N, Hugel S, Fisher BL. Effect of Cricket Frass Fertilizer on growth and pod production of green beans (Phaseolus vulgaris L.)

Cricket Frass Fertilizer (CFF) was tested for its efficiency and potential as a fertilizer on the growth of green beans (Phaseolus vulgaris L.) in central Madagascar from April 2020 to October 2020. We grew green beans experimentally for 93 days with seven different fertilizer treatments: NPK 200 kg/ha (0.47 g of N/plant), GUANOMAD (guano from bat) 300 kg/ha (0.26 g of N/ plant), CFF 100 kg/ha (0.12 g of N/plant), CFF 200 kg/ha (0.24 g of N/plant), CFF 300 kg/ha (0.38 g of N/plant), CFF 400 kg/ha (0.52 g of N/plant), and no fertilizer (0 g of N/plant). Three plant traits were measured: survival proportion, vegetative biomass, and pod biomass. The survival proportion of plants treated with the highest dose of CFF (400 kg/ha, 88.1%), NPK (79.8%), and GUANOMAD (81.2%) were similar, but plants treated with the former yielded significantly higher vegetative (35.5 g/plant) and pod biomass (11 g/plant). These results suggest that fertilizing green beans with CFF at a 400 kg/ha dose is sufficient for plant survival and growth, and improves pod production. In Madagascar where soil quality is poor, dependence on imported chemical fertilizers (NPK) and other organic fertilizer (GUANOMAD) can be reduced. Cricket Frass Fertilizer can be used as an alternative sustainable fertilizer for beans.

Response of Pasture Grasses to Organic Fertilizer Produced from Black Soldier Fly Frass

Livestock and dairy farmers are increasingly required to maintain productivity and profitability while mitigating the environmental harm associated with high-input agriculture. Accordingly, to reduce reliance on synthetic fertilizers, a wide range of organically derived products are being evaluated for their effects on sward growth and forage quality. This study used glasshouse experiments to investigate the responses of four grass species to a novel organic fertilizer derived from the mass production of black soldier fly larvae [Hermetia illucens, HexaFrass™, Meath, Ireland]. Although there was some variability among trials, overall our results indicate that application of HexaFrass produced increased shoot growth of Perennial Ryegrass (PRG; Lolium perenne L.), Timothy (Phleum pratense L.), and Cocksfoot (Dactylis glomerata L.) compared with growth achieved in no-fertilizer control plants. In addition to increases in shoot fresh and dry weight, shoot chlorophyll content was also positively related to the HexaFrass application rate. At nitrogen-equivalent application rates, HexaFrass resulted in lower shoot growth compared with the application of urea, suggesting that the nitrogen contained in HexaFrass may not be immediately plant-available. Of relevance to grazing or silage systems, the addition of HexaFrass resulted in increased shoot regrowth of PRG and Timothy after shoots had been cut. Based on our results, insect-frass-based fertilizers may have a role in low input, organic, and/or regenerative pasture-based livestock systems, although issues may occur due to the relatively high costs and low availability compared with other organic soil amendments such as farmyard manure and slurry.

Insect-based agri-food waste valorization: Agricultural applications and roles of insect gut microbiota

Meeting the demands of the growing population requires increased food and feed production, leading to higher levels of agri-food waste. As this type of waste seriously threatens public health and the environment, novel approaches to waste management should be developed. Insects have been proposed as efficient agents for biorefining waste, producing biomass that can be used for commercial products. However, challenges in achieving optimal outcomes and maximizing beneficial results remain. Microbial symbionts associated with insects are known to have a critical role in the development, fitness, and versatility of insects, and as such, they can be utilized as targets for the optimization of agri-food waste insect-based biorefinery systems. This review discusses insect-based biorefineries, focusing on the agricultural applications of edible insects, mainly as animal feed and organic fertilizers. We also describe the interplay between agri-food waste-utilizing insects and associated microbiota and the microbial contribution in enhancing insect growth, development, and involvement in organic waste bioconversion processes. The potential contribution of insect gut microbiota in eliminating pathogens, toxins, and pollutants and microbe-mediated approaches for enhancing insect growth and the bioconversion of organic waste are also discussed. The present review outlines the benefits of using insects in agri-food and organic waste biorefinery systems, describes the roles of insect-associated microbial symbionts in waste bioconversion processes, and highlights the potential of such biorefinery systems in addressing the current agri-food waste-related challenges.

