In the framework of a circular economy, organic solid wastes are considered to be resources useful for obtaining value-added products. Among other potential uses, biodegradable wastes from agricultural, industrial, and domestic sources are being studied to obtain biopesticides through solid-state fermentation (SSF), mainly at the laboratory scale. The suitability of biowaste (source-selected organic fraction of municipal solid waste) for use as a substrate for Bacillus thuringiensis (Bt) growth under non-sterile conditions in a 10 L SSF reactor was determined in this study. An operational strategy for setting up a semi-continuous process yielding a stabilised organic compost-like material enriched with Bt suitable for use as a soil amendment was developed. Concentrations of 1.7·107-2.2·107 and 1.3·107-2.1·107 CFU g-1 DM for Bt viable cells and spores, respectively, were obtained in the final material. As the results confirmed, Bt-enriched compost-like material with potential biopesticide properties can be produced from non-sterile biowaste.

There is a growing generation of biodegradable wastes from different human activities from industrial to agricultural including home and recreational activities. On the other hand, agricultural and horticultural activities require significant amounts of organic amendments and pesticides. In this framework, the present study evaluates the viability of soy fiber residue valorization as organic soil amendment with biopesticide properties through aerobic solid-state fermentation (SSF) in the presence of Bacillus thuringiensis (Bt). The experiments were performed first under sterile and non-sterile conditions at lab scale using 115 g of sample and controlled temperature (30 °C). Bt growth was successful in sterile conditions, obtaining 6.2 × 10(11) CFU g(-1) DM and 8.6 × 10(10) spores g(-1) DM after 6 days. Bt survived on solid culture under non-sterile conditions (3.8 × 10(9) CFU g(-1) DM and 1.3 × 10(8) spores g(-1) DM). Further, the valorization process was scaled-up to 10 L reactors (2300 g) under non-sterile conditions obtaining a final stabilized material with viable Bt cells and spores (9.5 × 10(7) CFU g(-1) DM and 1.1 × 10(8) spores g(-1) DM in average) after 9 days of SSF. These results confirm the possibility of managing biodegradable wastes by their transformation to a waste derived soil amendment with enhanced biopesticide effect, in comparison to traditional compost using a valuable and low-cost technique (SSF).

Indole-3-acetic acid (IAA) is a key plant hormone that plays crucial roles in plant growth and development. This study investigated the effects of exogenous application of IAA as a growth regulator in onion cultivation (Allium cepa L.). Various IAA concentrations were evaluated to determine their effects on onion growth and chemical parameters. Several agronomic properties and chemical parameters, including total fresh weight, plant height, chlorophyll content, nitrates, total phenols, and antioxidant capacity (DPPH), were analyzed. The results revealed that the exogenous application of different concentrations of IAA had a significant impact on onion growth and quality. Specifically, it was found that certain concentrations of IAA fostered a significant increase in fresh bulb weight and a notable elevation in the levels of phenolic compounds. However, the onion’s response to IAA was concentration dependent. In conclusion, the present study offers evidence that the exogenous application of IAA as a growth regulator can enhance onion growth and quality. These findings hold relevance for the advancement of sustainable agricultural practices and can be directed towards crop enhancement.

Agriculture has been experiencing a difficult situation because of limiting factors in its production processes. Natural biostimulants (NBs) have emerged as a novel alternative. This study reviews NBs produced through solid-state fermentation (SSF) from organic waste, focusing on processes and production methods. The aim is to highlight their potential for improving agricultural productivity and promoting sustainable agriculture. Through a literature review, the effects of NBs on crops were summarized, along with the challenges associated with their production and application. The importance of standardizing production processes, optimizing fermentation conditions, and assessing their effects on different crops is emphasized. Furthermore, future research areas are introduced, such as enhancing production efficiency and evaluating the effectiveness of SSF-produced NBs in different agricultural systems. In conclusion, SSF-produced NBs offer a promising alternative for sustainable agriculture, but further research and development are needed to maximize their efficacy and to enable large-scale implementation.

Food production faces important challenges such as water scarcity and the overall need of novel sustainable strategies. This study assesses the effect of the biostimulant produced through solid-state fermentation (SSF) of green waste (wood chips and grass residues) inoculated with Trichoderma harzianum with and without l-tryptophan as a precursor for indole-3-acetic acid (IAA) production, a well-known plant hormone. The fermented solid demonstrated significant positive effects on the growth of lettuce (Lactuca sativa L.) under different irrigation conditions. Substantial enhancements were observed in growth parameters such as fresh weight, plant height, leaf area and leaf quantity, along with chemical parameters including total phenol content, chlorophylls, carotenoids, and antioxidant activity (DPPH). The results also showed a positive impact on the nutritional quality of lettuce, particularly under normal irrigation conditions. In conclusion, this study highlights the biostimulant potential to improve the yield and nutritional quality of lettuce crops by reusing plant residues. Additionally, it poses the relevance of applying circular economy principles in sustainable agriculture and organic waste management.

The compost produced based on municipal/urban organic solid waste (RSOM/U), is a valuable resource as a biofertilizer for agriculture, gardening, forestry and especially for soil remediation, whose production contributes to sustainable development through recycling of organic matter and nutrients. However, due to the raw materials used, the compost can have a significant content of heavy metals such as: cadmium (Cd), lead (Pb), arsenic (As), mercury (Hg) and selenium (Se), and contaminants such as potentially toxic trace elements that harm human health. These components can accumulate in plant tissues by absorption, giving rise to the possibility of being bioavailable to humans and animals. The fungal bioremediation of heavy metals in RSOM/U compost is highly efficient, cost-effective, available and friendly to the environment, therefore the removal of metals through this technique is a priority, if the purpose is to use it in agricultural soils. This review summarizes the studies based on the potential of fungal biomass for the bioremediation of heavy metals in RSOM/U compost, reporting information on RSOM/U-based compost, fungal biomass production and mechanisms of bioremediation of heavy metals by fungal biomass. In conclusion, the bioremediation of heavy metals using the fungal biomass in RSOM/U compost, with adequate segregation of raw material, coupled with bioremediation, could improve the removal of heavy metals in RSOM/U compost, and could be an ecological and viable alternative, which must be valued by intensifying its use.