turn the net energy concentration is lowered. This results in pigs having poorer feed efficiency, thus increasing total manure production. Thus, the economic feed cost advantage has a tradeoff with increased nitrogen excretion and manure production. Pork producers will continue to be progressive and create opportunities to further combine sustainability, economics, and practical reality of implementation.

Potential of ESBL-producing Escherichia coli selection in bovine feces after intramammary administration of first generation cephalosporins using in vitro experiments

Selection and spread of Extended Spectrum Beta-Lactamase (ESBL) -producing Enterobacteriaceae within animal production systems and potential spillover to humans is a major concern. Intramammary treatment of dairy cows with first-generation cephalosporins is a common practice and potentially selects for ESBL-producing Enterobacteriaceae, although it is unknown whether this really occurs in the bovine fecal environment. We aimed to study the potential effects of intramammary application of cephapirin (CP) and cefalonium (CL) to select for ESBL-producing Escherichia coli in the intestinal content of treated dairy cows and in manure slurry, using in vitro competition experiments with ESBL and non-ESBL E. coli isolates. No selection of ESBL-producing E. coli was observed at or below concentrations of 0.8 µg/ml and 4.0 µg/ml in bovine feces for CP and CL, respectively, and at or below 8.0 µg/ml and 4.0 µg/ml, respectively, in manure slurry. We calculated that the maximum concentration of CP and CL after intramammary treatment with commercial products will not exceed 0.29 µg/ml in feces and 0.03 µg/ml in manure slurry. Therefore, the results of this study did not find evidence supporting the selection of ESBL-producing E. coli in bovine feces or in manure slurry after intramammary use of commercial CP or CL-containing products.

Farm-scale water-energy-food-waste nexus analysis for a closed-loop dairy system

Largely due to manure management, intensive livestock production is known to negatively impact air, water, and soil quality. Excessive manure is often applied to soil as fertilizer or stored in lagoon. However, some thermo-chemical methods, such as gasification and pyrolysis, can transform manure from waste into a valuable resource. The closed-loop dairy concept employs these methods to create biochar derived from cow manure for use as a soil amendment and a water filtration medium. This closed-loop concept has the potential to produce syngas and bio-oil for production of electricity, and to reduce excessive nutrients in liquid manure irrigation by filtering manure slurry stored in lagoons. It replaces solid manure with biochar in land applications to further reduce nutrient runoff and increase soil resilience against erosion. In this study, a Water-Energy-Food-Waste nexus-based analysis and resource allocation tool was developed to evaluate the economic, environmental, and social feasibility of the closed-loop dairy system. The tool utilizes several levers to simulate a user-specified dairy operation, such as number of livestock, acres farmed, quantity of effluent irrigation, distribution of manure and biochar products, and type of biomass conversions. Financial estimates from central Texas in 2018 were used to evaluate the profitability of these practices against the costs of a dairy and hay operation. The study showed that the closed-loop dairy system, while case dependent, could be profitable and, based on operational costs, a small dairy of approximately 200 cows could break even. Results also indicate that the benefits of biomass conversions to produce energy byproducts should increase with scale. This study can help many dairy farms that are considering the economic and environmental sustainability of the industry, which has been under scrutiny.

Yak rumen fluid inoculum increases biogas production from sheep manure substrate

Hydrolytic bacteria are essential for the degradation of lignocellulose to produce biogas and organic fertilizers. In this study, sheep manure was used as substrate, and sheep manure slurry, yak rumen fluid and slurry from a biogas reactor (SBR) were used as inocula in single-stage anaerobic digestion. The SBR and rumen fluid inocula increased biogas production by 23% and 43%, respectively, when compared to solely sheep manure in the single-stage anaerobic digestion. The two-stage anaerobic digestion, with yak rumen fluid as inoculum in the hydrolytic reactor, increased the biogas production by 59, 86, and 58% compared with the control. Microbial analysis of the effluent revealed that yak rumen fluid contained hydrolytic bacteria such as Proteiniphilum, Jeotgalibaca, Fermentimonas, and Atopostipes to enhance the degradation of sheep manure and increase biogas production. It was concluded that yak rumen fluid, rich in hydrolytic bacteria, increases the degradability of sheep manure and improves production of volatile fatt acids and biogas.

How the Agricultural Press Addresses the Slurry–Water Nexus: A Text Mining Analysis

Water pollution from intensive livestock husbandry is a persistent social-ecological problem. Since remedies require attention to the slurry–water nexus among practitioners, the agricultural press is a strategic entry point for agenda setting. Systematic content analysis can provide insights into how farming practices and sustainability issues are communicated, which may influence farmers’ attention to the issue and to potential solutions. To address this question, we present a semantic network analysis of three specialized farming magazines in Germany and analyze their coverage of the slurry–water nexus, in particular relationships of actors and issues and co-occurrence with political events. We used text mining methods in order to analyze a text corpus consisting of 4227 online articles published between 2010 and 2020. Results show that one fifth of all slurry-themed articles contained water-related content. We found a shift over time from dominantly management-oriented content towards a politicized debate with more actors and stronger semantic relationships with water protection constructed as an insulated stand-alone issue. This is accompanied by a shift from thematic reporting to episodic reporting focused on environmental legislation and compliance management. This implies less attention to innovations for water-conserving slurry management. Despite its shortcomings, episodic coverage may open up windows of opportunity to improve communication by experts and policy makers.

