Managing high fiber food waste for the cultivation of black soldier fly larvae

Improved nutritional and antioxidant properties of black soldier fly larvae reared on spent coffee grounds and blood meal by-products

Black Soldier Fly larvae (BSFL) are a promising and sustainable alternative to obtain proteins. Due to their high growth rate and ability to use different substrates as feeding stocks, BSFL can be also used to valorize food waste. Thus, the aim of this research was to unravel the potential use of Spent Coffee Grounds (SCG) and blood meal alone or mixed as feedstocks for BSFL and the nutritional changes for BSFL meal, especially after simulated human in vitro digestion and fermentation. Chicken feed was used as a control. Chicken feed showed the highest BSFL growth (P < 0.05) compared with blood meal and the mix made of blood meal and SCG; the latter caused the lowest growth. The meal obtained from BSFL fed with blood meal had the highest protein content, as well as the highest levels of short chain fatty acids (SCFAs) produced after in vitro fermentation by the human gut microbiota. On the other hand, the meal from larvae fed with SCG showed higher antioxidant capacity than the others in the DPPH, FRAP and ABTS assays. The digestibility of macronutrients, release of antioxidant capacity and production of SCFAs of the BSFL meal were improved when using these substrates, compared to chicken feed.

Physical pretreatment of three biowastes to improve black soldier fly larvae bioconversion efficiency

Black soldier fly larvae (BSFL, Hermetia illucens (L.)) are recognized for efficient biowaste reduction while yielding valuable proteins and fats for animals. However, lignocellulosic fibers in biowastes are difficult to digest by biowaste and larval digestive tract microorganisms as well as the larvae themselves. This study investigated two biowaste physical pretreatments (thermal, mechanical) for improving BSFL processing of fibrous biowastes. Cow manure, spent grain, and grass clippings were thermally pretreated at 90 °C for three durations (0.5, 1 and 4 h). Contrary to expectations, thermal pretreatment resulted in either no improvement or decreased larval performance on all substrates, regardless of treatment duration. In contrast, mechanical pretreatment of spent grain and grass clippings, involving milling with three screen sizes (0.5, 1 and 2 mm) showed promising results. Specifically, bioconversion rates on 0.5 mm-milled spent grain and grass clippings increased by 0-53 % and 25-44 % dry mass, respectively compared to untreated. Additionally, larval protein conversion increased by 41 % and 23 % on spent grain and grass clippings, respectively. However, mechanical pretreatment did not affect fiber degradation by larval conversion, as hemicellulose decreased by 25 % and 75 % for spent grain and grass clippings, respectively, regardless of particle size. Particle size reduction influenced substrate microbial respiration (CO2 mg/min), with 0.5-mm milled grass clippings exhibiting higher respiration compared to untreated, although this effect was not observed for spent grain. This study highlights mechanical pretreatment's potential in enhancing BSFL bioconversion of fibrous biowastes and the importance of understanding substrate physical properties influencing substrate microorganisms and BSFL.

Black soldier fly larvae recruit functional microbiota into the intestines and residues to promote lignocellulosic degradation in domestic biodegradable waste

Lignocellulose is an important component of domestic biodegradable waste (DBW), and its complex structure makes it an obstacle in the biological treatment of DBW. Here, we identify black soldier fly larvae (Hermetia illucens L., BSFL) as a bioreactor for lignocellulose degradation in DBW based on their ability to effectively recruit lignocellulose-degrading bacteria. This study mainly examined the lignocellulose degradation, dynamic succession of the microbial community, gene expression of carbohydrate-active enzymes (CAZymes), and co-occurrence network analysis. Investigation of lignocellulose degradation by BSFL within 14 days indicated that the lignocellulose biodegradation rate in the larvae treatment (LT, 26.5%) group was higher than in natural composting (NC, 4.06%). In order to gain a more comprehensive understanding of microbiota, we conducted metagenomic sequencing of larvae intestines (LI), along with the LT and NC. The relative abundance of lignocellulose-degrading bacteria and CAZymes genes in LT and LI were higher than those in NC based on metagenomics sequencing. Importantly, genes coding cellulase and hemicellulase in LI were 3.36- and 2.79-fold higher, respectively, than that in LT, while the ligninase genes in LT were 1.82-fold higher than in LI. A co-occurrence network analysis identified Enterocluster and Luteimonas as keystone taxa in larvae intestines and residues, respectively, with a synergistic relationship to lignocellulose-degrading bacteria. The mechanism of recruiting functional bacteria through the larvae intestines promoted lignocellulose degradation in DBW, improving the efficiency of BSFL biotechnology and resource regeneration.

