Pruning Waste Research Articles

Compost Production from Olive Tree Pruning Wastes Enriched with Phosphate Rock

ABSTRACTOlive production is increasing very fast in the last 20 years in Al-Jouf region, northern region of the Kingdom of Saudi Arabia. There are now more than 5 million olive trees in the productive stage. A huge amount of waste is produced annually from this sector, including pruning waste of olive trees and solid waste from olive oil mills of three-phase system. The waste of olive used to produce compost could be of safe disposal technique. Disposal of such waste is expensive and it causes some environmental hazards. Rock phosphate (RP), which is available in the same region, can be used to improve the nutrient value of the produced compost. In this experiment olive pruning waste was composted alone and in a mixture with different RP in two different ratios, namely 5% and 10%, on the dry weight basis of olive waste. Compost processing took place on plies for 8 months. Temperature and moisture were monitored daily while periodical samples were taken from all piles for testing pH, EC, C/N, and germination index. Composts in all treatments reached the theomorphic phase, which killed weed seeds and pathogens. The produced compost from all treatments fulfilled the requirements of maturity according to the California Compost Quality Council after 8 months of composting. In addition, the RP enhanced composting efficiency and improved the quality of the produced compost. Compost parameters met the standard requirements for the compost that was suitable for agriculture purposes with average values of pH ranging from (7.02–7.65) and EC (2.20–3.94 dS m−1). Nutrient concentrations in the produced compost were N (1.28–1.79%), P (0.23–2.15%), and K (2.59–4.22%).

Evaluation of the characteristics of vineyard pruning residues for energy applications: effect of different copper-based treatments

The role of biomass for increasing renewable energy sources mix is considered fundamental, despite some negative environmental impact of first-generation biofuels. The use of biomass obtained in a more sustainable way, as represented by agricultural wastes, should be favoured. The Mediterranean area and Italy in particular offer a large amount of vineyard pruning residues that can be converted into bioenergy. Since vineyards are exposed to treatments based on copper (Cu) and zinc, these metals last in wood residues during pruning and accumulate in the soil. In this study an evaluation of the concentrations of copper and other heavy metals in grapevine pruning wastes, when treated with common plant protection products, was carried out. The study was also extended to the soil, being potentially mixed to the biomass in the case of mechanical collection of pruning residues. The grapevine residues free of impurities that were collected during this study have typical values of copper in pruning wood, varying from 8.5 mg kg<sup>–1</sup> when treated with low Cu product, to 19.2 mg kg<sup>–1</sup> when treated with high Cu product. It was observed that contaminations during pruning with soil could increase the amount of copper in the residues. More in detail, every percentage point of soil that winds up on pruning residues involves an increase of 1 mg of Cu every kg of biomass. For this reason, we recommend the use of appropriate systems for the harvest of grapevine residues, particularly mechanical systems that avoid soil lifting. Moreover, we suggest the use of pruning residues preferably in large-scale power plants with appropriate emission filters instead of small-scale domestic boilers.

Agri-food sludge management using different co-composting strategies: study of the added value of the composts obtained

The growth of the agri-food industry has resulted in a strong increase in its sludge generation. This type of waste is often produced in high amounts, concentrated in certain areas, and shows characteristics similar to those of municipal sewage sludge (except for the absence of heavy metals). Composting has been widely studied as a viable alternative for the treatment and recycling of municipal sewage sludge, but little information is currently available concerning the composting of agri-food sludge. Thus, the aim of this work was to increase our knowledge of how the vegetable-derived sludge produced by the agri-food sector can be managed using different co-composting strategies. The work was concerned mainly with the characteristics of the bulking agents used (type and particle size) and their effects on the development of the process and on the potential added value of the composts obtained. For this, four composting piles were prepared using agri-food sludge and two bulking agents (vine shoot prunings and pepper plant pruning waste) at two particle sizes (<1 cm and <3 cm). The evolution of the process and the final properties of the composts obtained were studied using classical analytical methods together with advanced instrumental methods (thermal analysis and excitation–emission matrix (EEM) fluorescence spectroscopy). In addition, their physical characteristics and potential suppression of phytopathogens (Fusarium oxysporum f. sp. melonis) were determined. The results showed differences according to the type and size of bulking agent, the mixtures with vine shoot prunings having a higher biodegradability, which was confirmed by thermogravimetry and EEM fluorescence spectroscopy. Melon plants grown in a mixture which included compost produced using vine pruning waste had a greater shoot weight than those grown on peat alone, while the mixture including compost derived from pepper pruning waste gave a shoot weight similar to that of peat-grown plants. Furthermore, the composts elaborated using vine shoot prunings had added value with respect to their use as growing media components for seedling production of melon, due to their suppression of F. oxysporum f. sp. melonis. Therefore, this study has shown that the nature of the bulking agent used is of major importance not only for the development of the composting process, but also for the final properties and potential added value of the end-products obtained.

