Dario Priolo

The agrifood industry generates substantial amounts of waste to meet the increasing global food demand, raising environmental concerns. Valorization of these residues through the recovery of high-added-value compounds and renewable energy production, such as biogas via Anaerobic Digestion (AD), offers a sustainable solution. In this study, the potential of Olive Pomace (OP), Brewers’ Spent Grain (BSG), and Cereal Wheat Bran (BR) as substrates for AD was investigated. Lignin was removed from these biomasses using an Ionic Liquid (IL) composed of triethylamine and sulphuric acid ([Et₃N][HSO₄]), and the delignified residues, called Olive Pomace Pulp (OPP), Brewers’ Spent Grain Pulp (BSGP), and Cereal Wheat Bran Pulp (BRP), were evaluated for their biogas and biomethane production potential through the volumetric method, coupled with an alkaline trap for biogas upgrading. An analysis was performed, considering biogas and biomethane yields, AD duration, and energy requirements. Raw biomasses provided different biomethane concentrations, with OP reaching 53.73%, BSG 76.59%, and BR 77.36%. After IL treatment, the methane content was 55.6% for OPP, 60.0% for BSGP, and 54.6% for BRP. Owing to their similar composition, BSG and BR displayed comparable biomethane production profiles. The analysis highlighted BSG and BR as the most efficient substrates for AD following lignin removal. Overall, this approach demonstrates the potential of agro-industrial waste valorization to produce bioenergy and support the transition toward a circular economy.

This study focuses on biogas production within lab-scale semi-batch bioreactors using agro-industrial wastes and dry biomass of an invasive aquatic species. In particular, the primary objective is to increase the yield of anaerobic digestion processes, with a specific focus on reducing CO₂ emissions associated with the degradation of biomass, by co-digesting different raw biomasses and agro-industrial wastes. In detail, the experiments concerned the pulp of Brewery’s Spent Grain (BSGp), consisting of the residual of Brewery’s Spent Grain after fiber deconstruction with ionic liquids–based treatment, and Lemna minor L. (LM). The two biomasses were studied separately and then co-digested. Co-digestion was carried out using a 1:1 (VS basis) mixture of Lemna minor and Brewery’s Spent Grain pulp. Due to the lack of organic nitrogen, BSGp showed low biogas production if compared with untreated BSG (1.14 × 10⁻³ vs. 1.71 × 10⁻³ Nm³/gVS). Differently, LM has a high nitrogen content and, when digested alone, produced 9.79 × 10⁻⁴ Nm³/gVS. The co-digestion tests allowed us to reach the highest performance: 2.94 × 10⁻³ Nm³/gVS. In terms of bioenergy production, the two biomasses showed high synergy when used in co-digestion. The amount of energy produced was calculated using a lower heating value (LHV) of CH₄ equal to 52 MJ. The results showed that co-digestion yielded 64.9 ± 0.6 MJ/kgVS, followed by BSG (43.3 ± 5.3 MJ/kgVS), BSGp (25.6 ± 0.3 MJ/kgVS), and LM (19.3 ± 1.0 MJ/kgVS). In addition, in terms of CO₂ avoided, the following results were achieved: 0.38–0.40 gCO₂/gVS with BSGp, 0.73–0.8 gCO₂/gVS with LM. Conversely, co-digestion tests allowed for the avoidance of 1.68–1.91 gCO₂/gVS. In conclusion, co-digesting BSGp with Lemna minor yields more methane and less CO₂ per unit processed, providing an effective way to convert readily available waste and biomass into bioenergy.