Feasibility of housefly larvae-mediated vermicomposting for recycling food waste added digestate as additive

The development of methods for the efficient treatment and application of food waste digestate is an important research goal. Vermicomposting via housefly larvae is an efficient way to reduce food waste and achieve its valorization, however, studies on the application and performance of digestate in vermicomposting are rarely. The present study aimed to investigate the feasibility of the co-treatment of food waste and digestate as an additive via larvae. Restaurant food waste (RFW) and household food waste (HFW) were selected to assess the effects of waste type on vermicomposting performance and larval quality. Waste reduction rates of 50.9%-57.8% were observed in the vermicomposting of food waste mixed with digestate at a ratio of 25%, which were slightly lower than those for treatments without the addition of digestate (62.8%-65.9%). The addition of digestate increased the germination index, with a maximum value of 82% in the RFW treatments with 25% digestate, and decreased the respiration activity, with a minimum value of 30 mg-O₂/g-TS. The larval productivity of 13.9% in the RFW treatment system with a digestate rate of 25% was lower that without digestate (19.5%). Materials balance shows that larval biomass and metabolic equivalent had decreasing trends as the amount of digestate increased and HFW vermicomposting exhibited lower bioconversion efficiency than that of RFW treatment system regardless of the addition of digestate. These results suggest that mixing digestate at a low ratio (25%) during vermicomposting of food waste especially RFW could lead to considerable larval biomass and generate relatively stable residues.

Exploration of Converting Food Waste into Value-Added Products via Insect Pretreatment-Assisted Hydrothermal Catalysis

The environmental burden of food waste (FW) disposal coupled with natural resource scarcity has aroused interest in FW valorization; however, transforming FW into valuable products remains a challenge because of its heterogeneous nature. In this study, a two-stage method involving black soldier fly (BSF)-based insect pretreatment and subsequent hydrothermal catalysis over a single-atom cerium-incorporated hydroxyapatite (Ce-HAP) was explored to convert FW into high added-value furfurals (furfural and 5-hydroxymethylfurfural). FW consisting of cereal, vegetables, meat, eggs, oil, and salt was initially degraded by BSF larvae to generate homogeneous BSF biomass, and then, crucial parameters impacting the conversion of BSF biomass into furfurals were investigated. Under the optimized conditions, 9.3 wt % yield of furfurals was attained, and repeated trials confirmed the recyclability of Ce-HAP. It was proved that the revenue of furfural production from FW by this two-stage method ranged from 3.14 to 584.4 USD/tonne. This study provides a potential technical orientation for FW resource utilization.

Determination of black soldier fly larvae performance for oil palm based waste reduction and biomass conversion

Oil palm biomass, such as empty fruit bunches and palm kernel meal, has low digestibility. Thus, a suitable bioreactor is urgently needed to efficiently convert oil palm biomass into high-value products. The polyphagous black soldier fly (BSF, Hermetia illucens) has gained global attention for its role in biomass conversion. However, there is scarce information on the ability of the BSF to sustainably manage highly lignocellulosic matter, such as oil palm empty fruit bunches (OPEFB). Therefore, this study aimed to investigate the performance of the black soldier fly larvae (BSFL) in oil palm biomass management. Several formulations were fed to the BSFL five days after hatching (DAH), and the effects on oil palm biomass-based substrate waste reduction and biomass conversion were analyzed. Furthermore, the resulting growth parameters correlating to the treatments were evaluated, including feed conversion rate (FCR), survival rates, and developmental rates. The most optimal results were obtained by mixing 50% of palm kernel meal (PKM) with 50% of coarse oil palm empty fruit bunches (OPEFB), resulting in an FCR of 3.98 ± 0.08 and a survival rate of 87% ± 4.16. Moreover, this treatment is a promising method for waste reduction (11.7% ± 6.76), with a bioconversion efficiency (corrected for residue) of 71.5% ± 1.12. In conclusion, the study findings indicate that incorporating PKM into OPEFB substrate can substantially alter BSFL growth, reduce oil palm waste, and optimize biomass conversion.

Evaluation of ammonia pretreatment of four fibrous biowastes and its effect on black soldier fly larvae rearing performance

Biowaste treatment with black soldier fly larvae (BSFL, Hermetia illucens L.) can promote a more sustainable food system by reusing nutrients that would otherwise be wasted. However, many agri-food wastes and byproducts are typically high in lignocellulosic fibers (i.e., cellulose, hemicellulose, and lignin), making it resistant to efficient larval and/or microbial degradation. Ammonia pretreatment could be used to partially degrade lignocellulose, making the biowaste more easily degradable by the larvae and/or microorganisms. This study evaluated ammonia pretreatment for lignocellulose degradation and its effect on BSFL performance on four fibrous biowastes: brewers spent grain, cow manure, oat pulp, and grass clippings. First, the optimal ammonia dose (1 % or 5 % dry mass) and pretreatment time (three or seven days) were assessed by measuring fibers after treatment and further examined using Fourier transform infrared spectroscopy (FTIR) spectra and scanning electron microscopy (SEM) images. Second, BSFL rearing performance on ammonia-pretreated substrates was assessed with a 9-day feeding experiment. Three-day pretreatment with 5 % ammonia was chosen as it decreased the total fiber content by 8-23 % for all substrates except cow manure. Contrary to expectations, ammonia pretreatment with all substates decreased BSFL rearing performance metrics by more than half compared to the untreated control. Follow-up experiments suggested that ammonia pretreatment had a dose-dependent toxicity to BSFL. Interestingly, three-day fermentation of cow manure and oat pulp increased bioconversion rate by 25-31 %. This study shows that ammonia pretreatment is not suitable before BSFL rearing. Ammonia toxicity to BSFL and other pretreatments, such as fermentation, should be further studied.

