[Degradation Characteristics of Antibiotics During Composting of Four Types of Feces].

The widespread use of antibiotics in feed results in a large number of antibiotic residues in feces. Composting technology can degrade these residual antibiotics. A pilot-scale aerobic composting device was used to analyze the antibiotic residues and composting degradation characteristics of four types of feces (maggot manure, chicken manure, pig manure, and cow manure). Results showed that sulfonamides (SAs), fluoroquinolones (FQs), tetracycline (TCs), and macrolides (MAs) were the main antibiotics, and different type of feces had different dominant antibiotics. The contents of FQs and oxytetracycline (OTC) were none on the seventh day of the compost, and their degradation rates were the fastest. After composting, the degradation rate of doxycycline (DOX) in the four types of fecal composts was more than 85%. Meanwhile, the degradation rates of SAs in chicken, pig, and cow manure composts were also more than 80%, which was much lower in the one in maggot manure compost. MAs were only found in maggot manure, and the degradation rate was 70.79% after composting. Correlation analysis indicated that the water content and bulk density were the most important environmental factors affecting the degradation rates of antibiotics in the four types of fecal composts.

[Effects of Thermophilic Composting on Antibiotic Resistance Genes (ARGs) of Swine Manure Source].

To investigate the effects of thermophilic composting process on antibiotic resistance genes (ARGs) of swine manure source at a field scale, the abundance of four erythromycin resistance genes (ermA, ermB, ermC and ermF), three ß-lactam resistance genes (blaTEM, blaCTX and blaSHV) and two quinolone resistance genes (qnrA and qnrS) were quantified by quantitative PCR ( qPCR) during the composting process. The results suggested that the erm genes' copy numbers were significantly higher than those of the bla and qnr genes in the early stage of composting (P < 0.01). The maximum abundance of erm genes was ermB (9.88 x 108 copies · g⁻¹), following by ermF (9.4 x 108 copies · g⁻¹). At the end of the composting process, bla and qnr genes were at low levels, while erm genes were still at high levels. Even through ermF was proliferated comparing with the initial copies. These results indicated that thermophilic composting process could not effectively remove all ARGs. For some ARGs, compost may be a good bioreactor resulting in their proliferation. Application of composting products on farmland may cause transference of ARGs.

Housefly maggot-treated composting as sustainable option for pig manure management.

In traditional composting, large amounts of bulking agents must be added to reduce the moisture of pig manure, which increases the cost of composting and dilutes the N, P and K content in organic fertilizers. In this study, maggot treatment was used in composting instead of bulking agents. In experiment of selecting an optimal inoculum level for composting, the treatment of 0.5% maggot inoculum resulted in the maximum yield of late instar maggots, 11.6% (maggots weight/manure weight). The manure residue became noticeably granular by day 6 and its moisture content was below 60%, which was suitable for further composting without bulking agents. Moreover, in composting experiment with a natural compost without maggot inoculum and maggot-treated compost at 0.5% inoculum level, there were no significant differences in nutrient content between the two organic fertilizers from the two treatments (paired Student's t15=1.0032, P=0.3317). Therefore, maggot culturing did not affect the characteristics of the organic fertilizer. The content of TNPK (total nitrogen+total phosphorus+total potassium) in organic fertilizer from maggot treatment was 10.72% (dry weight), which was far more than that of organic fertilizer made by conventional composting with bulking agents (about 8.0%). Dried maggots as feed meet the national standard (GB/T19164-2003) for commercial fish meal in China, which contained 55.32 ± 1.09% protein; 1.34 ± 0.02% methionine; 4.15 ± 0.10% lysine. This study highlights housefly maggot-treated composting can be considered sustainable alternatives for pig manure management to achieve high-quality organic fertilizer and maggots as feed without bulking agents.

Rapid production of maggots as feed supplement and organic fertilizer by the two-stage composting of pig manure.

A two-stage composting experiment was performed to utilize pig manure for producing maggots as feed supplement and organic fertilizer. Seven-day composting of 1.8 ton fresh manure inoculated with 9 kg mixture of housefly neonates and wheat bran produced 193 kg aging maggots, followed by 12 week composting to maturity. Reaching the thermophilic phase and final maturity faster was characteristic of the maggot-treated compost compared with the same-size natural compost. Upon the transit of the maggot-treated compost to the second stage, the composting temperature maintained around 55 °C for 9 days and the moisture decreased to ~40%. Moreover, higher pH, faster detoxification and different activity patterns for some microbial enzymes were observed. There was a strong material loss (35% water-soluble carbon and 16% total nitrogen) caused by the maggot culture in the first stage. Our results highlight a higher economic value of pig manure achieved through the two-stage composting without bulking agents.