Current and Potential Use of Citrus Essential Oils.

Since the Middle Ages, citrus essential oils (EOs) have been widely used for their bactericidal, virucidal, fungicidal, antiparasitical, insecticidal, medicinal and cosmetic proprieties. Also nowadays, they find important applications in pharmaceutical, sanitary, cosmetic, agricultural and food industries. The best method to extract EOs from citrus plant tissue is steam distillation because of a variety of extracted volatile molecules such as terpenes and terpenoids, phenol-derived aromatic components and aliphatic components. In vitro physicochemical assays classify most of them as antioxidants

Zeolites for the nutrient recovery from wastewater

To meet the growing food demand of the world population, excessive use of chemical fertilizers is occurring to improve soil fertility and crop production. The excessive use of chemical fertilizers is not economically and environmentally sustainable. Indeed, from one hand, due to the increasing demand of fertilizers is rising their costs whereas, on the other hand, the accumulation of fertilizers in wastewaters is altering the homeostasis of the ecosystems thus causing serious damages to human health [1,2]. The recovery of nutrients, such as nitrogen (N) and phosphorus (P), from wastewaters is a good option to counteract both economic and environmental issues raised by the excessive use of fertilizers [3]. Adsorption is among the most widely used methods for nutrient recovery from wastewaters due to its efficiency and simplicity. The choice of appropriate adsorbent materials is a key issue for ensuring high performance and low costs of the process [4]. Over the years, several materials have been studied to absorb nutrients from wastewaters. Zeolites, both natural and modified, have attracted great attention due to their relevant specific capacity, selectivity, safety, and stability [5]. However, considering that in municipal effluents the inorganic P exists as the anionic forms of dihydrogen or monohydrogen phosphates (H2PO4 − and HPO42−, respectively) and N in both cationic (ammonium, NH4+) and anionic (nitrate, NO3−) form [6], natural zeolites can be only used for the direct recovery of NH4+

Phytotoxic potential of Citrus essential oils on weed species

Environmental constraints of crop production systems have stimulated interest in alternative weed management strategies. In fact, the continued use of synthetic herbicides may threaten sustainable agricultural production and result in serious ecological and environmental problems, such as the increased incidence of resistance in weeds to important herbicides and increased environmental pollution and health hazards. Public awareness and demand for environmentally safer herbicides with less persistence and less contaminating potential make searches for new weed control strategies. Citrus Essential oils are generally used in the cosmetic, medicinal, and food industries, and are thought to be safe compounds for humans, animals, and the environment. EOs can be extracted by hydro distillation and cold pressing. The two methods are based on different procedures. Hydro distillation is carried out with a Clevenger-apparatus that conducts the distillation process by boiling, condensing and decantation to separate the EOs. The cold pressing consist of crushing and pressing the peels thus leading to the formation of a watery emulsion. Then, the emulsion is centrifuged to separate out the EOs. Since no external substance are needed, this process ensures that the resulting EOs retains all their properties. The allelopathic and phytotoxic effects of EOs obtained from other species and their potential use for weed management has been well documented. The objectives of this study were to evaluate in vitro the phytotoxic effects of Citrus EOs (Citrus sinensis, Citrus limon and Citrus reticulata) extracted by hydro distillation and cold pressing on main weed species (Amaranthus retroflexus, Portulaca oleracea., Echinochloa crus-galli, Avena sativa). For all EOs six concentrations were tested (0.5, 1, 2, 4, 8, 12) μl/ml and 5 repetitions with 20 seeds each (for dicotyledons) or 10 repetitions with 10 seeds each (for monocotyledons) were performed. They were applied for one hundred seeds for concentration. Twenty seeds were placed into 9 cm diameter Petri dishes for Amarantus and Portulaca. In each Petri dish, 5 ml of distilled water were added. This volume kept the filter papers uniformly soaked-wet without flooding. For Avena and Echinocloa ten seeds were placed into petri dishes and 6 ml of distilled water was added. The essential oil was placed in a sheet of filter papers in contact with the seeds. The controls were prepared with the same quantities of distilled water. Petri dishes were incubated in the room germination (EQUITEC) at 20/30 °C (±1 °C), alternating temperature (6/18 h dark and light (cool white Radium NL 36W/840; 3100 lm)). Dishes were sealed to reduce evaporation, and no more additional water was supplied during the tests. To evaluate the possible phytotoxic effects of the essential oils and their main compounds on seed germination and seedling growth data were registered by taking photos after 3,5, 7, 10 and 14 days after incubation and will be processed using Digimizer. Then data will be analysed and discussed