Black Soldier Fly Larva Fat in Broiler Chicken Diets Affects Breast Meat Quality

This study aimed to evaluate the dose-dependent effect of black soldier fly (BFL) larvae fat inclusion in broiler chicken diets on breast meat quality. Four hundred 1-day-old male birds (Ross 308) were assigned to the following four treatments (10 replicates with 10 birds each): HI0, a basal diet without dietary fat inclusion, and HI03, HI06, and HI09, basal diets enriched with 30 g/kg, 60 g/kg, and 90 g/kg of BSF larvae fat, respectively. Principal component analysis showed noticeable differentiation between the selected plant, animal, and insect-origin dietary fats. The BSF fat exhibits a strong relationship with saturated fatty acids (SFAs), resulting in a high concentration of C12:0 and C14:0. The fatty acid (FA) profile in breast muscle obtained from broilers fed diets with increasing insect fat inclusion showed a significant linear effect in terms of C12:0, C15:0, C18:2, C18:3n6, and total FAs. The proportion of dietary insect fat had a quadratic effect on meat color. The water-holding capacity indices have stayed consistent with the meat color changes. Throughout the experiment, favorable growth performance results were noticed in HI06. The present study confirmed that BSF larvae fat negatively affects the n3 level in meat. However, the physicochemical indices related to consumer acceptance were not altered to negatively limit their final decision, even when a relatively high inclusion of insect fat was used.

Physical Properties of Substrates as a Driver for Hermetia illucens (L.) (Diptera: Stratiomyidae) Larvae Growth

The growth and nutritional profile of the black soldier fly larvae (BSFL) is usually investigated and compared when the larvae feed on substrates that differ in the chemical composition as well as physical properties. This study compares BSFL growth on substrates that differ primarily in physical properties. This was achieved by using various fibres in the substrates. In the first experiment, two substrates with 20% or 14% chicken feed were mixed with three fibres (cellulose, lignocellulose, or straw). In the second experiment, the growth of BSFL was compared with a 17% chicken feed substrate that additionally contained straw with different particle sizes. We show that the substrate texture properties values did not influence the BSFL growth, but the bulk density of the fibre component did. The substrate mixed with cellulose led to higher larvae growth over time in comparison to substrates with higher bulk density fibres. BSFL grown on the substrate mixed with cellulose reached their maximum weight in 6 days instead of 7. Neither the fibres nor the nutrient level changed the crude protein content of BSFL and the values ranged between 33.5% and 38.3%, but an interaction between the fibre and nutrient level was observed. The size of straw particles in the substrates influenced the BSFL growth and led to a 26.78% difference in Ca concentration, a 12.04% difference in Mg concentration, and a 35.34% difference in P concentration. Our findings indicate that the BSFL-rearing substrates can be optimised by changing the fibre component or its particle size. This can improve the survival rate, reduce the cultivation time needed to reach the maximum weight, and alter the chemical composition of BSFL.

Bioconversion of fruit waste and sewage sludge mixtures by black soldier fly (Diptera: Stratiomyidae) larvae

Bioconversion of fruit waste (FW) and sewage sludge (SS) sludge mixtures into valuable products was investigated using black soldier fly (Hermetia illucens) larvae (BSFL) under a lab-scale trial. For that, five different setups of FW and SS mixtures (100FW; 100SS; 70SS+30FW; 50SS+50FW; 70FW+30SS) were prepared and changes in larval biomass, feed loss, and residual waste physicochemical properties were estimated until the emergence of fly in all waste mixtures. BSFL caused a significant decrease in total organic carbon (11.71-34.79%) and carbon-to-nitrogen ratio (C/N ratio) while the increase in total nitrogen (8.35-123.30%), total phosphorus (17.02-143.36%), and total potassium (19.40-48.87%) contents in the feedstock. The germination index and C/N ratio of frass were below the standards decided for manure quality in a few setups suggesting the non-stability of frass for agronomic applications due to the short duration (20 d) of composting. Larval biomass yield, feed conversion ratio and nutrient mineralization were found to be higher in 50SS+50FW and 70FW+30SS feedstock combinations suggesting their suitability as ideal feedstock for optimal BSFL cultivation. The impact of toxic substances in sewage on BSFL survival, growth and waste stabilization processes, and frass metal enrichment could be investigated in future studies.

Performance evaluation of black soldier fly larvae fed on human faeces, food waste and their mixture

In this study, Black Soldier Fly Larvae (BSFL)-based technology has been proposed and tested for treatment and valorization of human faeces, food waste and a mixture of 75% human faeces with 25% food waste. Experiments were conducted between 15 and 45 °C and 55-75% relative humidity. BSFL's performance for the degradation of the mixed waste was significantly better than their performances when used for the degradation of either human faeces or food waste fed alone, primarily due to the availability of more conducive pH, and better microbial and nutrient balance. The abiotic factors, temperature and relative humidity impacted the decomposition rate and weight gain pattern of BSFL when they were fed on the waste streams. The results showed that the optimum conditions to conduct the proposed BSFL-based treatment was 31-35 °C and 55-75% RH. The protein content in the BSFL was not impacted significantly by the quality of the waste stream, whereas the fat content varied substantially. The abiotic factors also impacted the protein and fat content of BSFL. The investigation led to the estimation of the decomposition rates over a wide range of temperature and relative humidity conditions, which could be useful for the design of large-scale BSFL-based treatment plants.

