Treatment of Agro-Industrial Residue and Organic Community Waste Using Black Soldier Fly Larvae: Overall Performance Assessment

Abstract

The growing global population and rising organic waste generation necessitate innovative and sustainable waste management solutions. This study investigated the potential of black soldier fly larvae (BSFL) as a bioconversion agent for agro-industrial and community organic waste, with an emphasis on optimizing substrate composition for enhanced treatment performance of BSFL. Six rearing substrates were formulated by mixing brewery waste, vegetable and fruit waste, food waste, and sugar filter cake in varying ratios. The performance of BSFL was assessed using five key performance indicators, and an overall performance score was derived to compare substrate suitability across three dimensions: biomass yield, waste reduction, and larval development time. The results revealed that BSFL survival exceeded 97% for all substrates. The highest waste reduction rate of 67.52% was achieved with a 50:50 mixture of brewery waste and food waste. This mixture also attained an overall performance score of 0.77 out of 1, classified as “good”. In contrast, sugar filter cake proved unsuitable for BSFL rearing due to its low nutritional value. These findings offer practical guidelines for selecting optimal waste mixtures to improve the efficiency of BSFL-based waste management.

1. Introduction

Rapid population growth is intensifying pressure on global food systems and waste management infrastructure. The Food and Agriculture Organization (FAO) reported an increase of approximately 2 billion people between 1990 and 2014, reaching 7.2 billion in 2014, and projects a global population of about 9 billion by 2050 [1]. In low- and middle-income countries, organic waste constitutes roughly 48–81% of municipal solid waste streams [2]. A large share of this material is inadequately managed, creating environmental and public-health risks. Developing scalable, low-cost, and environmentally sound solutions that valorize organic waste is therefore essential. One widely recognized pathway is the use of black soldier fly larvae (BSFL) to convert agro-industrial and community organic waste into value-added products, aligning with circular-economy principles.

BSFL are known for their remarkable ability to efficiently convert organic waste into protein-rich biomass, making them valuable for various applications, including waste management, animal feed production, and even human consumption. Currently, BSFL are being used extensively around the world for the decomposition of organic waste such as animal manure [3], brewery waste [4], food waste, vegetable and fruit waste [5], municipal organic waste [6], commingled municipal solid waste [7], and agro-industrial waste [8], which could be converted into high-quality fertilizers and larval biomass, a substitute protein source for animal feed. In addition to investigating the utilization of individual organic waste in BSFL performance research, the design of BSFL feed formulations from various types of organic waste is another effort to improve growth performance and shorten BSFL development time. This goal can be achieved by developing a balanced BSFL substrate that optimizes the levels of protein, carbohydrates, and fats, which are key nutritional components that greatly influence BSFL performance [9].

A number of studies have sought to determine how to improve BSFL performance to promote a more sustainable organic waste management strategy and a circular economy [10]. According to previous studies, feed nutrition and abiotic factors (such as temperature, relative humidity, substrate aeration, larval density, and light) have an important impact on larval growth and development [11]. Most prior studies have largely concentrated on identifying feed compositions—both individual and mixed waste—that influence BSFL performance as measured by a single performance indicator such as survival rate, growth rate index, larval development time, waste reduction rate, bioconversion rate, feed conversion rate, etc. [12,13]. There have also been studies employing statistical correlation analysis with a single performance indicator between waste composition and BSFL performance [14]. Nonetheless, the performance of BSFL will depend not only on attaining a high waste reduction rate or the shortest larval development time but also on its performance across all other aspects.

To the best of our knowledge, no systematic analysis has been conducted on the overall efficacy of organic waste treatment using BSFL that considers all performance aspects. This study addresses that gap by evaluating BSFL performance on mixed organic substrates using an integrated, multi-metric framework. We formulate six diets from brewery waste, leftover food, vegetable and fruit waste, and sugar-industry filter cake and measure five performance indicators—namely, survival rate, development time, waste reduction rate, bioconversion rate, and feed conversion ratio—while characterizing substrate chemistry, including volatile solids, total organic carbon, total Kjeldahl nitrogen/crude protein, C/N ratio, and lignocellulosic fractions. Our objectives are threefold: to determine how substrate composition, particularly protein/nitrogen content and lignocellulosic profile, influences BSFL performance across all five indicators; to identify formulation archetypes that preferentially enhance waste reduction versus biomass production; and to assess the practical feasibility of using agro-industrial and community organic waste as BSFL rearing substrates for sustainable waste-to-resource conversion. The findings aim to inform substrate-formulation guidelines that advance sustainable waste management, support circular-economy outcomes, and help meet growing demand for alternative protein sources.

