The treatment of municipal wastewater produces clean water and sewage sludge (MSS), the management of which has become a serious problem in Europe. The typical destination of MSS is to spread it on land, but the presence of heavy metals and pollutants raises environmental and health concerns. Bioconversion mediated by larvae of black soldier fly (BSFL) Hermetia illucens (Diptera, Stratiomyidae: Hermetiinae) may be a strategy for managing MSS. The process adds value by generating larvae which contain proteins and lipids that are suitable for feed and/or for industrial or energy applications, and a residue as soil conditioner. MSS from the treatment plant of Ladispoli (Rome province) was mixed with an artificial fly diet at 50% and 75% (fresh weight basis) to feed BSFL. Larval performance, substrate reduction, and the concentrations of 12 metals in the initial and residual substrates and in larval bodies at the end of the experiments were assessed. Larval survival (> 96%) was not affected. Larval weight, larval development, larval protein and lipid content, and waste reduction increased in proportion the increase of the co-substrate (fly diet). The concentration of most of the 12 elements in the residue was reduced and, in the cases of Cu and Zn, the quantities dropped under the Italian national maximum permissible content for fertilizers. The content of metals in mature larvae did not exceed the maximum allowed concentration in raw material for feed for the European Directive. This study contributes to highlight the potential of BSF for MSS recovery and its valorization. The proportion of fly diet in the mixture influenced the process, and the one with the highest co-substrate percentage performed best. Future research using other wastes or by-products as co-substrate of MSS should be explored to determine their suitability.

Black soldier fly larvae (BSFL) can convert various organic substrates into high added-value biomass. In addition, the residue can be used as a soil conditioner. Several studies have been conducted on a laboratory scale that may not represent what happens on a prototype scale. Using fruit and vegetable waste as a basic substrate, mixing them with agro-industry by-products (called co-substrates), the Hermes project set up a process on medium (2 kg) and large (10 kg) scales with two different feeding regimes (1.25 g/BSFL and 2 g/BSFL). At the mature stage, larval biomass was separated from frass (the by-product of the larval rearing). The production of larval proteins and fats and the use of frass as soil conditioning were evaluated. The lowest feeding regime (1.25 g/BSFL) provided the best waste valorization. The shift towards higher production scales is not completely linear. The addition of co-substrates to fruit and vegetable waste, as they are provided by the large-scale retail trade, can help to standardize a process as part of an insect farm. The frass recovered from the residue of rearing (on the diet or on the agrifood leftovers) was composted and used in field to grow a processing tomato variety. The addition of composted frass assured a slightly lower yield than synthetic fertilizer but there was no statistically significant difference (p > 0.10). This suggests that partial replacement of synthetic fertilizer with composted frass has potential. Overall, the work demonstrated that, using a multidisciplinary approach, the interest and the value in building a supply chain based on bioconversion mediated by Hermetia illucens can be emphasized.

The red palm weevil Rhynchophorus ferrugineus is an invasive pest from southeastern Asia and Melanesia that has spread widely across the Middle East and the Mediterranean Basin over the last 30 years. Its endophagous larvae cause huge amounts of damage to several palm tree species from the Arecaceae family. Many of these palms are economically important for agricultural and ornamental purposes. Therefore, a lot of attention has recently been focused on studying this species with the aim of identifying sustainable and effective eradication strategies. Sterile insect techniques are biological control strategies that are currently being investigated for their potential to eradicate this pest in selected invasion areas. Mating system features (e.g., polyandry and related features) can affect the success and suitability of these approaches. The main goal of this research was to assess the performance of a previously developed microsatellite panel in terms of the paternity assignment of progeny from laboratory mating experiments. Using a simulation approach, we evaluated the reliability of the microsatellite markers in the paternity tests both in complex laboratory experiment scenarios and on the progeny of wild-caught gravid females to help future studies on the RPW mating system. As a case study of the simulation results, we performed two double-mating experiments, genotyped the progeny and estimated the P₂ values to compare to the expected progeny genotypes according to the crossing scheme of each experiment. The results of our simulations on laboratory experiments showed that it was possible to carry out paternity assignments for all progeny with reliable statistical confidence using our 13 microsatellites set. On the contrary the low genetic variability measured in red palm weevil populations in invaded areas made the resolution power of our loci too low to carry out paternity analyses on natural populations. Results of laboratory crossing were completely congruent with the expectations from the Mendelian laws.

Fruit and vegetable waste (FVW) from large-scale retail is an abundant, relatively homogeneous feedstock for black soldier fly (Hermetia illucens) larvae, an alternative to composting. This study assessed, by life cycle assessment (LCA), the environmental performance of a pilot plant producing 15-day-old larvae as animal protein and tested whether the additive conditioning of the FVW changes that performance. Three substrates were compared (FVW with 20% bakery waste, 20% bran, and 2% sawdust, respectively) using climate change (GWP100a, IPCC 2007), economic allocation, Monte Carlo simulation, and transport distance sensitivity. The scenario ranking depended on the functional unit: per Mg of waste, the sawdust substrate was lowest (39.75 kg CO₂eq), whereas, per kg of protein, the bran substrate was best (8.87 kg CO₂eq, ~66% below bakery waste). Electricity, additive, and starter diet dominated the footprint. The conditioning additive, not the waste itself, governed sustainability; the bran–bakery waste difference was statistically discernible.

Black Soldier Fly larvae (BSFL) bioconvert a wide variety of organic waste into value compounds including the residual frass, a by-product exploitable as compost for plant growth. The use of a non-standardized waste diet that varies in terms of properties does not ensure the maintenance of a highly fertile and healthy BSF colony able to produce viable inoculum (5–7-day-old larvae) for waste bioconversion. The Gainesville diet (GD) is a balanced formulation to ensure full larval development in fertile adults, resulting in a stable rearing colony. On a large scale, the bioconversion supply chain can produce different types of frass. Frass derived from the Gainesville diet (GDf), from fruit and vegetable waste (FVWf), and from milled fruit and vegetable waste (MWf) was composted and then compared to evaluate its fertilizing effect on lettuce growth in two pot-growing experiments. Each compost was added at concentrations of 2.5, 5, and 10%. The growth of lettuce improved significantly with the addition of composted frass in a dose-dependent manner when compared to unfertilized soil. GDf 10% gave the significantly best performance in terms of plant height (20.8 cm versus 17.9 cm) and fresh weight (113.5 g versus 87.7 g) compared to FVWf. In the experiment, the combined use of composted frass at 10% of both GDf and FVWf with a double mineral fertilizer application showed no significant differences compared to triple application. However, GDf provided significantly greater chlorophyll content than FVWf. These results highlight how, under the conditions tested in the present work, the frass of the entire productive chain of BSF is a high value by-product.