Almond Prunings Research Articles

Optimisation of sugar and solid biofuel co-production from almond tree prunings by acid pretreatment and enzymatic hydrolysis.

Almond pruning biomass is an important agricultural residue that has been scarcely studied for the co-production of sugars and solid biofuels. In this work, the production of monosaccharides from almond prunings was optimised by a two-step process scheme: pretreatment with dilute sulphuric acid (0.025M, at 185.9-214.1℃ for 0.8-9.2min) followed by enzyme saccharification of the pretreated cellulose. The application of a response surface methodology enabled the mathematical modelling of the process, establishing pretreatment conditions to maximise both the amount of sugar in the acid prehydrolysate (23.4kg/100kg raw material, at 195.7℃ for 3.5min) and the enzymatic digestibility of the pretreated cellulose (45.4%, at 210.0℃ for 8.0min). The highest overall sugar yield (36.8kg/100kg raw material, equivalent to 64.3% of all sugars in the feedstock) was obtained with a pretreatment carried out at 197.0℃ for 4.0min. Under these conditions, moreover, the final solids showed better properties for thermochemical utilisation (22.0MJ/kg heating value, 0.87% ash content, and 72.1mg/g moisture adsorption capacity) compared to those of the original prunings.

Evaluation of Biological Control Agents for the Protection of Almond Pruning Wounds Against Infection by Fungal Canker Pathogens.

Fungal canker pathogens of almond initiate infection in trees primarily through pruning wounds. Biological control agents (BCAs) have the potential to provide long-term protection of pruning wounds by colonizing the wound surfaces and underlying tissues. Laboratory and field tests were performed to assess the efficacy of various commercial and experimental BCAs as wound protectants against almond canker pathogens. Four Trichoderma-based BCAs were evaluated using detached almond stems in the laboratory against the canker pathogens Cytospora plurivora, Eutypa lata, Neofusicoccum parvum, and Neoscytalidium dimidiatum. Results indicated that Trichoderma atroviride SC1 and T. paratroviride RTFT014 significantly reduced infections by all four pathogens. The abilities of these four BCAs to protect almond pruning wounds against E. lata and N.parvum were further evaluated in field trials using two almond cultivars and during two consecutive years. Both T. atroviride SC1 and T. paratroviride RTFT014 protected almond pruning wounds against E. lata and N. parvum as efficiently as thiophanate-methyl, the recommended fungicide for treatment of almond pruning wounds. Comparisons of different application timings of BCA in relation to pathogen inoculation revealed a significant improvement in wound protection when inoculations were conducted 7 days versus 24 h post-BCA application for N. parvum, but not for E. lata. T. atroviride SC1 and T. paratroviride RTFT014 are promising candidates for the preventive protection of almond pruning wounds and for inclusion in integrated pest management programs and organic almond production systems.

Impact of biochar amendments on soil water and plant uptake dynamics under different cropping systems

AbstractApplication of biochar amendments in agricultural systems has received much attention in recent years. In this study, we assess the 5‐year impacts of biochar application on soil water and plant interactions for an irrigated fresh market tomato (Solanum lycopersicum) and a rainfed pasture (Poaceae) cropping system. In particular, we focus on three varieties of locally produced biochar from agricultural waste materials—almond shell, walnut shell, and almond pruning residues that are pyrolyzed using a mobile pyrolysis unit. We used the soil hydrological model HYDRUS‐1D to explicitly track seasonal and annual soil water fluxes through changes in water retention, drainage, evaporation, and plant water uptake under biochar application. Modeling results show that the application of biochar at 5% increased soil water availability within the top 20 cm for a rainfed system, irrespective of biochar amendment type. This is clearly indicative of higher plant water uptake and greater water use efficiency (WUE) under biochar application. In contrast, a similar biochar amendment for the irrigated system did not affect WUE, instead reducing seasonal soil evaporation loss and thereby reducing irrigation demand. In both cropping systems, year‐to‐year variability in precipitation significantly impacted the total amount of water saved under biochar application with certain amendments retaining more water than others. Given that biochar application increased water retention irrespective of cropping systems, we further used a simple approach to determine yield trade‐off, if any, between control and biochar treatments. Our economic balance clearly demonstrates that the water saved by amending soil with biochar does not offset the yield disparity if compensated with carbon credits and therefore, application of biochar should be actively considered for both its direct and indirect benefits to potential greenhouse gas mitigation (e.g., diverting orchard waste from open burning), water savings, and soil health.