2. Results and Discussion

2.1. Nutrient Composition of the Substrates

Black soldier fly larvae (BSFL) can thrive on a wide range of organic substrates, though optimal growth depends on both the larval strain and substrate composition. The nutritional content, proximate analysis, and lignocellulosic fractions of the rearing substrates are summarized in

Table 1. Properties of formulated rearing substrates used in this study.

Parameter	BF55	BF73	BV55	BV73	CF55	CF73
pH	4.97 ± 0.14 b	4.66 ± 0.11 a	4.84 ± 0.13 ab	4.76 ± 0.09 ab	5.69 ± 0.11 c	5.85 ± 0.14 c
Moisture content (%)	79.28 ± 0.86 b	80.16 ± 0.52 b	83.88 ± 0.68 d	81.90 ± 0.73 c	75.82 ± 0.38 a	76.72 ± 0.76 a
Volatile solid (%) db	88.22 ± 0.70 c	89.46 ± 0.78 d	87.08 ± 0.79 c	90.01 ± 0.60 d	75.34 ± 0.18 b	72.73 ± 0.68 a
Total organic carbon (%)	46.41 ± 0.16 c	47.72 ± 0.05 d	50.54 ± 0.32 f	50.19 ± 0.03 e	38.28 ± 0.18 b	36.33 ± 0.15 a
Total nitrogen (%)	3.79 ± 0.02 d	4.33 ± 0.02 e	3.65 ± 0.09 c	4.25 ± 0.05 e	2.31 ± 0.04 b	2.20 ± 0.06 a
Crude protein (%)	23.69 ± 0.14 d	27.04 ± 0.14 e	22.78 ± 0.57 c	26.56 ± 0.32 e	14.44± 0.25 b	13.74 ± 0.38 a
C/N ratio	12.25 ± 0.10 b	11.03 ± 0.19 a	13.87 ± 0.12 c	11.84 ± 0.30 b	16.86 ± 0.76 d	16.53 ± 0.36 d
Cellulose (%)	7.99 ± 0.08 a	10.68 ± 0.08 b	14.63 ± 0.27 c	14.66 ± 0.15 c	21.20 ± 0.15 d	29.18 ± 0.27 e
Hemicellulose (%)	27.47 ± 0.21 d	31.27 ± 0.19 f	25.62 ± 0.43 c	30.16 ± 0.28 e	20.26 ± 0.24 a	21.17 ± 0.17 b
Lignin (%)	2.16 ± 0.01 b	2.69 ± 0.05 c	4.41 ± 0.04 e	4.04 ± 0.01 d	0.89 ± 0.02 a	0.91 ± 0.01 a

db = dry basis. Values within rows marked with same letters are not significant different (p < 0.05). Value presented are mean ± standard error (se) (n = 3).

.

The pH of the rearing substrate significantly influences BSFL growth and development. In this study, pH values ranged from 4.66 to 5.85, reflecting the acidic nature of the raw materials. Fruits and vegetables contribute organic acids such as citric, malic, and oxalic acids [15], while brewery waste introduces lactic and acetic acids from fermentation. Filter cake, derived from sugar refining, also contains organic acids. This acidity can enhance nutrient solubility and uptake, but it may also mobilize compounds that are detrimental to larval health.

Moisture content affects microbial activity, which breaks down organic matter and makes nutrients accessible to larvae. Inadequate moisture can reduce substrate carbon availability and impair larval survival as microorganisms convert carbon to CO₂ [16]. Excess moisture, on the other hand, may compact the substrate and hinder the movement and feeding of larvae. In this study, moisture content (MC) was not pre-standardized; MC ranged from 75.82% to 83.88% (mean ≈ 79.6%, SD ≈ 3.05%). CF substrates tended to lie at the lower end (~76–77%), consistent with mechanical dewatering, while blends containing fruit and vegetable waste were higher (~80–84%), in line with their naturally high water content. As MC was not standardized, we acknowledge this as a limitation and interpret performance outcomes accordingly.

