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Article

Productivity and Characterization of Biomass Obtained from Pruning of Walnut Orchards in México

by
Donaji Sierra-Zurita
1,
Saúl Santana-Espinoza
1,
Rigoberto Rosales-Serna
1,
Julio César Ríos-Saucedo
1 and
Artemio Carrillo-Parra
2,*
1
INIFAP—Campo Experimental Valle del Guadiana, Carretera Durango–El Mezquital km 4.5, Durango 34170, Mexico
2
Instituto de Silvicultura e Industria de la Madera (ISIMA), Universidad Juárez del Estado de Durango (UJED), Boulevard del Guadiana Núm. 501, Colonia Torre de Institutos, Durango 34120, Mexico
*
Author to whom correspondence should be addressed.
Energies 2023, 16(5), 2243; https://doi.org/10.3390/en16052243
Submission received: 25 November 2022 / Revised: 16 February 2023 / Accepted: 23 February 2023 / Published: 26 February 2023
(This article belongs to the Special Issue Energy Production from Biomass Wastes)
Versions Notes

Abstract

:
Walnut tree (Carya illinoensis (Wangenh.) K. Koch) is a plant species showing ecological, social, and economic importance in México. The objective was to determine biomass productivity and to characterize the raw material and biomass briquettes obtained from walnut thinning pruning. The variables evaluated were tree total height (TH), fresh biomass (FB) and dry biomass (DB) per hectare (kg ha−1). Briquettes were made by using the biomass obtained in both orchards. Laboratory tests for original biomass included moisture content (MC), ash content (AC), volatile matter (VM) and fixed carbon (FC), as well as high heating value (HHV). Briquette studies also included diameter (D), weight (W), length (L), volume (V), density (Ds), and HHV. The data were analyzed by using descriptive statistics and analysis of variance (ANOVA) under a completely randomized design with factorial arrangement. Thinning pruning in walnut orchards provides 12 kg tree−1 (998 kg ha−1) of dry biomass, with acceptable levels of AC ≤ 5%, FC (75 to 76%), VM (18.7 to 19.7%) and HHV (16.2 to 16.7 MJ kg−1). The briquette international quality standards were fulfilled: MC≤ 10%, AC ≤ 5% and HHV > 18 MJ kg−1. The integrated use of walnut residues reduces the management problems registered during nut production and the sustainable options to generate bioenergy will be expanded.

1. Introduction

The production of walnut pecan (Carya illinoensis (Wangenh.) K. Koch) has acquired relevance from the ecological, social, and economic point of view in México and the world. The pecan is the most economically important and valuable native North American nut crop, and 98% of the world’s annual pecan production is obtained in the Southern USA and Northern México [1]. The pecan-planted area in the USA has reached 413,000 acres (167,135 ha), producing 132,075 t [2]. In 2021, total planted area with pecan nut in México reached 146,239 ha, 111,589 ha was harvested, 136,947 t was produced and the mean yield was 1.2 t ha−1 [3]. In Durango, México, during 2021, an area of 7632 hectares was cultivated with walnut trees, 6252 ha was harvested, and 9007 t of nuts was produced [3]. The yield average was 1.4 t ha−1 and the most popular commercial cultivars were ‘Western’ and ‘Wichita’; however, low levels for total production are obtained compared to other states in México, such as Puebla (4.0 t ha−1), State of México (3.7 t ha−1) and Morelos (3.3 kg ha−1) [3]. Low walnut productivity per hectare in Durango has been compensated by reducing production costs (<USD 4113) and maximizing walnut prices (>USD 4146), obtaining significant economic benefits (USD 1524 to 2768) [4,5].
The low walnut yield obtained in Durango is due to reduced use of inputs and soils that are narrow, sandy, with reduced fertility and limited water-holding capacity [6]. In addition, reduced availability of irrigation and drinking water causes competition between agricultural water demand and urban water provision. Therefore, the main factors that limit walnut production in Durango are water stress (drought) caused by scarcity and competition for water as well as agricultural soil degradation. In recent years, techniques for walnut cultivation have been perfected in Durango as a strategy to increase walnut yield and total production. The implementation of pruning as an arboriculture practice [7] is carried out between the months of February and March and is intended to favor the entry of light into a dense canopy developed in walnut trees, balancing between the source and the demand for photoassimilates [8].
In Durango, several types of pruning are carried out in walnut trees along their life cycle, such as training, selective pruning, thinning and production [9]. The major reason to carry out the pruning in walnut trees is to stimulate production and improve the quality of the fruits [10]. From an ecological point of view, it is necessary to remove dead and pest-infested branches to prevent the spread of diseases and, finally, avoid the risk of falling trees. Pruning is also carried out as a silvicultural practice to improve the quality of the wood, increasing the diameter of the tree and to expand the area to establish intercropping systems [11], including cover crops, alfalfa, oats and other forage crops. Benefits obtained by using intercropping systems include weed control, increased productivity and improved incomes for farmers. Walnut tree pruning residues, including branches, twigs and stems, are considered as worthless residue, showing low volume at the tree level, but when collecting waste from one hectare, high amounts of biomass are obtained.
Biomass from walnut pruning is underutilized, considered as undesirable residue and, in the best of cases, is collected to be used as domestic firewood. Owing to the above, it is necessary to establish the biomass productivity in the pruning carried out in walnut orchards to determine its importance as an input for firewood, organic amendments, industrial use, biofuel production and as an improver of organoleptic properties for cooking and smoking meat and other grilled foods. Studies are also necessary to establish the possibilities of using pruning wastes to obtain value-added products, which include the characterization of its industrial properties and utility as firewood and raw material to produce charcoal, wooden chips and engineered wood. The use of walnut biomass as an industrialized biofuel will be based on the study of the chemical composition and physical characteristics during the densification process, while, to obtain charcoal and wood, the diameter classes of the branches during pruning must also be established. In obtaining odorant woodchips for grilled meat and vegetables, it is necessary to evaluate the level and quality of volatile compounds that are present in walnut waste. It is also important to characterize the obtained biomass, since one of the important parameters is the moisture content, to evaluate its possible use in the elaboration of briquettes. The objective was to determine biomass productivity and to characterize the raw material and biomass briquettes obtained from walnut thinning pruning carried out in commercial plantations established in Northern México.