Organic plum cultivation in the Mediterranean region: The medium-term effect of five different organic soil management practices on crop production and microbiological soil quality

Organic farming practices recommended by European regulations offer an alternative to conventional soil management, but these practices should be analyzed in greater depth to assess their effectiveness on different plants and in different local conditions. Accordingly, this study evaluates the efficacy of five different organic management strategies on an organic plum farm in Southeastern Spain. This study was conducted for a period of six years and the five different organic treatments were applied in triplicate in 256m2 plots randomly distributed in three blocks (15 plots in total); each plot had 16 plum trees. Every year crushed pruning wastes were incorporated into the soil in all the experimental plots. One triplicated plot only received this aforementioned treatment (crop biomass treatment, CB). The rest of the plots also received one of the following treatments: (i) the addition of a commercial product for organic agriculture based on bacteria (biofertilizer), composed of Azospirillum brasilense (bacteria fixing N) and Pantoea dispersa (bacteria with a capacity for solubilising phosphates and stimulating plant growth) (biofertilizer treatment, B); (ii) the annual addition of 20t/ha of certified commercial organic compost (annual compost treatment, AC); (iii) the biennial addition of 20t/ha of certified commercial organic compost (biennial compost treatment, BC); and (iv) the sowing and subsequent incorporation of a mixture of 60% Avena sativa and 40% Vicia sativa (green manure treatment, GM). Each year the following indicators of ecosystem sustainability related to soil microbiological characteristics and carbon fixation were measured after harvest, in addition to plum yield: organic carbon (Corg), water soluble C, humic substances and humic acid C, microbial biomass C, respiration, ATP, dehydrogenase activity and hydrolase enzymes (alkaline phosphatase, urease and beta-glucosidase) activities. The two way ANOVA of the results indicated that all the above parameters were significantly affected (p≤0.001) by both, treatment and time. The interaction of treatment and time also significantly affected all of these parameters, except for yield and dehydrogenase activity. Composts not only produced better results than green manure cover crops and biofertilizer treatments in terms of plum yields, but they also brought about higher increases in the soil C pool and greater improvements in soil microbiological characteristics. In the six years of the study, compost-treated soils showed higher average plum yields and higher organic carbon, humic substance and humic acid contents than the rest of treatments. The size and activity of microbial population was also greater in the compost-treated soils, reflected in the higher values found in these soils for microbial biomass C, soil respiration, ATP (adenosine-tri-phosphate) content and dehydrogenase and hydrolases activity. Nevertheless, yields when compost was added biennially (BC) tended to be higher than in the annual compost treatment (AC) in most years as well as on average, although the differences were usually not significant. Yields in the sixth crop showed a high positive correlation with soil humic substances and humic C content (p≤0.01), as well as with Corg, microbial biomass C and phosphatase and urease activity (p≤0.05).

