Effects of handling parameters on hydrogen sulfide emission from stored dairy manure

Utilization of nanoparticles for biogas production focusing on process stability and effluent quality

Abstract

One of the most important techniques for converting complex organic waste into renewable energy in the form of biogas and effluent is anaerobic digestion. Several issues have been raised related to the effectiveness of the anaerobic digestion process in recent years. Hence nanoparticles (NPs) have been used widely in anaerobic digestion process for converting organic wastes into useful biogas and effluent in an effective way. This review addresses the knowledge gaps and summarizes recent researchers’ findings concentrating on the stability and effluent quality of the cattle manure anaerobic digestion process using single and combinations nanoparticle. In summary, the utilization of NPs have beneficial effects on CH4 production, process optimization, and effluent quality. Their function, as key nutrient providers, aid in the synthesis of key enzymes and co-enzymes, and thus stimulate anaerobic microorganism activities when present at an optimum concentration (e.g., Fe NPs 100 mg/L; Ni NPs 2 mg/L; Co NPs 1 mg/L). Furthermore, utilizing Fe NPs at concentrations higher than 100 mg/L is more effective at reducing H2S production than increasing CH4, whereas Ni NPs and Co NPs at concentrations greater than 2 mg/L and 1 mg/L, respectively, reduce CH4 production. Effluent with Fe and Ni NPs showed stronger fertilizer values more than Co NPs. Fe/Ni/Co NP combinations are more efficient in enhancing CH4 production than single NPs. Therefore, it is possible to utilize NPs combinations as additives to improve the effectiveness of anaerobic digestion.

Article highlights

Effects of the Powder from Hoggery Desulfurization Tanks on the Salinity Resistance of Lettuce

Lettuce is an important vegetable cultivated worldwide, even in regions with highly saline soils. A large amount of research discusses the application of sulfur on the increase of antioxidation in plants. The powder from hoggery desulfurization tanks contained high amounts of sulfur and small amounts of other nutrients for plants. This powder can be added to liquid fertilizer to create high-sulfur liquid fertilizer (HSLF). This study observed the cell morphologies of lettuce root apices under salt stress after the application of HSLF. Lettuce plants were cultivated in hydroponic solutions containing one of two NaCl (0 and 40 mM) and three HSLF (0.0, 1.5, and 3.0 g L−1) concentrations. Salinity reduced the K+/Na+ ratio in the plant leaves; however, this reduction was smaller in the HSLF-treated plants. Except for phosphate and potassium, nutrient absorption is inhibited under conditions of high salinity. Using scanning electron microscopy, we observed apices more integrated on cell roots after increasing HSLF supplement under non-salt-stressed conditions. In addition, the cells were repaired after increasing the supplement of HSLF under the condition of 40 mM NaCl. Although salt stress reduced plant growth, the reductions were minimized in the HSLF-treated plants. The application of HSLF potentially alleviated salt injury in lettuce root apices and was probably associated with the improvement of phosphorus and potassium absorption and increasing K+/Na+ ratios in lettuce plants.

Hydrogen sulfide emissions from a midwestern manure slurry storage basin

Hydrogen sulfide (H₂ S) emissions from midwestern U.S. dairy lagoons are episodic and seasonal. Emissions were determined using an inverse diffusion model in conjunction with measured upwind and downwind line-averaged H₂ S concentrations and turbulence. Mean daily H₂ S emissions from manure stored in earthen basins was 0.97 μg m^-2 s^-1 (σ = 1.35 μg m^-2 s^-1 ). Mean live animal basis daily emission from the basins was 1.1 g d^-1 hd^-1 (0.84 g d^-1 AU^-1 ). Daily emission was modeled using the van't Hoff function with air temperature as a surrogate for slurry surface temperature and a linear function of friction velocity. The mean standard error of estimate of the model was 1.8 μg m^-2 s^-1 (2.0 g d^-1 hd^-1 , 1.6 g d^-1 AU^-1 ) and accounted for 60% of emissions variability. H₂ S emissions were enhanced for short periods during the year when the stored slurry was loaded onto trucks for removal. Emissions from the basins were not statistically different as barn manure handling changed from flushing to scraping. More measurements are needed to verify annual emissions estimates for these manure slurry storage basins and derive emission factors for these slurry storage systems.