2. Materials and Methods

2.1. Study Site

In February 2022, biomass samples were taken at two walnut orchards established under a drip irrigation system at the Valle del Guadiana region, in Durango, México. The cultivars used in the orchards were ‘Western’ and ‘Wichita’ (pollinator), showing adult trees (10 to 22 years old), which were found in production during 2021. The plantation system in both orchards was in a real frame, with a distance between rows and plants of 10 × 10 m (100 trees−ha) in the first orchard (S1) and 12 × 12 m (70 trees−ha) in the second orchard (S2). Tree management in both orchards included training, thinning and production pruning performed annually in the months of February and early March.
The sampling process was carried out only on the ‘Western’ cultivar, from which several rows were planted due to its improved nut quality, while the ‘Wichita’ cultivar was mainly considered as a pollinator, showing a longer period for pollen shedding. The predominant soil in the study area is the loam type (sandy and clayey) and belongs to the Kastañozem class, showing intermediate capacity for moisture retention, medium depth, slope, ranging from 0 to 2%, pH 7.9 and poor values for organic matter, phosphorus and nitrogen content. The climate of the region is temperate, semi-arid, with summer rainfall (BS1 Kw (w) (e)) and the mean annual temperature is 17.4 °C, with strong variations throughout the day and the year [12]. The mean value for accumulated rainfall during the year reaches 476 mm, with higher values during the wet season between June and September [13].

2.2. Evaluated Variables

In each orchard, ten trees were taken randomly to evaluate total height (TH) and the fresh weight of the biomass collected after thinning pruning in each walnut tree. Subsequently, a sub-sample of complete branches was separated, chopped, placed in paper bags and dried in an electric oven at 105 °C until constant weight (dry weight) was obtained. The moisture content was determined by the gravimetric method after samples registered constant weight and used to calculate the yield of fresh and dry biomass per hectare (kg ha−1). In each orchard, the mean value for fresh biomass yield per tree was obtained by averaging across the ten replicates (trees) in each plantation. Three sub-samples of complete and representative branches were taken to determine moisture content and then calculate dry biomass yield in each tree. The average for fresh and dry biomass per tree was multiplied by the number of trees per hectare to calculate biomass yield (kg ha−1). The biomass obtained in the field was transported to the laboratory for its conditioning, chemical analysis and to determine possibilities of its use as an input to produce fuel briquettes.