Low-Quality Irrigation Water Treated Using Waste Biofilters

Although in water-deficient regions, agricultural runoff, drainage water or surplus irrigation water is often used, there are constraints related to its quality to be considered (salinity, nutrients and pollutants). Thus, it is necessary to treat surplus irrigation water considering the low-energy supply systems available to farmers. This work focuses on a nature-based water treatment system consisting of two prototypes of anaerobic bioreactors with horizontal or vertical flow. To enhance the circular economy strategy, two different wastes (coarse sand and almond pruning) were used as bioreactor components. The aim of the research was to monitor the quality of the water (pH, electrical conductivity, suspended solids, chemical oxygen demand, alkalinity and bicarbonate, carbonate and nitrogen contents) before and after the treatment. All the parameters studied (except chemical oxygen demand) were reduced by the treatments, but with large variations. Furthermore, there was 100% nitrogen reduction in the horizontal water flow treatment with the filter bed formed by coarse sand and almond pruning. It was observed that the variation in the concentration of some parameters was associated with the type of filter bed (i.e., the C/N ratio of the residue) and with the design for water circulation flow. Although the findings are promising, further research is needed to achieve reductions in all studied parameters.

Temporal susceptibility of almond pruning wounds to infection by fungal canker pathogens in California

AbstractNumerous fungal canker pathogens threaten almond production in California, causing high tree mortality and reducing orchard longevity. Pruning wounds are the main infection sites for these pathogens. This study aimed to identify the lowest risk period for pruning almond trees and to determine the duration of susceptibility of pruning wounds to fungal infections. During 2 years at two locations, pruning wounds were made monthly from September to January and inoculated with Botryosphaeria dothidea, Eutypa lata, Neofusicoccum parvum or Neoscytalidium dimidiatum, at 0, 1, 2, 3, 5 and 8 weeks after pruning. Pruning wounds were susceptible to infection by N. parvum and N. dimidiatum from September to December, with a significant decrease in susceptibility for wounds made in January relative to September. Fresh wounds had the highest probability of infection by N. dimidiatum, as wounds 1 week or older were less likely to be infected. Pruning month did not significantly impact wound susceptibility to B. dothidea; susceptibility decreased sharply with wound age. Wound susceptibility to E. lata significantly differed amongst pruning months, with pruning wounds of 1 week or older made in December and January being the least susceptible. These results indicated that delayed pruning in December and January can reduce the risks of canker pathogen infections compared to early pruning from September to November. This study showed that pruning wounds were most susceptible to infection during the first 2 weeks following pruning; thus, pruning wounds should be protected for at least 2 weeks shortly after pruning.

Boiler Combustion Optimization of Vegetal Crop Residues from Greenhouses

This work presents an alternative for adding value to greenhouse crop residues, used for (1) heating and (2) as a CO2 source. Both options are focused on greenhouse agricultural production, but could be applied to other applications. The influence of factors, such as the air/fuel rate and turbulence inside the combustion chamber, is studied. Our results show that for pine pellets, olive pits, tomato-crop residues, and a blend of the latter mixed with almond prunings (75–25%), the thermal losses ranged from 19.5–53.1, 20.5–58.9, 39.9–95%, and 29.4–75.5%, respectively, while the NOX emissions were 30–247, 411–1792, and 361–2333 mg/Nm3, respectively. The above-mentioned blend was identified as the best set-up. The thermal losses were 39.2%, and the CO, NOX, and SO2 concentrations were 11,690, 906, and 1134 mg/Nm3, respectively (the gas concentration values were recalculated for 0% O2). Currently, no other work exists in the literature include a similar analysis performed using a boiler with a comparable thermal output (160.46 kW). The optimal configurations comply with the relevant local legislation. This optimization is important for future emission control strategies relating to using crop residues as a CO2 source. The work also highlights the importance of ensuring a proper boiler set-up for each case considered.