Olive cultivation is one of the most widespread agro-industrial activities in the Mediterranean area. However, required pretreatments often affect the anaerobic digestion process, promoting or inhibiting the overall yield. Therefore, the efficiency of Anaerobic Digestion (AD) processes cannot be established in advance but needs to be experimentally validated for each biomass-pretreatment combination. Following the present purpose, these biomasses were firstly treated: the olive pomace (OP) with a procedure based on the use of an ionic liquid (IL) composed of triethylamine and sulfuric acid [Et₃N][HSO₄] to remove hemicellulose and lignin and recover the insolubilized OP, while olive mill wastewater (OW) was processed via freeze-drying. The resulting materials, the pulp from olive pomace (POP) and freeze-dried OW (FDOW), were then digested using lab-scale anaerobic reactors. The biogas production was then compared with the quantity obtained by digesting the same untreated biomasses (OW and OP). The FDOW showed the highest biogas production due to the freeze-drying treatment that led to some morphological and structural surface modifications of OW (respectively, 658 mL vs. 79 mL/g for the two matrices), prompting microorganism activity. Conversely, the method based on the use of IL significantly reduced the nitrogen content of POP, thus resulting in the lowest biogas production, which ceased by the second day. To address this issue, we co-digested POP with the brewery’s spent grain, a biomass rich in nitrogen. This step enhanced the biogas yield of POP, resulting in an extended anaerobic digestion period and the production of 466 mL/g. Additionally, we tested FDOW in co-digestion with BSG to evaluate improvements in production. The codigestion of the two matrices increased the biogas yield of FDOW from 944 to 1131 mL/g.

Brewery’s spent grain (BSG) consists of the largest by-product by volume in the beer production sector and offers potential for both bio-composite material production, high-added-value molecular extraction and bioenergy recovery. Aiming at exploring the ideal biorefinery approach for this agro-industrial residual, the present study experimentally investigated several methodologies to enhance the reuse of BSG and proposed a scheme of biorefinery focused on it. According to it, BSGs were firstly tested to produce high-added-value byproducts, such as protein hydrolysates and for the extraction of lignin via ionic liquids-based methods. The residuals were then used for biogas/biomethane production via anaerobic codigestion. The different matrices were rearranged in varying mixtures, aiming at ensuring high availability of nutrients for methanogens, thus achieving higher energy production than what achievable with untreated BSG. For the scope, further agro-industrial wastes were considered. The resulted digestate was finally composted. Untreated BSGs were also directly tested as fillers for bio-composite material production (in a mixture with PHB). Different concentrations were tested and the mechanical properties of each sample were compared with those of pure PHB. Disintegration tests were finally carried out to measure the improved biodegradability of the produced bio-composite material.

The control of bacterial plant diseases is very challenging and often relies on the application of copper compounds, although the frequent emergence and spread of resistant bacterial strains compromise their efficacy. Additionally, copper-based compounds raise environmental and human health concerns, leading to their inclusion in the European Commission’s list of candidates for substitution. As a promising and sustainable alternative, we investigated the efficacy of biogenic zinc oxide nanoparticles (ZnO-NPs) in protecting tomato plants against Pseudomonas syringae pv. tomato (Pst), the causal agent of bacterial speck disease. ZnO-NPs exhibited significant in vitro antibacterial activity (EC₉₅ = 17.0 ± 1.1 ppm) against the pathogen. Furthermore, when applied to the foliage of tomato plants at 100 ppm before or following Pst inoculation, they induced significant reductions in symptom severity and bacterial growth in planta, which were comparable to those shown by plants treated with acibenzolar-S-methyl, a plant defense inducer. Gene expression assessed by qPCR revealed the involvement of the systemic acquired resistance (SAR) pathway in tomato plants treated with ZnO-NPs before inoculation, suggesting that the observed protection could be due to a priming effect. Finally, infected plants showed oxidative stress, with higher H₂O₂ and malondialdehyde (MDA) contents. ZnO-NPs reverted this effect, containing the content of the above molecules, and stimulated the production of metabolites involved in dealing with oxidative perturbations (carotenoids and phenols), while unaffecting flavonoids and anthocyanins.

Nanotechnology offers promising applications in agriculture by enhancing crop growth, yield, and antioxidant defenses. This study is the first to evaluate the effect of biogenic zinc oxide nanoparticles (ZnO-NPs) on the in vitro growth of two blueberry cultivars, Brigitta and Duke. The ZnO-NPs were synthesized biogenically using an extract of Lemna minor L., which is a free-floating aquatic plant, as a capping and modulating agent, and were added to the plant’s growth media at different dosages (0, 2, 6, and 18 mg L−¹). The ZnO-NPs significantly increased the shoot number, fresh biomass, and dry weight in both cultivars without affecting shoot vitality, length, or basal callus formation. Moreover, the increases in carotenoids in both cultivars, as well as chlorophyll and and soluble proteins in the ‘Brigitta’ cultivar, confirm the prompted benefits and possibly evidence genotype-specific metabolic adaptations in response to ZnO-NPs. These results demonstrate that biogenic ZnO-NPs can effectively promote the in vitro growth of blueberry explants, offering improvements in micropropagation efficiency.