Soil bioindicators and weed emergence as affected by essential oils extracted from leaves of three different Eucalyptus species

The widespread use of synthetic herbicides has resulted in herbicide-resistant weeds, altered ecological balance and negative effects on human health. To overcome these problems, efforts are being made to reduce the reliance on synthetic herbicides and shift to natural products. Essential oils (EOs) extracted from plants have been demonstrated to have potential herbicide activity. EOs, composed by volatile organic compounds and characterized by a strong odor, are used in the cosmetic, pharmaceutical and food industries as they are thought to be safe compounds for humans, animals, and the environment. EOs extracted from Eucalyptus leaves have antimicrobial, antiviral, fungicidal, insecticidal, anti-inflammatory, anti-nociceptive and anti-oxidant effects. Moreover, in vitro studies have demonstrated that they have inhibitory effects on germination of seeds of many crops and weeds. The aim of this work was to evaluate the in vivo effects of EOs extracted from Eucalyptus leaves on both weed emergence and biochemical soil properties. Furthermore, since the diverse species of Eucalyptus have shown to have different biological activities, EOs were extracted from three Eucalyptus species (E. camaldulensis, E. globulus, E. occidentalis). Fresh leaves were collected from an afforested area near Piazza Armerina (province of Enna, Italy) and their EOs extracted by hydrodistillation. Soil samples were collected from the topsoil (<5 cm) of an Inceptisol within the experimental farm of the University of Palermo, air-dried and sieved at 1 cm. Five hundred grams of this soil were filled in each of 20 aluminum pots (10×20 cm). The soil samples were brought up to 100% of the water holding capacity (WHC) by adding 150 mL of tap water, followed by 70 mL of tap water containing 8 mL L-1 of one of the three extracted EOs. This experimental test was repeated for remaining two EOs. Fitoil was used as emulsifier at a concentration of 0.1% (v/v). The control consisted of the soil treated as the EO treatment but with Fitoil only. The soils were incubated in greenhouse conditions. After 2 days, the 100% WHC halved and then it was kept to this level (50% WHC) by watering soil daily. The experiment was carried out in quadruplicate. After one month the soil were brought up to 100% of WHC, plant biomass and height of germinated weeds and soil biochemical properties were evaluated. This work reports the results and discuss them

Can the presence of Biochar negatively affect the ability of chloroform to lyse soil microbial cells?