The volatile solid (VS) contents quantify the organic fraction of a substrate, with higher values generally indicating greater nutrient availability. A VS range of 70–90% is recommended for effective BSFL rearing [17]. In this study, VS content ranged from 72.73% to 90.01%. BF and BV substrates had high VS contents (88–90%) due to their rich organic material. Conversely, CF substrates had lower VS contents (72–75%), with filter cake contributing approximately 60%, which is notably lower than other organic waste investigated in the current study.

The Carbon-to-Nitrogen (C/N) ratio indicates the nutritional quality of a substrate. In this study, the C/N ratio varied between 11.03 and 16.86. The CF substrates had a higher C/N ratio due to their lower crude protein content in the filter cake (about 13%) compared to brewery waste (approximately 32%). As a result, substrates containing brewery waste (BF and BV) had a lower C/N ratio, suggesting they were more suitable for larval development.

Hemicellulose, cellulose, and lignin are the three primary components of plant cell walls, each exhibiting distinct properties that influence their digestibility by BSFL [18]. A balanced ratio of cellulose and hemicellulose in the rearing substrate can support the growth and development of BSFL by providing essential nutrients and energy sources. Understanding these differences is crucial for optimizing the growth and development of BSFL, particularly in waste bioconversion processes. The composition of lignocellulosic materials in the studied rearing substrates is compared in Figure 1.

Hemicellulose, a branched heteropolysaccharide composed of various sugar monomers, is less crystalline and therefore more susceptible to hydrolysis. This trait makes hemicellulose an effective energy source for BSFL, supporting higher growth rates when included in the diet. In contrast, cellulose is a linear polymer of glucose linked by β-1,4 glycosidic bonds; its high crystallinity resists enzymatic attack, requiring more time and enzymatic activity for effective digestion. Consistently, BSFL show reduced growth on cellulose-rich substrates [19]. Lignin is a complex aromatic polymer that provides structural integrity to plant cell walls but poses significant challenges for degradation due to its intricate structure and high resistance to enzymatic breakdown. Consequently, high lignin content in substrates can markedly diminish the overall digestibility of feed, leading to slower growth rates in BSFL [20]. Prior research underscores the importance of optimizing substrate composition—particularly by increasing hemicellulose content and applying pretreatments to mitigate lignin recalcitrance—in improving the processing of lignin-rich substrates [21]. Such strategies can significantly enhance bioconversion efficiency, positioning BSFL as a sustainable option for organic waste management and nutrient recycling.

2.2. BSFL Rearing Performance Evaluation Using Five Performance Indicators

In this study, substrate quality and suitability were assessed using five performance indicators—namely, survival rate, development time, waste reduction rate, bioconversion rate, and feed conversion ratio, as displayed in

Table 2. BSFL rearing performance of different substrates.

Substrate	Survival Rate (%)	Development Time * (Days)	Waste Reduction Rate (%)	Bioconversion Rate (%)	Feed Conversion Ratio
BF55	99.42 ± 0.58 a	18.83	67.52 ± 0.87 c	10.62 ± 0.20 d	6.03 ± 0.09 a
BF73	98.33 ± 0.82 a	18.12	64.17 ± 0.34 c	9.57 ± 0.16 c	6.29 ± 0.13 a
BV55	98.75 ± 0.92 a	19.17	56.58 ± 0.39 ab	14.03 ± 0.39 f	6.32 ± 0.14 a
BV73	99.00 ± 0.59 a	18.25	57.90 ± 1.85 b	13.12 ± 0.21 e	6.14 ± 0.17 a
CF55	99.08 ± 0.62 a	20.21	59.18 ± 0.97 b	6.78 ± 0.26 a	8.44 ± 0.32 b
CF73	97.83 ± 0.48 a	20.75	54.30 ± 1.57 a	7.89 ± 0.17 b	8.59 ± 0.40 b
ANOVA p-value	0.642	N/A	0.000	0.000	0.000

* Note: Development time was determined by simultaneous termination of all replicate trays per substrate. No within-substrate variance is available; inferential statistics are not applicable. Values within columns marked with same letters are not significant different (p < 0.05). Value presented are mean ± standard error (se) (n = 3).

. The survival rate of BSFL was consistently high across all substrates, ranging from 97.83% to 99.42%. The statistical analysis yielded a p-value of 0.642 (>0.05), indicating no significant differences in survival rates among the six substrates. This suggests that all substrates were equally effective in supporting BSFL survival and growth.