Statistical optimization of a sustainable fertilizer composition based on black soldier fly larvae as source of nitrogen

In the present work, a statistical optimization of a sustainable coating for core-shell NPK (Nitrogen-Phosphorus-Potassium) fertilizers was investigated. The environmental green coating was enriched in nitrogen using a biomass and renewable source, namely the nitrogen rich fraction of black soldier fly larvae (BSFL) (Hermetia Illucens, Diptera: Stratiomyidae) reared on vegetable waste. A rational approach was proposed with the aim of calculating the best formulation of the coating, considering both its manufacturing behavior, such as adhesion to the core, and its physical properties, such as homogeneity or plasticity. From a circular economy perspective, together with the nitrogen-rich fraction from BSFL (from 51 to 90 wt.%), water and glycerol were considered for the coating formulation in different proportion: from 10 to 32 wt.% and from 0 to 17 wt.% respectively. The Design of Experiments technique was implemented to limit the total number of tests for the coating formulation (18 tests). ANOVA was employed, with the aim of obtaining mathematical models to derive a better precise and objective formulation. The results show that the use of glycerol can be avoided, as well as only a limited amount of water (11 wt.%) is necessary to obtain an optimized coating formulation, thereafter, satisfying the more relevant technological and physical properties for the coating manufacturing.

Black soldier fly full-fat meal in Atlantic salmon nutrition – Part B: Effects on growth performance, feed utilization, selected nutriphysiological traits and production sustainability in pre-smolts

Black soldier larva meal (BSFM) seems to be a competitive protein and fat source for widely used fish meal (FM) and fish oil. Because of the still present problem of overfished seas and oceans for feed purposes, even a low substitution of the mentioned feed materials could have a positive impact on the environment. Due to the specificity of salmon metabolic processes, with particular attention to smoltification and the various requirements for nutrients related to individual stages, it is important to implement similar dietary inclusion levels of innovative feed materials in different life stages of Atlantic salmon. Thus, a holistic approach was undertaken in the cycle of two studies carried out: on fries and pre-smolts. This study aims to evaluate the effect of FM replacement by full-fat BSFM in Atlantic salmon pre-smolt diets on growth performance, feed utilization, somatic indices, histomorphology of intestines, colorimetric assessment and raw meat quality, as well as environmental sustainability. The following groups were applied: CON – without addition of full-fat BSFM and with 30% FM; BSFM5 – with 5% addition of full-fat BSFM and 27.1% FM; BSFM10 – with 10% full-fat BSFM and 24.3% FM; and BSFM15 – with 15% addition of full-fat BSFM and 21.3% FM. The present study showed satisfactory results of BSFM inclusion up to 15% as a replacement for FM in feeds for Atlantic salmon pre-smolts. The present study showed that BSFM is a suitable feed material for Atlantic salmon proper diet balancing and may be used to decrease FM content. The semi-technical application of BSFM containing diets confirmed their effectiveness during the growth phase of Atlantic salmon. According to our results, BSFM can be recommended as an alternative feed component in Atlantic salmon pre-smolt nutrition at levels up to 15%. Simultaneously, insect inclusion significantly improved the environmental sustainability of the rearing process.

Are resource recovery insects safe for feed and food? A screening approach for bioaccumulative trace organic contaminants

Most bioaccumulation assessments select one or several compound classes a priori for analysis performed by either liquid or gas chromatography coupled with mass spectrometry (LC-MS or GC-MS). When organisms are exposed to complex mixtures of trace organic contaminants (TOrCs), targeted chemical assays limit understanding of contaminant profiles in biological tissues and associated risks. We used a semi-quantitative suspect-screening approach to assess the bioaccumulation potential of diverse TOrCs in black soldier fly larvae (BSFL) using almond hulls (by-products of the booming almond industry in California) as test substrates. BSFL digestion is gaining traction as a resource recovery strategy to generate animal feed from low-value organic wastes. We screened almond hulls from six California farms for the presence of 5728 TOrCs using high resolution mass spectrometry. We then categorized the risk potential of 46 TOrCs detected in the hulls based on their predicted bioaccumulation, persistence, and toxicity in order to select two hulls for an in situ BSFL bioaccumulation screening study. We analyzed larvae tissues and feeding substrate initially and after 14 days of growth using targeted, suspect-screening, and nontarget-screening methods. The survival rate of BSFL in all rearing reactors was greater than 90%, indicating low toxicity of the substrates to BSFL. Esfenvalerate, cyhalothrin, and bifenthrin were the most abundant pyrethroids quantified (81.7 to 381.6 ng/g-dw) in the hulls. Bifenthrin bioaccumulated in BSFL tissues (14-day bioaccumulation factor, BAF, of 2.17 ± 0.24). For nontarget analysis, kendrick mass defect (KMD) analysis of PFAS homologous series revealed hydrogen-substituted perfluoroalkyl carboxylic acids (H-PFCAs) in the hulls and BSFL tissues after growth. Our approach demonstrates the utility of suspect-screening in chemical safety assessments when organic wastes with highly diverse and variable contaminant profiles are used in resource recovery pipelines.