Effect of Using Aluminum Sulfate (Alum) as a Surface Amendment in Beef Cattle Feedlots on Ammonia and Sulfide Emissions

The objective of this study was to measure NH3 from feedlot surface material (FSM) containing aluminum sulfate (alum). A 33-day lab-scale study was conducted using pans containing FSM and either 0, 2.5, 5, or 10% alum. The pH of the FSM was significantly lower (p < 0.01) when treated with 2.5, 5, and 10% alum as opposed to the 0% alum treatment. No NH3 volatilization occurred below a pH of 6.5. A second study determined that small, weekly doses of 5% alum did not lower NH3 emissions further than a single dose of 5% alum. Two studies on the feedlot surface demonstrated a significant decrease (p < 0.01) in pH in the areas of the pens where alum was added compared to those that did not receive alum. Ammonia concentrations were lower (p < 0.05) for the areas that received alum compared to those that did not receive alum for 7 days when 5% alum was applied and 14 days when 10% alum was applied. In all the studies, sulfide emissions increased when alum was added to the FSM. We concluded 10% alum may reduce NH3 emissions from beef feedlots temporarily, but higher sulfide emissions offset this benefit.

Manure Flushing vs. Scraping in Dairy Freestall Lanes Reduces Gaseous Emissions

The objective of the present study was to mitigate ammonia (NH3), greenhouse gases (GHGs), and other air pollutants from lactating dairy cattle waste using different freestall management techniques. For the present study, cows were housed in an environmental chamber from which waste was removed by either flushing or scraping at two different frequencies. The four treatments used were (1) flushing three times a day (F3), (2) flushing six times a day (F6), (3) scraping three times a day (S3), and (4) scraping six times a day (S6). Flushing freestall lanes to remove manure while cows are out of the barn during milking is an industry standard in California. Gas emissions were measured with a mobile agricultural air quality lab connected to the environmental chamber. Ammonia and hydrogen sulfide (H2S) emissions were decreased (p < 0.001 and p < 0.05) in the flushing vs. scraping treatments, respectively. Scraping increased NH3 emissions by 175 and 152% for S3 and S6, respectively vs. F3. Ethanol (EtOH) emissions were increased (p < 0.001) when the frequency of either scraping or flushing was increased from 3 to 6 times but were similar between scraping and flushing treatments. Methane emissions for the F3 vs. other treatments, were decreased (p < 0.001). Removal of dairy manure by scraping has the potential to increase gaseous emissions such as NH3 and GHGs.

Swine diets impact manure characteristics and gas emissions: Part I protein level

Crude protein (CP) is a key nutrient in swine diets supplying essential amino acids, N, and S to animals for growth are fed in excess to maximize growth. Swine diets reduced in CP and supplemented with crystalline amino acids have been shown effective at maintaining animal growth while increasing overall CP use efficiency. A feeding trial study was conducted to determine the effects of reduced dietary CP levels on manure slurry chemical properties and gas emissions. A total of 24 gilts averaging 111 kg BW were fed corn and soybean meal diets formulated with 8.7, 14.8, and 17.6% CP using crystalline amino acid supplementation in the 8.7 and 14.8% CP diets, but only intact protein, soybean meal, in the diet containing 17.6% CP. Diets were fed for 45 d with an average daily feed intake (ADFI) of 2.70 kg across all diets. Animals were fed twice daily with both feces and urine collected during each feeding and added to animal-specific manure storage containers. At the end of the study, manure slurries were monitored for gas emissions and chemical properties. Increasing dietary CP levels increased manure pH, total solids, total N, and total S, including increased levels of ammonia (NH₃), volatile fatty acids, and phenolic compounds. Pigs fed lower CP diets had lower emissions of NH₃, branched chain fatty acids (BCFA), and phenol compounds which translated into lower emissions in total odor. Emissions of NH₃ and odor were reduced by 8.9% and 4.2%, respectively, for each unit percent decline in dietary CP. Hydrogen sulfide was the dominate odorant associated with manure odor emissions. Based on nutrient mass balance, animal retention of dietary N and S increased by 7.0% and 2.4%, respectively, for each unit percent drop in crude protein fed animals, while C retention in the animal declined by 2.1%.

Adsorptive-Oxidative Removal of Sulfides from Water by MnO2-Loaded Carboxylic Cation Exchangers

Hybrid ion exchangers (HIX) containing manganese(IV) oxide (MnO₂) based on macroporous and gel-type carboxylic cation exchangers as supporting materials were obtained. The hybrid materials were characterized using scanning electron microscopy with energy dispersive spectrometry (SEM/EDS), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and nitrogen adsorption isotherms at 77 K and mercury porosimetry. HIX with introduced MnO₂ (20.0–32.8 wt% Mn) were tested for removal of dissolved sulfides from anoxic aqueous solutions with 100–500 mg S²⁻/dm³ concentrations. The process proceeded effortlessly at pH 10–13 despite unfavorable electrostatic interactions of the reactants. The highest exhibited sorption capacity was 144.3 ± 7.1 mg S²⁻/g. Approximately 65% of dissolved sulfides were oxidized to S₂O₃²⁻ ions and repelled from HIX structure. On average, 13% of sulfide removal products were adsorbed by the MnO₂ surface. The impact of MnO₂ load and the ionic form of HIX functional groups on removal of sulfides and resulting products was examined. The mechanism of the process is suggested.