Production of struvite by magnesium anode constant voltage electrolytic crystallisation from anaerobically digested chicken manure slurry

Nitrogen and phosphorus levels in livestock manure and digestive fluid are high, posing a threat to soil and water quality and necessitating nutrient removal and recovery. Phosphorus recovery has the potential to alleviate the global phosphorus resource crisis. This study proposed a magnesium anode constant voltage electrolysis method to crystallise struvite (magnesium ammonium phosphate hexahydrate, MgNH4PO4·6H2O) from anaerobically digested chicken manure slurry using reaction kinetics at variable constant voltages ranging from 2 V to 12 V. The recovery of nitrogen and phosphorus was shown to be effective over a wide initial pH range (3.00 ± 0.03–7.90 ± 0.10) using synthetic digestion fluids. Moreover, the pH gradually increased during the reaction without any external chemical adjustments. The phosphorus recovery rates conformed to the first-order kinetic model, with a maximum rate constant of 2.13 h−1. When the best voltage of 2 V was used at 25 ± 1 °C, the recovery rate reached 5.24 mg P h−1cm−2 in the synthetic digestion fluids during 90 min and 4.60 mg P h−1cm−2 in the anaerobically digested chicken manure slurry. The crystalline products recovered were identified as high-purity struvite by XRD and XPS. The purity of recovered struvite with an initial pH of 3.00 and 7.90 was 96.5% and 98.9%, respectively. These results demonstrated that the magnesium electrode could rapidly react with nitrogen and phosphorus to generate high-purity struvite.

Effects of the Addition of Different Additives before Mechanical Separation of Pig Slurry on Composition and Gaseous Emissions

The treatment of animal slurry is used to improve management on a farm scale. The aim of this laboratory study was to assess the effects of the addition of the additives biochar, alum and clinoptilolite before the mechanical separation of whole pig slurry (WS) on the characteristics and emission of NH3, N2O, CO2 and CH4 from solid (SF) and liquid fractions (LF). The additives were mixed with WS (5% w/w), followed by separation, in a total of 12 treatments with 3 replicates, including the controls and WS with additives. Gaseous emissions were measured for 30 d by a photoacoustic multigas monitor, and initial characteristics of the slurries were assessed. The results indicated that the separation of the WS modified the initial physicochemical characteristics and increased the GWP emissions of the SF and LF, but not the NH3 losses. However, the addition of additives before separation increased the nutrient value and reduced the GWP emissions from the SF and LF. Additionally, just the additive alum was effective in the reduction of E. coli. The additives led to significant reductions in NH3 and N2O emissions, with higher reductions in NH3 losses for alum (51% for NH3) and similar N2O losses for all additives (70% for N2O) observed, whereas the CO2 and CH4 emissions were reduced by biochar (25% for CO2 and 50% for CH4) and alum (33% for CO2 and 30% for CH4) but not by clinoptilolite. Although the additives had a positive effect on slurry management, it can be concluded that the addition of alum before mechanical separation has the potential to be the best mitigation measure because it improves the nutrient content and sanitation and decreases gaseous losses from slurry management.

Life cycle assessment of Parmigiano Reggiano PDO cheese with product environmental footprint method: A case study implementing improved slurry management strategies

The environmental impact of Parmigiano Reggiano PDO cheese was quantified using the Product Environmental Footprint Category Rules (PEFCRs) in a Traditional System (TS) and in an Improved Management System (IMS). The TS differs from IMS with respect to slurry management (raw slurry storage vs anaerobic digestion and storage of the liquid fraction of digestate) and application of nutrients to the field (by slurry tanker with a diverter plate vs soil injection at pre-sowing and side dressing).Two additional scenarios were evaluated by considering the possible environmental enhancement achievable by reducing enteric methane production and by using soybean grain produced in Italy as the protein source for animals' diets. The environmental impact was quantified both for 1 kg of fat and protein corrected milk (FPCM) and for the production of 10 g dry matter equivalent of cheese as single score. For the first assessment, the environmental impact results were 124 and 112 μPt kg FPCM−1 for TS and IMS, respectively. In the second case, it was 10.8 μPt and 9.9 μPt 10 g dry matter equivalent−1 of cheese, for TS and IMS, respectively. The specific cost for reducing the GHG emissions in this production chain was equal to 34 € Mg−1 milk produced. Finally, although specific studies should consider the reduction of enteric methane emissions and the use of soybean grain nationally produced as feed source, the scenarios evaluated in this study highlighted some potential for environmental improvements. Even small environmental improvements to the Parmigiano Reggiano PDO cheese supply chain can bring substantial improvements to the sustainability of the food market, because of the widespread demand on the global market of Parmigiano Reggiano and of its chance of attracting consumers who are sensitive to environmental problems.