Waste to value: Global perspective on the impact of entomocomposting on environmental health, greenhouse gas mitigation and soil bioremediation

The innovative use of insects to recycle low-value organic waste into value-added products such as food, feed and other products with a low ecological footprint has attracted rapid attention globally. The insect frass (a combination unconsumed substrate, faeces, and exuviae) contains substantial amounts of nutrients and beneficial microbes that could utilised as fertilizer. We analyse research trends and report on the production, nutrient quality, maturity and hygiene status of insect-composted organic fertilizer (ICOF) generated from different organic wastes, and their influence on soil fertility, pest and pathogen suppression, and crop productivity. Lastly, we discuss the impact of entomocomposting on greenhouse gas mitigation and provide critical analysis on the regulatory aspects of entomocomposting, and utilization and commercialisation ICOF products. This information should be critical to inform research and policy decisions aimed at developing and promoting appropriate standards and guidelines for quality production, sustainable utilization, and successful integration of entomocompost into existing fertilizer supply chains and cropping systems.

The Effects of Two Organic Soil Amendments, Biochar and Insect Frass Fertilizer, on Shoot Growth of Cereal Seedlings

To mitigate the environmental harm associated with high-input agriculture, arable farmers are increasingly required to maintain productivity while reducing inputs of synthetic fertilizers. Thus, a diverse range of organic products are now being investigated in terms of their value as alternative fertilizers and soil amendments. This study used a series of glasshouse trials to investigate the effects of an insect frass-based fertilizer derived from black soldier fly waste [HexaFrass™, Meath, Ireland] and biochar on four cereals grown in Ireland (barley, oats, triticale, spelt) as animal feed and for human consumption. In general, the application of low quantities of HexaFrass™ resulted in significant increases in shoot growth in all four cereal species, along with increased foliage concentrations of NPK and SPAD levels (a measure of chlorophyll density). These positive effects of HexaFrass™ on shoot growth were observed, however, only when a potting mix with low basal nutrients was used. Additionally, excessive application of HexaFrass™ resulted in reduced shoot growth and, in some cases, seedling mortality. The application of finely ground or crushed biochar produced from four different feedstocks (Ulex, Juncus, woodchip, olive stone) had no consistent positive or negative effects on cereal shoot growth. Overall, our results indicate that insect frass-based fertilizers have good potential in low-input, organic, or regenerative cereal production systems. Based on our results, biochar appears to have less potential as a plant growth promoting product, but could be used as a tool for lowering whole-farm carbon budgets by providing a simplistic means of storing carbon in farm soils.

The Effect of Mealworm Frass on the Chemical and Microbiological Properties of Horticultural Peat in an Incubation Experiment

Insect farming is growing in popularity, and in addition to insect meal, it generates waste products such as exuviae and frass, which can be recycled in agriculture. The aim of this incubation experiment was to evaluate the effect of Tenebrio molitor L. frass on selected chemical and biological properties of deacidified peat, which is widely used in horticulture. The optimal rate of frass fertilizer in peat for growing vegetables and ornamental plants was determined, with special emphasis on mineral nitrogen levels. Peat was fertilized with five nitrogen rates, 0, 50, 100, 200, and 400 mg dm^-3, and supplied with frass or urea. The study demonstrated that frass can be used as organic fertilizer. An increase in the nitrogen rate significantly increased mineral nitrogen content and electrical conductivity and decreased Ca content in peat. Both frass and urea increased the ammonification rate at the beginning of incubation and the nitrification rate from the second week of the experiment. Higher frass rates (5 and 10 g dm^-3) increased the content of plant-available nutrients (nitrogen, phosphorus, magnesium, potassium, and sodium) in peat as well as the abundance of microorganisms supporting organic matter mineralization. Unlike frass, urea increased the counts of nitrogen-fixing bacteria in peat.

Management Practices Affecting Lesser Mealworm Larvae (Alphitobius diaperinus) Associated Microbial Community in a Broiler House and After Relocating With the Litter Into Pastureland

Lesser mealworms are often found infesting production houses used to raise broiler chickens. Previous studies have investigated pathogenic microorganisms associated with the larvae, but a more thorough study relating total microbiome changes due to management procedures and flock rotations was needed. Additionally, there is a question of what microbiota are transferred into the environment when the litter, in which larvae reside, is piled in pastureland for use as fertilizer and where interactions with the soil and other fauna can occur. This study chronicled, by the 16S rRNA sequencing, the bacterial community profile of larvae in a broiler grow-out house synchronizing to when birds were added to and removed from the house over 2.5 years. The profile was found to be relatively constant despite 11 flock rotations and management disruptions, specifically litter cleanout procedures and the addition of new birds or bedding. In contrast, once removed from the controlled broiler house environment and placed into open pastureland, the substantial microbial diversity brought with the larvae showed greater fluctuation in structure with environmental conditions, one of which was rainfall. Surprisingly, these larvae survived at least 19 weeks, so the potential for moving larval-associated microbes into the environment needs further assessment to minimize the risk of relocating foodborne pathogens and also to assess those bacteria-generating metabolites that have benefits to plant growth when using the litter as a fertilizer. The characterization of their microbiome is the first step to investigating the influences of their microbes on the manmade and environmental ecosystems.

