Electrochemical mitigation of hydrogen sulfide in deep-pit swine manure storage

Odorous gas emissions from swine production have been a concern for neighbors and communities near livestock farms. Manure storage is one of the main sources of gaseous emissions. Manure additive products are marketed as a simple solution to this environmental challenge. Manure additives are user-friendly for producers and can be applied (e.g., periodically poured into manure) without changing the current manure storage structure. Little scientific data exist on how these products perform in mitigating gaseous emissions from swine manure. The research objective was to evaluate the effectiveness of 12 marketed manure additives on mitigating odor, ammonia (NH3), hydrogen sulfide (H2S), greenhouse gases (GHG), and odorous volatile organic compounds (VOCs) from stored swine manure. A controlled pilot-scale setup was used to conduct 8-week long trials using manufacturer-prescribed dosages of additives into swine manures. Manure was outsourced from three swine farms to represent a variety of manure storage types and other factors affecting the properties. Measured gaseous emissions were compared between the treated and untreated manure. None of the tested products showed a significant reduction in gaseous emissions when all (n = 3) manures were treated as replicates. Selected products showed a wide range of statistically-significant reduction and generation of gaseous emissions when emissions were compared in pairs of manure types from one farm. The latter observation highlighted the lack of consistent mitigation of gaseous emissions by manure additives. The results of this study do not warrant full-scale trials with the tested products.

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Can Biochar Save Lives? The Impact of Surficial Biochar Treatment on Acute H2S and NH3 Emissions During Swine Manure Agitation Before Pump-out

10.20944/preprints202006.0104.v1 ◽

2020 ◽

Author(s):

Baitong Chen ◽

Jacek A. Koziel ◽

Myeongseong Lee ◽

Hantian Ma ◽

Zhanibek Meiirkhanuly ◽

...

Keyword(s):

Swine Manure ◽

Pilot Scale ◽

Total Emission ◽

Maximum Flux ◽

Deep Pit ◽

Peak Flux ◽

Manure Storage ◽

High Concentrations ◽

The Impact ◽

Thick Layers

Hydrogen sulfide and ammonia are always a concern in the livestock industries, especially when farmers try to clear their manure storage pits. Agitation of manure can cause dangerously high concentrations of harmful agents such as H2S and NH3 to be emitted into the air. Biochar has the ability to sorb these gases. We hypothesized that applying biochar on top of manure can create an effective barrier to protect farmers and animals from exposure to NH3 and H2S. In this study, two kinds of biochar were tested, highly alkaline, and porous (HAP, pH 9.2) biochar made from corn stover and red oak biochar (RO, pH 7.5). Two scenarios of (6 mm) 0.25” and (12 mm) 0.5” thick layers of biochar treatments were topically applied to the manure and tested on a pilot-scale setup, simulating a deep pit storage. Each setup experienced 3-min of agitation using a transfer pump, and measurements of the concentrations of NH3 and H2S were taken in real-time and measured until the concentration stabilized after the sharp increase in concentration due to agitation. The results were compared with the control in the following 3 situations: 1. The maximum (peak) flux 2. Total emission from the start of agitation until the concentration stabilized, and 3. The total emission during the 3 min of agitation. For NH3, 0.5” HAP biochar treatment significantly (p<0.05) reduced maximum flux by 63.3%, overall total emission by 70%, and total emissions during the 3-min agitation by 85.2%; 0.25” HAP biochar treatment significantly (p<0.05) reduced maximum flux by 75.7%, overall, total emission by 74.5%, and total emissions during the 3-min agitation by 77.8%. 0.5” RO biochar treatment significantly reduced max by 8.8%, overall total emission by 52.9%, and total emission during 3-min agitation by 56.8%; 0.25” RO biochar treatment significantly reduced max by 61.3%, overall total emission by 86.1%, and total emission during 3-min agitation by 62.7%. For H2S, 0.5” HAP biochar treatment reduced the max by 42.5% (p=0.125), overall total emission by 17.9% (p=0.290), and significantly reduced the total emission during 3-min agitation by 70.4%; 0.25” HAP treatment reduced max by 60.6% (p=0.058), and significantly reduced overall and 3-min agitation’s total emission by 64.4% and 66.6%, respectively. 0.5” RO biochar treatment reduce the max flux by 23.6% (p=0.145), and significantly reduced overall and 3-min total emission by 39.3% and 62.4%, respectively; 0.25” RO treatment significantly reduced the max flux by 63%, overall total emission by 84.7%, and total emission during 3-min agitation by 67.4%.

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Simulation of Hydrogen Sulfide Emission from Deep-Pit Manure Storage During Agitation

Transactions of the ASABE ◽

10.13031/trans.12866 ◽

2018 ◽

Vol 61 (6) ◽

pp. 1951-1967

Author(s):

Hongjian Lin ◽

Weiwei Liu ◽

Jing Gan ◽

Yuchuan Wang ◽

Bo Hu

Keyword(s):

Mass Transfer ◽

Hydrogen Sulfide ◽

Main Part ◽

Molecular Diffusion ◽

Mass Transfer Rate ◽

Swine Manure ◽

Health And Safety ◽

Sulfide Concentration ◽

Deep Pit ◽

Simulation Results

Abstract. Human and animal exposure to hydrogen sulfide (H2S) in animal barns has long been a serious issue due to the acute and chronic toxicity of H2S. The H2S concentration in the room air of deep-pit swine barns is usually within hundreds of parts per billion by volume; however, it can sharply increase to hundreds and even thousands of parts per million (ppm) during manure agitation and pump-out. To explore the sudden release and concentration distribution of H2S, this study collected and analyzed samples from varying depths of a normal non-foaming barn and a foaming barn and then mathematically simulated the H2S concentrations and emissions in the pit headspace and room air for both barns during pit agitation. Simulations were conducted for six ventilation scenarios, or six different combinations of pit fan and wall fan ventilation rates. The simulation results suggested that pit ventilation was more effective than wall ventilation in decreasing H2S concentration in room air where pigs may be housed during agitation. A minimal pit ventilation rate of 40 cfm per pig was necessary to lower the peak concentration in room air to less than the permissible exposure limit of 20 ppm. The simulation results also indicated that gas bubble release during agitation accounted for the main part (81%) of H2S emission in the foaming barn, and expedited molecular diffusion contributed the main part (70.2%) of H2S emission in the non-foaming barn. The disturbed air-manure interface during agitation induced a pH decrease and therefore increased the apparent overall mass transfer coefficient of H2S, resulting in a substantially increased mass transfer rate and concentration. The immediately dangerous to life or health (IDLH) concentration of 100 ppm may be reached during pit agitation if pit fan ventilation is not fully provided, and the duration of the exceedance could be more than 30 min. The results provide empirical data for future simulation of spatial and temporal H2S distribution and are beneficial for developing methods to control H2S below hazardous levels so that the health and safety of workers can be better secured. Keywords: Agricultural safety, Deep-pit storage, Hydrogen sulfide concentration, Sulfide distribution, Swine manure.

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