Influence of Aerobic Pretreatment of Poultry Manure on the Biogas Production Process

Anaerobic digestion of poultry manure is a potentially-sustainable means of stabilizing this waste while generating biogas. However, technical, and environmental protection challenges remain, including high concentrations of ammonia, low C/N ratios, limited digestibility of bedding, and questions about transformation of nutrients during digestion. This study evaluated the effect of primary biological treatment of poultry manure on the biogas production process and reduction of ammonia emissions. Biogas yield from organic matter content in the aerobic pretreatment groups was 13.96% higher than that of the control group. Biogas production analysis showed that aerobic pretreatment of poultry manure has a positive effect on biogas composition; methane concentration increases by 6.94–7.97% after pretreatment. In comparison with the control group, NH3 emissions after aerobic pretreatment decreased from 3.37% (aerobic pretreatment without biological additives) to 33.89% (aerobic pretreatment with biological additives), depending on treatment method.

Operator and Potential Exposure to Hydrogen Sulfide: A Study of the British Columbia Dairy Industry

Hydrogen Sulfide (H2S) is produced in manure storage facilities and released during manure agitation. Exposure to this gas presents health risks to workers at daily exposure of greater than 10 parts per million (ppm). Exposure levels on BC dairy farms are unknown. The aim of this study was to document peak H2S exposure levels to operators and bystanders during manure agitation on British Columbia dairy farms to determine if action levels were exceeded. Farms were evaluated at two time points during manure agitation. Both operator exposure and potential exposure sampling were undertaken. Peak hydrogen sulfide levels were measured and categorized as greater than or less than the ceiling level (10 ppm) and action level (5 ppm). Associations between H2S levels above the ceiling level and farm factors were assessed. Measures were recorded at 43 dairy farms with 91 total measures recorded. Action levels were exceeded in 30% of operator measures and 64% of potential exposure measures while 20% of operator and 53% of potential peak H2S measures exceeded 10 ppm. Manure storage facilities were evenly distributed between indoor and outdoor locations with under-barn (43%) and outdoor storage (47%) most common. Sawdust was the most prominent bedding type (65%). Tractor operated propeller was the most common type of agitation equipment (62%). Manure temperature remained a significant predictor in the multivariate model for operator peak exposure. Exposure to H2S above the action level commonly occurs on BC Dairy farms. Given that Worksafe BC requires exposure control plans for H2S levels above 5 ppm, and that on dairy farms, measures of operator and potential H2S exposures were recorded above these levels, best practices to reduce potential H2S exposure are necessary to reduce possible operator and bystander exposure.

A Novel Application of Electroactive Polyimide Doped with Gold Nanoparticles: As a Chemiresistor Sensor for Hydrogen Sulfide Gas

This research paper presents a new application of electroactive polyimide doped with gold nanoparticles (PI/AuNPs) as a chemiresistor sensor for detecting hydrogen sulfide gas. The synthesis of PI/AuNPs was done in a simple 3-step process of polymerization using the as prepared amine-capped aniline trimer (ACAT), followed by imidization, and doping. Spectral analyses via FTIR, LC-MS and ¹H-NMR confirmed the formation of amine-capped aniline trimer with a MW of 288 g mol⁻¹. Comparison of ACAT, BSAA, and PI FTIR spectra showed successful polymerization of the last, while XRD validated the incorporation of metal nanoparticles onto the polymer matrix, showing characteristic diffraction peaks corresponding to gold. Furthermore, TEM, and FE-SEM revealed the presence of well-dispersed Au nanoparticles with an average diameter of about 60 nm. The electroactive PI/AuNPs-based sensor showed a sensitivity of 0.29% ppm⁻¹ H₂S at a linear concentration range of 50 to 300 ppm H₂S (r = 0.9777). The theoretical limit of detection was found at 0.142 ppm or 142 ppb H₂S gas. The sensor provided a stable response reading at an average response time of 43 ± 5 s, which was easily recovered after an average time of 99 ± 5 s. The sensor response was highly repeatable and reversible, with RSD values of 8.88%, and 8.60%, respectively. Compared with the performance of the conventional conducting polyaniline also doped with gold nanoparticles (PANI/AuNPs), the fabricated electroactive PI/AuNPs exhibited improved sensing performance making it a potential candidate in monitoring H₂S in the environment and for work-related safety.