Biochar is the solid product of the thermochemical decomposition of biomass at moderate temperatures (350–700 °C)[1] under oxygen-limiting conditions. It is nowadays utilized in various applications, for example, in the synthesis of new materials for environmental remediation, catalysis, animal feeds, adsorbent for odours, etc.[2]. In recent decades, interest has grown in the application of biochar as a soil amendment due to its beneficial effects on soil fertility and crop productivity. Biochar amendment is known to alter soil porosity, improve soil structure, increase soil surface area[3], cation exchange capacity, soil organic carbon content and soil microbial biomass[1]. The latter variable is one of the most widely adopted biological indicator for the evaluation of soil fertility status. In fact, the microbial component is the engine that governs energy transfers and nutrient transformations in the soil, thus playing a key role in its fertility. The most widely used methods for determining soil microbial biomass are the chloroform-incubation (FI) and chloroform-extraction (FE) methods[4][5], both relying on the ability of chloroform (CHCl3) fumigation to lyse soil microbial cells and release their contents. Over the years, several critical issues related to the use of CHCl3 have risen due to its toxicity to humans and the environment, as well as due to its not fully proved ability to lyse soil microbial cells. Toyota et al.[6] showed that approximately 10% of bacterial colony forming units in a sandy loam soil survived a 5-day CHCl3 fumigation. This percentage was much higher when fumigating a clayey soils. Alessi et al.[7] demonstrated that significant concentrations of CHCl3 were adsorbed, and thus retained by the clay fraction of soils thus negatively affecting the extractability of microbial-derived constituents. Such a controversial ability of CHCl3 to lyse microbial cells may be even more critical when applied to soils amended with biochar. Indeed, biochar, due to its porous structure and high specific surface area can adsorb several volatile organic compounds, including CHCl3[8]. Therefore, the aim of this study was to assess the ability of CHCl3 to lyse microbial cells in soils amended with two different biochars (EG) and (NB). Treatments were: soil without biochar (control), soil amended with 16 g of EG or NB biochar per kg of air dry soil (corresponding to 20 t ha-1) and soil amended with double amount of EG or NB biochar (corresponding to 40 t ha-1). The ability of the CHCl3 to lyse soil microbial cells in soils with or without biochar was assessed by quantifying either the amount of CO2-C released during incubation or the extractable C and N in fumigated soils, and comparing with the corresponding amount of C obtained from soil pressurized with CO2 (CO2HP). The latter is a new method, under evaluation, that causes lysis of soil microbial cells by high CO2 pressurization and subsequent rapid decompression. Since the CO2HP method is based on a physical approach, it should not be influenced by the presence of biochar in the soil samples being analyzed. Results showed that the amount of CO2-C emitted during the incubation of pressurized soils amended with biochar is higher than that of the same soils but fumigated, thus suggesting higher cell lysis efficiency of the CO2HP method than the CHCl3 in soil amended with biochar. Moreover, extractable C and N results suggested that the ability of CHCl3 depends on the type and concentration of biochar used. CHCl3 could be partly adsorbed and thus retained in the soil after fumigation and risks overestimating the C of the microbial biomass or does not allow for complete lysis of soil microbial cells. Bibliography [1] Brassard, P., Godbout, S., Lévesque, V., Palacios, J. H., Raghavan, V., Ahmed, A., Houge R., Jeanne T. &amp; Verma, M., 2019. Char and Carbon Materials Derived from Biomass,109-146. Elsevier. [2] Conte, P., Bertani, R., Sgarbossa, P., Bambina, P., Schmidt, H.P., Raga, R., Lo Papa, G., Chillura Martino, D.F. &amp; Lo Meo, P., 2021. Agronomy, 11(4), 615. [3] Hardie, M., Clothier, B., Bound, S., Oliver, G., &amp; Close, D., 2014. Plant and Soil, 376(1), 347-361. [4] Jenkinson, D. S., Powlson, D. S., 1976. Soil Biology and Biochemistry, 8, 209- 2013 [5] Vance, E. D., Brookes, P. C., Jenkinson, D. S., 1987. Soil Biology and Biochemistry, 19, 703-707 [6] Toyota, K., Ritz, K., Young, I.M., 1996. Soil Biology and Biochemistry 28, 1545-1547. [7] Alessi, D.S., Walsh, D.M., Fein, J.B., 2011. Chemical Geology, 280 (1-2), 58-64 [8] Kumar, A., Singh, E., Khapre, A., Bordoloi, N., &amp; Kumar, S., 2020. Sorption of volatile organic compounds on non-activated biochar. Bioresource Technology, 297, 122469

