Catalytic pyrolysis of swine manure using CO2 and steel slag.

Pyrolysis of swine manure (SM) was conducted as a case study to establish an environmentally sound management of livestock manure. To build a more renewable pyrolysis platform for SM, this study selected carbon dioxide (CO2) as the reaction medium. In addition, CO2 was used in pyrolysis of SM to restrict the formation of toxic compounds, such as benzene derivatives and polycyclic aromatic hydrocarbons (PAHs). A series of thermo-gravimetric analysis (TGA) tests was done to understand the thermolysis of SM in the CO2 environment. The TGA tests elucidated no occurrence of heterogeneous reactions between the SM sample and the CO2. Moreover, the TGA tests of SM suggested that SM contains more volatile matter (VM) than lignocellulosic biomass. Non-catalytic transesterification of SM lipids confirmed that the dried SM sample contained 8.85 ±â€¯0.05 wt% of lipids. This study also confirmed that the mechanistic role of CO2 was realized through the gas phase reactions between volatile pyrolysates evolved from the thermolysis of SM and CO2. In summary, CO2 donates O, enhancing the generation of CO through homogeneous reactions. In parallel, this study confirmed that CO2 suppress dehydrogenation. Therefore, the identified gas phase reactions between volatile pyrolysates and CO2 led to the compositional modifications in the condensable pyrolysates. However, such mechanistic features arising from CO2 only initiated at ≥520 °C. To expedite the reaction kinetics of the homogeneous reaction triggered by CO2, steel slag (SS) was used as a catalyst. Hence, the reaction kinetics associated with the mechanistic role of CO2 were substantially enhanced (up to 80%) when SS was used as a catalyst. Therefore, all experimental findings strongly suggest that CO2 can be utilized as a raw material in a thermo-chemical process. More importantly, all observations suggest that CO2 lopping can also be achieved in a thermo-chemical process. Lastly, this study shows that the high Cu content in SM was effectively immobilized through pyrolysis. Conclusively, this study experimentally proved that CO2 could be promising for restricting the formation of toxic pollutant in the thermo-chemical treatment in that CO2 offers an innovative and strategic means for controlling the ratio of C to H. Note that aromaticity and toxicity of chemical compounds are highly contingent on the ratio of C to H.

Major environmental characteristics of swine husbandry that affect exposure to dust and airborne endotoxins.

Inhalation of organic dust or endotoxin in the dust is considered a major risk factor for occupational respiratory illnesses. Eighteen environmental characteristics associated with animal husbandry were surveyed at 36 swine farms in seven provinces throughout South Korea. Association of these factors with levels of indoor inhalable or respirable dust or endotoxin in each type of dust was analyzed using backward stepwise multiple linear regression models. Mean levels of inhalable and respirable dust were 0.5 ± 0.35 and 0.13 ± 0.12 mg/m3 air, respectively, and mean endotoxin levels were 676 ± 463 and 48.4 ± 68.2 EU/m3, respectively, in each dust. Factors negatively associated with inhalable dust levels included pig age, indoor farm temperature, number of pigs in the building, hr/week of indoor farm work, and partly slatted floor. Factors positively associated with inhalable dust levels included floor cleaning by manual scraping and slurry deposit duration. Factors negatively associated with the level of endotoxin in inhalable dust included pig age, temperature, number of pigs, hr/week of indoor farm work, and partly slatted floor. Factors negatively associated with respirable dust level included area of the confinement building, whereas factors positively associated with respirable dust level included the number of pigs and stocking density. Endotoxin levels in respirable dust were negatively associated with h/week of indoor farm work and partly slatted floor. Overall, data suggest that husbandry variables may be adjusted to control dust and airborne endotoxin levels in swine farms.

Evaluation of pilot-scale in-vessel composting for Hanwoo manure management.

The study investigated the effect of in-vessel composting process on Hanwoo manure in two different South Korea regions (Pyeongchang and Goechang) with sawdust using vertical cylindrical in-vessel bioreactor for 42days. The stability and quality of Hanwoo manure in both regions were improved and confirmed through the positive changes in physico-chemical and phytotoxic properties using different commercial seed crops. The pH and electrical conductivity (EC, ds/m) of composted manure in both regions were slightly increased. At the same time, carbon:nitrogen (C:N) ratio and ammonium nitrogen:nitrate nitrogen (NH4+-N:NO3--N) ratio decreased to 13.4-16.1 and 0.36-0.37, respectively. The germination index (GI, %) index was recorded in the range of 67.6-120.9%, which was greater than 50%, indicating phytotoxin-free compost. Although, composted manure values in Goechang region were better in significant parameters, overall results confirmed that the composting process could lead to complete maturation of the composted product in both regions.

Evaluation of integrated ammonia recovery technology and nutrient status with an in-vessel composting process for swine manure.