2.3. Laboratory Study

The dry walnut wood sub-samples were crushed in an SM 300 cutting mill to obtain sawdust with a particle size of 2 mm. The sawdust sample was passed through several sieves to separate the portion that remained in sieves number 40 (0.420 mm) and 60 (0.250 mm), and the powder was stored and later used in laboratory analyses. Chemical tests included the proximate analysis, including the moisture content determined according to the UNE-EN 14774-3 standard [14], ash content with the UNE-EN 14775 method [14], as well as volatile matter and fixed carbon based on the ASTM D 1762-84 standard [15]. A semi-automatic calorimeter (LECO AC 600) was used to evaluate High Heating Value (HHV) according to the ASTM D 5865 11a standard [16].

2.4. Briquettes Production

Briquetting of the biomass obtained in both walnut orchards (S1 and S2) was performed by using two moisture levels (6% and 10%) and two pressure treatments (15 Mpa and 20 Mpa) (Table 1). Briquettes were produced for each moisture and pressure combination, with ten replications per treatment. Briquetting process was performed using 40 g of walnut sawdust introduced into LIPPEL equipment (Lippel model LB32, Agrolândia—SC, Brazil), with process time of 5 min and a temperature of 80 °C. Particle density was evaluated immediately after briquette production when the hygroscopic balance was reached on an area maintained at 20 °C and 60% relative humidity. Briquettes were weighed and measured (length and diameter) using a digital caliper with a precision to 0.01 mm. The calculation of the bulk density was obtained by dividing the total mass of each briquette by its volume. Immediate analyses were performed, based on the same specifications used in the characterization of original walnut biomass.

2.5. Statistical Analysis

The field data were analyzed using descriptive statistics (mean and standard error of the mean) to determine the yield and industrial quality of the initial biomass obtained in each of the two orchards under study. Data obtained in the laboratory were used for the analysis of variance (ANOVA) under a completely randomized design with a factorial arrangement (orchard, moisture content, and pressure) and three replications. When significant differences were observed, Tukey test (p ≤ 0.05) was applied for the multiple comparisons of means. The ANOVA and the multiple means comparison were obtained by using SAS® Ver. 9.4.

3. Results and Discussion

3.1. Field Study

Lower tree height (8.1 m) was observed in S1, the youngest plantation (10 years), compared to the old one (S2: 22 years), showing trees with an average height of 12.5 m and fluctuations between 9.5 m and 17.6 m (Table 2). In S1, more uniform tree heights were observed, showing fluctuations between 7.2 and 9.4 m. The average height of walnut tree (Carya illinoensis) was higher than values registered in common walnut tree (Junglans regia L. (4.4 m) [17]. Variation observed in S2 was related to a constant change in trees, based on modification of planting layout and variation in farmer criteria to satisfy consumer demand at the walnut market. For this reason, three walnut cultivars were identified at this orchard: ‘Whichita’, ‘Western’ and ‘Cheroke’. In addition, some technical recommendations were attended, including the practice of thinning in walnut trees favoring light penetration into the plant canopy to increase the nut yield [18]; because of this, the average tree height of the plantation was constantly modified. Significant and positive correlation was observed between walnut tree height and fresh or dry biomass weight at S1 (r = 0.91 **) and S2 (r = 0.80 *). Results suggest that biomass yield estimates were possible by using predictive models generated from plant height measuring, aim of the pruning and age of the plants [19].
Average value for moisture content of the biomass harvested in both orchards was similar, despite the age differences among the walnut trees. The results coincided with previous reports, showing that in different populations (forests), similar wood composition was observed, although the combustion process may differ [20]. Biomass moisture content in both orchards was within a range observed in forest species, which showed between 15 and 72% of dry matter portion (moisture between 28 and 85%) [21]. The moisture content in the freshly cut walnut branches was influenced by the low level of physiological activity registered during the winter season, related to natural effects of climatic factors (low temperature and reduced water availability) and seasonal changes over the plant physiology [22].
Fresh and dry biomass yield was similar between orchards, mainly due to the difference in planting density, which was compensated by variation in plant age and height, recorded in S1 (Table 2) [23]. It was concluded that differences in age and population density, as well as the intrapopulation and varietal diversity in walnut orchards, influenced the results obtained in the present study. The yield average in both orchards was 2336 kg ha−1 for fresh biomass and 998 kg ha−1 in the case of dry biomass production. Biomass yield from walnut thinning pruning was lower than that established annually in orchards of the same cultivated species, which generated a total of 1.5 t ha−1 [24]. In other studies, it was established that the dry biomass yield average from pruning in different fruit trees reached 5.4 t ha−1 year−1 [25].
It is necessary to advance with studies that allow one to establish precise levels of production and utility of biomass derived from pruning in walnut orchards in Northern México. With that, the availability of raw material will be established for different purposes, such as direct use as firewood, odorant woodchips and its use in the production of engineered wood and various types of biofuels (solid, liquid and gaseous). Therefore, the analysis of the chemical composition and physical properties of the biomass obtained from pruning in walnut trees grown in Durango and other states of the Mexican Highlands is necessary.