Zeolite – Ammonium interaction: physical-chemistry of adsorption process

Zeolites are crystalline microporous tectosilicates, either natural or synthetic. Natural zeolites were formed as a result of the interaction of volcanic rocks and volcanic ash with alkaline groundwater. Due to the formation process, there are more than 50 types of natural zeolites, the most common being clinoptilolite, which belongs to the heulandite family and has the simplified ideal formula of (Na,K,Ca)2-3Al3(Al,Si)2Si13O36·12(H2O). Geological settings and conditions during zeolite formation and geological weathering influence several parameters such as mineralogy, rock porosity/permeability and reaction rate, all of which affect their operational capabilities, hence their use in technical applications. Indeed, zeolites, due to their properties, can be used in several operations, including gas separation, adsorption, ion exchange and catalysis. In recent years, they have been playing an important role in the recovery and removal of nutrients from treated wastewater due to their ion exchange property. Their ability to adsorb cations (such as ammonium ions) comes from the substitution of Si4+ by Al3+, which increases the negative charge of the mineral lattice. The resulting negative charge is balanced by exchangeable cations such as Na+, K+ and Ca2+. The recovery of nutrients (nitrogen and phosphorus) from wastewater is necessary, as their presence in wastewater accelerates the eutrophication of receiving water bodies, creating a potentially toxic environment for fish and other aquatic life. In addition, nutrient recovery from wastewater allows solving problems i.e. the poor access to fertilizers in developing countries and the looming high cost of fertilizers; in fact, the recovered fraction of nutrients can be reused as fertilizer in agriculture promoting a circular economy approach. Furthermore, the use of natural adsorbent materials, such as zeolites, to recover nutrients from wastewater overcomes the problem associated with existing technologies. Which are often expensive and difficult to apply, limiting their use in economically poor countries due to lack of infrastructure and maintenance costs. However, the removal of ammonium by ion exchange on zeolites is influenced by the origin of the zeolites used. Previous studies on clinoptilolites with different lithological matrix have shown how the ability to adsorb NH4+ varies in clinoptilolites of different origin. For example, a Canadian clinoptilolite was capable of adsorbing about 20 mg NH4+ g-1, while a Chinese clinoptilolite did not exceed 5 mg NH4+ g-1. The original matrix may also have an influence on the treatment when natural zeolites are treated to increase the adsorption capacity. Based on the above considerations, the objectives of the PhD project, carried out within the Wider Uptake project (Horizon2020 EU project), are: i) to compare the ammonium adsorption rate on two clinoptilolites of different origin (Slovakia and Cuba), ii) to evaluate the effect that the matrix had on the treatment carried out to improve the adsorption capacit

Catalytic hydrothermal liquefaction of municipal sludge in subcritical water

In the last decades, the dwindling of the fossil sources of energy coupled with the growth of energy demand and of waste production prompted the research in developing novel industrial technologies for renewable energy production and waste valorization. Hydrothermal liquefaction (HTL) is a good alternative to transform wet biomasses as microalgae, macroalgae, agricultural residues, food waste, and municipal sludge (MS) into value-added products with high efficiency and decreasing the amounts that has to be disposed of. HTL takes place in an aqueous environment, without the energy cost of drying the biomass, at 300-400°C and pressure of 10-40 MPa [1,2]. At these operative conditions, an integral degradation of wet biomass produces a bio-oil termed biocrude and other C-containing products i.e. a solid residue, a gaseous phase rich in CO2 and an aqueous phase with soluble organics. The development of the process to the industrial scale is hindered by many challenges related both to the heterogeneous nature of the raw material and the complexity of the phase behavior downstream of the process and the poor quality of the biocrude produced as fuel precursor. This work aims to investigate the potentiality of catalytic HTL to obtain a biocrude more competitive as fuel precursor. We have studied catalytic HTL of MS in a stirred AISI 316 high-pressure batch reactors at 325 °C and 30 min as reaction temperature and time using NiMo/Al2O3, CoMo/Al2O3 and activated carbon felt as catalysts and formic acid (FA) as liquid hydrogen donor. Optimized work-out procedures were used to separate and quantify the products with the aim to decrease the amount of not detected mass [3]. With adopted methods the formation of an hydrocarbon fraction (HC) recovered from the biocrude, was detected in the presence of the catalysts. This result indicates that tested catalysts promote the in-situ up-grading of the produced biocrude. Furthermore, the addition of FA as liquid hydrogen donor allowed us to achieve higher H/C and HHV of biocrude as it was possible to increase the biocrude yield at more than 50% with energy recovery approaching 100%. Collected results suggest that use of catalysts can increase the yield and quality of biocrude in the HTL of municipal sludge