The larval stage of BSFL is divided into early, mid, and late instar stages, each contributing to the overall development time. After hatching from their eggs, BSFL consume significant amounts of organic waste and grow rapidly. During this period, they progress through several instar stages, shedding their exoskeletons to accommodate their increasing size. Prior to pupation, larvae enter the prepupal stage, marked by behavioral and physiological changes as they prepare for metamorphosis into pupae. During this prepupal stage, larvae often cease feeding and exhibit reduced activity [22].

The differences in the development time of BSFL were observed across different substrates. The shortest development time of 18.12 days was recorded with the BF73 substrate, while the longest development time of 20.75 days was observed with the CF73 substrate. Various factors in the rearing substrate influence BSFL growth. Nitrogen-rich substrates high in crude protein significantly enhance larval growth and shorten development time, as proteins and amino acids are essential for BSFL development and metabolism. In our study, the BF and BV substrates (containing brewery waste and vegetable/fruit or food waste) had relatively high total nitrogen (≈3.6–4.3%) and high crude protein levels (22–27% dry matter), which correlate with faster larval development and greater biomass gain. In contrast, the CF substrates (with sugar filter cake) had much lower protein content (~13–14%) and higher fiber (cellulose and lignin) content, explaining why larvae on these diets grew more slowly and took longer to reach the prepupal stage. This finding aligns with prior work showing a positive correlation between dietary protein and both the total final weight of larvae and their growth rate [23] and that nutritionally poor, high-fiber diets can extend BSFL development time. Energy density, reflected in volatile solid (VS) and total organic carbon (TOC) contents, set the ceiling for conversion. BF/BV exhibited high VS (≈87–90%) and TOC (≈46–51%) contents, whereas CF showed lower VS (≈72–75%) and TOC (≈36–38%) contents. Higher VS/TOC contents facilitated feed consumption and conversion, contributing to superior feed efficiency on BF/BV compared with CF.

Fiber quality was then used to partition outcomes between the waste reduction rate (WRR) and bioconversion rate (BCR). Substrates rich in hemicellulose (such as those containing brewery grains and vegetable waste) are more readily digested by BSFL, whereas high cellulose and lignin fractions (as in filter cake) are recalcitrant and reduce digestibility. BF possessed high hemicellulose (≈27–31%) contents, with low cellulose (≈8–11%) and modest lignin (≈2.2–2.7%) contents. This more labile carbohydrate profile supports rapid hydrolysis and ingestion, explaining the highest WRR on BF55 (67.52%), alongside efficient FCR (6.03) [24]. In contrast, BV carried higher cellulose (≈14.6%) and lignin (≈4.0–4.4%) contents; although this slightly tempered WRR (≈56–58%), the combination of very high TOC (up to 50.54% in BV55) and adequate protein enabled the highest BCR (BV55: 14.03%), with competitive FCR (6.32). Finally, CF exhibited very high cellulose (≈21–29%), low nitrogen/protein, and lower VS/TOC, jointly constraining both WRR (54.30–59.18%) and BCR (6.78–7.89%) while inflating FCR (8.44–8.59). The C/N ratio further reinforced these patterns: BF/BV ≈11–14 favored growth, whereas CF ≈16.5–16.9 shifted larvae toward nitrogen limitation, requiring more intake per unit biomass, thereby raising FCR. Moisture also modulated accessibility: BV (≈82–84%) and BF (≈79–80%) likely supported stronger microbial pre-digestion and palatability than CF (≈76–77%), complementing their higher VS/TOC contents to improve net conversion.

The longer larval development times observed on CF substrates are also consistent with a previous study that reported a growth duration of 22.20 days for a lower-nutritional-value winery by-product [25]. Other factors that can affect larval development include larval density, feeding rate, and the pH of the feeding substrate. pH remained mildly acidic across blends (≈4.7–5.9); within this narrow range, it was not the dominant factor, though larval density, feeding rate, and pH are known to influence development [26].

The waste reduction and bioconversion performances of BSFL are depicted in Figure 2. The highest waste reduction rate of 67.52% was achieved with BF55, while the lowest waste reduction rate of 54.30% was found with the CF73 substrate. Basically, the BSFL reared on the BF substrates showed a higher waste reduction rate. This advantage could be due to the higher portion of hemicellulose in the BF substrates, which was more easily digested. However, it is worth noticing that the waste reduction rate of the BV and CF was not significantly different, and those waste reduction rates were in the range of 54.30–59.18%. Generally, substrates with higher volatile solid contents contain more organic material for the larvae to consume and convert into biomass and nutrient-rich frass through larval excrement [27].

