Domestic biodegradable wastes (DBW) pose a threat to environmental quality and human health. Bioconversion via black soldier fly larvae (BSFL; Hermitia illucens L.) is an expedient way for converting ‘waste to resource’ (insect protein and biofertilizer). Although researches abounded in laboratory-reared experiments and bioconversion mechanisms were pertinent, the void of data from actual and full-scale operation restricts the intensification of BSFL technology and its global adoption. Hence, a full-scale BSFL bioconversion system lasting 4 years in Hangzhou (China) was investigated, and the feasibility and efficiency of 15 tonnes of DBW per day were studied. Through continuous technical optimization, the average production of fresh larvae was increased from 8.5% in 2017 to 15.3% in 2020, along with bioconversion rate of final vermicompost decreased from 35.4% to 14.5%. The total biomass reduction rate in 2020 was 68.7 ± 17.4 kg/(m3 d), equivalent to 0.735 ± 0.215 kg/(kg d) in the form of fresh larvae. Crude fat in fresh larvae accounted for 13.4%, and crude protein accounted for 16.2% in which the determined amino acid profile bore a strong resemblance to fish meal only except histidine and tyrosine. Its economic benefits proved the feasibility of this technology, and the profit reached up to 35.9 US$ per tonne of DBW in 2019. In conclusion, BSFL bioconversion system under current ‘insect-farm’ operation was a promising solution for DBW treatment with value-added waste recycling.

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Abstract Background: Rice paddy soil-associated microbiota participate in biogeochemical processes that underpin rice yield and soil sustainability, yet continental-scale biogeographic patterns of paddy soil microbiota remain elusive. Here, the soil bacteria of four typical Chinese rice-growing regions were characterized over large-scale space and compared with adjacent non-paddy soils.Results: The geographic patterns of paddy soil bacteria were significantly different from non-paddy soils, with lower alpha diversity, unique taxonomic and functional composition, and distinct co-occurrence network topology. Both stochastic and deterministic processes shaped soil bacteria assembly, but paddy exhibited a stronger deterministic signature than non-paddy samples, especially due to the roles of climate determinants. The continental biogeographic variance in bacterial community structure was driven by the competition between two mutually-exclusive bacterial modules in the co-occurrence network, and suggested antagonistic species-to-species interactions as potential selective forces may greatly shape their community structures. Keystone taxa identified in network models, such as Actinobacteria, Chloroflexi, and Proteobacteria, were demonstrated to be preferentially affected by environmental factors than other community members and showed high sensitivity to environmental changes, whereby the environmental factors greatly shaped the paddy soil bacterial communities by leveraging changes in keystones.Conclusions: The strong interplay between biotic/abiotic factors may greatly construct paddy soil microbial community and their uniqueness as compared with non-paddy soils. Microbial biogeographical analyses with novel insights into underlying determinants investigated on intensively-cultivated paddy field soils may aid in elucidating microbial changes subjected to land-use changes following the transformation between natural and agro-ecosystem, and also facilitate microbial community manipulation for better crop productivity and soil sustainability worldwide.