Bioplastic Film from Black Soldier Fly Prepupae Proteins Used as Mulch: Preliminary Results

Leonardo Setti,Laura Ioana Macavei,Enrico Francia,Lara Maistrello,Domenico Ronga,Riccardo De Leo,Monia Montorsi,Silvia Barbi,Andrea Pulvirenti,Simone Martinelli

doi:10.3390/agronomy10070933

Abstract

A protein-based film (PBF), obtained from black soldier fly prepupae proteins, was assessed for its agronomic performance as mulch. PBF was investigated in a potting experiment and compared with Mater-Bi (MB), polyethylene (PE) and bare soil. During the experiment, degraded surface area, weight and thickness of the film, water evaporated from the pot, and the soil microbiological content (SMC) were recorded. In addition, films were buried to assess their biodegradability and impact on SMC. During the mulching process, the PBF showed a significant degradation. In terms of evaporated water, the PBF performed similarly to MB and worse than PE. Regarding SMC, film of any nature caused an increase in the Clostridia spp. and a decrease of total mesophilic aerobic bacteria and fungi contents. When buried, only PBF recorded a faster biodegradability, showing a reduction of surface area, thickness and weight. PBF and MB highlighted a significant increase in contents of Clostridia spp., mesophilic aerobic bacteria and fungi. Our results reported, for the first time, the valorization of black soldier fly (BSF) prepupae proteins as a biodegradable film for mulching purposes. However, further study is needed to reduce the PBF biodegradability and allow it to be used for the most important mulched crops.

Highlights

In the Mediterranean basin as well as in Northern Europe, the global temperature has steadily risen over the last years [1,2], negatively affecting agricultural irrigation water and energy consumptions [3].Several studies demonstrated the usefulness of mulching in enhancing crop yield and quality [4], reducing the volume of irrigation water [4,5] and contributing to the avoidance of soil erosion phenomena [6]
In order to demonstrate the full circularity of the process, the aim of the present work was to assess the suitability of the innovative black soldier fly (BSF) protein bioplastic film for mulching purposes and to evaluate its biodegradability in the soil, comparing its performance with commercially available mulching films
Bacterial populations increase under organic mulch due to the different chemical composition and decomposition rates of these materials [41]

Summary

Introduction

Several studies demonstrated the usefulness of mulching in enhancing crop yield and quality [4], reducing the volume of irrigation water [4,5] and contributing to the avoidance of soil erosion phenomena [6]. Mulching offers various benefits to crop production, such as weed control and early development due to the increase in the soil temperature and increased effectivity of fertilizers [7]. Mulching materials are generally classified into three main groups: organic materials (agricultural, industrial and animal by-products), inorganic materials (plastic films) and special materials. Concerning organic mulching, straw represents the most used material, showing numerous benefits after field application, such as increased soil moisture [8]. Organic mulches are cheap, available and improve soil quality and crop yield [3]

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Conclusion