The study investigated the effect of different initial moisture (IM) content (55, 60, 65, and 70%) of composting mixtures (swine manure and sawdust) for the production of nutrient rich manure, and the recovery of ammonia through a condensation process using a vertical cylindrical in-vessel composter for 56days. The composting resulted in a significant reduction in C:N ratio and electrical conductivity (EC), with a slight increase in pH in all products. The NH3 were emitted notably, and at the same time the NO3--N concentration gradually increased with the reduction of NH4+-N in the composting mixtures. The overall results confirmed, the 65% IM showed the maximum nutritional yield, maturity and non-phytotoxic effects (Lycopersicon esculentum L.), with the results of ideal compost product in the following order of IM: 65%>60%>70%>55%. Finally, the recovered condensed ammonia contained considerable ammonium nitrogen concentrations and could be used as fertilizer.

Optimization of electrochemical reaction for nitrogen removal from biological secondary-treated milking centre wastewater.

In order to remove the residual nitrogen from the secondary-treated milking centre wastewater, the electrochemical reaction including NH4-N oxidation and NOx-N reduction has been known as a relatively simple technique. Through the present study, the electrochemical reactor using the Ti-coated IrO2 anode and stainless steel cathode was optimized for practical use on farm. The key operational parameters [electrode area (EA) (cm(2)/L), current density (CD) (A/cm(2)), electrolyte concentration (EC) (mg/L as NaCl), and reaction time (RT) (min)] were selected and their effects were evaluated using response surface methodology for the responses of nitrogen and colour removal efficiencies, and power consumption. The experimental design was followed for the central composite design as a fractional factorial design. As a result of the analysis of variance, the p-values of the second-order polynomial models for three responses were significantly fit to the empirical values. The nitrogen removal was significantly influenced by CD, EC, and RT (p < .05), whereas colour removal was significantly governed by EA, CD, RT, the interaction of EA and EC (p < .05). For higher efficiency of nitrogen removal over 90%, the combination of [EA, 20 cm(2)/L; CD, 0.044 A/cm(2); EC, 3.87 g/L as NaCl; RT, 240 min] was revealed as an optimal operational condition. The investigation on cathodic reduction of NOx-N may be required with respect to nitrite and nitrate separately as a future work.

Nitrogen Removal from Milking Center Wastewater via Simultaneous Nitrification and Denitrification Using a Biofilm Filtration Reactor.

Milking center wastewater (MCW) has a relatively low ratio of carbon to nitrogen (C/N ratio), which should be separately managed from livestock manure due to the negative impacts of manure nutrients and harmful effects on down-stream in the livestock manure process with respect to the microbial growth. Simultaneous nitrification and denitrification (SND) is linked to inhibition of the second nitrification and reduces around 40% of the carbonaceous energy available for denitrification. Thus, this study was conducted to find the optimal operational conditions for the treatment of MCW using an attached-growth biofilm reactor; i.e., nitrogen loading rate (NLR) of 0.14, 0.28, 0.43, and 0.58 kg m(-3) d(-1) and aeration rate of 0.06, 0.12, and 0.24 m(3) h(-1) were evaluated and the comparison of air-diffuser position between one-third and bottom of the reactor was conducted. Four sand packed-bed reactors with the effective volume of 2.5 L were prepared and initially an air-diffuser was placed at one third from the bottom of the reactor. After the adaptation period of 2 weeks, SND was observed at all four reactors and the optimal NLR of 0.45 kg m(-3) d(-1) was found as a threshold value to obtain higher nitrogen removal efficiency. Dissolved oxygen (DO) as one of key operational conditions was measured during the experiment and the reactor with an aeration rate of 0.12 m(3) h(-1) showed the best performance of NH4-N removal and the higher total nitrogen removal efficiency through SND with appropriate DO level of ~0.5 mg DO L(-1). The air-diffuser position at one third from the bottom of the reactor resulted in better nitrogen removal than at the bottom position. Consequently, nitrogen in MCW with a low C/N ratio of 2.15 was successfully removed without the addition of external carbon sources.

Recovery of struvite from animal wastewater and its nutrient leaching loss in soil.

Contaminants in swine wastewater were recovered in the form of struvite, a crystal of magnesium ammonium phosphate (MAP), using a newly designed process, and the leaching loss of MAP in soil was examined. The continuous flow process was operated under optimal conditions: 1.0 molar ratio of magnesium (Mg) addition with respect to orthophosphate (OP) and an aeration rate of 0.73 L/L min. Five treatments were performed with three replications for soil pH and nutrient leaching loss tests. It was found that 93% of the OP in the swine wastewater was crystallized, and the MAP crystal formation was verified by X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses. The analyses revealed that the pattern of pH change and N leaching losses for MAP-treated soil were remarkably different from those for fused super phosphate (FSP)-urea-treated soils. The pH levels for the control and FSP-urea-treated soils after a five-week experiment were unchanged or slightly decreased, whereas an increase in pH was observed in the MAP-treated soils. Leaching loss of N was higher in FSP-urea treatments, with MAP treatments showing N losses of only 1.93 and 2.05%, respectively, while FSP-urea treatments showed N losses of 7.82 and 6.47%, respectively, during the same period. Phosphate (P) leaching was very slow in both MAP- and FSP-treated groups.