Preliminary Study on Sustainable NPK Slow-Release Fertilizers Based on Byproducts and Leftovers: A Design-of-Experiment Approach

Abstract

In this study, an organic nitrogen-based coating was developed based on black soldier fly (BSF) prepupae reared on poultry dejections and deposited on ceramic lightweight aggregates (LWAs), containing phosphorous (P) and potassium (K) from agroresidues, leading to a complete nitrogen, phosphorus, and potassium (NPK) fertilizer. To obtain a resistant coating with good adhesion to LWAs, different plasticizing agents were tested (e.g., glycerol, cellulose, and polyethylene glycol). The coating formulation was optimized through a design-of-experiment (DoE) approach to correlate the effect of each mixture component on the coating’s performance. BSF biomass was characterized through chemical and thermal routes, as well as the final coated LWAs, confirming their general agreement to fertilizer’s requirements. Release tests in static conditions highlighted the barrier action of the coating, preventing uncontrolled release of potassium and phosphorus contained in the LWAs as well as the release of nitrogen after 21 days (near to 20%). Germination and growth tests indicated a valuable increase of the growth index, whereas the germination process is limited by the coating barrier effect. This work proposes a new product in the field of slow-release fertilizers designed by rational methodologies and innovative materials based on waste valorization, fully in agreement with a circular economy perspective.

From Food Processing Leftovers to Bioplastic: A Design of Experiments Approach in a Circular Economy Perspective

“…3c) shows a strong and linear augmentation when the highest BSF Protein (50%) amount and lowest Temperature (130 °C) are applied, probably because temperature is involved in into the BSF proteins degradation. Increasing the Temperature, the BSF proteins are more sensitive to a partial degradation, leading to a weaker network structure with LDPE, as also suggested from the DSC diagram of BSF proteins reported in literature [23,24]. In addition, from Fig.…”

Effects of Different LED Light Recipes and NPK Fertilizers on Basil Cultivation for Automated and Integrated Horticulture Methods

“…Detailed specifications of these substrates are reported in Table 1. With the aim to evaluate the combined effect of a very specific type of controlled release fertilizer and different light sources, in the second part of this study, a NPK lightweight aggregate from agro-residues, wastes, and by-products resulted from previous research [27,28] was employed and compared with the employment of only soil enriched in fertilizers (Floradur B). According to the literature, the NPK controlled-release fertilizer demonstrated a relevant content of nutrients such as nitrogen (8%), potassium (8%), and phosphorous (5%) [27].…”

“…According to it, under standard soil conditions, the quantity of allowed nutrients such as nitrogen phosphorus and potassium (NPK) are 100-70-80 kg/ha, respectively. In particular, considering the nitrogen amount in the coating, the amount of nitrogen provided is equal to the maximum allowed according to the above-mentioned guidelines and previous NPK characterization, assuming a final release of 50% of the nitrogen contained in the coating [27].…”

“…In addition, specific LED light recipes of hyper red and deep blue were investigated, also in combination with different soils and the addition of a specific controlled-release fertilizer based on nitrogen, phosphorus, and potassium macronutrients (NPK). Moreover, in a circular economy perspective, this controlled-release NPK fertilizer was derived from agri-food, industrial, and post-consumer activities as previously described in the literature [27,28]. In the first part of the experimental procedure, different substrates with a negligible quantity of fertilizers were tested to identify the most promising one capable to clearly highlight the effect of light source only on the plant germination and growth.…”

A New System of Sustainable Silico-Aluminous and Silicate Materials for Cultivation Purpose within Sustainable Buildings: Chemical-Physical, Antibacterial and Cytotoxicity Properties

“…This study represents the evolution of previous research aimed at the engineering of materials (glasses and lightweight aggregates) based on waste from the agro-and postconsumer sector, some of which having fertilizing properties. Active glasses and ceramic lightweight aggregates with controlled release of NPK macronutrient have been created and described in previous works [5][6][7][8][9][10][11][12]. In addition, total particulate emissions during heat treatment and carbon footprint have been assessed for some aggregates compositions, and the encouraging results described in a previous paper [13].…”