The effect of pruning waste and biochar addition on brown peat based growing media properties

Peat is a crucial carbon sink in the terrestrial ecosystem, but it is jeopardized by its use as fuel or as growing media. In the last years, much research has been performed aiming to find high quality and low cost substrates from different organic wastes in order to decrease peat consumption. Biochar is a carbon-rich material that has attracted important research as soil amendment. However, its potential utilization as peat substitute for growing media formulation remains less well explored. The main objective of this work was to study the effect on peat based growing media of pruning waste (PW) and three biochars: a commercial charcoal (CC), biochar from slow pyrolysis of PW at 300°C (B300) and 500°C (B500) added at different ratios. The chemical properties of some mixtures were adequate as growing media materials. Hydrophysical properties of peat changed with biochar and pruning waste additions. B500 and CC additions (in 50 and 75vol%) increased air space volume. All mixtures showed lower water holding capacities than peat and only mixtures with B500 lead to adequate holding capacity and porosity values for substrate materials. Finally, lettuce (Lactuca sativa) was grown in the different substrates and, after 5 weeks, the results have shown that lettuce biomass was substantially higher with peat plus biochar samples obtained from pyrolysis of pruning waste at 300 and especially 500°C than with peat alone. Our results imply that pruning residue biochar can be an improved growing media as peat substitute for soilless vegetable production.

Preparation of Activated and Non-Activated Carbon from Conocarpus Pruning Waste as Low-Cost Adsorbent for Removal of Heavy Metal Ions from Aqueous Solution

Conocarpus pruning waste, an agricultural byproduct, was converted into low-cost activated and non-activated carbons and used for the remediation of Cd2+, Cu2+, and Pb2+ from aqueous solutions. The carbonization was carried out at 400 °C, while the activation was carried out in the presence of KOH and ZnCl2. Batch single-solute and multi-solute equilibrium and kinetic experiments were carried out to determine the adsorption capacities of the prepared activated and non-activated carbons, and these were further compared with commercially available activated carbon. The results showed that KOH-activated carbon (CK) outperformed the other activated and non-activated carbons in terms of adsorption efficiency. CK removed >50% of the applied Cd2+ and Cu2+ and 100% of Pb2+ at the initial concentration of 40 mg L-1. Interestingly, the performance of Conocarpus-derived non-activated carbon was better than that of the commercial activated carbon, as observed from the Langmuir maximum adsorption capacities of 65.61, 66.12, and 223.05 µmol g-1 for Cd2+, Cu2+, and Pb2+, respectively. The Pb2+ was the metal most easily removed from aqueous solution because of its large ionic radius. The kinetic dynamics were well described by the pseudo-second order and Elovich models.

Kinetic and morphology study of alginate-vineyard pruning waste biocomposite vs. non modified vineyard pruning waste for dye removal

In this work a comparative bioadsorption study between a biocomposite consisting of hydrolysed vineyard pruning waste entrapped in calcium alginate spheres and non entrapped vineyard residue was carried out. Results have demonstrated that the biocomposite based on lignocellulose-calcium alginate spheres removed 77.3% of dyes, while non entrapped lignocellulose eliminated only removed 27.8% of colour compounds. The experimental data were fitted to several kinetic models (pseudo-first order, pseudo-second order, Chien–Clayton model, intraparticle diffusion model and Bangham model); being pseudo-second order the kinetic model that better described the adsorption of dyes onto both bioadsorbents. In addition, a morphological study (roughness and shape) of alginate-vineyard biocomposite was established under extreme conditions, observing significant differences between hydrated and dehydrated alginate-vineyard biocomposite. The techniques used to carry out this morphological study consisted of scanning electron microscopy (SEM), perfilometry and 3D surface analysis.

Antioxidant properties of leaves from different accessions of grapevine (Vitis vinifera L.) cv. Tempranillo after applying biotic and/or environmental modulator factors