Cardboard supplementation on the growth and nutritional content of black solider fly (Hermetia illucens) larvae and resulting frass

A 10-day trial was conducted to compare the production and fatty acid composition of black soldier fly (Hermetia illucens) larvae (BSFL) when grown without or with cardboard supplementation at 2.2% on a dry weight basis. The final biomass of BSFL or waste reduction was not significantly impacted by cardboard. The fatty acids of C10 and C22:6n-3 were significantly higher in BSFL in the cardboard treatment, but crude lipid significantly reduced. The leftover BSFL frass had significantly higher sulfur, zinc, manganese and boron at the expense of lower nitrogen (91.2% versus 8.73% in control versus cardboard, respectively). These preliminary results appear to indicate that the growth and nutritional value of BSFL were not adversely compromised while the frass can be enhanced by adding relatively small amounts (2.2%) of cardboard. Further studies could be conducted to investigate the implications of higher inclusion levels.

Growth efficiency, intestinal biology, and nutrient utilization and requirements of black soldier fly (Hermetia illucens) larvae compared to monogastric livestock species: a review

In recent years, interest in the larvae of black soldier fly (BSF) (Hermetia illucens) as a sustainable protein resource for livestock feed has increased considerably. However, knowledge on the nutritional and physiological aspects of this insect, especially compared to other conventional farmed animals is scarce. This review presents a critical comparison of data on the growth potential and efficiency of the BSF larvae (BSFL) compared to conventional monogastric livestock species. Advantages of BSFL over other monogastric livestock species includes their high growth rate and their ability to convert low-grade organic waste into high-quality protein and fat-rich biomass suitable for use in animal feed. Calculations using literature data suggest that BSFL are more efficient than broilers, pigs and fish in terms of conversion of substrate protein into body mass, but less efficient than broilers and fish in utilization of substrate gross energy to gain body mass. BSFL growth efficiency varies greatly depending on the nutrient quality of their dietary substrates. This might be associated with the function of their gastrointestinal tract, including the activity of digestive enzymes, the substrate particle characteristics, and their intestinal microbial community. The conceived advantage of BSFL having an environmental footprint better than conventional livestock is only true if BSFL is produced on low-grade organic waste and its protein would directly be used for human consumption. Therefore, their potential role as a new species to better close nutrient cycles in agro-ecological systems needs to be reconsidered, and we conclude that BSFL is a complementary livestock species efficiently utilizing organic waste that cannot be utilized by other livestock. In addition, we provide comparative insight into morpho-functional aspects of the gut, characterization of digestive enzymes, gut microbiota and fiber digestion. Finally, current knowledge on the nutritional utilization and requirements of BSFL in terms of macro- and micro-nutrients is reviewed and found to be rather limited. In addition, the research methods to determine nutritional requirements of conventional livestock are not applicable for BSFL. Thus, there is a great need for research on the nutrient requirements of BSFL.

Growth and Fatty Acid Composition of Black Soldier Fly Hermetia illucens (Diptera: Stratiomyidae) Larvae Are Influenced by Dietary Fat Sources and Levels

A 16-day rearing trial was performed to investigate the influence of two supplemental levels (5% and 10%) of six dietary fat sources (linseed oil, peanut oil, coconut oil, soybean oil, lard oil and fish oil) on the growth, development and nutrient composition of black solider fly larvae. Our results demonstrated that the pre-pupa rate of larvae was linearly influenced by dietary C18:0, C18:3n-3 and C18:2n-6 content (pre-pupa rate = 0.927 × C18:0 content + 0.301 × C18:3n-3 content-0.258 × C18:2n-6 content p < 0.001)), while final body weight was linearly influenced by that of C16:0 (final body weight = 0.758 × C16:0 content, p = 0.004). Larval nutrient composition was significantly affected by dietary fat sources and levels, with crude protein, fat and ash content of larvae varying between 52.0 and 57.5, 15.0 and 23.8, and 5.6 and 7.2% dry matter. A higher level of C12:0 (17.4-28.5%), C14:0 (3.9-8.0%) and C16:1n-9 (1.3-4.3%) was determined in larvae fed the diets containing little of them. In comparison, C16:0, C18:1n-9, C18:2n-6 and C18:3n-3 proportions in larvae were linearly related with those in diets, with the slope of the linear equations varying from 0.39 to 0.60. It can be concluded that sufficient C16:0, C18:0 and C18:3n-3 supply is beneficial for larvae growth. Larvae could produce and retain C12:0, C14:0, and C16:1n-9 in vivo, but C16:0, C18:1n-9, C18:2n-6 and C18:3n-3 could only be partly incorporated from diets and the process may be enhanced by a higher amount of dietary fat. Based on the above observation, an accurately calculated amount of black soldier fly larvae could be formulated into aquafeed as the main source of saturated fatty acids and partial source of mono-unsaturated and poly-unsaturated fatty acids to save fish oil.

