Fly ash superficially modified with humic substances from the Megalopolis lignitic power plant was prepared and evaluated for agricultural uses. UV‐vis spectrophotometry and IR spectroscopy revealed that fly ash shows high sorption efficiency towards humic substances. Adsorption proceeds stepwise via strong Coulombic and hydrophophic forces of attraction between guest and host materials. Langmuir, Freundlich, BET, Harkins‐Jura, and Dubinin‐Radushkevich isotherm models were employed to evaluate the ongoing adsorption and shed light to the physicochemical properties of the sorbent‐adsorbate system. Humic substances desorption and microbial cultivation experiments were also carried out to examine the regeneration of the humates under washing and explore the possibility of this material acclimatizing in real soil conditions, both useful for biofunctional agricultural applications.

A new, simple, and rapid one-step integrated method for the biotechnology treatment of raw olive oil mill waste (OMW) is discussed. The innovations introduced involve primarily the application of microaerobic composting processes for OMW bioremediation plus the addition of both a zeolite and a tailor-made biocatalyst extremely rich in soil microorganisms. The latter operates at a wide pH range and provides, apart from soil microorganisms, nutrients to the compost, enhancement to the bio-oxidative phase and acceleration of biochemical reactions during bioremediation. The basic parameters affecting the bioprocess, i.e., electrical conductivity, pH, C/N ratio, specific weight, ash, organic matter, total organic carbon, total Kjeldahl nitrogen, microorganisms, humic substances, and total polyphenols, were monitored systematically to provide insight into the process and evaluate the product obtained. After a biotreatment of just 60 d, a significant reduction in polyphenols (91.4%) and an increased humic substances content (8%)—both serving as maturation indices—were observed. The OMW compost received is stable, free of toxic compounds and pathogens, affords a richness in cenose and a high humic substances content, both vital for soil fertility. Applications of the OMW product received, both in laboratory-scale and field cultivations, confirm its suitability as a first-class soil conditioner for organic farming.

This study aimed to highlight the positive effects of various recycled organic substrates on lettuce plants (Lactuca sativa L.) and to promote sustainable waste management practices, contributing to the concept of a circular economy. Over a two-month period, the growth potential and rhizosphere microflora of lettuce plants grown in soil amended with different recycled substrates were investigated. All data were compared, and the effects of the culture substrates were evaluated. All groups containing soil improvers offered a significant increase in the number of leaves per plant and, in two cases, an increase in dry biomass as well as an increase in the concentration of all leaf pigments. Both MDA and H₂O₂ concentrations were the lowest in two groups containing soil improvers (VG 5% and PLUS 10%). At the end of the culture period, isolation and culture of bacteria from the plant rhizosphere were performed. Different bacterial strains were isolated and tested for the production of antimicrobial agents against six microbial indicators (B. subtilis, E. coli, S. aureus, S. cerevisiae, C. albicans, and P. aeruginosa). The greater percentage of the isolated strains showed an ability to inhibit the growth of the B. subtilis index. Most of the strains with antimicrobial activity were isolated from the soil samples of the plain soil group and the soil amended with the commercial fertilizer. Three of the isolated strains originating from the Ginagro 5% group are multiproducers as they inhibit the growth of three microbial indicators or more.