Life cycle assessment of hydrogen production from biomass gasification. Evaluation of different Spanish feedstocks

Gasification of biomass can be used for obtaining hydrogen reducing the total greenhouse gases emissions due the fixation of CO2 during photosynthetic processes. The kind of raw materials is an important variable since has a great influence on the energy balance and environmental impacts. Wastes from forestry are considered as the most appropriate raw materials since they do not compete for land. The aim of this work is to determine the environmental feasibility of four Spanish lignocellulosic wastes (vine and almond pruning and forest waste coming from pine and eucalyptus plantation) for the production of hydrogen through gasification. LCA methodology was applied using global warming potential, acidification, eutrophication and the gross energy necessary for the production of 1 Nm3 of hydrogen as impact categories. As expected, the use of biomass instead of natural gas leads to the reduction of CO2 emissions. Regarding to the different feedstocks, biomass coming from forestry is more environmental-friendly since does not need cropping procedures. Finally, the distribution of environmental charges between pruning wastes and fruits (grape and almond) and the use of obtained by-products have a great influence, reducing the environmental impacts.

Quantification of the residual biomass obtained from pruning of trees in Mediterranean almond groves

This research quantified the available residual biomass obtained from pruning almond trees. The additional biomass quantified could be used as a source of energy or as raw material for the wood industry and would provide additional income for fruit producers and also a more sustainable system. Several factors were analyzed: Variety, aim of the pruning, age of the plants, size of the plantation, crop yield and irrigation. Regression models were also calculated to predict the weight of dry biomass obtained per tree and tonnes of dry biomass obtained per hectare according to the significant factors. These equations could implement logistic planning as the Borvemar model, which defines a logistics network for supplying bioenergy systems. Almond tree varieties were classified into three groups: a first group with high residual biomass productivity (average yield 12.6 kg dry biomass/tree), a second group with low productivity (average yield 4.5 kg dry biomass/tree) and a transition group with a intermediate biomass yield of 7 kg dry biomass/tree. This means that in Mediterranean areas the residual biomass from almond pruning reaches an average 1.34 t/ha annual.

Size distribution of polycyclic aromatic hydrocarbon particulate emission factors from agricultural burning

Burning of agricultural waste residue is a common method of disposal when preparing land following crop harvest. This practice introduces volatile organic compounds, including polycyclic aromatic hydrocarbons (PAHs), into the atmosphere. This study examines the particle size distribution in the smoke emissions of two common agricultural waste residues (biofuels) in California, almond prunings and rice straw. The residues were burned in a combustion chamber designed specifically for this purpose, and the smoke emissions were collected on 10-stage MOUDI impactors for analysis of PAH and total particle mass. The results, in units of emission factors, show that combustion temperature is an important factor in determining the smoke particle PAH composition. Total PAH emissions from rice straw burns were 18.6 mg kg −1 of fuel, while the emissions from almond prunings were lower at 8.03 mg kg −1. The less volatile five- and six-ring PAH was predominately on smaller particles where it condensed in the early stages of combustion while the more volatile three- and four-ring PAH formed on larger particles as the smoke cooled.

Use of energy crops for domestic heating with a mural boiler

The combustion process of two residues from energy crops in a 12 kW mural boiler for domestic heating was studied. The fuels used were common reed ( Arundo donax L.), sorghum ( Sorghum bicolor L.) and forest pellet recommended by the boiler manufacturer. A comparison with the combustion process of two industrial residues (tomato residue and almond pruning) and other energy crop ( Cynara cardunculus L.) has been established. The experimental tests carried out in “La Orden” farm on common reed and sorghum cultivation revealed a production of dry biomass of 35 and 30 t/ha, respectively. Previously, the fuels were characterised by means of the higher heating value, proximate and ultimate analyses. The influence of the residue type, fuel mass flow, draught and residues mixture on the combustion parameters has been studied. A TESTO 300 M-I analyzer was employed to determinate the principal parameters of the combustion process (CO 2, CO, and O 2 contents, fumes temperature, not-burnt gaseous and sensitive heat losses in the fumes, air excess coefficient, flow rate and velocity of the fumes, and efficiency). The behaviour shown by the two studied residues was similar to that of the forest pellet. The boiler efficiencies obtained with the maximum fuel mass flow (100%) and minimum draught (0%) were 84% and 85.3% for reed and sorghum pellets, respectively. The obtained efficiency with the forest pellet was 90.5%. The optimum residue mixture assayed was almond pruning (75%) and sorghum (25%), with a boiler efficiency of 87.2% for a mass flow and draught of 100% and 0%, respectively.

