Reducing greenhouse gas emissions and enhancing carbon and nitrogen conversion in food wastes by the black soldier fly.

Currently, sustainable utilisation, including recycling and valorisation, is becoming increasingly relevant in environmental management. The wastes bioconversion by the black soldier fly larva (BSFL) has two potential advantages: the larvae can convert the carbon and nitrogen in the biomass waste, and improve the properties of the substrate to reduce the loss of gaseous carbon and nitrogen. In the present study, the conversion rate of carbon, nitrogen and the emissions of greenhouse gases and NH3 during BSFL bio-treatment of food waste were investigated under different pH conditions. The results showed that the pH of the raw materials is a pivotal parameter affecting the process. The average wet weight of harvested BSFL was 13.26-95.28 mg/larva, with about 1.95-13.41% and 5.40-18.93% of recycled carbon and nitrogen from substrate at a pH from 3.0 to 11.0, respectively. Furthermore, pH is adversely correlated with CO2 emissions, but positively with NH3 emissions. Cumulative CO2, NH3, CH4 and N2O emissions at pH ranging from 3.0 to 11.0 were 88.15-161.11 g kg-1, 0.15-1.68 g kg-1, 0.19-2.62 mg kg-1 and 0.02-1.65 mg kg-1, respectively. Compared with the values in open composting, BSFL bio-treatment of food waste could lead greenhouse gas (especially CH4 and N2O) and NH3 emissions to decrease. Therefore, a higher pH value of the substrate can increase the larval output and help the mitigation of greenhouse gas emissions.

Probing the interaction of Paenibacillus larvae bacteriophage as a biological agent to control the american foulbrood disease in honeybee.

American foulbrood (AFB) is a harmful honeybee disease primarily caused by Paenibacillus larvae. The study aims to isolate and identify the AFB causative agent P. larvae and their specific phages to use as a new biological method for AFB disease control. Eight apiaries were inspected for AFB infections. Symptoms of diseased brood comb, were odd brood cells with soft brown decayed brood amongst healthy brood, were identified in the field and demonstrated the prevalence of AFB in every apiary. Three P. larvae isolates were identified using traditional techniques using a 452-bp PCR amplicon specific to the bacterial 16SrRNA gene and was compared between Paenibacillus isolates. Additionally, specific phages of P. larvae strains were applied to examine their efficiency in reducing the infection rate under the apiary condition. The infection rate was reduced to approximately 94.6 to 100 % through the application of a phage mixture, as opposed to 20 to 85.7 % when each phage was administered individually or 78.6 to 88.9 % when antibiotic treatment was implemented. Histological studies on phage-treated bee larvae revealed some cells regaining normal shape, with prominent nuclei and microvilli. The gastrointestinal tract showed normal longitudinal and circular muscles, unlike bee larvae treated with bacterial strains with abnormal and destroyed tissues, as shown by the basement membrane surrounding the mid-gut epithelium. Phage techniques exhibited promise in resolving the issue of AFB in honeybees due to their ease of application, comparatively lower cost, and practicality for beekeepers in terms of laboratory preparation.

The influence on carbon, nitrogen recycling, and greenhouse gas emissions under different C/N ratios by black soldier fly.

Currently, sustainable utilization, including recycling and valorization, is becoming increasingly popular in waste management. Black soldier fly larvae (BSFL) can convert the carbon (C) and nitrogen (N) from organic waste into biomass and improve properties of the substrate to reduce greenhouse gas and NH3 emissions. In this study, the recycling of C and N and the emissions of greenhouse gas and NH3 during BSFL bio-treatment of mixtures of pig manure and corncob were investigated under different C/N ratios. The results indicated that initial C/N ratios of feedstock are a crucial parameter affecting the biomass generation of larvae. The BSFL recycled approximately 4.17-6.61% of C and 17.45-23.73% of N from raw materials under different C/N ratios. Cumulative CO2, CH4, NH3, and N2O emissions at the different C/N ratios ranging from 15 to 35 were 107.92-151.68, 0.08-0.76, 0.14-1.17, and 0.91-1.18 mg kg-1, respectively. Compared with conventional composting, BSFL treatment could reduce the total greenhouse gas emissions by over 90%. The study showed that bio-treatment of mixtures of pig manure and corncob with a proper C/N ratio by BSFL could become an avenue to achieve higher nutrient recycling, which is an eco-friendly process.

Effect of moisture content on greenhouse gas and NH3 emissions from pig manure converted by black soldier fly.

The effects of different moisture contents on greenhouse gas (GHG) emissions from pig manure (PM) digested by black soldier fly larvae (BSFL) as well as the accompanying changes of nitrogen and carbon contents in gaseous emissions and residues were studied. A mixture of PM and corncob at the ratio of 2.2:1 was prepared with a moisture content of 45%. Then, distilled water was added to adjust the moisture contents of the mixture to 55%, 65%, 75% and 85%, respectively. The prepared mixtures were digested by BSFL for eight days. The results indicated that BSFL could reduce CH4, N2O and NH3 emissions respectively by 72.63-99.99%, 99.68%-99.91% and 82.30-89.92%, compared with conventional composting, while CO2 emissions increased potentially due to BSFL metabolism. With increasing moisture content, the cumulative CH4 emissions increased, while cumulative NH3 emissions peaked at 55% moisture content and then decreased. Interestingly, the tendency of total cumulative CO2 emissions was consistent with that of the total weight of BSFL. The total GHG emissions were about only 1% those from of traditional composting at the optimum moisture content (75%), which was the most favorable for the growth of BSFL. The nitrogen and carbon contents of BSFL content in all treatments accounted for 1.03%-12.67% and 0.25%-4.68% of the initial contents in the raw materials, respectively. Moreover, the residues retained 71.12%-90.58% carbon and 67.91%-80.39% nitrogen of the initial raw materials. Overall, our results suggest that BSFL treatment is an environment-friendly alternative for decreasing CH4, N2O and NH3 emissions as well as reducing global warming potential (GWP).