Within climate change scenario, the maintenance of grape quality and wine characteristics will be the main concern for viticulture in the future years. However, changes in the composition of grapevine pruning wastes (i.e., leaves and stems) could be another interesting aspect as important antioxidant source for pharmaceutical industry due its richness in phenolic compounds beneficial for human health. To date, the effect of biotic and environmental factors in the accumulation of these compounds in leaves had received little attention. Therefore, the aims of study were (1) to evaluate the effect of biotic (mycorrhizal inoculation) and environmental (temperature) factors, alone or combined, on phenolic composition and antioxidant activity of leaf extracts of grapevine and (2) to determine whether such effects differed among accessions of the same cultivar of grapevine. The study was carried out using container-grown grapevines grown in greenhouses. Dormant Vitis vinifera (L.) cuttings of different accessions of Tempranillo were selected to get fruit-bearing cuttings. At transplanting, half of the plants of each accession were inoculated with the mycorrhizal inoculum and after fruit set, plants were exposed to two temperature regimes (24°C/14°C and 28°C/18°C (day/night)) to commercially berry ripe. Results showed that total phenolic content, antioxidant compounds like flavonols and anthocyanins, and antioxidant activity of leaves were improved with mycorrhizal inoculation under high temperature conditions. It was concluded that mycorrhizal inoculation of grapevines could contribute to preserve high level of antioxidant compounds of leaves in a future climate change scenario. However, the effects were strongly dependent of accession assayed, which indicated a significant intra-varietal diversity in the response of Tempranillo to biotic and environmental factors.

Remediation of saline soils by a two-step process: Washing and amendment with sludge

Soil salinization is a serious land-degradation problem that affects soil, plants and groundwater within ecosystems. In this work, the effect of washing saline–sodic soils with CaCl2 at 2% (w/v) and amendment with composted and dry sewage sludge was evaluated in a remediation assay. The effectiveness of amendments to improve the soil fertility was investigated with seed germination assays of Raphanus sativus L. Two different organic wastes were used: sewage sludge composted with pruning wastes (CP) and thermally dried sewage sludge (T) at rates of 1 and 2% (w/v) on organic matter basis. In general, there was an increase of germination percentage in the amended washed soils. The best indices were obtained at the 1% amendment dose with CP. The low exchangeable sodium percentage (ESP) in washed–amended soil (3 to 6 times lower than that of saline–sodic soil) could partially explain the increase in seed germination percentage of R. sativus L. The incorporation of organic amendments to washed soil also seemed to be beneficial as a step in the restoration process according to the chemical characteristics, especially by increasing the level of nutrients such as carbon, nitrogen, and phosphorus. A significant multiple linear regression of radish germination index in terms of pH values, sodium adsorption ratio of soil (SAR), and different forms of nitrogen (NH4+ and NO2−) was found.Overall, saline–sodic soil washing with CaCl2 followed by addition of organic amendments seems to be a promising strategy for restoration of such soils with simultaneous improvements of cation balance and nutrient/organic matter contents.

Respiration and enzymatic activities as indicators of stabilization of sewage sludge composting

The objective of this work was to study the evolution of physico-chemical and microbial parameters in the composting process of sewage sludge (SS) with pruning wastes (PW) in order to compare these parameters with respect to their applicability in the evaluation of organic matter (OM) stabilization. To evaluate the composting process and organic matter stability, different microbial activities were compared during composting of anaerobically digested SS with two volumetric ratios, 1:1 and 3:1 of PW:SS and two aeration techniques including aerated static piles (ASP) and turned windrows (TW). Dehydrogenase activity, fluorescein diacetate hydrolysis, and specific oxygen uptake rate (SOUR) were used as microbial activity indices. These indices were compared with traditional parameters, including temperature, pH, moisture content, organic matter, and C/N ratio. The results showed that the TW method and 3:1 (PW:SS) proportion was superior to the ASP method and 1:1 proportion, since the former accelerate the composting process by catalyzing the OM stabilization. Enzymatic activities and SOUR, which reflect microbial activity, correlated well with temperature fluctuations. Based on these results it appears that SOUR and the enzymatic activities are useful parameters to monitor the stabilization of SS compost.

The effects of fresh and stabilized pruning wastes on the biomass, structure and activity of the soil microbial community in a semiarid climate

