The disposal of organic waste by the biocomposting of black soldier fly larvae (BSFL) has drawn broad attention. However, the discrepancies in heavy metal immobilization between BSFL biocomposting with different inoculation densities and aerobic composting need to be further researched. In this study, BSFL with inoculation densities of 0.08%, 0.24% and 0.40% was added to swine manure to investigate its influence on heavy metal bioaccumulation and bioavailability. The physicochemical properties, BSFL growth performance and amino acid contents were measured. The results showed that the germination index, total prepupal yield and bioavailable fraction removal rate (%) of Cr and Pb at an inoculation density of 0.40% of BSFL were the highest among all of the BSFL biocomposting groups. Although the bioaccumulation factor and heavy metal (Cd, Cr, Cu and Zn) concentrations of the BSFL body from swine manure with inoculation densities of 0.24% and 0.40% of BSFL were similar, the BSFL inoculation density of 0.40% had the best absorption effect on these heavy metals in terms of total prepupal yield. Therefore, this study provides a basis for exploring the optimal inoculation density of BSFL biocomposting to reduce the harmful effects of heavy metals in swine manure.
This study investigates the effect of Chinese environmental regulations on the quality of export products. As the main way for the government to protect the environment, environmental regulations have greatly influenced the production behavior of enterprises. Based on the data of China’s pollutant discharge fee implementation and industrial enterprise-pollution panel data, we find that the government’s environmental regulations have significantly improved the quality of export products, and this conclusion is still valid after a series of robustness tests. Further analysis shows that the increase in the quality of export products originating from the regulated areas could be attributed to promoting enterprise innovation and reducing resource misallocation. The results in this study provide evidence that the Chinese government could coordinate economic and environmental protection in the new era.