The bioconversion rate and feed conversion ratio (FCR) of BSFL varied markedly across substrates. BV55 and BV73 achieved the highest bioconversion rates (14.03% and 13.12%, respectively), indicating efficient conversion of feed into larval biomass. In contrast, the CF substrates showed significantly lower bioconversion (6.78–7.89%), likely due to their higher fiber contents and lower volatile solid contents. FCR values were lowest for BF55 and BV73 (6.03 and 6.14, respectively), reflecting more efficient feed utilization. Conversely, CF55 and CF73 exhibited considerably higher FCRs (8.44–8.59), indicating reduced feed conversion efficiency. These variations underscore the strong influence of substrate composition on both bioconversion and feed conversion performance.

A key limitation is that substrate moisture content was not pre-standardized (75.82–83.88%). Moisture can alter microbial pre-digestion, substrate structure/compaction, larval mobility, and apparent intake, thereby confounding the independent effects of nutrient composition and fiber fractions on WRR, BCR, FCR, and DT. Accordingly, our between-formula differences reflect the joint effects of composition and moisture and should not be ascribed to composition alone. Future work will control MC (e.g., target 80% ± 1–2%) and report dry matter-normalized intake/outputs.

2.3. The Overall Performance of BSFL

The overall performance of BSFL in treating agro-industrial residues and organic community waste is assessed across three dimensions: biomass yield, waste reduction, and larval development time. The scoring metrics, which summarize the mean performance values, provide a quantitative basis for evaluating the effectiveness of BSFL in sustainable waste management and agricultural applications. These scoring metrics are detailed and illustrated in Figure 3.

The mean scores plotted in this evaluation represent averages from four experimental replicates. Survival was uniformly high (>97%) and did not differ significantly by substrate (ANOVA p = 0.642). Survival scores remained uniformly high across treatments (scores 0.83–0.97). BF55 and CF55 led (0.97), followed by BV73 (0.93) and BF73/BV55 (0.90), with CF73 exhibiting the lowest survival (0.83). Differences remain small in practical terms.

Development time ranged from 18.12 to 20.75 days, which is still somewhat extended relative to typical BSF periods. BF73 was fastest (0.60), followed by BF55 and BV73 (0.50), BV55 declined (0.30), and CF55 and CF73 with the slowest performance (0.20 and 0.10, respectively). This pattern mirrors nutrient quality and fiber recalcitrance.

Waste reduction showed moderate variation and was significantly affected by the substrate (ANOVA p = 0.000). BF55 achieved the top performance (0.87), followed by BF73 (0.70). Mid-tier values were clustered around CF55 (0.53), BV55 (0.50), and BV73 (0.47), CF73 achieving the lowest performance (0.33), consistent with higher cellulose/lignin fractions being harder to digest than hemicellulose.

The bioconversion rate also differed significantly (ANOVA p = 0.000). BV55 remained the best (0.97), with BV73 close behind (0.87). BF55 (0.60) and BF73 (0.50) were moderate, and CF73 (0.33) and CF55 (0.23) had the lowest bioconversion rates.

The feed conversion ratio (lower is better) was, likewise, significant (ANOVA p = 0.000): BF55 and BV73 led, with scores of 0.93. BF73 and BV55 each scored 0.90 (FCR 6.01–6.50), whereas CF55 and CF73 lagged, at 0.47 and 0.43, respectively.

Based on the evaluation of scoring metrics, the overall performance results for BSFL across various substrates are summarized in Figure 4. The BF55 substrate, composed of 50% brewery waste and 50% food waste, emerged as the most suitable for BSFL rearing, achieving the highest mean score of 0.77. The second highest performance was observed with the BV73 substrate (70% brewery waste and 30% vegetable and fruit waste), with a mean score of 0.74. BF73 and BV55 followed closely and were comparable, with mean scores of 0.72 and 0.71, respectively. These BF and BV substrates all fall within the good band (≈0.61–0.80), reflecting their higher volatile solid and crude protein levels, as well as better digestibility.

