Next Article in Journal
Bioprocessed Guishe Juice (Agave lechuguilla Residue) as a Dual-Action Bioagent for Weed and Fungal Control in Sustainable Agriculture
Previous Article in Journal
The Flow Field Characteristics and Separation Performance of the Compact Series Gas–Liquid Separator
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Processes
Volume 13
Issue 7
10.3390/pr13072059
processes-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Production of Biochar from Plantain Rachis and Cassava Peel Towards Sustainable Management of Caribbean Agricultural Waste

by
Adriana Patricia Herazo
1,
Alejandra Zambrano
2,
Lorena Marín
3,
Julio Mass
4 and
Diana Nathalie Montenegro
1,*
1
Group of Material Physics, Universidad del Atlántico, Puerto Colombia 081007, Colombia
2
Group of Heterocyclic Compounds, Universidad del Atlántico, Puerto Colombia 081007, Colombia
3
Group of Thin Films, Universidad del Valle, Cali 760031, Colombia
4
Group of Applied Physics, Universidad del Norte, Puerto Colombia 081007, Colombia
*
Author to whom correspondence should be addressed.
Processes 2025, 13(7), 2059; https://doi.org/10.3390/pr13072059
Submission received: 5 November 2024 / Revised: 21 March 2025 / Accepted: 23 April 2025 / Published: 29 June 2025
(This article belongs to the Section Sustainable Processes)
Browse Figures
Versions Notes

Abstract

The Caribbean faces many environmental issues, and the mitigation and adaptation strategies to address the challenges of global warming are not sufficient in this geographical region. Considering that agriculture is a relevant activity in most countries around this region, our study proposes to enhance Caribbean waste management by transitioning to a sustainable and resilient process in the framework of a green, circular economy. The research has been focused on the thermochemical transformation of the typical residues of Caribbean farm products (plantain rachis, and cassava peel). Biochar samples were synthesized from these biomasses by the slow pyrolysis method at different temperatures (300 °C, 400 °C, and 500 °C). Biochar samples with a smooth surface were synthesized from plantain rachis biomass, while biochar samples with a porous surface were obtained from cassava peel biomass. At the same pyrolysis temperature, all biochar samples derived from plantain rachis exhibited higher production biochar yields than those biochar samples derived from cassava peel. The yield percentages were determined to be 65.7% and 62.0% at a pyrolysis temperature of 300 °C; 45.6% and 37.5% at 400 °C; and 33.7% and 25.4% at 500 °C, respectively. XRD measurements revealed that both biomass-derived biochar samples were found to be enriched with several compounds, such as kalicinite, arcanite, sylvite, CaO3Si, and MgO3Si, which vary according to the pyrolysis temperature. FTIR analysis revealed the presence of carbonyl and carboxyl functional groups on the surface of all biochar samples. However, only the aliphatic functional groups were observed on the surface of the biochar samples derived from cassava peel. These characteristics are of particular relevance due to their potential application in soil amendment or water remediation.

