Design and development of indoor device for recycling of domestic vegetable scrap

Performance exploration and microbial dynamics of urine diverting composting toilets in rural China

The ongoing "toilet revolution" in China provides new opportunities to improve the rural living environment and sanitation, and the introduction of new sanitation facilities such as urine diverting composting toilets (UDCTs) is conducive to the effective treatment and resource utilization of feces. This study revealed the degradation performance and microbial community dynamics of UDCTs and clarified the influence mechanism of fecal volume in aerobic composting treatment. The results showed that UDCTs could effectively decompose human feces, with an organic matter degradation rate of 25%⁓30%. The temperature, water content, NH₄⁺-N and nutrient accumulation were higher in the high fecal volume treatment than in the low fecal volume treatment. Bacterial community composition and structure in UDCTs varied with composting stage and fecal volume. The diversity and richness of bacterial community in compost were changed with different fecal volumes, but the dominant groups were similar. Redundancy analysis (RDA) showed that nitrogen and organic carbon were the main drivers of bacterial community changes during composting. Highly nutritious and non-phytotoxic compost products were suitable for agronomic uses. Based on these results, UDCTs can be an effective way to solve the problem of fecal pollution in rural areas, and fecal dosage is a potential influencing factor in the operation and maintenance of composting systems.

Efficiency and mechanism of a vermicompost additive in enhancing composting of swine manure

Vermicompost was used as an additive in swine manure composting to investigate the expression of bacterial functional genes on nutrients biotransformation. Three treatments with vermicompost compositions of 10%, 20%, and 30% in swine manure were set up. Raw manure was used as the control. The thermophilic period increased to 12 days, the NH₄⁺ -N/NO₃^- -N ratio decreased to 0.85, and the germination index (GI) increased to 166% after vermicompost addition. Furthermore, higher relative abundances of Firmicutes were observed in the substrate during the initial stages of experiment. The abundance of the dominant phylum Proteobacteria and its related pathogenic genera Acinetobacter and Stenotrophomonas decreased in the thermophilic stage while the potentially beneficial genera Actinomadura and Chryseolinea increased. The expression of primary functional genes associated with the metabolism of carbohydrates, amino acids, xenobiotics, and fatty acids was enhanced during the thermophilic phase. Besides, most dominant genera showed strengthened correlations with NO₃^--N and GI, which were the strongest environmental factors for bacterial communities. Network analysis revealed a new metabolic pathway associated with dominant genera Pseudomonas, Acinetobacter, Stenotrophomonas, and Oceanobacter, whose abundance increased with vermicompost addition. Collectively, the results of this study indicate that vermicompost can promote composting efficiency by increasing the potentially beneficial bacteria, decreasing pathogenic bacteria, and enhancing the metabolic capacity of bacterial communities.

Effects of Exogenous Microbial Agents on Soil Nutrient and Microbial Community Composition in Greenhouse-Derived Vegetable Straw Composts

Vegetable waste causes resource waste and environmental pollution, giving rise to the spread of harmful organisms and causing disease in normal vegetable cultivation. Random distribution of vegetable waste can increase the risk of non-point agricultural pollution and explore the feasibility of its resource utilization. This study was designed to evaluate the effects of different doses of exogenous microbial agents on soil microbial communities after in situ composting of cucumber straw on plots with biodegradable mulch films. The cucumber straw and chicken manure were used as the base materials, and the next generation sequencing was used to analyze changes in the microbiome following composting. The results demonstrate that the addition of exogenous microbial agents had prolonged the high-temperature duration, reduced the total organic carbon (TOC) content, and accelerated the decline in the C/N ratio, ensuring compost maturity and effectively shortening the composting time. The predominant bacterial phyla of the four treatment groups were Proteobacteria and Firmicutes; while among fungal phyla, these treatments decreased the relative abundance of Ascomycota. The treatment of 300 t/ha microbial agents significantly increased the richness and diversity of both the bacterial and fungal communities. Redundancy analysis suggested that soil total nitrogen (TN) content had a significant effect on the bacterial community, while TN content, pH, and temperature influenced the fungal community in these samples. Collectively, the treatment of 300 t/ha exogenous microbial agents improved the quality of composting and promoted microbiome diversity.