Emissions of ammonia and hydrogen sulfide from typical dairy barns in central China and major factors influencing the emissions

There are few studies on the concentrations and emission characteristics of ammonia (NH₃) and hydrogen sulfide (H₂S) from Chinese dairy farms. The purpose of this study was to calculate the emission rates of NH₃ and H₂S during summer and to investigate influencing factors for NH₃ and H₂S emissions from typical dairy barns in central China. Eleven dairy barns with open walls and double-slope bell tower roofs from three dairy farms were studied. Five different locations in each barn were sampled both near the floor and at 1.5 m above the floor. Concentrations of NH₃ and H₂S were measured using the Nessler’s reagent spectrophotometry method and the methylene blue spectrophotometric method, respectively. NH₃ concentrations varied between 0.58 and 4.76 mg/m³ with the average of 1.54 mg/m³, while H₂S concentrations ranged from 0.024 to 0.151 mg/m³ with the average of 0.092 mg/m³. The concentrations of NH₃ and H₂S were higher during the day than at night, and were higher near the ground than at the height of 1.5 m, and were higher in the manure area than in other areas. NH₃ and H₂S concentrations in the barns were significantly correlated with nitrogen and sulfur contents in feed and manure (P < 0.05), and with temperature inside the barns (P < 0.05). Calculated emission rates of NH₃ ranged from 13.8 to 41.3 g NH₃/(AU·d), while calculated emission rates of H₂S ranged from 0.15 to 0.46 g H₂S/(AU·d). These results will serve as a starting point for a national inventory of NH₃ and H₂S for the Chinese dairy industry.

Impacts of iron oxide and titanium dioxide nanoparticles on biogas production: Hydrogen sulfide mitigation, process stability, and prospective challenges

Anaerobic digestion for biogas production is one of the most used technology for bioenergy. However, the adoption of nanoparticles still needs further studies. Therefore, this study was designed to examine the effect of metal oxide nanoparticles (MONPs) at four different concentrations in two different combinations, 20 (R1) and 100 (R2) mg/L for Fe₂O₃, 100 (R3) and 500 (R4) mg/L for TiO₂, and a mixture of Fe₂O₃ and TiO₂ at rates of 20, 500 (R5) and 100, and 500 (R6), on hydrogen sulfide (H₂S) mitigation, biogas, and methane (CH₄) yield during the anaerobic digestion of cattle manure (CM) using an anaerobic batch system. The results showed that H₂S production was 2.13, 2.38, 2.37, 2.51, 2.64, and 2.17 times lower than that of the control (R0), respectively, when the CM was treated by the aforementioned MONPs. Additionally, biogas and CH₄ production were 1.09 and 1.105, 1.15 and 1.191, 1.07 and 1.097, 1.17 and 1.213, 1.10 and 1.133, and 1.13 and 1.15 times higher than those of R0 when R1, R2, R3, R4, R5, and R6 were supplemented with MONPs, respectively. The highest specific production of biogas and CH₄ was 336.25 and 192.31 mL/gVS, respectively, which was achieved by R4 supplemented with 500 mg/L TiO₂ NPs, while the corresponding values in the case of R0 were 286.38 and 158.55 mL/gVS.

Odorous compounds sources and transport from a swine deep-pit finishing operation: A case study

Odor emissions from swine finishing operations are an air quality issue that affects residents at the local level. A study was conducted at a commercial swine deep-pit finishing operation in central Iowa to monitor odorous compounds emitted and transported offsite. Gaseous compounds were sampled using either sorbent tubes or canisters with GC/MS analysis, and particulates matter (PM₁₀) were sampled with high volume samplers and thermally extracted onto sorbent tubes for GC/MS analysis. Major odorous chemical classes detected at the swine facility included volatile sulfur compounds (VSC), volatile fatty acids (VFA), phenol and indole compounds. Manure storage was the main source of odorous compounds of which hydrogen sulfide (H₂S), methanethiol, 4-methylphenol, and 3-methylindole were key offenders. Only H₂S and 4-methylphenol were detected above odor threshold values (OTV) at all locations around the facility and both 4-methylphenol and 3-methylindole were detected above their OTV 1.5 km downwind from the swine facility. Odorous compounds generated during agitation and pumping of the deep pits was mainly H₂S. Odorants were mainly transported in the gas phase with less than 0.1% being associated with PM₁₀. Odor mitigation efforts should focus on gaseous compounds emitted from deep-pits and especially during manure agitation and deep-pit pumping.