Biochar, because of its unique physiochemical properties and sorption capacity, may be an ideal amendment in reducing gaseous emissions during composting process but there has been little information on the potential effects of different types of biochar on undesired gaseous emissions. The objective of this study was to examine the ability and mechanism of different types of biochar, as co-substrate, in mitigating gaseous emission from composting of layer hen manure. The study was conducted in small-scale laboratory composters with the addition of 10% of one of the following biochars: cornstalk biochar, bamboo biochar, woody biochar, layer manure biochar and coir biochar. The results showed that the cumulative NH3 production was significantly reduced by 24.8±2.9, 9.2±1.3, 20.1±2.6, 14.2±1.6, 11.8±1.7% (corrected for initial total N) in the cornstalk biochar, bamboo biochar, woody biochar, layer manure biochar and coir biochar treatments, respectively, compared to the control. Total CH4 emissions was significantly reduced by 26.1±2.3, 15.5±2.1, 22.4±3.1, 17.1±2.1% (corrected for the initial total carbon) for cornstalk biochar, bamboo biochar, woody biochar and coir biochar treatments than the control. Moreover, addition of cornstalk biochar increased the temperature and NO3(-)-N concentration and decreased the pH, NH4(+)-N and organic matter content throughout the composting process. The results suggested that total volatilization of NH3 and CH4 in cornstalk biochar treatment was lower than the other treatments; which could be due to (i) decrease of pH and higher nitrification, (ii) high sorption capacity for gases and their precursors, such as ammonium nitrogen from composting mixtures, because of the higher surface area, pore volumes, total acidic functional groups and CEC of cornstalk biochar.
Antibiotic residues that enter the soil through swine manure could disturb the number, community structure and functions of microbiota which could also degrade antibiotics in soil. Five different concentrations of doxycycline (DOX) incorporated into swine manure were added to soil to explore the effects of DOX on microbiota in soil and degradation itself. The results showed that the soil microbiome evolved an adaptation to the soil containing DOX by generating resistance genes. Moreover, some of the organisms within the soil microbiome played crucial roles in the degradation of DOX. The average degradation half-life of DOX in non-sterile groups was 13.85 ± 0.45 days, which was significantly shorter than the 29.26 ± 0.98 days in the group with sterilized soil (P < 0.01), indicating that the soil microbiome promoted DOX degradation. DOX addition affected the number of tetracycline resistance genes, depending on the type of gene and the DOX concentration. Among these genes, tetA, tetM, tetW, and tetX had significantly higher copy numbers when the concentration of DOX was higher. In contrast, a lower concentration of DOX had an inhibitory effect on tetG. At the same time, the microbial compositions were affected by the initial concentration of DOX and the different experimental periods. The soil chemical indicators also affected the microbial diversity changes, mainly because some microorganisms could survive in adversity and become dominant bacterial groups, such as the genera Vagococcus and Enterococcus (which were associated with electrical conductivity) and Caldicoprobacter spp. (which were positively correlated with pH). Our study mainly revealed soil microbiota and DOX degradation answered differently under variable concentrations of DOX mixed with swine manure in soil.
Ammonia emissions is an important issue during composting because it can cause secondary pollution and a significant of nitrogen loss. Based on research adding Bacillus stearothermophilus can reduce ammonia emissions during composting because it can use sugar in organic matter fermentation to produce organic acids over 50 °C. This study conducted the batch experiments by adding different concentrations of Bacillus stearothermophilus to reduce the ammonia emissions and find out its characteristic during layer manure composting by using an aerobic composting reactor with sawdust as a bulking agent. The results show that the application of Bacillus stearothermophilus can accelerate the rate of temperature and significantly decrease pH, the warming period was 2 days in the treatment with Bacillus stearothermophilus, while it was 4 days in the treatment without Bacillus stearothermophilus. Ammonia emissions were mainly occurred in warming and high temperature period during composting. The ammonia emissions in the treatment with 8.00 g/kg initial Bacillus stearothermophilus were significantly lower than the other lower Bacillus stearothermophilus treatment and control during composting (p 0.05). MiSeq System Sequencing results find that the addition of Bacillus stearothermophilus changed the bacterial community structure under warming and high-temperature periods during composting, increased the relative abundance of lactic acid bacillus and nitrification bacteria. Therefore, the reason for the low ammonia emission in 8.00 g/kg initial Bacillus stearothermophilus treatments might be not only due to the Bacillus stearothermophilus itself, but also Bacillus stearothermophilus can change the indigenous microorganism community, including increase the relative content of lactic acid Bacillus and nitrification bacteria, thus reducing the pH and promoting nitrification, and reducing ammonia emissions.