Wastewater treatment sludge composting

In recent years, the amount of sewage sludge generated by wastewater treatment plants (WWTPs) has increased due to worldwide population growth and to efficiency of biological treatment processes [1,2]. Sludge is an important source of secondary pollution to aquatic environments and a potential risk to human health; moreover, it represents one of the most important cost items in the functioning of water treatment plants [3–5]. About 60% of the operating costs of secondary wastewater treatment plants in Europe can be associated with the treatment and disposal of products [6]. For this reason, proper sludge management becomes increasingly important, at both national and international level, and it becomes necessary to find effective measures to limit the environmental impacts and to reuse sludge as a resource, within a circular economy vision [2,7]. Current methods of utilization of sewage sludge include agricultural application, landfilling, incineration, drying, and composting and/or vermicomposting. Composting is a widely used cost-effective and socially acceptable method for treating solid or semisolid biodegradable waste [8]. In agriculture sewage sludge is used for rehabilitation of degraded soils, reclamation, or adaptation of land to specific needs [9]. The above consideration comes from several studies showing that the application of sludges to agricultural land can improve soil fertility and, therefore, crop productivity [10–12]. This field of use is also possible due to its composition; in fact, it is rich in organic matter, nitrogen, phosphorus, calcium, magnesium, sulfur, and other microelements needed by plants and living native organisms in the soil. However, sewage sludge may contain a wide range of harmful toxic substances such as heavy metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins and dibenzo-p-furans, polychlorinated biphenyls, di(2-ethylhexyl) phthalate, polybrominated diphenyl ethers, detergent and drug residues, pharmaceutical and personal care products (PPCPs), endogenous hormones, synthetic steroids and pathogenic organisms [13,14], which can cause harm to the environment and humans. Due to the presence of those toxic elements, stabilization of sewage sludge is necessary to avoid any environmental risk [15]. Stabilization of sewage sludge is defined as “biological, chemical or thermal treatment, long-term storage or any other appropriate process aimed at reducing its fermentability and the health hazards arising from its use” [16]. This definition is found in Council Directive 86/278/EEC, which was issued to regulate the use of sludge in agriculture, the primary objective of which is the environment, in particular the soil, and the protection of human health. European Directive 86/278/EEC was implemented in Italy by Legislative Decree 99/1992 [17]. Both the European Directive and the Italian legislative decree can be considered obsolete, this is why the European Union is moving towards amending them to reflect the new needs of the sector and to keep up with technological innovations. Currently, there are several processes for sludge stabilization, including composting, which is one of the most widely used methods for stabilizing organic matter in general, reducing the number of pathogenic microorganisms and the amount of toxic elements [18]. This is possible because during the composting process the organic compounds present in the biomass to be composted are converted into chemically recalcitrant, that is, stabilized, humic substances, while pathogens are eliminated due to the heat generated during the process thermophilic phase [19,20]. During the composting of sludges, the addition of bulking agents is needed, as they ameliorate the composting performance by providing structural support that improves aeration and regulates moisture content and C/N ratio of composting mass [21,22]. Sludge composting, however, has to be focused on limiting some secondary causes of pollution related to the process itself, such as greenhouse gas (GHG) emissions and heavy metal contamination [23]. Indeed, in the last decades, the handling of sewage sludge with traditional methods has led to the release of an enormous amount of greenhouse gases. The choice of an appropriate bulking agent is, therefore, fundamental to limit the emission of climate-altering gases, and, at the same time, to increase the microbial activity thus improving the quality of the compost [24,25]. This chapter aims (1) to give an overview of the national and international legislation on sludge management and reuse, (2) to analyze the composting process and the state of the art regarding sludge composting to understand the limitations at large-scale application, and (3) to discuss the technological innovations in the field and highlight future perspectives

