Ecotoxicological investigations of milking cow slurry and changes of oestrogenic compounds in the solid and liquid phase

Due to the appearance of intensive livestock-rearing systems since the 1970s, a vast amount of liquid manure (slurry) has been produced. The application and utilization are partly regulated for this special substance, which contains urine, excrement, process water, and other chemicals, such as insecticides and disinfectants. Our research was conducted on a slurry management system of a dairy cattle farm, focusing on the investigation of the presence of oestrogenic substances and toxicity of slurry before and after using a separator technology. Yeast oestrogen screen shows in this study that the separation of the liquid and solid phases of slurry contributes to the reduction in oestrogenic substances. Based on the toxicological studies, the growth inhibition of algae was 93%, and the inhibition of the germination of higher plant seeds was 25%, without separation. After separation of the phases, growth and germination were comparable with the negative control; moreover, some stimulation was detected. Consequently, harmful substances were removed with the suspended solid phase. From the present study, we can conclude that stakeholders should support separation technology in intensive livestock-rearing systems, and ecotoxicological investigations obviously help the risk management of slurry utilization. To our best knowledge, this is the first paper presenting detailed and complex toxicological study on slurry samples.

Effect of Flushing Milk and Acidic Whey on pH and Nitrogen Loss of Cattle Manure Slurry

With the increasing demand for food worldwide, the use of fertilizers in the agricultural industry has grown. Natural fertilizers derived from the use of animal manure slurry, especially cattle and cow, are responsible for 40% of the agricultural ammonia emission. The EU defined the goal to reduce NH3 emission drastically until 2030, yet until today an overall increase has been observed, making it more difficult to reach the target. In this study, we used two by-products from the dairy industry, namely flushing milk and acidic whey, to lower the pH of cattle manure slurry and therefore mitigate the loss of nitrogen in the form of ammonia into the atmosphere, making it available in the soil. Measurements of pH, ammonium nitrogen, total Kjeldahl nitrogen, and lactic acid bacteria colonies were conducted in a lab-scale experiment to test the hypothesis. Afterwards, pH measurements were conducted on bigger samples. We found that whey effectively reduced the pH of manure below 5, therefore moving the ammonia/ammonium equilibrium strongly towards ammonium. Flushing milk on the other hand lowered the pH to a smaller extent, yet allowed for faster hydrolysis of urea into ammonium. The findings in this study present a suitable and environmentally friendly approach to help reach the climate goals set by the EU by using by-products from the same industry branch, therefore being a suitable example of circular economy.

Mineralization of Farm Manures and Slurries under Aerobic and Anaerobic Conditions for Subsequent Release of Phosphorus and Sulphur in Soil

A good understanding of nutrient release from manure or compost after application through mineralization is important to assure meeting the nutrient demand of crops, to secure timely fertilizer application and to enhance nutrient use efficiency. The current study was done to evaluate phosphorus (P) and sulphur (S) release patterns from different types of manures viz. cow dung, cow dung slurry, tricho-compost, vermicompost, poultry manure, poultry manure slurry and mungbean residues. The mineralization study was performed under aerobic (field capacity) and anaerobic (waterlogging) conditions for 180 days at 25 ± 1 °C in the laboratory. The release of P and S showed the highest values within 75–180 and 75–150 days, respectively, and was always higher in aerobic conditions than in anaerobic conditions. The first-order kinetic cumulative model was a good fit for mineralization, which was significantly influenced by manure type, soil moisture level and incubation period. Poultry manure slurry exerted the highest P and S release under both moisture conditions. Both slurries showed higher potential mineralization, with a lower rate constant for these elements compared to that in their manure states. Hence, appropriate manures should be chosen and applied in the proper quantity to provide exact amounts of nutrients, to increase crops nutrient use efficiency and to formulate correct fertilizer recommendations.

Response Curves for Ammonia and Methane Emissions From Stored Liquid Manure Receiving Low Rates of Sulfuric Acid

Addition of sulfuric acid (H2SO4) to liquid dairy manure (slurry) reduces methane (CH4), nitrous oxide (N2O), and ammonia (NH3) emissions. There is interest in understanding how gaseous emissions respond to decreasing rates of acidification, to determine economically optimum application rates. Acidification rates were tested ranging from 0 to 2 g sulfuric acid (H2SO4) L−1 slurry in six meso-scale outdoor storage tanks, each filled with 10.6 m3 slurry and stored for 114 d. Results showed that the rate of acidification for maximum inhibition of CH4 and NH3 emissions varied markedly, whereas N2O reductions were modest. Reductions of CH4 increased with acid rate from 0 to 1.2 g L−1, with no additional response beyond >1.2 g L−1. In contrast to CH4, inhibitions of NH3 showed a linear response across all rates, although reductions were ≤ 30%. Thus, higher acidification rates would be required to achieve greater NH3 emission reductions. Our findings indicate that achieving >85% NH3 emissions reductions would require 4 × more acid than achieving >85% CH4 reductions. Decisions on optimum H2SO4 rates will depend on the need to mitigate CH4 emissions (the primary greenhouse gas emitted from stored liquid manure) or reduce NH3 emissions (which is regulated in some regions). These results will help develop guidelines related to the potential costs and benefits of reducing emissions through acidification.