The incorporation of organic amendments from pruning waste into soil may help to mitigate soil degradation and to improve soil fertility in semiarid ecosystems. However, the effects of pruning wastes on the biomass, structure and activity of the soil microbial community are not fully known. In this study, we evaluate the response of the microbial community of a semiarid soil to fresh and composted vegetal wastes that were added as organic amendments at different doses (150 and 300tha−1) five years ago. The effects on the soil microbial community were evaluated through a suite of different chemical, microbiological and biochemical indicators, including enzyme activities, community-level physiological profiles (CLPPs) and phospholipid fatty acid analysis (PLFA). Our results evidenced a long-term legacy of the added materials in terms of soil microbial biomass and enzyme activity. For instance, cellulase activity reached 633μg and 283μg glucoseg−1h−1 in the soils amended with fresh and composted waste, respectively. Similarly, bacterial biomass reached 116nmolg−1 in the soil treated with a high dose of fresh waste, while it reached just 66nmolg−1 in the soil amended with a high dose of composted waste. Organic amendments produced a long-term increase in microbiological activity and a change in the structure of the microbial community, which was largely dependent on the stabilization level of the pruning waste but not on the applied dose. Ultimately, the addition of fresh pruning waste was more effective than the application of composted waste for improving the microbiological soil quality in semiarid soils.

Optimization of Medlar Pruning Waste Composting Process by Cattle Manure Addition

In this study, medlar pruning waste (MPW) was composted with and without cattle manure (CM). Two piles were prepared: one contained only MPW (pile 1) and one contained MPW augmented with CM (pile 2). Both piles were composted in an enclosed composting vessel with passive aeration and aeration by turning. During the composting process, temperature, pH, electrical conductivity (EC), organic matter (OM), OM losses, total organic carbon (Corg), total nitrogen (NT), Corg/NT ratio, and germination index (GI) were measured. Pile 2 produced a faster increase of the temperature and had a longer thermophilic phase than pile 1. However, the rate of OM degradation was faster in pile 1 than in the pile containing CM (pile 2). The addition of CM also resulted in an increased pH and salt content. In both piles, C/N ratio decreased throughout the process, presumably as a result of the faster organic carbon degradation compared to N mineralization. However, only pile 2 had a final C/N ratio <20, the limit accepted for compost by the Spanish legislation on fertilizer. Also, both composts had GI > 50 percent, indicating an absence of phytotoxicity.

New Biomass Sources to Reduce Peat Dependence in Mediterranean Substrates: Validation of Morus alba L., Sorghum vulgare L., and Phoenix canariensis Pruning Wastes

The use of alternative materials to peat in soilless crop production, such as woody pruning wastes, has been reported by several researchers. In Mediterranean countries, several potential alternatives have been identified such as palm species or woody pruning wastes coming from different plant species. Mulberry (Morus alba L.) is a tree crop widely used in Europe for urban landscaping and to provide shade. Mulberry trees are pruned in sericulture two or three times a year to obtain a better yield of leaves. In an urban landscape, the trees are pruned once a year to form the canopy. Sorghum (Sorghum vulgare L.) is a cereal crop widely cultivated because it is considered the fourth most important summer crop in the world after soy, corn, and sunflower. It is one among the few resilient crops that can adapt well to future climate change conditions, particularly increasing drought, soil salinity, and high temperatures. After the harvest, the inedible parts of the plant, the stalks and leaves, are left over and must be disposed of, most of the time by burning. Palm trees in Spain, as in most of the European regions where palms are cultivated, are mainly used as ornamental plants in urban areas. One of the most commonly used palm tree in landscaping is the Canary Island date palm (Phoenix canariensis Hort. Ex Chavaud). These palm trees are pruned up to twice a year in this region, producing huge amounts of biomass that are disposed of in landfills. In this experiment, physical and chemical parameters were determined in the different particle sizes (<0.25, 0.25–1, 1–2, and 2–4 mm) of the raw residual materials from pruning activities of mulberry (Morus alba L.), sorghum (Sorghum vulgare L.), and palm (Phoenix canariensis) to evaluate their suitability for use as growing substrate. According to the results obtained, it can be concluded that the alternative materials for substrate preparation obtained from the pruning wastes of Morus alba (MAPW), Sorghum vulgare (SVPW), and Phoenix canariensis (PCPW) had suitable values of physical properties related to substrate porosity and wetting capacity. These materials also had high or very high total organic carbon (C) to total nitrogen (N) ratio values and low nutrient contents, except for potassium (K) in SVPW and PCPW.