WOOD CHIPPING ALMOND BRUSH AND ITS EFFECT ON THE ALMOND RHIZOSPHERE, SOIL AGGREGATION AND SOIL NUTRIENTS

WOOD CHIPPING ALMOND BRUSH AND ITS EFFECT ON THE ALMOND RHIZOSPHERE, SOIL AGGREGATION AND SOIL NUTRIENTS

Fiber dimensions, lignin and cellulose content of various plant materials and their suitability for paper production

Fiber dimensions and lignin and cellulose content of various highly productive, non-wood plants and agricultural residues were examined to assess their suitability for paper production. Plants like kenaf ( Hibiscus cannabinus L.) and giant reed ( Arundo donax L.) internodes gave very good derived values, especially slenderness ratio, which is directly comparable to some softwood and most hardwood species. Cotton ( Gossypium hirsutum L.) stalks, miscanthus ( Miscanthus × giganteus) and switchgrass ( Panicum virgatum L.) have shorter fibers resulting to poorer flexibility and Runkel ratios, but still satisfactory slenderness ratios. Finally, fibers from olive tree ( Olea europea L.) and almond tree ( Prunus dulcis L.) prunings presented relatively short and thick fibers producing the poorest derived values among all the species examined. Fiber dimensions did not differ significantly within each species, when samples from different stalks/branches or different positions (base, middle top) were examined. The only exception were cotton stalks, where those differences did not have any significant effect on fiber derived values. Chemical analysis of the raw plant materials revealed satisfactory levels of α-cellulose content (close to 40%) and Klason lignin content (<30%) compared to those of hardwoods and softwoods. Relatively increased (>25%) lignin content in miscanthus, switchgrass and almond prunings may require additional pulping time and chemical charge compared to those of other non-wood raw materials. Analysis of samples at various heights/lengths of the plant materials showed that lignin and cellulose content depends on tissue maturity, but does not change significantly within each species.

Elemental characterization of particulate matter emitted from biomass burning: Wind tunnel derived source profiles for herbaceous and wood fuels

Particulate matter emitted from wind tunnel simulations of biomass burning for five herbaceous crop residues (rice, wheat and barley straws, corn stover, and sugar cane trash) and four wood fuels (walnut and almond prunings and ponderosa pine and Douglas fir slash) was collected and analyzed for major elements and water soluble species. Primary constituents of the particulate matter were C, K, Cl, and S. Carbon accounted for roughly 50% of the herbaceous fuel PM and about 70% for the wood fuels. For the herbaceous fuels, particulate matter from rice straw in the size range below 10 μm aerodynamic diameter (PM10) had the highest concentrations of both K (24%) and Cl, (17%) and barley straw PM10 contained the highest sulfur content (4%). K, Cl, and S were present in the PM of the wood fuels at reduced levels with maximum concentrations of 6.5% (almond prunings), 3% (walnut prunings), and 2% (almond prunings), respectively. Analysis of water soluble species indicated that ionic forms of K, Cl, and S made up the majority of these elements from all fuels. Element balances showed K, Cl, S, and N to have the highest recovery factors (fraction of fuel element found in the particulate matter) in the PM of the elements analyzed. In general, chlorine was the most efficiently recovered element for the herbaceous fuels (10 to 35%), whereas sulfur recovery was greatest for the wood fuels (25 to 45%). Unique potassium to elemental carbon ratios of 0.20 and 0.95 were computed for particulate matter (PM10 K/C(e)) from herbaceous and wood fuels, respectively. Similarly, in the size class below 2.5 μm, high‐temperature elemental carbon to bromine (PM2.5 C(eht)/Br) ratios of ∼7.5, 43, and 150 were found for the herbaceous fuels, orchard prunings, and forest slash, respectively. The molar ratios of particulate phase bromine to gas phase CO2(PM10 Br/CO2) are of the same order of magnitude as gas phase CH3Br/CO2reported by others.

Fall almond pruning has practical advantages, no adverse effects

Labor for pruning during the winter is becoming increasingly scarce. To help retain a permanent labor force, more farmers would like to keep employees working in the fall. This study shows that almond trees can be pruned in the fall without adversely affecting yield, growth or nutrition.

Chemical Protection of Almond Pruning Wounds from Infection by Phytophthora syringae

Chemical Protection of Almond Pruning Wounds from Infection by Phytophthora syringae

Energy and Force Requirements for Shearing Moduled Almond Prunings

ABSTRACT CROSS grain shear tests were conducted on small groupings of almond tree prunings. Differing specimen size distributions were tested for their relation to shear force and energy. Tests were conducted with various shear chamber widths and blade geometries. Compression and bending tests were also conducted on individual samples. The results are analyzed and extrapolated to determine force and power requirements for shearing modules of almond prunings made with conventional or modified heavy duty cotton module builders.