A mechanistic model of methane emission from animal slurry with a focus on microbial groups

Liquid manure (slurry) from livestock releases methane (CH4) that contributes significantly to global warming. Existing models for slurry CH4 production—used for mitigation and inventories—include effects of organic matter loading, temperature, and retention time but cannot predict important effects of management, or adequately capture essential temperature-driven dynamics. Here we present a new model that includes multiple methanogenic groups whose relative abundance shifts in response to changes in temperature or other environmental conditions. By default, the temperature responses of five groups correspond to those of four methanogenic species and one uncultured methanogen, although any number of groups could be defined. We argue that this simple mechanistic approach is able to describe both short- and long-term responses to temperature where other existing approaches fall short. The model is available in the open-source R package ABM (https://github.com/sashahafner/ABM) as a single flexible function that can include effects of slurry management (e.g., removal frequency and treatment methods) and changes in environmental conditions over time. Model simulations suggest that the reduction of CH4 emission by frequent emptying of slurry pits is due to washout of active methanogens. Application of the model to represent a full-scale slurry storage tank showed it can reproduce important trends, including a delayed response to temperature changes. However, the magnitude of predicted emission is uncertain, primarily as a result of sensitivity to the hydrolysis rate constant, due to a wide range in reported values. Results indicated that with additional work—particularly on the magnitude of hydrolysis rate—the model could be a tool for estimation of CH4 emissions for inventories.

Microbial sulfate reduction by Desulfovibrio is an important source of hydrogen sulfide from a large swine finishing facility

There is still a lack of understanding of H2S formation in agricultural waste, which leads to poor odour prevention and control. Microbial sulfate reduction is a major process contributing to sulfide formation in natural and technogenic environments with high sulfate and low oxygen concentration. Agricultural waste can be considered a low-sulfate system with no obvious input of oxidised sulfur compounds. The purpose of this study was to characterise a microbial community participating in H2S production and estimate the microbial sulfate reduction rate (SRR) in manure slurry from a large-scale swine finishing facility in Western Siberia. In a series of manure slurry microcosms, we identified bacterial consortia by 16S rRNA gene profiling and metagenomic analysis and revealed that sulfate-reducing Desulfovibrio were key players responsible for H2S production. The SRR measured with radioactive sulfate in manure slurry was high and comprised 7.25 nmol S cm−3 day−1. Gypsum may be used as a solid-phase electron acceptor for sulfate reduction. Another plausible source of sulfate is a swine diet, which often contains supplements in the form of sulfates, including lysine sulfate. Low-sulfur diet, manure treatment with iron salts, and avoiding gypsum bedding are possible ways to mitigate H2S emissions from swine manure.

Influence of soil environmental factors on N2O fluxes just after application of three types of organic fertilizers - 4 years study in a grassland on Andosol in southern Hokkaido, Japan