Impact of slurry removal frequency on CH4 emission and subsequent biogas production; a one-year case study

Anaerobic digestion of animal slurry to produce biogas is the dominated treatment approach and a storage period is normally applied prior to digestion. Pre-storage, however, contributes to CH4 emissions and results in loss of biogas potential. Manure management was found to be an efficient approach to reduce not only the on-site CH4 emission but may also have extended influence on CH4 emission/losses for storage and subsequent biogas process, while the connection remains unclear. The objective of this study was therefore to evaluate the impact of slurry management (e.g. removal frequency) on CH4 emission (both on-site and storage process prior to biogas) and biogas yield. An experimental pig house for growing-finishing pigs (30–110 kg) and the relevant CH4 emission was monitored for one year. In addition, the specific CH4 activity (SMA) test was conducted and used as an alternative indicator to reflect the impact. Results showed that the manure management affected both on-site and subsequent methane emission; with increased manure removal frequencies, the methane emission became less dependent on variation of temperatures and the specific methanogenesis activity was significantly lower. The highest SMA (100 mL CH4 gVS-1), for instance, was observed from the slurries with limited emptied times, which was 10 times of that from the slurries being emptied three times a week. These findings could enlighten the development of environmentally friendly strategies for animal slurry management and biogas production.

The Influence of Different Chemical Methods of Pig Manure Treatment on the Emission of Odor-Forming Substances

Background: The research on optimal composition of chemical reagents for deodorization and disinfection of liquid manure slurry of pig breeding complex facility was performed. Results: It was established, that all three compositions (sulfuric acid combined with sodium hypochlorite, ammonium persulphate in combination with peracetic acid, and also the mixture of sodium nitrite and ammonium molybdate) provide the removal of unpleasant odors, however, more preferable from the point of preservation of disinfecting effect, are the mixtures containing ammonium persulphate plus peracetic acid and sodium nitrite combined with ammonium molybdate (high deodorizing and disinfecting effect was observed after 21 days). Conclusion: Manure mixtures obtained as a result of such treatment are harmless for the environment and could be used as a main component of organo-mineral fertilizers.

Methane, Nitrous Oxide, and Ammonia Emissions on Dairy Farms in Spain with or without Bio-Activator Treatment

Intensive livestock farming substantially impacts the environment, especially farm and slurry management. Slurries are significant sources of greenhouse gases and ammonia. The present study was conducted in an intensive livestock production system in Galicia, Spain. The measurements were taken at six different farms in that region along with one control using common management practices in Galicia without the addition of a bio-activator. This study aimed to quantify GHGs and NH3 fluxes and their reductions during slurry treatment using a dynamic chamber through FTIR analysis and to examine the potential of usage of bio-activators for slurry management. In addition, gas concentrations were measured at the barns and compared with their slurry management and architectural volume to obtain influences on their management and the architectural volume of the barns. Additionally, the effects of using a bio-activator in the barns inside the facility areas were addressed. Moreover, qPCR analysis was conducted to understand the correlations between syncoms and methanogen populations when a bio-activator is added to the slurry with at least a 30% reduction in methanogenic populations. The outcomes suggest encouraging results for GHG reductions in the livestock sector, giving farmers future options for climate change mitigation among their standard practices.

Evaluating scenarios to reduce phosphorus transport in surface waters from slurry applications in temperate grasslands

ABSTRACT This study evaluates a range of scenarios to reduce soluble reactive phosphorus (SRP) losses using the surface runoff phosphorus transport model (Surphos) to simulate the application of liquid manure (slurry) to grassland catchments. Surphos was applied using data from two contrasting sites in the Republic of Ireland and Northern Ireland. It explored scenarios that investigated changes to the timing of slurry applications, based both on policy (i.e. a “closed” period where regulations prohibit any slurry spreading) and on climate-based restrictions, where soil moisture and antecedent rainfall were important factors. The observed data showed a considerable spatial variability in runoff at both sites, which resulted in a corresponding variable range of SRP losses predicted by the model. However, at both sites the model results showed that maintaining a closed period led to a greater reduction in SRP losses than opening this period up to slurry applications under climate-based restrictions.

Long-term study on the nitrogen retention potential of bark extracts and a polymer based thereof in cattle manure slurry

The addition of tree bark extracts, commercial tannin powder and a tannin-based polymer to cattle manure was investigated for its influence on the gaseous emission and nitrogen conservation potential for 28 days. In lab trials with ammonia solution as reference, the retention of ammonia was 13%, 40% and up to 65% for untreated solution, spruce bark extract and chestnut tannin respectively. The gaseous emission from manure was reduced by 40%, 58% and 66% for chestnut tannin and spruce bark extract, larch bark extract and the tannin polymer, and oak tannin, respectively. For long-term nitrogen loss mitigation, 20% more nitrogen was preserved when spruce or larch bark extract or oak tannin was added to the manure compared to the reference measurements. A combination of the pH lowering effect of tannins and covalently bonding ammonia to flavonoid hydroxy groups provides a viable method for reduction of nitrogen loss in cattle manure.