1. Introduction

Environmentally, the Caribbean is one of the most decisive regions in the world. Coastal and marine ecosystems of this geographic zone cover an area of 16 million km2 and own 50% of plant life not found anywhere else on the planet [1,2]. Despite their meager contributions to global greenhouse gas emissions, the Caribbean are suffering the worst effects of global warming (stronger storms, worsening droughts, forest fires, and severe floods). The last Ecological Threat Report (ETR), which measures the impact of ecological threats (food insecurity, water risk, natural disasters, and demographic pressure), has revealed there is considerable variation in such impact within regions of the world [3]. While territories around the Caribbean have a high level of ecological threat, North America and Europe are the two regions with the lowest average score. Therefore, the implementation of strategies and technologies towards the sustainable management of natural resources within healthy ecosystems is a crucial issue for the Caribbean.
Historically, agriculture has been a significant economic activity in the Caribbean. Despite its displacement by tourism, it continues to be promoted to ensure food security in the region. The surrounding coasts and islands of the Caribbean share similar climatic conditions, resulting in comparable agricultural crops. Several reports show the primary crops in the Caribbean include banana–plantain, citrus, coffee, cocoa, sugarcane, roots and tubers (cassava, sweet potato, and yam), beans, corn, and some fruits (mangos, oranges, and pineapples) [4,5]. According to the Food and Agriculture Organization of the United Nations (FAO), Latin America and the Caribbean account for 13% of global roots and tubers, 8% of the global production of fruits, and 7% of global cereal production [5]. Thus, the countries and territories around the Caribbean are potential biomass producers because they generate millions of tons of organic waste from the agroindustry and agricultural harvest process. However, there is a poor implementation of waste management and research in this regard.
According to the United Nations Environment Report about the waste management outlook for Latin America and the Caribbean, the region generated 541,000 tons of waste per day in 2014. The current generation rate indicates that this figure could reach 671,000 tons per day by the year 2050 [6]. The report indicates that approximately 90% of the waste generated in this region remains unused, with organic waste accounting for an average of 50% of the total. Additionally, the report evidenced that many countries in the region have significant deficiencies in their waste collection management, generating significant environmental impact. For instance, in several Caribbean territories, the waste is deposited in open dumpsites or burned in the open, resulting in the emission of toxic and greenhouse gases (GHG), as well as water and soil pollution [6].
Commonly, higher-income countries tend to have high levels of waste collection coverage. In fact, some studies have found that the coverage of waste collection was 36% for low-income countries, 64% for lower–middle-income countries, and 82% for upper–middle-income countries. For higher-income countries, the value approaches 100 percent [7]. As shown in Table 1, the income level of most countries and territories around the Caribbean is classified as lower-middle and upper-middle [7]. Therefore, effective management practices and final waste disposal methods must be incorporated in this geographic region.
In recent years, biochar has attracted renewed interest because it is looked upon as an engineered material for environmental remediation, such as decontamination of water (surface, groundwater, and wastewater) [8,9] and soil amendment [10,11]. This is based on the properties exhibited by biochar, such as high resistance to biodegradation (similar to the natural soil humus) and the microporous structure, which helps to retain molecules of water-soluble compounds and microorganisms. The porous structure of biochar also allows reducing the mobility and bioavailability of contaminants and heavy metals [12,13]. In addition, biochar can be synthesized from organic waste (human, agricultural, and industrial), offering other benefits such as (i) a gradual reduction in solid waste, reducing the associated effects (greenhouse gas (GHG) emissions and contamination of water sources), and (ii) added value for waste, enabling the opening of new work activities based on the “recycling” of renewable sources towards the implementation of the desired circular economy [14,15].
Several studies have shown biochar can exhibit unique characteristics depending on the type of biomass and the synthesis parameters [13,14]. This is because the chemical reactions that occur during the biomass transformation process define the morphological, physical, and chemical properties of the biochar. Therefore, for industrial applications, the selection of biomass and parameter synthesis will depend on the organic waste sources from each geographic region as well as the desired biochar application [16,17]. According to the literature, there is a large number of studies about biochar derived from typical organic waste from the European, East Asian, and North American regions [12,17]. However, this information is far less reported in developing countries such as the countries and territories around the Caribbean geographic area.
As outlined in the preceding introduction, our work is focused on the production of biochar from the agricultural waste of the Caribbean derived from cassava and plantain crops by using a widely used thermochemical conversion method such as slow pyrolysis. In this method, the biomass is heated in the complete absence of oxygen or with a limited supply of oxygen, thereby preventing significant combustion [18]. Thus, this technique has relevant advantages, including its contribution to efficient waste management and reduction in the environmental impact. As is commonly understood, the accumulation of waste in landfills leads to anaerobic decomposition, which in turn produces leachate and methane, one of the most potent GHGs. Pyrolysis, on the other hand, avoids the combustion of the waste during the thermochemical transformation, minimizing the emission of environmental pollutants, such as volatile organic compounds (VOCs) and particulate matter.
In this study, we have used wastes such as the cassava peel and the plantain rachis. We have emphasized the synthesis process, the effect of biomass feedstock, and the pyrolysis temperature on the physical and chemical properties of biochar. Some studies have been published on various applications from cassava peel and the plantain rachis, or banana stem. For example, several authors have shown the potential of banana stem and plantain rachis in the production of bioethanol [19,20], yarns [21], and paper pulp [22]. Similarly, there are reports on the application of cassava peel in the production of biofuels [23,24,25] and animal food concentrate [26]. On the other hand, the biochar synthesis from plantain rachis [27] and cassava peel [28,29] has also been a subject of recent research, primarily from authors in Asia and Africa, reflecting the significant interest in these biomasses, particularly in low- and low–middle-income countries. Nonetheless, the biochar production from these biomasses is still rare and virtually non-existent, particularly in the Caribbean. Therefore, our research contributes to the advancement of knowledge on carbon-based materials derived from agricultural biomass with promising prospects for environmental applications. Also, it promotes strategies for sustainable agriculture and a green, circular economy in the Caribbean by giving added value to its agricultural waste.