Livestock farms are commonly regarded as the main sources of antibiotic resistance genes (ARGs), emerging pollutants with potential implications for human health, in the environment. This study investigated the occurrence and contamination profiles of nine ARGs of three types from swine manure to receiving environments (soil and water) in Guangdong Province, southern China. All ARGs occurred in 100% of swine manure samples. Moreover, the absolute concentration of total ARGs varied from 3.01 × 108 to 7.18 × 1014 copies/g, which was significantly higher than that in wastewater and manured soil (p 0.05). However, the number of ARGs (ermB, qnrS, acc(6')-Ib, tetM, tetO and tetQ) decreased but were not eliminated by wastewater treatment components (p
Antibiotic residues in swine manure when entered the soil would most likely affect the complex composition and functions of the soil microbiome, which is also responsible for degrading these antibiotics. Three different methods of adding ciprofloxacin (CIP), a common antibiotic used in the swine industry, to the soil were used to investigate the effects of CIP on the soil microbiome and the degradation of CIP. Results of the study showed that the microbiome could promote the degradation of CIP in the soil when CIP was incorporated into the soil together with manure. However, the CIP degradation time was prolonged when adding the manure of swine fed with diet containing CIP in the soil. All treatments did not affect the copy number of the resistance genes, except for aac(6')-Ib-cr, as compared with the initial numbers of each treatment. MiSeq Illumina sequencing and Biolog-ECO microplates results showed that CIP had a significant effect on the abundance, structure, and function of the soil microbiome, but different addition methods resulted in distinct effects. Results of the present study demonstrated that the microbiome and fate of CIP responded differently to the different methods of adding CIP to the soil.
Using manure collected from swine fed with diet containing antibiotics and antibiotic-free swine manure spiked with antibiotics are the two common methods of studying the degradation behavior of veterinary antibiotic in manure in the environment. However, few studies had been conducted to co-compare these two different antibiotic addition methods. This study used oxytetracycline (OTC) as a model antibiotic to study antibiotic degradation behavior in manure under the above two OTC addition methods. In addition, the role of microorganisms present in the manure on degradation behavior was also examined. The results showed that degradation half-life of OTC in manure from swine fed OTC (9.04 days) was significantly shorter than that of the manure directly treated with OTC (9.65 days). Concentration of 4-epi-OTC in manure from swine fed OTC peaked earlier than that in manure spiked with OTC, and the degradation rates of 4-epi-OTC and α-apo-OTC in the manure from swine fed OTC were faster, but the peak concentrations were lower, than those in manure spiked with OTC. Bacterial diversity and relative abundance of Bacillus cereus data demonstrated that sterilization of the manure before experiment significantly decreased OTC degradation rate in both of the addition methods. Results of the present study demonstrated that the presence of the metabolites (especially 4-epi-OTC) and microorganisms had significant influence on OTC degradation.