In contrast, the CF substrates, comprising a mixture of filter cake and food waste, performed less well. CF55 achieved an overall mean score of 0.48 (satisfactory), while CF73 scored 0.41 (satisfactory). Notably, increasing the filter-cake proportion from 50% in CF55 to 70% in CF73 correlated with a further decline in overall performance, suggesting that the filter cake either lacks adequate nutrition or contains properties unfavorable for BSFL growth. Additionally, the lower hemicellulose and relatively higher cellulose/lignin fractions in CF substrates likely constrained digestibility and overall BSF performance. In conclusion, mixtures dominated by brewery waste with food waste and/or vegetable–fruit waste (BF55, BV73, BF73, and BV55, with mean scores of 0.71–0.77) are well-suited for BSFL rearing and consistently outperform filter cake-based blends (CF55 and CF73, with mean scores of 0.41–0.48).

3. Materials and Methods

3.1. Source of Agro-Industrial and Community Waste

The brewery waste was obtained from Khon Kaen Brewery Company Limited. The filter cake was obtained from sugarcane processing at the Thai Roong Ruang Sugar Company. The leftover food was collected from restaurants and the university cafeteria. Vegetable and fruit waste was obtained from Siam Makro Public Company Limited. All organic waste was blended to ensure homogeneity, and the mixtures were stored in plastic containers at −20 °C until use. Prior to the feeding experiment, substrates were thawed at room temperature for 24 h.

3.2. Rearing Substrate Formulation

Six rearing substrates were prepared by mixing the two waste categories, e.g., agro-industrial residue and organic community waste, including brewery waste, filter cake, vegetable and fruit waste, and food waste, in defined ratios. The details of formulation are tabulated in

Table 3. Composition of organic waste in the formulated substrates.

Rearing Substrate	Composition (% Wet Basis)
	Brewery Waste	Filter Cake	Vegetable and Fruit Waste	Food Waste
BF55	50	-	-	50
BF73	70	-	-	30
BV55	50	-	50	-
BV73	70	-	30	-
CF55	-	50	-	50
CF73	-	70	-	30

. The formulated rearing substrate properties were based on natural characteristics of each component. The waste was directly mixed without further adjustments for its properties (moisture or pH).

3.3. Chemical Analysis of Experimental Substrates

Dry matter and volatile solids were measured in accordance with ASTM D5511. Cellulose, hemicellulose, and lignin contents in the feed substrates were analyzed using the AOAC (2000) standard method. Total organic carbon (TOC) was determined by the Walkley–Black method. Total Kjeldahl nitrogen (TKN) was quantified using the Kjeldahl method as specified in the AOAC official method 2001.11. The C/N ratio was calculated as TOC divided by the TKN. Crude protein content was estimated as 6.25 × nitrogen content (N), where N was determined through mineralization by the abovementioned Kjeldahl method.

3.4. Source of Black Soldier Fly Larvae

Twenty-four-hour-old BSF eggs were sourced from a colony at the Non Sala Organic Waste Management Center (Sakon Nakhon Province, Thailand). The BSF eggs were incubated in a climatic room with an ambient temperature of 29–36 °C and relative humidity of 45–60% with a photoperiod of 12 h. For the first 6 days post hatching, the neonate BSFL were fed an 80% moisture neonatal diet consisting of 0.5 kg of rice bran, 0.5 kg of soybean curd residue, 500 mL of molasses, and 500 mL of bioferments [28]. On day 6, the BSFL were separated using a 1.18 mm mesh sieve and weighed to initiate the experiments. The research was approved for animal care and use for scientific research by the Kasetsart University Institutional Animal Care and Use Committee (ACKU68-AGR-005).

3.5. Experimental Design and Setup

Rearing containers (21 × 33 × 9 cm) were prepared with an initial 180 g of substrate, into which 300 six-day-old larvae were introduced. Translucent plastic lids with 0.5 mm ventilation holes were used to cover the rearing containers. Every three days, ten BSFL were randomly sampled, cleaned, and weighed using a Sartorius BSA224S-CW balance then placed back into their respective containers, and an additional 180 g of fresh feed was added to each container (equivalent to 200 mg of feed per larva per day), without removing the remaining residue. This refeeding schedule was maintained until ~40% of the larvae had turned black (prepupal stage), at which point feeding ceased and all larvae were harvested [29]. All the experiments were carried out in 4 replications, and the averaged values are reported.

3.6. Analysis of BSFL Performance

To analyze BSFL performance, five performance indicators—namely, larval development time (DT), survival rate (SR), waste reduction rate, bioconversion rate (BCR), and feed conversion ratio (FCR)—were evaluated.

Laval development time (DT) refers to the duration required for 40% of the BSFL to reach the prepupal stage. Because termination occurred simultaneously for all replicates of a given substrate, DT is a cohort-level measure with a single value per substrate; thus, SD/SE and inferential tests are not applicable.