Nutrient quality and maturity status of frass fertilizer from nine edible insects

Globally, there is growing interest to recycle organic waste using insect larvae into high-quality frass fertilizer through circular economy approach. This paper presents the first comparative report on the nutrient concentrations, fertilizing indices, nutrient supply potentials and compost maturity of nine edible insect frass fertilizers. Our results revealed that frass fertilizers from all the insect species had adequate concentrations and contents of macronutrients [nitrogen (N), phosphorus (P), potassium (K)], secondary nutrients (calcium, magnesium, and sulphur) and micro-nutrients (manganese, copper, iron, zinc, boron, and sodium). The fertilizing indices of the frass fertilizers were above 3. However, black soldier fly (BSF) frass fertilizer had significantly higher N (20-130%) and K (17-193%) concentrations compared to others. The P concentration of Gryllus bimaculatus frass fertilizer was 3-800% higher compared to those of frass fertilizers from other insect species. The potential N and K supply capacities of BSF frass fertilizer was 19-78% and 16-190% higher, respectively. The P supply capacity of cricket frass fertilizer was 17-802% higher compared to others. The highest seed gemination rate (> 90%) and germination index (267%) were observed in seeds treated with BSF frass fertilizer. Frass fertilizer obtained from the other eight insect species showed medium to high phytotoxicity. These findings demonstrate that insect frass fertilizers are promising alternatives to existing commercial fertilizers (i.e., mineral, and organic) for improved soil health and crop yield.

Frass derived from black soldier fly larvae treatment of biodegradable wastes. A critical review and future perspectives

Inadequately treated biodegradable waste is considered an environmental, social and economic threat worldwide, which call for great attention. Waste treatment with larvae of the black soldier fly (BSF, Hermetia illucens) complies with the concepts of circular economy, as it enables the transformation of these wastes into marketable products, closing loops and promoting circularity. The processing residues of the treatment (frass) is constantly generated in waste management facilities in large volumes, and this product can be used as an organic fertilizer in agriculture, stimulating a transition to a circular economy. However, many aspects related to frass are still unknown, such as its varying composition of nutrients, microorganisms and bioactive compounds, its post-processing requirements for improved biological stabilization, its behavior in the soil and action in the plants' metabolism, among other aspects. In this review article, we highlight the potential of frass from BSF larvae treatment of biodegradable waste in the world market regarding its possible use as a fertilizer, summarize recent results with this novel product and point towards future research perspectives.

The Impacts of Black Soldier Fly Frass on Nitrogen Availability, Microbial Activities, C Sequestration, and Plant Growth

Using insects, notably black soldier fly (BSF), is becoming one of the emerging technologies to valorize agrifood waste into high-value products, such as proteins for animal feed. Its market is expected to grow more rapidly following the new European legislation extending larvae protein use in poultry farming. The anticipated increase in larvae protein also results in a parallel increase in frass, a residue leftover after rearing the larvae and selling as a biofertilizer. Little is known about the impacts of frass made from different feedstocks used for raising the larvae on plant growth and soil quality. We set up an incubation and pot experiment to understand their effect on plant growth and soil quality and tested seven frass fertilizers made from various types of food waste and anaerobic digestate and potato pulp as reference materials using maize as a test plant. We found that the effect of frass on N availability and soil microbial quality significantly (p < 0.05) varied depending on the feedstock used for rearing the BSF larvae. N immobilization occurred up to more than 70 days, and 4–20% net N was released at the end of the 103-day-long experiment. In line with N availability dynamics, most of the frass treatments did not significantly increase the plant growth. All frasses significantly increased the microbial biomass C and enzyme activities. About 56–70% of the applied C in frass is estimated to be stable in the soil. Our data confirm that frass is a valuable product to improve soil quality but need to be applied with N sources that are readily available to avoid nutrient shortage during plant growth.

Adult Alphitobius diaperinus Microbial Community during Broiler Production and in Spent Litter after Stockpiling

The facilities used to raise broiler chickens are often infested with litter beetles (lesser mealworm, Alphitobius diaperinus). These beetles have been studied for their carriage of pathogenic microbes; however, a more comprehensive microbiome study on these arthropods is lacking. This study investigated their microbial community in a longitudinal study throughout 2.5 years of poultry production and after the spent litter, containing the mealworms, was piled in pastureland for use as fertilizer. The mean most abundant phyla harbored by the beetles in house were the Proteobacteria (39.8%), then Firmicutes (30.8%), Actinobacteria (21.1%), Tenericutes (5.1%), and Bacteroidetes (1.6%). The community showed a modest decrease in Firmicutes and increase in Proteobacteria over successive flock rotations. The beetles were relocated within the spent litter to pastureland, where they were found at least 19 weeks later. Over time in the pastureland, their microbial profile underwent a large decrease in the percent of Firmicutes (20.5%). The lesser mealworm showed an ability to survive long-term in the open environment within the spent litter, where their microbiome should be further assessed to both reduce the risk of transferring harmful bacteria, as well as to enhance their contribution when the litter is used as a fertilizer.