The degradation behavior of veterinary antibiotics in soil is commonly studied using the following methods of adding antibiotics to the soil: (i) adding manure collected from animals fed with a diet containing antibiotics, (ii) adding antibiotic-free animal manure spiked with antibiotics and (iii) directly adding antibiotics. No research simultaneously comparing different antibiotic addition methods was found. Oxytetracycline (OTC) was used as a model antibiotic to compare the effect of the three commonly used antibiotic addition methods on OTC degradation behavior in soil. The three treatment methods have similar trends, though OTC degradation half-lives show the following significant differences (P<0.05): manure from swine fed OTC (treatment A)
The excretion rates and ecological risk to the environment of three commonly used veterinary antibiotics (VAs), amoxicillin, ciprofloxacin, and doxycycline, in layer hen manure during the application and withdrawal periods were investigated in a study consisting of a control group fed with VA-free basal diet and nine treatment groups consisted of three levels (200 mg/kg, 100 mg/kg, and 50 mg/kg) of amoxicillin (AMX), ciprofloxacin (CIP), or doxycycline (DOC). Each treatment group was replicated seven times with three layer hens per replication. Results of the study showed that the average excretion rates of AMX in the 200, 100, and 50 mg/kg groups were 67.88, 55.82, and 66.15%, respectively, while those for CIP and DOC were 47.84, 51.85, and 44.87% and 82.67, 94.39, and 95.72%, respectively. The concentrations of the above veterinary drugs in manure decreased sharply in the withdrawal period (7, 28, and 10 d, respectively), for AMX, DOC, and CIP. Neither AMX nor DOC was detected in the manure after the withdrawal period. In contrast to AMX and DOC, the excretion rate of CIP was significantly lower and thus had a longer residence time. Ecological risk study, estimated using hazard quotient values, showed that AMX in the 100 and 50 mg/kg groups posed no risk to the environment after d 1 of withdrawal, while CIP in the 50 mg/kg group posed no risk to the environment from d 5 of withdrawal. CIP in the 200 and 100 mg/kg groups required 10 d withdrawal in order to pose no risk to the environment. In contrast, DOC residue during withdrawal in the manure posed no risk to the environment, thus making it more environmentally safe.
The behavior of veterinary antibiotics in the soil is commonly studied using the following methods to add antibiotics to the soil: (A) adding manure collected from animals fed a diet that includes antibiotics; (B) adding antibiotic-free animal manure spiked with antibiotics; and (C) the direct addition of antibiotics. However, most studies have only used methods (B) and (C) in their research, and few studies have simultaneously compared the different antibiotic addition methods. This study used tylosin A (TYLA) as a model antibiotic to compare the effects of these three commonly used antibiotic addition methods on the dissipation rates of TYLA and the numbers of resistance genes in laboratory incubation experiments. The results showed that the three treatment methods produced similar TYLA degradation trends; however, there were significant differences (P<0.05) in the TYLA degradation half-life (t1/2) among the three methods. The half-life of TYLA degradation in treatments A, B and C was 2.44 ± 0.04, 1.21 ± 0.03 and 5.13 ± 0.11 days, respectively. The presence of manure resulted in a higher electrical conductivity (EC), higher relative abundance of Citrobacter amalonaticus, higher macrolide resistant gene (ermB, ermF and ermT) count and lower ecological toxicity in the soil, which could partially explain the higher TYLA degradation rate in the treatments containing manure. The higher degradation rate of TYLA in treatment B when compared to treatment A could be due to the lower concentrations of tylosin B (TYLB) and tylosin D (TYLD). The main route for veterinary antibiotics to enter the soil is via the manure of animals that have been administered antibiotics. Therefore, the more appropriate method to study the degradation and ecotoxicity of antibiotic residues in the soil is by using manure from animals fed/administered the particular antibiotic rather than by adding the antibiotic directly to the soil.