A Review of Pretreatment Methods to Improve Agri-Food Waste Bioconversion by Black Soldier Fly Larvae

As the world population increases, food demand and agricultural activity will also increase. However, ~30–40% of the food produced today is lost or wasted along the production chain. Increasing food demands would only intensify the existing challenges associated with agri-food waste management. An innovative approach to recover the resources lost along the production chain and convert them into value-added product(s) would be beneficial. An alternative solution is the use of the larvae of the black soldier fly (BSFL), Hermetia illucens L., which can grow and convert a wide range of organic waste materials into insect biomass with use as animal feed, fertilizer and/or bioenergy. However, the main concern when creating an economically viable business is the variability in BSFL bioconversion and processing due to the variability of the substrate. Many factors, such as the nutritional composition of the substrate heavily impact BSFL development. Another concern is that substrates with high lignin and cellulose contents have demonstrated poor digestibility by BSFL. Studies suggest that pretreatment methods may improve the digestibility and biodegradability of the substrate by BSFL. However, a systematic review of existing pretreatment methods that could be used for enhancing the bioconversion of these wastes by BSFL is lacking. This paper provides a state-of-the-art review on the potential pretreatment methods that may improve the digestibility of substrates by BSFL and consequently the production of BSFL. These processes include but are not limited to, physical (e.g., mechanical and thermal), chemical (alkaline treatments), and biological (bacterial and fungal) treatments.

Conversion of Mixtures of Soybean Curd Residue and Kitchen Waste by Black Soldier Fly Larvae (Hermetia illucens L.)

The production of insect biomass from organic waste is a major challenge in terms of reducing the environmental impacts of waste and maintaining feed and food security. The feasibility of the co-conversion of soybean curd residue (SCR) and kitchen waste (KW) to breed black soldier fly (BSF, Hermetia illucens) larvae was evaluated so as to enhance biomass conversion efficiency and supply animal feed and allow it to be used in biodiesel production. Co-digestion was found to significantly increase larval yield, bioconversion rate, and bioaccumulation of lipid. Partial least squares regression showed that the conversion of 30% SCR with 70% KW is an appropriate proportion. The appropriate performance parameters of BSF were: survival rate (98.75%), prepupal rate (88.61%), larval biomass (30.32 g fresh and 11.38 g dry mass), bioconversion rate (18.45%), efficiency conversion of ingested food (ECI) (28.30%), and FCR (2.51). Our results show that conversion of mixtures (e.g., SCR with KW) by BSF larvae (BSFL) could play an important role in various organic materials management.

Valorization of Macroalgae through Fermentation for Aquafeed Production: A Review

The increased development of aquaculture has resulted in increased demand for high-protein aquafeed. An increased demand for high-protein aquafeed means an increase in exploitation of unsustainable protein sources such as fishmeal for aquafeed production. Thus, alternative protein sources such as fermented macroalgae is explored. Fermented macroalgae had been tested as aquaculture diets in some studies, but with limited coverage in relation to aquaculture. Therefore, this review provides a new perspective regarding their nutritional qualities as aquaculture diets, and their impacts on growth performances of aquaculture animals.

Predicting black soldier fly larvae biomass and methionine accumulation using a kinetic model for batch cultivation and improving system performance using semi-batch cultivation

Global demand for poultry and associated feed are projected to double over the next 30 years. Insect meal is a sustainable alternative to traditional feeds when produced on low-value high-volume agricultural byproducts. Black soldier fly (BSF) larvae (Hermetia illucens L.) are high in protein and contain methionine, an essential amino acid that is critical to poultry health. BSF larvae can be grown on many organic residues, however, larvae growth and quality vary based on feedstock and cultivation processes. Experiments were completed to monitor temporal changes in BSF larvae growth and composition using almond hulls as a growth substrate under batch and semi-batch processes and with varying substrate carbon to nitrogen ratio (C/N). A logistic kinetic growth model was developed to predict larval biomass and methionine accumulations during batch production. Estimated ranges of model parameters for larvae maximum specific growth rate and carrying capacity were 0.017–0.021 h⁻¹ and 9.7–10.7 g larvae kg⁻¹ hulls dry weight, respectively. Methionine content in larvae increased from 11.1 to 17.1 g kg⁻¹ dry weight over a 30-day batch incubation period. Larvae-specific growth and yield increased by 168% and 268%, respectively, when cultivated in a semi-batch compared to a batch process. Increasing C/N ratio from 26 to 40 increased density of methionine content in larvae per unit feedstock by 25%. The findings demonstrate a logistic model can predict larvae biomass accumulation, harvest time can achieve specific methionine contents, and a semi-batch process is more favorable for larvae biomass accumulation compared to a batch process.