Streptomyces griseorubens JSD-1 promotes rice straw composting efficiency in industrial-scale fermenter: Evaluation of change in physicochemical properties and microbial community

The influence of Streptomyces griseorubens JSD-1 on microbial community succession during rice straw composting in an industrial-scale fermenter was assessed by high-throughput sequencing technology. Compared to uninoculated control, JSD-1 inoculation effectively raised composting temperature and improved other maturation indices. JSD-1 inoculation increased the relative abundance of Actinobacteria in thermophilic phase and Firmicutes in cooling and maturation phases. At the genus level, JSD-1 inoculation increased the abundance of organic matter degrading bacteria (Virgibacillus) and lignocellulose degrading fungi (Chaetomium and Melanocarpus); while it decreased the abundance of pathogenic fungi (Geosmithia and Acremonium). Moreover, JSD-1 changed microbes that differed significantly and altered the key connecting nodes of microbial community. Organic matter and temperature were the most significant indices that had mutual influences on bacterial and fungal communities, respectively. This study demonstrated that JSD-1 was an effective inoculant on rice straw fast composting in the industrial-scale fermenter.

Succession and diversity of microorganisms and their association with physicochemical properties during green waste thermophilic composting

A comprehensive characterization of the bacterial diversity associated to thermophilic stages of green waste composting was achieved. In this study, eight different treatments (T1-T8) and three replicated lab-scale green waste composting were carried out to compare the effect of the cellulase (i.e. 0, 2%), microbial inoculum (i.e. 0, 2 and 4%) and particle size (i.e. 2 and 5 mm) on bacterial community structure. Physicochemical properties and bacterial communities of T1-T8 composts were observed, and the bacterial structure and diversity were examined by high-throughput sequencing via a MiSeq platform. The results showed that the most abundant phyla among the treatments were the Firmicutes, Chloroflexi and Proteobacteria. The shannon index and non-metric multidimensional scaling (NMDS) showed higher bacterial abundance and diversity at the metaphase of composting. Comparing with 5-mm treatments, particle size of 2-mm had a richer diversity of bacterial communities. The addition of cellulase and a microbial inoculum could promote the fermentation temperature, reduce the compost pH and C/N ratio and result in higher GI index. The humic substance (HS) and humic acid (HA) contents for 2-mm particle size treatments were higher than those of 5-mm treatments. Canonical correspondence analysis suggested that differences in bacterial abundance and diversity significantly correlated with HA, E₄/E₆ and temperature, and the relationship between bacterial diversity and environmental parameters was affected by composting stages. Based on these results, the application of cellulase to promote green waste composting was feasible, and particle size was identified as a potential control of composting physicochemical properties and bacterial diversity.

Role of psychrotrophic bacteria in organic domestic waste composting in cold regions of China

To study the influence of psychrotrophic bacteria on organic domestic waste (ODW) composting in cold regions, twelve new efficient psychrotrophic composting strains were isolated. Together with the published representative composting strains, a phylogenetic tree was constructed showing that although the strains belong to the same phylum, the genera were markedly different. The twelve strains were inoculated into the ODW in the composting reactor at 13°C. After treatment, the indices of temperature, moisture content, pH, electrical conductivity, C/N, ammonium nitrogen, and nitrate nitrogen indicated that the compost had reached maturity. The thermophilic phase was reached at 17d, and composting was completed at 42d, a markedly shorter composting time than that in previous studies. High-throughput sequencing indicated that the inoculative strains became the dominant community during the mesophilic phase and that they enhanced the stability of the microbial community structure. Thus, psychrotrophic bacteria played a key role in low-temperature composting.