Assisted attenuation of a soil contaminated by diuron using hydroxypropyl-β-cyclodextrin and organic amendments

Diuron desorption and mineralisation were studied on an amended and artificially contaminated soil. The amendments used comprised two different composted organic residues i.e., sewage sludge (SS) mixed with pruning wastes, and urban solid residues (USR), and two different solutions (with inorganic salts as the micronutrients and hydroxypropyl-β-cyclodextrin (HPBCD)). After applying micronutrients to activate the soil flora, 15.5% mineralisation could be reached after 150days, indicating that the soil has a potential capacity to mineralise the herbicide through biostimulation-assisted attenuation. Diuron mineralisation was also improved when HPBCD solutions were applied. Indeed, the extent of herbicide mineralisation reached 29.7% with this application. Moreover, both the lag phase and the half-life time (DT50) were reduced to 33 and 1778days, respectively, relative to the application of just micronutrients (i.e., 39 and 6297days, respectively). Organic amendments were also applied (i.e., USR and SS) on the contaminated soil: it was found that the diuron mineralisation rate was improved as the amendment concentration increased. The joint application of all treatments investigated at the best conditions tested was conducted to obtain the best diuron mineralisation results. The micronutrient amendment plus 4% USR or SS amendment plus HPBCD solution (10-fold diuron initially spiked) caused an extent of diuron mineralisation 33.2 or 46.5%, respectively.

Evaluation of composition and performance of composts derived from guacamole production residues

The utilization of organic wastes to improve soils or for growth media components in local farms and nurseries can reduce the environmental pollution linked to waste disposal while increasing the sustainability of crop production. This approach could be applied to waste products generated from the production of guacamole (an emerging activity in the avocado production areas in mainland Spain), where appropriate treatment of this oily and doughy waste product has not been previously reported. The aim of this work is to study the feasibility of co-composting guacamole production residues (GR) with garden pruning waste (PW) as bulking agent, and the possible use of the compost produced depending on its quality. A windrow composting trial using three GR:PW ratios, 2:1, 1:2, and 1:7 was carried out. Temperature, moisture, organic matter, and C/N ratio were used to follow the evolution of the composting process during 7 months. After an additional 3-month curing period, composts were sieved to less than 10 mm and a set of European quality criteria was used to assess compost quality and intended use. In general, the 3 composting mixtures followed the classical process evolution, with minor differences among them. The 1:2 GR:PW ratio appeared most adequate for combining better process evolution and maximum GR ratio. Except for their high pH that limits their use as growing media component in some particular cases, the obtained composts fulfilled the more stringent European standards for commercial composts. Self-heating tests confirmed the high stability of the composts produced. The germination of cress by the direct contact method was satisfactory for composts GR:PW 1:2 and 1:7, showing no signs of toxicity. Avocado seedlings planted in substrates containing 67% of the GR:PW composts exhibited greater plant growth than those in the control treatment, and with no signs of phytotoxicity. The results open an interesting opportunity for the sustainable treatment of avocado fruit by-products derived from guacamole and avocado oil processing.

Study of the physical properties of calcium alginate hydrogel beads containing vineyard pruning waste for dye removal

In this work the morphological and surface properties of a biocomposite formulated with vineyard pruning waste entrapped in calcium alginate hydrogel beads were studied. The formulation of the calcium alginate hydrogel beads, containing vineyard pruning waste, was based on the capacity of this green adsorbent to remove dye compounds from wastewater, observing that in the optimum condition (1.25% of cellulosic residue, 2.2% of sodium alginate and 0.475molL−1 CaCl2) the percentage of dyes was reduced up to 74.6%. At lower concentration of CaCl2, high-resolution optical images show that the elongation of the vineyard-alginate biocomposite decreased, whereas the compactness increased. Moreover, higher concentrations of cellulosic residue increased the biocomposite roundness in comparison with biocomposite without the cellulosic residue. Interferometric perfilometry analysis (Ra, Rq, Rz and Rt) revealed that high concentrations of CaCl2 increased the roughness of the of the calcium alginate hydrogel beads observing vesicles in the external surface.