Sulfadimidine (SM2) is commonly used in the swine industry and enters the environment via faeces. In recent years, advances in the ecotoxicology of SM2 have become a popular research interest with two common research methods including swine manure collection from swine fed with a diet containing SM2 and directly adding SM2. The purpose of this experiment was to compare SM2 degradation behaviour in pig manure with two different SM2 addition methods. The results showed that the degradation half-lives of SM2 in manure from SM2-fed swine treatment were 33.2 and 32.0 days at the initial addition level of SM2 at 32.1 and 64.3 mg/kg, respectively. This was significantly longer than that in manure directly adding SM2 treatment with the half-lives of 21.4 and 14.8 days. The metabolite of SM2 N(4)-acetyl-sulfamethazine occurred in manure from SM2-fed swine treatment but was not detected in directly adding SM2 treatment. The pH in manure from SM2-fed swine treatment was significantly lower than that in directly adding SM2 treatment, but the values of organic carbon, total nitrogen, and electrical conductivity in manure from SM2-fed swine treatment were significantly higher than those in manure directly adding SM2 treatment. Meanwhile, although the copy number of bacteria had no significant difference between two treatments, there was a significant difference in bacteria diversity. Results of the present study demonstrated that the presence of the metabolites, chemical property, and microbial diversity might be the reason for different SM2 degradation behaviours on different addition methods. Thus, the method using manure with SM2 collected from swine could obtain more accurate results for the ecotoxicological study of SM2.
Cat manure (CM) possesses high level of nutrients for growing food crop. However, animal manure may contain toxic elements that may contaminate food crop. Spent coffee ground (SCG) may be used to reduce mobility of heavy metals and reduce crop uptake. In this study, SCG was composted with CM for 31 days to produce a co-compost (SCG-CM) for growing spinach (Spinacia oleracea). The growth rate of spinach was assessed until its maturity, and the metal uptake of spinach shoot was determined thereafter using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The effect of soil treatment with SCG-CM on the height and elemental composition of spinach were compared with that of chicken manure compost (CMC). The prepared composts were primarily organic matter (72.9-81.4 % w/w) with the rest are ash (13.3-23.4 % w/w) and moisture (1.2-2.6 % w/w). Zinc content in SCG-CM (1261 ± 0.1 mg/kg) is significantly higher than that of soil and CMC (p < 0.05) and has exceeded the maximum permissible limit set by European Union Standard (2002) and the Malaysian Compost Quality Standard and Guidelines (2000). Matured spinach reached maximum plant height after 33 days. The amendment of SCG-CM significantly increased the height of spinach (32 ± 6 cm) compared to that of CMC (13 ± 1 cm) (p < 0.05). However, contents of Zn, Cu, Pb and Cd were not increased for spinach grown in the SCG-CM-amended soil, and the level of those elements are below permissible limit set by the Malaysian Food Act 1983 and Food Regulations 1985. This study shows that SCG-CM is effective in improving yield without causing accumulation of toxic trace elements in spinach.
Energy is widely used in industry for heating and cooling, with natural gas (NG) being the largest primary energy source in Malaysia, closely followed by coal. Renewable energy, such as biogas upgrading to biomethane, could cut the use of fossil fuels by supplementing NG usage due to their similar physicochemical and thermochemical characteristics. Biogas production plants in Malaysia are more commonly seen in waste-to-energy scenarios, with the technology anaerobic digestion, and their deployment is supported via feed-in tariffs (FiT) for power generation. Other potential applications such as the conversion of biogas into biomethane, injection into the natural gas grid or transportation through a virtual pipeline may still need further technical development. This paper presents spatial techno economic optimisation modelling using BeWhere to determine decentralised biomethane production plants using feedstock from multiple sources of biogas, including palm oil mill effluent (POME), food waste, cattle manure and chicken manure. This model considered potential configurations and sizes of the biomethane plants, the transportation of biomethane using a virtual pipeline (at 250 psig) and demand in one of the states in Malaysia, namely Johor. It was found that two to four biomethane plants with capacities ranging between 125 and 700 m3/h were located in densely populated areas or heavier industrial consumers when the carbon tax was implemented at 167.71 EUR/tCO2 (800 MYR/tCO2). Sensitivity analysis suggested that biomethane production increases with the increasing country renewable energy share target to beyond 2080 MW. It is recommended that specific policy regulations and Feed-in Tariff (FiT) mechanisms are used to expand the biomethane market share in the country.