Applications of food waste-derived black soldier fly larval frass as incorporated compost, side-dress fertilizer and frass-tea drench for soilless cultivation of leafy vegetables in biochar-based growing media

Black soldier fly (BSF) larval bioconversion can recycle nutrients in organic wastes into larval biomass and frass. While the frass has been commonly marketed as a soil amendment, its usefulness in soilless cultivation remains largely unexplored. Growth experiments were conducted to investigate the effectiveness of surplus food-derived and okara-derived BSF larval frass as an incorporated compost, side-dress fertilizer and frass-tea drench for the cultivation of pak choi and lettuce in waste-wood derived biochar growing media. Pak choi yields from treatments with surplus food-derived frass and biochar at a 10:90 (v/v) ratio and inorganic fertilizer were comparable to those of the control which consisted of soil, peat-based compost and inorganic fertilizer. However, yields decreased with increasing frass incorporation rates owing to high salinity and potentially low oxygen conditions in the growing media. When used as a fertilizer on biochar-coir growing media, the direct application of frass as a side-dress fertilizer was 1.6-6.8 times more effective in promoting lettuce growth than the application as a frass-tea drench. Frass fertilizers derived from surplus food outperformed those derived from okara by 1.3-5.3 times. Lettuce yields were not significantly different between the treatment with surplus food-derived frass applied as a side-dress fertilizer and the control of liquid inorganic fertilizer. Variations in fertilizing potential were attributed to nutrient availability and the presence of plant growth promoting microbes in the growing media. BSF larval frass derived from food waste shows promise in partially replacing unsustainable agricultural inputs for leafy vegetable cultivation, including soil and inorganic fertilizers.

Determining the Black Soldier fly larvae performance for plant-based food waste reduction and the effect on Biomass yield

Management of Municipal solid waste in low-income countries with high population densities such as India has always been a strenuous task. With perpetual advancements, there are many available technologies dealing with waste management such as incineration, pyrolysis and landfill operations. But such technologies are often accompanied with some limitations (operational and maintenance problems) and have negative environmental impacts. In this regard, continuous efforts are currently spent to develop the sustainable technologies for coping with the problems of waste management. Confronted with such problems, BSF larval composting has emerged as a green approach for waste management which outshines the various current technologies. However, it is not widely explored and therefore in the present study, BSF larval treatment efficiency has been tested against different types of food waste treatments viz., mix food waste (T1), restaurant waste (T2), fruit waste (T3), and vegetable waste (T4). We have also evaluated the Biomass Conversion Ratio (BCR) of BSF larvae. The waste reduction efficiency was found to be 72% for T1 followed by T3 and T2 whereas the efficiency was least for T4 corresponding to lower BCR comparatively. BCR obtained for T1 treatment was almost 25% which was exceptionally high in comparison to other published studies. The highest waste reduction efficiency and the BCR values for T1 may be attributed to appropriately balanced food nutrition and C/N ratio Therefore, it may be concluded that substrate type and its nutritional value strongly determines the growth and development of larva influencing the waste ingestion rate.

Method for Zero-Waste Circular Economy Using Worms for Plastic Agriculture: Augmenting Polystyrene Consumption and Plant Growth

Polystyrene (PS) is one of the major plastics contributing to environmental pollution with its durability and resistance to natural biodegradation. Recent research showed that mealworms (Tenebrio molitor) and superworms (Zophobas morio) are naturally able to consume PS as a carbon food source and degrade them without observable toxic effects. In this study, we explored the effects of possible food additives and use of worm frass as potential plant fertilizers. We found that small amounts of sucrose and bran increased PS consumption and that the worm frass alone could support dragon fruit cacti (Hylocereus undatus) growth, with superworm frass in particular, supporting better growth and rooting than mealworm frass and control media over a fortnight. As known fish and poultry feed, these findings present worms as a natural solution to simultaneously tackle both the global plastic problem and urban farming issue in a zero-waste sustainable bioremediation cycle.

Soil Application of Almond Residue Biomass Following Black Soldier Fly Larvae Cultivation

Insect farming has the potential to transform abundant residual biomass into feed that is compatible with non-ruminant animal production systems. However, insect cultivation generates its own by-products. There is a need to find valuable and sustainable applications for this material to enable commercial-scale insect farming. Soil application of by-products, which may be either basic broadcasting incorporation or part of a sustainable soil borne pest management practice, such as biosolarization, could offer an agricultural outlet. The objective of this study was to assess the potential of applying black soldier fly larvae (BSFL)-digested substrate as soil amendment for soil biosolarization and evaluate its impact on soil health. Sandy loam (SL) and sandy clay loam (CL) soils amended with BSFL-digested almond processing residues, i.e., spent pollinator hulls (SPH), at 2% dry weight (dw) were incubated under aerobic and anaerobic conditions for 15 days under a daily fluctuating temperature-interval (30–50°C). The microbial respiration, pH, electrical conductivity, volatile fatty acids, macronutrients, and germination index using radish seeds (Raphanus sativus L.) were quantified to assess the soil health after amendment application. Incubation showed a statistically significant (p &lt; 0.05) increase in electrical conductivity related to amendment addition and a decrease potentially linked to microbiological activity, i.e., sequestering of ions. Under aerobic conditions, SPH addition increased the CO2-accumulation by a factor of 5–6 compared to the non-amended soils in SL and CL, respectively. This increase further suggests a higher microbiological activity and that SPH behaves like a partially stabilized organic material. Under anaerobic conditions, CO2-development remained unchanged. BSFL-digested residues significantly increased the carbon, nitrogen, C/N, phosphate, ammonium, and potassium in the two soil types, replenishing soils with essential macronutrients. However, greenhouse trials with lettuce seeds (Lactuca sativa) lasting 14 days resulted in a decrease of the biomass by 44.6 ± 35.4 and 35.2 ± 25.3% for SL and CL, respectively, compared to their respective non-amended soil samples. This reduction of the biomass resulted from residual phytotoxic compounds, indicating that BSFL-digested SPH have the potential to be used for biosolarization and as soil amendments, depending on the concentration and mitigation strategies. Application and environmental conditions must be carefully selected to minimize the persistence of soil phytotoxicity.