3.2. Proximate Analysis of Biomass

The ash content was significantly higher in the biomass of walnut trees sampled in S1 (4.7%) (Table 3), mainly due to the age of the plantation and the clayed soil type pre-dominant in this orchard. A tendency to high ash accumulation was observed and related to minerals present in clayed soils, especially silicon, which positively influences the amount of ash present in plant tissues [26]. Additionally, it has been shown that the availability of nutrients in soil is more important in young trees compared to older ones [27]. This favored the formation of ash in walnut trees sampled in S1, which are younger than those of S2; their branches showed recent growth and high absorption mobility of minerals [28].
Fixed carbon was statistically similar in both orchards, with values between 74.9 and 76.4%, which were lower than those previously recorded in a wild bush species known as jarilla (Dodonaea viscosa) (78.3%), classified in Durango as a plant with bioenergetic potential [22]. New branches in walnut trees show high accumulation of multiple compounds related to the proportion of fixed carbon in biomass, since a high level of carbon accumulation rate was observed in plant live biomass of young forest trees compared to old-growth forests [28]. Fixed carbon values were within the range observed in other studies, including diverse plant species (65.0 to 82.4%) [29]. Content of volatile matter showed similar levels between walnut orchards, with a mean value of 19.2% and a fluctuation between 18.7% and 19.7%. Newly grown walnut tree branches showed low levels of lignification, related to plant growth stage [30], and an increase in volatile compounds compared to other species cultivated for bioenergy purposes, showing values between 9.8 and 14.7% [31]. Despite the above, the levels of volatile compounds were within the range recorded in studies, including multiple plant species (8.7 to 23.4%) [29]. HHV of the walnut pruning biomass showed a mean value of 16.5 MJ kg−1 and values between 16.2 and 16.7 MJ kg−1, resulting in similar values to those registered in fast-growing species (16.1 to 17.9 MJ kg−1) [31] but low compared to other agricultural residues, such as corn stover (18.5 MJ kg−1) and walnut shell (21.6 MJ kg−1) [32].

3.3. Physical Properties of Briquettes

Significant differences (p ≤ 0.05) were observed between treatments (moisture and pressure) for briquette diameter, length and volume (Table 4). Most of the treatments showed an average briquette diameter of 3.2 cm and only treatments T1 and T3 produced briquettes with significant reductions for this variable (3.1 cm). The decrease in diameter observed in treatments T1 and T3 was considered to be a result of the physicochemical properties of the original biomass obtained from S1, which required a greater amount of humidity to optimize the briquetting process. Lower biomass moisture content was related to tree age, interval between pruning and biomass water retention capacity. It has been shown that when humidity is low, particles are not spread out enough and the surrounding ones do not stick together closely, hindering briquette formation [33]. It has been shown that some biomass types were molded with a moisture content between 12 and 18%, with an optimal level at 15% [34]. Briquette length showed high variation between treatments, with a mean value of 4.2 cm and fluctuation between 4.0 and 4.5 cm. Treatments T5 (4.5 cm) and T7 (4.4 cm) showed significant differences for briquette length, while treatments T3 and T4 registered the lowest value (4.0 cm). The importance of biomass moisture during the briquetting process was corroborated since it was observed that the biomass from S1 (T5 and T7) showed acceptable properties with moisture content of 10%, according to previous reports [33].
The differences observed for briquette weight were not statistically significant between treatments, with a mean value of 39.6 g and a fluctuation between 38.7 and 39.8 g. Results were related to the uniformity in the production of briquettes, mainly favored by the efficiency of the equipment used. The differences for the briquette volume between treatments were statistically significant (p ≤ 0.05), with a mean value of 33.0 cm3 and a fluctuation between 30.7 and 35.2 cm3. Treatments T5 (35.2 cm3) to T8 (34.7 cm3) showed higher values for briquette volume, while treatments T1, T3 and T4 registered a significant reduction for this trait (30.7 to 31.7 cm3). Results showed the importance of humidity control when briquettes were produced by using biomass residues from tree pruning in walnut orchards. Low biomass moisture content (6%) favored reductions in briquette volume, considered as an important trait, lowering storage and transportation costs.
Bulk density of the briquettes showed statistically significant differences (p ≤ 0.05) between treatments, with values ranging from 1.14 ± 0.03 to 1.30 ± 0.06 g cm−3, with T1 being statistically superior. A density reduction was observed according to increments in moisture content and pressure, and this effect is consistent with equipment manufacturer recommended values for biomass humidity, ranging from 6 to 14% [35]. Efficiency in compaction and increased bulk density are preferred by reducing costs in briquette transportation and storage. Outstanding levels for bulk density were obtained in all the treatments, compared to those obtained in a previous study producing briquettes made from different feedstocks, showing values between 285 and 964 kg m−3 (0.285–0.964 g cm−3) [36].