<p>Appropriate application of organic fertilizer is required to reduce environmental impact from grassland and to achieve sustainable livestock production. However, N<sub>2</sub>O fluxes from soil increase mainly due to changes in soil environmental factors such as temperature, moisture, soil pH and soil mineral nitrogen content, immediately just after fertilization, and it may be different among the types of fertilizer. In this study, we investigated that how N<sub>2</sub>O fluxes are influenced by the application of three types of organic fertilizer (manure, slurry, and digestive fluid) for 4 years in a grassland on Andosol in southern Hokkaido, Japan. Five treatment plots: no fertilizer, chemical fertilizer, manure, slurry, and digestive fluid were established in a managed grassland in Shizunai Livestock farm, Hokkaido University. Fertilizers were applied in late April every year from 2017 to 2020. Organic fertilizers were applied such that the NPK not exceed the regional recommendation rate, and the shortage was compensated by chemical fertilizer. N<sub>2</sub>O flux was measured by using a closed chamber method. At the same time of the flux measurements, soil temperature at 5 cm soil, and soil moisture (WFPS), soil pH, NO<sub>3</sub>-N contents in 0-5 cm soil were measured to see the relationship with N<sub>2</sub>O fluxes.</p><p>In 2017, a large peak of N<sub>2</sub>O flux was observed in slurry plot (195.8μg m<sup>-2</sup>h<sup>-1</sup>) and digestive fluid plot (347.8 μg m<sup>-2</sup>h<sup>-1</sup>), whereas in 2018 and 2019, there were no large peak after the fertilization at all plots, however, in 2020, a large peak of N<sub>2</sub>O flux was observed in manure plot (472.7 and 475.7μg m<sup>-2</sup>h<sup>-1</sup>) and slurry plot (194.9μg m<sup>-2</sup>h<sup>-1</sup>). These peaks of N<sub>2</sub>O flux were significantly larger than those in no fertilizer and chemical fertilizer plots. All N<sub>2</sub>O flux peaks were observed when the soil temperature ranged 10-14 ℃. In 2017 and 2020, a large peak of N<sub>2</sub>O flux was observed although WFPS was always above 80% which is the soil moisture level leading to the complete denitrification. There was a negative relationship between N<sub>2</sub>O flux and soil pH. Low soil pH might reduce the N<sub>2</sub>O reductase activity, leading to the large peak of N<sub>2</sub>O flux at high WFPS above 80%. In addition, there was a positive relationship between N<sub>2</sub>O flux and soil NO<sub>3</sub><sup>-</sup>-N contentin 2017 and 2020. However, in 2018 and 2019, when WFPS was below 80% in most days, there was no positive relationship between N<sub>2</sub>O flux and soil NO<sub>3</sub><sup>-</sup>-N content. In conclusion, the peak of N<sub>2</sub>O flux was different depending on the year and fertilizer, In order to reduce N<sub>2</sub>O flux just after fertilization, it is especially important not to lower the soil pH and not to increase the WFPS.</p><div> </div>

Phosphorus Runoff from Soils Receiving Liquid Dairy and Swine Manures Amended with Mine Drainage Residual

HighlightsConcern over nutrient runoff from agriculture has prompted research to limit phosphorus (P) mobility.Mine drainage residuals (MDRs) can reduce phosphorus solubility in soils, sediments and liquid manure slurries.MDR amendment resulted in lower dissolved phosphorus in runoff from sites treated with dairy manure slurry, but not with swine manure slurry.This study underscores the value of testing under field conditions before making recommendations.Abstract. Concern over nutrient runoff from agriculture has prompted considerable research on amendments to limit phosphorus (P) solubility of manure slurries and P mobility following land application of the slurry. The concept of solving one industry’s problem with another industry’s problem is attractive, but successful examples are uncommon. Mine drainage residual (MDR), generated from the process of neutralizing acid discharge from coal mines, has been shown to reduce soluble P in soils, sediments and manure slurries. We therefore sought to test whether amending manure slurries with MDR was effective at reducing P in runoff once that slurry was applied to agricultural soils. A series of simulated rainfall experiments revealed that amending dairy manure slurry with MDR resulted in significantly less flow weighted dissolved P concentrations and loads in runoff. However, the same effect was not observed with runoff from soils amended with swine manure slurry, despite a greater reduction of water extractable P in swine manure slurry with MDR addition than in dairy manure slurry. This study underscores the value of testing amendments under field conditions before making manure management recommendations. Keywords: Manure, Phosphorus, Mine drainage residual, Engineered treatment, Simulated rainfall.

Waste-Free Animal Agriculture that Co-Produces Biogas Energy and Organic Fertilizer: A Holistic Approach

A novel anaerobic digester system called Holistic DigesterTM System (HDS) was developed. The pilot prototype was constructed and tested twice (4 months each) at the NCSU Field Laboratory for raising 60 feeder pigs to market age for each test. The structure and operation of HDS, the performance of live animal growth, chemical analyses of biogas and the resulting digestate, and the production of a potential organic fertilizer, are presented in this communication. It was concluded that: 1) this operation demonstrated the feasibility of HDS with live animals on farm; 2) daily biogas (approximately 50% methane) was produced consistently during each of the two studies; 3) animals grew well in the modified house with a pit for manure slurry collection. The weight gain of the pigs and feed conversion rate met the top 25% of the industrial average; and 4) the liquid digestate of the primary digester flowed into the secondary digester preloaded with dry switchgrass, which absorbed the liquid and incubated into a final product. Chemical analysis indicated that NPK values were retained and enriched in the final product, potentially, an organic fertilizer. The new prototype HDS that co-produces biogas and organic fertilizer was successfully tested and, furthermore, HDS left no waste nor wastewater on farm. It is believed that HDS will not only improve the cyclic bioeconomy, but also enforce the environmental and economic sustainability of animal agriculture.