Growth and metabolic performance of black soldier fly larvae grown on low and high-quality substrates

We have measured growth and respiration in black soldier fly (BSF) larvae fed with mixtures of a low-quality substrate (degassed sludge, DS), and a high-quality substrate (chicken feed, CF) in order to elucidate how substrate quality affect larval metabolism and feed conversion into new biomass. The BSF larvae grew faster and became larger the higher the content of CF was in the substrate. Growth followed a sigmoidal curve from where the specific growth rate was determined and compared to measured specific respiration rates, in order to estimate costs of growth, maintenance metabolism, rates of feed assimilation, and net growth efficiency. Specific feed assimilation rates were similar on all substrate mixtures. Maximal specific growth rates were also affected only little unless the larvae were grown in pure DS. In contrast, the cost of growth and the maintenance metabolism were larger the higher the proportion of DS was. High specific growth rates were, in addition, sustained for shorter periods of the time the more DS was included in the substrate mixtures. In effect, higher proportions of the assimilated feed were spent on respiratory purposes instead of being converted into larval biomass and the net growth efficiency decreased the more DS was included in the substrate mixtures. We conclude that substrate quality may affect the conversion of feed into new biomass via alterations of the metabolic performance of BSF larvae and thereby the overall performance of BSF larval cultures.

Rethinking organic wastes bioconversion: Evaluating the potential of the black soldier fly (Hermetia illucens (L.)) (Diptera: Stratiomyidae) (BSF)

Population growth and unprecedented economic growth and urbanization, especially in low- and middle-income countries, coupled with extreme weather patterns, the high-environmental footprint of agricultural practices, and disposal-oriented waste management practices, require significant changes in the ways we produce food, feed and fuel, and manage enormous amounts of organic wastes. Farming insects such as the black soldier fly (BSF) (Hermetia illucens) on diverse organic wastes provides an opportunity for producing nutrient-rich animal feed, fuel, organic fertilizer, and biobased products with concurrent valorization of wastes. Inclusion of BSF larvae/pupae in the diets of poultry, fish, and swine has shown promise as a potential substitute of conventional feed ingredients such as soybean meal and fish meal. Moreover, the bioactive compounds such as antimicrobial peptides, medium chain fatty acids, and chitin and its derivatives present in BSF larvae/pupae, could also add values to the animal diets. However, to realize the full potential of BSF-based biorefining, more research and development efforts are necessary for scaling up the production and processing of BSF biomass using more mechanized and automated systems. More studies are also needed to ensure the safety of the BSF biomass grown on various organic wastes for animal feed (also food) and legalizing the feed application of BSF biomass to wider categories of animals. This critical review presents the current status of the BSF technology, identifies the research gaps, highlights the challenges towards industrial scale production, and provides future perspectives.

Prospects of insects as food and feed

In the last 10 years, the interest to use insects as food and feed has increased exponentially. In tropical zones, insects are a common food item as they are more readily available as food in nature than in other climate zones. However, if we want to promote insects as food and feed, harvesting from nature is not an option and the farming of these animals is required. This can be done in environmentally controlled facilities. Insects are not only nutritionally excellent food; they may also have health benefits. When using organic side streams as substrate, chemical and biological contaminants need to be considered. People in western countries are not used to eating insects, and therefore, strategies to “convince” consumers of their hygienic safety, environmental sustainability, and tastiness are necessary. The insect sector is maturing fast, but still faces many challenges, which can only be met when all stakeholders cooperate closely.

In-Situ Yeast Fermentation Medium in Fortifying Protein and Lipid Accumulations in the Harvested Larval Biomass of Black Soldier Fly

Recently, worldwide researchers have been focusing on exploiting of black soldier fly larval (BSFL) biomass to serve as the feed mediums for farmed animals, including aquaculture farming, in order to assuage the rising demands for protein sources. In this study, yeast was introduced into coconut endosperm waste (CEW) whilst serving as the feeding medium to rear BSFL in simultaneously performed in situ fermentation. It was found that at a 2.5 wt% yeast concentration, the total biomass gained, growth rate and rearing time were improved to 1.145 g, 0.085 g/day and 13.5 days, respectively. In terms of solid waste reduction, the inoculation of yeast over 0.5 wt% in CEW was able to achieve more than 50% overall degradation, with the waste reduction indexes (WRIs) ranging from 0.038 to 0.040 g/day. Disregarding the concentration of yeast introduced, the protein productivity from 20 BSFL was enhanced from only 0.018 g/day (the control) to 0.025 g/day with the presence of yeast at arbitrary concentrations. On the other hand, the larval protein yield was fortified from the control (28%) to a highest value of 35% with the presence of a mere 0.02 wt% yeast concentration. To summarize, the inclusion of a minimal amount of yeast into CEW for in situ fermentation ultimately enhanced the growth of BSFL, as well as its protein yield and productivity.