The waste reduction rate (WRR) quantifies the percentage of the initial organic waste consumed or reduced by the larvae during the feeding period. The waste reduction rate was calculated using Equation (1):

$$\mathrm{Waste} \mathrm{reduction} \mathrm{rate} \left(\%\right) = ({\displaystyle \frac{{\mathrm{W}}_1 -{ \mathrm{W}}_2}{{\mathrm{W}}_1}}) \times 100$$

(1)

where W₁ refers to the initial mass of waste and W₂ refers to the mass of waste residue after ingestion by BSFL.

The survival rate (SR) measures the percentage of larvae that survive from the initial stage to the final stage of the experiment. The survival rate was calculated using Equation (2):

$$\mathrm{Survival} \mathrm{rate} (\%) = {\displaystyle \frac{{\mathrm{L}}_{\mathrm{f}}}{{\mathrm{L}}_{\mathrm{i}}}}\times 100$$

(2)

where L_i and L_f refer to the number of larvae alive at the beginning and the end of experiment, respectively.

The bioconversion rate (BCR) measures the efficiency with which the larvae convert organic waste into larval biomass. The bioconversion rate can be calculated using Equation (3):

$$\mathrm{Bioconversion} \mathrm{rate} (\%) =\left({\displaystyle \frac{\mathrm{Total} \mathrm{final} \mathrm{mass} \mathrm{of} \mathrm{BSFL} - \mathrm{Total} \mathrm{initial} \mathrm{mass} \mathrm{of} \mathrm{BSFL}}{\mathrm{Total} \mathrm{mass} \mathrm{of} \mathrm{substrate} \mathrm{fed}}}\right)\times 100$$

(3)

The feed conversion ratio (FCR) evaluates the amount of feed required to produce a unit of larval biomass. A lower FCR indicates better feed efficiency. The feed conversion ratio was calculated using Equation (4):

$$\mathrm{Feed} \mathrm{conversion} \mathrm{ratio} ={\displaystyle \frac{\mathrm{Wet} \mathrm{weight} \mathrm{of} \mathrm{food} \mathrm{ingested}}{\mathrm{Wet} \mathrm{weight} \mathrm{of} \mathrm{larval} \mathrm{biomass} \mathrm{gained}}}$$

(4)

3.7. Statistical Analysis

To determine differences in BSFL characteristics across various feed formulas, a one-way Analysis of Variance (ANOVA) was performed [30]. The null hypothesis posited no differences among formulas; a p-value < 0.05 led to rejection. When ANOVA indicated significance, Duncan’s New Multiple Range Test (DNMRT) was used for post hoc comparisons to identify which formulas differed [31]. Results are reported as mean ± standard error (SE) with a 95% confidence interval; means sharing a letter (a, b, c, etc.) are not significantly different at p < 0.05. Consistent with the definition presented above, DT was excluded from inferential testing (cohort-level single value per substrate) and is reported descriptively. Future work will record replicate-level time-to-event data to enable ANOVA tests.

3.8. Assessment of the Overall Performance of BSFL Treatment

This assessment aimed to evaluate the overall performance of BSFL to determine the substrate composition that optimizes organic waste reduction, minimizes rearing time, and maximizes larval production by the end of the experiment. The effectiveness of each rearing substrate was assessed by combining results across various performance indicators.

An appropriate scoring system for overall performance was established by first reviewing published studies with similar rearing substrates, from which the ranges of values for each performance indicator were documented (

Table 4. Summary of BSFL performance indicator ranges from the literature.

Indicator	Reported Values	Rearing Substrates	References
Survival rate (%)	92.00–99.33	Brewery waste, canteen waste, soybean curd residual, food waste, municipal organic waste, vegetable and fruit waste, dairy manure, and commingled MSW	[7,32,33,34,35,36,37,38,39,40]
Development time (days)	14.97–20.20
Waste reduction rate (%)	55.30–72.40
Bioconversion rate (%)	3.80–13.33
Feed conversion ratio	3.82–10.10

). A 0–1 scoring scale was then defined to encompass these literature ranges, as well as the results of the present study. The five performance indicators for each substrate were normalized to this scale, as tabulated in

Table 5. Details of the BSFL rearing performance assessment criteria.