Formulation of an alginate-vineyard pruning waste composite as a new eco-friendly adsorbent to remove micronutrients from agroindustrial effluents

The cellulosic fraction of vineyard pruning waste (free of hemicellulosic sugars) was entrapped in calcium alginate beads and evaluated as an eco-friendly adsorbent for the removal of different nutrients and micronutrients (Mg, P, Zn, K, N–NH4, SO4, TN, TC and PO4) from an agroindustrial effluent (winery wastewater). Batch adsorption studies were performed by varying the amounts of cellulosic adsorbent (0.5–2%), sodium alginate (1–5%) and calcium chloride (0.05–0.9M) included in the biocomposite. The optimal formulation of the adsorbent composite varied depending on the target contaminant. Thus, for the adsorption of cationic contaminants (Mg, Zn, K, N–NH4 and TN), the best mixture comprised 5% sodium alginate, 0.05M calcium chloride and 0.5% cellulosic vineyard pruning waste, whereas for removal of anionic compounds (P, SO4 and PO4), the optimal mixture comprised 1% sodium alginate, 0.9M calcium chloride and 0.5% cellulosic vineyard pruning waste. To remove TC from the winery wastewater, the optimal mixture comprised 3% of sodium alginate, 0.475M calcium chloride and 0.5% cellulosic vineyard pruning waste.

Impact of biochar application on plant water relations in Vitis vinifera (L.)

Soil water status plays an important role in growth-yield and grape quality of Vitis vinifera (L.). In some cases, periods of moderate water stress have been indicated to exert a positive effect on the quality of grape production. However, prolonged water stress may have a strong negative affect grapevine photosynthesis and grape yield, especially in dry Mediterranean environments. Biochar is a co-product of a thermochemical conversion of biomass that is recognized to be a beneficial soil amendment, which when incorporated into the soil increases soil water retention. We investigated the effect of two rates of biochar application (22 and 44tonha−1) on plant water relations of V. vinifera in a field experiment in central Italy. Biochar obtained from the carbonization of orchard pruning waste was applied to the soil over two consecutive growing seasons. The treatments did not show a significant increase in soil hydrophobicity. Moreover, soil analysis and ecophysiological measurements indicated a substantial relative increases in available soil water content compared to control soils (from 3.2% to 45% in the 22 and 44tonha−1 application rates, respectively) and in leaf water potential (24–37%) during droughts.

Predicting the syngas hydrogen composition by using a dual stage equilibrium model

This paper presents an analysis of hydrogen syngas composition obtained by biomass gasification when simulated by a dual stage equilibrium model. The numerical model takes advantage of the carbon boundary point (CBP) concept to study the hydrogen production at maximum energetic and exergetic efficiencies. The numerical simulation was carried out using three large biomass residues available in Portugal: coffee husks, pine residues and vine pruning wastes. It was concluded that the three biomass substrates showed similar trends at different operating conditions and the vine pruning wastes showed the best hydrogen outputs. The computed results were also compared with pilot scale experimental data obtained for coffee husk residues. The numerical results differ from experimental data, but in both cases the hydrogen composition has similar changes taking into consideration the effect of different operating conditions. It was concluded that the hydrogen molar composition increases steeply with a steam to biomass ratio (SBR) below the CBP and with a slow rate above the CBP, up to an asymptotic value. Similar behavior was found considering the temperature effect on hydrogen production. It was also found that energy efficiency first increases with the SBR up to a maximum value and then decreases.

Thermal exploitation of fruit tree pruning wastes in a novel conical spouted bed combustor

In order to determine the optimum operation conditions for thermal exploitation of fruit-tree pruning wastes in conical spouted bed combustors, operation maps for gas–solid flow regimes have been obtained from the experimental hydrodynamic study of beds of inert material (sand) in conical spouted bed contactors at high temperatures. To this end, minimum spouting and minimum dilute spouting (jet spouted bed) velocities and maximum bed pressure drop have been obtained for different systems. The effects of particle size and gas inlet temperature has been also studied. Combustion of fruit-tree pruning wastes has been successfully carried out in batch mode in a conical spouted bed combustor, with high combustion efficiencies, for gas inlet temperatures from 350 to 550°C. Radial and axial temperature profiles have been measured both in uniform beds of inert material and also in beds composed of mixtures of sand and combusting wastes.