PHYTOTOXIC POTENTIAL OF EUCALYPTUS ESSENTIAL OILS FOR WEED CONTROL

The widespread use of synthetic herbicides has resulted in herbicide-resistant weeds, disturbed ecological balance and negative effects on human health. Due to this fact, it is necessary to rely on alternative weed control strategies using natural compounds released by plants, such as essential oils (EOs). EOs have a short half-life since they are biodegradable, and are safer than synthetic compounds, with little damage to the environment, without even contaminating ground water (Topal and Kocaçalıskan 2006). Essential oils from different species contain allelochemical compounds that possess significant phytotoxic activity. Azizi and Fuji (2006) demonstrated that Eucalyptus (family Myrtaceae) EOs showed strong inhibitory effects on germination of seeds of many crops and weeds. The aim of this work is to evaluate the phytotoxic potential effect of four Eucalyptus species (E. camaldulensis, E. lesouefi, E.occidentalis, E. torquata) EOs, on weed seed germination of two dicotyledons (Amaranthus retroflexus and Portulaca oleracea) and two monocotyledons (Avena fatua and Echinochloa crus-galli) which are considered among the most serious weeds for the Mediterranean crops. Fresh leaves of E. camaldulensis and E. occidentalis were collected in afforested area near Agrigento (Sicily, Italy) during November and December of 2017. The leaves of E. lesouefi and E. torquata were collected during March, April and May from Gabes, located in the South of Tunisia on 2015. The EOs were extracted from each species by steam distillation with a Clevenger apparatus according to the standard procedure described in the European Pharmacopoeia (1975), and stored at 4 °C until they were used. Weed seeds of A. retroflexus, P. oleracea, A. fatua and E. crus-galli were purchased from Herbiseed (England). To test the phytotoxicity activity of the EOs, different concentrations were prepared: 0.125; 0.25; 0.5; 1; 2; 4 µl/ml for dicotyledons and 0.5; 1; 2; 4; 8; 12 µl/ml for monocotyledons. The oils were loaded on the inner side of two layer of filter paper (73 g/m2) in Petri dishes (9 cm diameter), after sowing twenty seeds of each weed type (10 in case of monocotyledons) on the base of the Petri dishes, in two other layers of filter paper wetted with 5 ml of distilled water, in case of the dicotyledons, and 6 ml for the monocotyledons. The controls were prepared with the same quantities of distilled water. For each concentration, five replications were maintained (10 in case of monocotyledons). All the Petri dishes were kept in a growth chamber maintained alternating 30.0 +/- 0.1 °C, 16 h in light and 20.0 +/- 0.1 °C, 8 h in dark. To register germination and seedling length data, photos were taken after 3, 5, 7, 10 and 14 days, and they will be processed with Digimizer. In the poster, the results will be illustrated and discussed

SHORT-TERM RESPONSE OF SOIL MICROORGANISMS TO ESSENTIAL OILS WITH ALLELOPATHIC POTENTIAL EXTRACTED FROM MEDITERRANEAN PLANTS

Essential oils (EOs) with allelopathic compounds have been used to reduce or avoid weed germination and growth. The aim of this study was to evaluate the potential phytotoxic effects of EOs extracted from different Mediterranean plants on soil microbial biomass and activity. EOs were extracted from leaves of Eucalyptus camaldulensis Dehnh (EUC); Eriocephalus africanus L. (ERI); Thymus capitatus (L.) Hoffmanns. & Link (TCP); Citrus reticulata Blanco var. ‘Clemenules’ (TAN) and Citrus limon (L.) Osbeck var. ‘Eureka’ (LEM). Each EO was supplied to pots containing 560 g of soil at three different doses (low, medium, high). After 15, 30, 90, 120 days the supply of EOs, soils were destructively analyses for microbial biomass carbon (MBC) and microbial respiration. EOs extracted from E. camaldulensis (EUC), C. limon (LEM) and T. capitatus (TCP), at the highest concentration decreased MBC up to 30 days since their addition, with no further effects at two last samplings. EOs extracted from ERI and TAN did not affect MBC. Soil respiration was not affected by any experimental factor, whereas the metabolic quotient was increased by EO extracted from TCP. Our results suggested that essential oils with allelopathic potential extracted from mediterranean plants can negatively affect soil microorganisms and, consequently, their use as herbicides should take into account these findings