Agriculture has a significant environmental impact and is simultaneously called to major challenges, such as responding to the need to develop more sustainable cropping systems with higher productivity. In this context, the present study aimed to obtain lignin nanoparticles (LNs) from pomace, a waste product of the olive oil chain, to be used as a nanobiostimulant in tomato plants. The biostimulant effect of this biopolymer is known, but its reduction to nanometer size can emphasize this property. Tomato plants were subjected to different LN dosages (25, 50, and 100 mg L⁻¹) by foliar application, and inductive effects on photosynthetic machinery, aerial and root biomass production, and root morphology were observed. The treated plants showed increased efficiency in catching and using light, while they reduced the fraction dissipated as heat or potentially toxic to cells for the possibility of creating reactive oxygen species (ROS). Finally, this benefit was matched by increased pigment content and a stimulatory action on the content of nitrogen (NBI) and antioxidant substances such as flavonoids. In conclusion, the present study broadens the horizon of substances with biostimulant action by demonstrating the validity and efficacy of nanobiostimulants obtained from biological residues from the olive oil production chain.

Agricultural systems must improve their sustainability and productivity to meet the growing global demand for food. A cost-effective and sustainable way is the development of biostimulants from plants rich in bioactive compounds. This study aimed to test an aqueous extract from Lemna minor L. (duckweed) on tomato plants at different concentrations (LE—0.1, 0.5 and 1.0%—weight/volume, w/v). Photosystem I and II activity, linear electron flow (LEF), electrochemical gradient across the thylakoid membrane (ECSt), shoot biomass production, root phenotyping, pigment and metabolite content were studied. LE improved many of these traits, with LE 0.5% being the most effective dosage. Compared to the untreated samples, LE significantly stimulated photosystems to use light energy while reducing the amount lost as heat (PhiNPQ and NPQt) or potentially toxic to chloroplasts (PhiNO). These results were supported by the improved shoot biomass production (number of leaves and fresh and dry weight) and root traits (number of tips, surface, volume and fresh and dry weight) found for LE-treated samples compared to untreated controls. Finally, the study highlighted that LE increased pigment and flavonoid contents. In conclusion, the research indicates that this species can be an effective and eco-friendly tool to stimulate beneficial responses in tomato.

Using biomass to develop and obtain environmentally friendly and industrially applicable biomaterials is increasingly attracting global interest. Herein, cellulose nanocrystals (CNCs) and lignin nanoparticles (LNPs) were extracted from Lemna minor L., a freshwater free-floating aquatic species commonly called duckweed. To obtain CNCs and LNPs, two different procedures and biomass treatment processes based on bleaching or on the use of an ionic liquid composed of triethylammonium and sulfuric acid ([TEA][HSO₄]), followed by acid hydrolysis, were carried out. Then, the effects of these treatments in terms of the thermal, morphological, and chemical properties of the CNCs and LNPs were assessed. The resulting nanostructured materials were characterized by using Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, thermo-gravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that the two methodologies applied resulted in both CNCs and LNPs. However, the bleaching-based treatment produced CNCs with a rod-like shape, length of 100–300 nm and width in the range of 10–30 nm, and higher purity than those obtained with ILs that were spherical in shape. In contrast, regarding lignin, IL made it possible to obtain spherical nanoparticles, as in the case of the other treatment, but they were characterized by higher purity and thermal stability. In conclusion, this research highlights the possibility of obtaining nanostructured biopolymers from an invasive aquatic species that is largely available in nature and how it is possible, by modifying experimental procedures, to obtain nanomaterials with different morphological, purity, and thermal resistance characteristics.