3.4. Proximate Analysis of Briquettes

Differences registered between treatments were non-statistically significant for moisture content (5.3 to 5.9%) (Table 5). In both orchards, moisture levels in walnut biomass were lower than the range reported in other studies performed by using residues from walnut production (8.2 to 11.5%) [37]. Low-density briquettes were obtained when biomass moisture content was less than 11%, also showing a facility for disintegration during handling [38]. In this work, briquettes obtained by using biomass from walnut pruning residues met the requirements of international standards (<10%) [39,40]. Significant differences were detected (p ≤ 0.05) between treatments for ash content, and the pruning residues from the youngest orchard (S1) showed the highest value (4.7 ± 0.21%), although in both orchards, the ash content was lower than the range reported in a study with pecan pericarp (8.2 to 11.5%) [37]. The low ash content values were mainly attributed to the absence of leaves [41], since at the sampling date, pruned trees were in a state of dormancy. In several plant species, leaves were considered as an important plant fraction related to higher ash content (18–19%), of which 76% consisted of silica [42].
The moisture pressure treatments applied during the briquetting process modified the original composition of the walnut biomass. Modification was mainly observed for the ash content reduction when briquettes were compared to the base material obtained in both walnut orchards. Increments in commercial quality of the briquettes were also achieved by reducing the ash content, which limits biofuel acceptance according to international standards. The results showed that the biomass derived from thinning pruning in walnut trees met the quality requirements for briquette production, since all the treatments showed ash values below the limits established in the international standards (<5%) [39,40]. Low ash content is an important attribute in high-quality fuels [40,43] and it has been observed that ash in densified biofuels depends mainly on the minerals present in the original fuel, biomass management during the process and efficiency in the combustion [44]. The proportion of volatile material showed an average value of 77.1% and fluctuations between 76.7 and 77.7%. Volatile material increased the mass of gas during pyrolysis [45], in relation to the base material, because of compression exerted during the elaboration of the briquettes. Values obtained exceeded those observed with pecan pericarp, which varied between 63.0 and 66.7% [37]. It was observed that the content of volatile material varies mainly according to the composition of the pyrolyzed material, as well as conditions under which this process is performed [46] and the particle size used [37].
Non-significant differences were recorded between treatments for fixed carbon content, with an average value of 19.2% and variations between 18.7% and 19.7%. These values were similar to those registered in maralfalfa pellets (19.2%), being higher than the commercial control represented by young pine (4.6%), which registered the lowest level for fixed carbon [47]. Results corroborated the need for establishing an appropriate humidity content during the walnut biomass briquetting to reduce problems during the compression and molding process. Species showing high growth rates also register low levels for volatile material [48], due to the accelerated lignification process related to higher fixed carbon levels [49]. Fixed carbon values obtained in this study were similar to those reported previously [37], showing an interval between 16.1 and 18.6%, established by using pecan fruit pericarps. Increased values for fixed carbon were obtained when branches and leaves were used [41], influencing the energy potential [50].
High heating value in briquettes obtained from walnut pruning residues ranged from 17.7 ± 0.10 to 18.4 ± 0.14 MJ kg−1, slightly superior to HHV interval obtained in briquettes elaborated from pecan pericarps (17.0 to 17.5 MJ kg−1) [37]. The results suggest that walnut biomass is a sustainable source for biofuel production; however, it is important to evaluate briquette efficiency during the combustion process. Increments for HHV were registered in the briquettes compared to those obtained in raw biomass, reinforcing the densification benefits in walnut vegetative biomass obtained from the pruning practice. Treatments T1, T2, T3, T5 and T7 showed statistically similar values (18.1 to 18.4 MJ kg−1) and exceeded the rest of the treatments, which showed values between 17.7 and 17.8 MJ kg−1. Values obtained in this study were similar to those previously reported with pecan pericarp, in which briquetting increased the calorific value of the base material from 17.0–17.5 MJ kg−1 to 18.2–18.5 MJ kg−1 [37]. Most of the treatments met international standards, establishing a minimum of 18.0 MJ kg−1; then, both orchards produced briquettes with the calorific quality required in the biofuel market [39,40].

