New publication: Praeg and Klammsteiner (2024) J Environ Manage 356, 120622

Our latest study delves deep into the world of insect frass, shedding light on its potential as a nutrient-rich organic fertilizer. By analyzing frass from black soldier fly, yellow mealworm, and Jamaican field cricket, we’ve discovered interesting variations in properties and nutrient concentrations, highlighting its effectiveness in enriching soil health and promoting plant growth. In addition, our research explores the impact of heat treatment on frass properties and microbiota, ensuring clean production practices. These findings not only revolutionize our understanding of insect frass but also pave the way for regulatory standards and its widespread adoption in agriculture.

Link to full study: doi.org/10.1016/j.jenvman.2024.120622

Graphical abstract - Physicochemical and microbiological assessment of frass from black soldier fly (BSF), yellow mealworm (YMW), and Jamaican field cricket (JFC) and the impact of heat treatment. TS = total solids, VS = volatile solids, C:N = carbon to nitrogen ratio, NH₄⁺-N = ammonium nitrogen, NO₂–NO₃^--N = nitrite and nitrate nitrogen, EC = electrical conductivity, TDS = total dissolved solids, MR = microbial respiration, C_mic = microbial biomass carbon, MQ = metabolic quotient. ns: p > 0.05, *: p ≤ 0.05, **: p ≤ 0.01, ***: p ≤ 0.001, ****: p ≤ 0.0001, STD-I = standard I nutrient agar, ooR = out of range, bdl = below detection limit..

References

2024

Primary study on frass fertilizers from mass-reared insects: Species variation, heat treatment effects, and implications for soil application at laboratory scale

Nadine Praeg, and Thomas Klammsteiner

Journal of Environmental Management, Apr 2024

Abstract doi Bib PDF

Insect farming has gained popularity as a resource-efficient and eco-friendly method for managing organic wastes by converting them into high-quality protein, fat, and frass. Insect frass is a powerful organic fertilizer that enriches the soil with essential plant nutrients and enhances plant defense mechanisms through chitin stimulation. Given the importance of frass commercialization for many insect farmers and the use of increasingly diverse organic wastes as insect feedstocks, there is a need for legal guidelines to enable clean production practices. The recent introduction of a legal definition for frass and heat treatment requirements by the EU commission marks a significant step towards standardizing its quality; however, little is known about the processes shaping its nutritional profiles and contributing to its maturation. Our study addresses key knowledge gaps in frass composition and production practices. Here, we analyzed the physicochemical, plant-nutritional, and microbiological properties of black soldier fly, yellow mealworm, and Jamaican field cricket frass from mass-rearing operations and assessed the impact of hygienizing heat treatment on fertilizer properties and frass microbiota. The results showed that frass properties varied significantly across insect species, revealing concentrations of plant-available nutrients as high as 7000 μg NH4+-N, 150 μg NO2–NO3–N, and 20 mg available P per g of total solids. Heat treatment reduced microbial activity, biomass, and viable counts of pathogenic Escherichia coli and Salmonella spp. In terms of frass microbiome composition, alpha diversity showed no significant differences between fresh and heat-treated frass samples; however, significant differences in microbial community composition were observed across the three insect species. Despite heat treatment, soil application of frass reactivated and boosted soil microbial activity, inducing up to a 25-fold increase in microbial respiration, suggesting no long-term detrimental effects on microorganisms. These findings not only enhance our understanding of insect frass as a nutrient-rich organic fertilizer but also have implications for regulatory frameworks, underscoring its promising potential for soil health and nutrient cycling. However, it is important to recognize the primary nature of this research, conducted at laboratory scale and over a short term. Future studies should aim to validate these findings in agricultural settings and explore additional factors influencing frass properties and its (long-term) interaction with soil ecosystems.
@article{praeg_frassterile_2024, title = {Primary study on frass fertilizers from mass-reared insects: Species variation, heat treatment effects, and implications for soil application at laboratory scale}, volume = {356}, copyright = {All rights reserved}, issn = {0301-4797}, url = {https://www.sciencedirect.com/science/article/pii/S030147972400608X}, doi = {10.1016/j.jenvman.2024.120622}, language = {English}, urldate = {2024-03-21}, journal = {Journal of Environmental Management}, author = {Praeg, Nadine and Klammsteiner, Thomas}, month = apr, year = {2024}, publisher = {Elsevier}, pages = {120622}, dimensions = true, }