Upcycling of recycled minerals from sewage sludge through black soldier fly larvae (Hermetia illucens): Impact on growth and mineral accumulation

Unlocking the potential of black soldier fly frass as a sustainable organic fertilizer: A review of recent studies

Using Hermetia illucens, or Black Soldier Fly (BSF) frass as an organic fertilizer is becoming increasingly popular in many countries. As a byproduct derived from BSF larvae that feed on organic waste, BSF frass has tremendous potential for preserving the environment and promoting the circular economy. Since it has diverse biochemical properties influenced by various production and environmental factors, further research is needed to evaluate its potential for extensive use in crop production and agriculture. Our review summarizes recent findings in BSF frass research by describing its composition and biochemical properties derived from various studies, including nutrient contents, biostimulant compounds, and microbial profiles. We also discuss BSF frass fertilizers' effectiveness on plant growth and contribution to environmental sustainability. Great compositions of BSF frass increase the quality of plants/crops by establishing healthy soil and improving the plants' immune systems. Special emphasis is given to potentially replacing conventional fertilizer to create a more sustainable cropping system via organic farming. Besides, we discuss the capability of BSF bioconversion to reduce greenhouse gas emissions and improve the socioeconomic aspect. The prospects of BSF frass in promoting a healthy environment by reducing greenhouse gas emissions and improving the socioeconomic aspects of communities have also been highlighted. Overall, BSF frass offers an alternative approach that can be integrated with conventional fertilizers to optimize the cropping system. Further studies are needed to fully explore its potential in establishing sustainable system that can enhance socioeconomic benefits in the future.

Biotransformation of Pb and As from sewage sludge and food waste by black soldier fly larvae: Migration mechanism of bacterial community and metalloregulatory protein scales

The accumulation and transformation of lead (Pb) and arsenic (As) during the digestion of sewage sludge (SS) by black soldier fly larvae (BSFL) remain unclear. In this study, we used 16 s rRNA and metagenomic sequencing techniques to investigate the correlation between the microbial community, metalloregulatory proteins (MRPs), and Pb and As migration and transformation. During the 15-day test period, BSFL were able to absorb 34-48 % of Pb and 32-45 % of As into their body. Changes in bacterial community abundance, upregulation of MRPs, and redundancy analysis (RDA) results confirmed that ZntA, EfeO, CadC, ArsR, ArsB, ArsD, and ArsA play major roles in the adsorption and stabilization of Pb and As, which is mainly due to the high contribution rates of Lactobacillus (48-59 %) and Enterococcus (21-23 %). Owing to the redox reaction, the regulation of the MRPs, and the change in pH, the Pb and As in the BSFL residue were mainly the residual fraction (F4). The RDA results showed that Lactobacillus and L.koreensis could significantly (P < 0.01) reduce the reducible fraction (F2) and F4 of Pb, whereas Firmicutes and L.fermentum can significantly (P < 0.05) promote the transformation of As to F4, thus realizing the passivation Pb and As. This study contributes to the understanding of Pb and As in SS adsorbed by BSFL and provides important insights into the factors that arise during the BSFL-mediated migration of Pb and As.

Larval Frass of Hermetia illucens as Organic Fertilizer: Composition and Beneficial Effects on Different Crops

Hermetia illucens has received a lot of attention as its larval stage can grow on organic substrates, even those that are decomposing. Black soldier fly breeding provides a variety of valuable products, including frass, a mixture of larval excrements, larval exuviae, and leftover feedstock, that can be used as a fertilizer in agriculture. Organic fertilizers, such as frass, bringing beneficial bacteria and organic materials into the soil, improves its health and fertility. This comprehensive review delves into a comparative analysis of frass derived from larvae fed on different substrates. The composition of micro- and macro-nutrients, pH levels, organic matter content, electrical conductivity, moisture levels, and the proportion of dry matter are under consideration. The effect of different feeding substrates on the presence of potentially beneficial bacteria for plant growth within the frass is also reported. A critical feature examined in this review is the post-application beneficial impacts of frass on crops, highlighting the agricultural benefits and drawbacks of introducing Hermetia illucens frass into cultivation operations. One notable feature of this review is the categorization of the crops studied into distinct groups, which is useful to simplify comparisons in future research.

Response of Propsilocerus akamusi (Diptera: Chironomidae) to the leachates from AMD-contaminated sediments: Implications for metal bioremediation of AMD-polluted areas

Acid mine water (AMD) is a global environmental problem caused by coal mining with the characteristics of low pH and high concentrations of metals and sulfates. It is a pertinent topic to seek both economical and environmentally friendly approaches to minimize the harmful effects of AMD on the environment. Insect larvae are considered a promising solution for pollution treatment. Chironomidae is the most tolerant family to contaminants in pools and its larvae have a strong capacity for metal accumulation from sediment. This paper aimed to evaluate the larvae of Propsilocerus akamusi, a dominant species in the chironomid community, as a new species for entomoremediation in AMD-polluted areas. We detected the toxic effects of AMD on P. akamusi larvae based on their survival and the trace metals bioaccumulation capabilities of P. akamusi larvae. Moreover, we analyzed the expression patterns of four stress-response genes, HSP70, Eno1, HbV, and Hb VII in P. akamusi larvae. Our results revealed that AMD exposure did not significantly affect the survival of the P. akamusi larvae and individuals exposed to some AMD gradients even exhibited higher survival. We also observed the significantly accumulated concentrations of Fe, Ni, and Zn as well as higher bioaccumulation factors (BAFs) for Ni and Zn in the P. akamusi larvae exposure to AMD. Induced expression of Eno1 and Hb VII may play important roles in the AMD tolerance of P. akamusi larvae. This study indicated the potential application of P. akamusi larvae in the metal bioremediation of AMD-polluted areas. STATEMENT OF ENVIRONMENTAL IMPLICATION: Acid mine drainage (AMD) is a global environmental problem related to coal mining activities. AMD pollution has become a long-term, worldwide issue for its interactive and complex stress factors. Bioremediation is an effective method to remove the metals of AMD from wastewater to prevent downstream pollution. However, the disadvantages of the slow growth rate, susceptibility to seasonal changes, difficult post-harvest management, and small biomass of hyperaccumulating plants greatly limit the usefulness of phytoremediation. Insect larvae may be useful candidate organisms to overcome these shortcomings and have been considered a promising pollution solution. Propsilocerus akamusi is a dominant species in the chironomid community and is distributed widely in many lakes of eastern Asia. This species has extraordinary abilities to resist various stresses. This research is the first time to our knowledge to evaluate the application of P. akamusi as a new species in entomoremediation in AMD-contaminated areas.