4. Conclusions

Biomass from walnut pruning represents a sustainable source of raw material to produce high-quality biofuels, mainly briquettes. The pruning performed in walnut trees, showing eight to thirteen meters in height and ages between 10 and 22 years, produces 1 t ha−1 of dry biomass on average. Walnut vegetative biomass could be directly used as fuel and as a raw material to produce densified biofuels, mainly briquettes. Walnut tree pruning residues provide biomass, showing acceptable levels for the content of ash (<5%), fixed carbon (75 to 76%), volatile matter (18.7 to 19.7%) and HHV (16.2 to 16.7 MJ kg−1). Biomass moisture content is an important factor in obtaining high-quality briquettes from walnut vegetative residues, and levels ranging from 7 to 14% are recommended during the briquetting process. Briquettes based on walnut vegetative biomass met the international quality standards: humidity < 10%, ashes < 5% and HHV > 18 MJ kg−1. The integral use of walnut tree residues reduced the management problems registered during walnut production. In addition, increased biofuel production will expand sustainable bioenergy options while improving farmers’ income and productivity.

Author Contributions

Conceptualization and design, R.R.-S. and A.C.-P.; biomass collection, S.S.-E., A.C.-P. and J.C.R.-S.; resources, J.C.R.-S.; investigation, A.C.-P. and D.S.-Z.; formal analysis, R.R.-S. and S.S.-E.; writing—original draft preparation, R.R.-S., S.S.-E. and D.S.-Z.; writing—review and editing, J.C.R.-S., R.R.-S. and A.C.-P. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Not applicable.

Acknowledgments

The authors thank the Laboratory of Instituto de Silvicultura e Industria de la Madera (ISIMA) (Universidad Juárez del Estado de Durango).

Conflicts of Interest

The authors declare no conflict of interest.