Indicator	Assessment criteria
Survival rate (%)	0.0 = below 90.00% 0.1 = between 90.01 and 91.00% 0.2 = between 91.01 and 92.00% 0.3 = between 92.01 and 93.00% 0.4 = between 93.01 and 94.00% 0.5 = between 94.01 and 95.00% 0.6 = between 95.01 and 96.00% 0.7 = between 96.01 and 97.00% 0.8 = between 97.01 and 98.00% 0.9 = between 98.01 and 99.00% 1.0 = greater than 99.01%
Development time (day)	0.0 = greater than 21.00 days 0.1 = between 20.51 and 21.00 days 0.2 = between 20.01 and 20.50 days 0.3 = between 19.51 and 20.00 days 0.4 = between 19.01 and 19.50 days 0.5 = between 18.51 and 19.00 days 0.6 = between 18.01 and 18.50 days 0.7 = between 17.51 and 18.00 days 0.8 = between 17.01 and 17.50 days 0.9 = between 16.51 and 17.00 days 1.0 = shorter than 16.50 days
Waste reduction rate (%)	0.0 = below 47.51% 0.1 = between 47.51 and 50.00% 0.2 = between 50.01 and 52.50% 0.3 = between 52.51 and 55.00% 0.4 = between 55.01 and 57.50% 0.5 = between 57.51 and 60.00% 0.6 = between 60.01 and 62.50% 0.7 = between 62.51 and 65.00% 0.8 = between 65.01 and 67.50% 0.9 = between 67.51 and 70.00% 1.0 = greater than 70.00%
Bioconversion rate (%)	0.0 = below 5.01% 0.1 = between 5.01 and 6.00% 0.2 = between 6.01 and 7.00% 0.3 = between 7.01 and 8.00% 0.4 = between 8.01 and 9.00% 0.5 = between 9.01 and 10.00% 0.6 = between 10.01 and 11.00% 0.7 = between 11.01 and 12.00% 0.8 = between 12.01 and 13.00% 0.9 = between 13.01 and 14.00% 1.0 = greater than 14.0%
Feed conversion ratio	0.0 = greater than 10.50 0.1 = between 10.01 and 10.50 0.2 = between 9.51 and 10.00 0.3 = between 9.01 and 9.50 0.4 = between 8.51 and 9.00 0.5 = between 8.01 and 8.50 0.6 = between 7.51 and 8.00 0.7 = between 7.01 and 7.50 0.8 = between 6.51 and 7.00 0.9 = between 6.01 and 6.50 1.0 = less than 6.01

.

The overall performance score for each substrate was calculated as the average of the five indicator scores. Finally, overall performance was categorized into five levels—poor (0.00–0.20), fair (0.21–0.40), satisfactory (0.41–0.60), good (0.61–0.80), and very good (0.81–1.00)—following an approach adapted from Greene and Tonjes [41].

4. Conclusions

This study comprehensively evaluated BSFL performance on six different organic waste mixtures and identified practical feed formulations for optimal results. The 50:50 brewery waste + food waste (BF55) substrate yielded the highest overall performance (score 0.77 out of 1, categorized as ‘good’), achieving 99.42% larval survival, a waste reduction rate of 67.52%, and superior biomass conversion efficiency. In contrast, substrates containing a high proportion of sugar filter cake were the poorest performers—for instance, the CF73 diet (70% filter cake) had an overall score of 0.41 (‘satisfactory’ level) and prolonged larval development time (>20 days) due to its low nutrient content and high fiber content. These results underscore the practical potential of BSFL: by selecting nutrient-rich waste combinations (high in protein and easily digestible organics), one can maximize waste reduction and larval biomass yield, whereas high-fiber, low-nutrient residues should be limited in BSFL feed. Because moisture was not standardized, the observed performance differences should not be attributed solely to nutrient composition.

Our findings provide actionable guidelines for waste management: mixing agro-industrial residues like brewery grains with food or vegetable waste produces a balanced diet that significantly improves larval growth and conversion rates. This method not only enhances the efficiency of organic waste treatment but also contributes to a circular economy by converting waste into valuable insect biomass and frass. Optimizing BSFL rearing conditions and feed mixtures in this way can help municipalities and industries manage organic waste more sustainably. Finally, while our study demonstrates clear benefits of tailored waste mixtures, it is limited to the specific types of waste and ratios tested. We suggest that future research explore a broader range of waste types and environmental conditions (e.g., temperature, humidity, and aeration) to validate and extend these guidelines for BSFL rearing.