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Table
Table 1. Moisture conditions and pressure used in each treatment applied to the biomass used to produce briquettes.
Table 1. Moisture conditions and pressure used in each treatment applied to the biomass used to produce briquettes.
TreatmentSiteMoisture Content (%)Pressure (Mpa)
T1S1620
T2S2620
T3S1615
T4S2615
T5S11020
T6S21020
T7S11015
T8S21015
Table
Table 2. Total height, moisture content and biomass yield in walnut trees grown in two orchards established in Durango, México.
Table 2. Total height, moisture content and biomass yield in walnut trees grown in two orchards established in Durango, México.
Orchard Total Height
(m)		Moisture Content (%)Fresh Biomass
(kg ha−1)		Dry Biomass
(kg ha−1)
S18.1 ± 0.68 a42.5 ± 0.7523591000
S212.5 ± 2.40 b42.8 ± 0.262312995
Average10.342.32336998
Mean values ± standard deviation. Different letters in columns indicate statistically significant differences (p ≤ 0.05) between orchards.
Table
Table 3. Chemical and energetic properties of the biomass obtained in thinning pruning at two walnut orchards established in Durango, México.
Table 3. Chemical and energetic properties of the biomass obtained in thinning pruning at two walnut orchards established in Durango, México.
OrchardAsh (%)Fixed Carbon (%)Volatile Matter (%)High Heating Value (MJ kg−1)
S14.7 ± 0.21 a74.9 ± 0.7119.7 ± 0.9816.2 ± 0.32
S23.4 ± 0.66 b76.4 ± 1.5518.7 ± 1.2916.7 ± 0.23
Average4.175.719.216.5
Mean values ± standard deviation. Different letters in columns indicate statistically significant differences (p ≤ 0.05) between orchards.
Table
Table 4. Physical properties of briquettes in each moisture x pressure treatment.
Table 4. Physical properties of briquettes in each moisture x pressure treatment.
TreatmentDiameter
(cm)		Length
(cm)		Weight (g)Volume (cm3)Particle Density (g cm−3)
T13.1 ± 0.06 b4.1 ± 0.07 bc38.7 ± 0.1030.7 ± 1.36 d1.30 ± 0.06 a
T23.2 ± 0.05 a4.1 ± 0.06 bc39.7 ± 0.0832.5 ±1.04 bc1.22 ± 0.04 bc
T33.1 ± 0.05 b4.0 ± 0.05 c39.8 ± 0.0731.2 ± 1.06 cd1.28 ± 0.05 ab
T43.2 ± 0.05 a4.0 ± 0.05 c39.7 ± 0.0731.7 ± 1.20 cd1.25 ± 0.05 ab
T53.2 ± 0.04 a4.5 ± 0.07 a39.7 ± 0.1035.2 ± 1.17 a1.13 ± 0.05 d
T63.2 ± 0.05 a4.3 ± 0.06 b39.6 ± 0.1233.9 ± 1.23 ab1.17 ± 0.04 cd
T73.2 ± 0.05 a4.4 ± 0.07 ab39.7 ± 0.0934.3 ± 1.35 a1.16 ± 0.05 cd
T83.2 ± 0.013 a4.3 ± 0.05 b39.7 ± 0.1234.7 ± 0.88 a1.14 ± 0.03 d
Average3.24.239.633.01.21
Mean values ± standard deviation. Different letters within the same column indicate statistically significant differences (Tukey p ≤ 0.05).
Table
Table 5. Physicochemical properties of briquettes of several moisture pressure treatment.
Table 5. Physicochemical properties of briquettes of several moisture pressure treatment.
TreatmentMoisture Content (%)Ash Content (%)Volatile Matter (%)Fixed Carbon (%)1HHV
(MJ kg−1)
T15.3 ± 0.313.5 ± 0.25 ab76.7 ± 0.7714.5 ± 0.5018.3 ± 0.11 a
T25.7 ± 0.673.1 ± 0.29 b76.8 ± 0.3414.4 ± 0.8218.4 ± 0.14 a
T35.4 ± 0.033.4 ± 0.22 ab77.1 ± 0.4514.1 ± 0.2618.3 ± 0.19 a
T45.3 ± 0.173.5 ± 0.16 ab77.3 ± 0.6113.9 ± 0.6817.8 ± 0.12 bc
T55.9 ± 0.353.2 ± 0.16 b76.8 ± 0.6514.2 ± 0.8418.1 ± 0.13 abc
T65.3 ± 0.153.9 ± 0.15 a77.6 ± 0.7613.2 ± 0.7417.7 ± 0.10 c
T75.5 ± 0.043.8 ± 0.03 a76.8 ± 0.5413.8 ± 0.5218.2 ± 0.14 ab
T85.7 ± 0.063.9 ± 0.30 a77.7 ± 2.4212.8 ± 2.7217.7 ± 0.14 c
Average5.53.577.113.918.1
1HHV = High Heating Value, Mean values ± standard deviation. Different letters within the same column indicate statistically significant differences (Tukey p ≤ 0.05).
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Sierra-Zurita, D.; Santana-Espinoza, S.; Rosales-Serna, R.; Ríos-Saucedo, J.C.; Carrillo-Parra, A. Productivity and Characterization of Biomass Obtained from Pruning of Walnut Orchards in México. Energies 2023, 16, 2243. https://doi.org/10.3390/en16052243

AMA Style

Sierra-Zurita D, Santana-Espinoza S, Rosales-Serna R, Ríos-Saucedo JC, Carrillo-Parra A. Productivity and Characterization of Biomass Obtained from Pruning of Walnut Orchards in México. Energies. 2023; 16(5):2243. https://doi.org/10.3390/en16052243

Chicago/Turabian Style

Sierra-Zurita, Donaji, Saúl Santana-Espinoza, Rigoberto Rosales-Serna, Julio César Ríos-Saucedo, and Artemio Carrillo-Parra. 2023. "Productivity and Characterization of Biomass Obtained from Pruning of Walnut Orchards in México" Energies 16, no. 5: 2243. https://doi.org/10.3390/en16052243

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