2. Materials and Methods

2.1. Chemicals

In the course of this research, no chemical reagents were used in any of the following procedures: the treatment of biomass, the production of the biochar, or the characterization of samples. The procedures employed are based on the principle of non-pollution and minimal environmental impact.

2.2. Collection of Biomasses

The lignocellulosic biomass used in this study is derived from the plantain and cassava agricultural crops from the two local farms of the Colombian Caribbean region. Farms with small-scale production were selected in the Palmar de Varela village, which belongs to the Atlantico state of Colombia. This selection was based on the following criteria: (i) farms with a short spatial distance to the laboratory site, which reduces the collection time and also provides the opportunity to obtain agricultural waste without organic decomposition; and (ii) farms with soil quality and minimal use of pesticides and agrochemical products, ensuring agricultural products with a low contamination and a suitable nutrient content.
The waste of plantain rachis and cassava peel was packed and brought in portable coolers to prevent the decomposition and contamination of biomass during the transfer of them from the farms to the research laboratory.

2.3. Treatment of Biomass

In order to remove the soil residues, bacteria, and other contaminants present in the biomass samples, they were carefully washed three times with deionized water and subsequently dried in a furnace at 90 °C for 12 h.

2.4. Production of Biochar

The biochar samples were obtained by the slow pyrolysis method, which involves the thermal degradation of a biomass in an oxygen-free environment. This process was carried out using a furnace muffle KSL-1200X, coupled to an inert gas flow system manufactured by MTI Corporation (Richmond, CA, USA). The clean and dried biomass samples were pyrolyzed in a muffle furnace for 30 min at different temperatures (300 °C, 400 °C, and 500 °C) under nitrogen gas flow (0.5 L/min). All samples were pyrolyzed using the same heating rate program at 15 °C/min. Once the pyrolysis process had finished, the samples were left inside the furnace cooling to room temperature.
The biochar samples were manually macerated in an agate mortar to improve the homogeneity of their powder texture. In this study, each experiment was repeated five times to ensure the accuracy and repeatability of the data.
The evaluation of the mass yield of biochar production was conducted using the following equation:
Y i e l d   o f   b i o c h a r   ( % ) = m a s s   o f   s o l i d   p r o d u c t m a s s   o f   d r i e d   b i o m a s s × 100 .
In this study, the proximate analyses were determined to obtain information like moisture content (MC) and volatile matter (VM), which were evaluated by the American Society for Testing and Materials (ASTM) standards such as D3173 and D3175, respectively. To determine the MC of the samples, 1.0 g of the biochar was placed in a clean, dried, and weighed crucible covered with a lid. The crucible was placed in an oven at 150 °C for 3 h, and it was then placed in a desiccator for cooling. The percentage of MC was computed as follows:
M C   ( % ) = m 0 − m 2 m 0 − m 1 × 100 .
m0: mass of empty crucible;
m1: mass of crucible biochar sample before heating;
m2: mass of crucible biochar sample after heating.

2.5. Characterization of Biomass and Biochar

Regarding the characterization of samples, the thermogravimetry analysis of the raw material was carried out using a TGA 2950 manufactured by TA Instruments (New Castle, DE, USA). The measurements were performed in a nitrogen atmosphere, heating from room temperature to 850 °C with a heating rate of 15 °C/min. The morphology properties of the biochar samples were examined by a Phenom Pro X scanning electron microscope (SEM) by Thermo Fisher Scientific (USA), equipped with an energy dispersive X-ray (EDX) probe for the elemental chemical analyses. All samples had to be previously coated with gold thin film to improve the measure quality. For SEM images, the electron beam was set at 30 kV, while during the EDX measures, it was 15 kV. Otherwise, the structural properties of the biochar were examined using -D8 Advance ECO X-ray diffraction (XRD) equipment fabricated by Bruker (Bremen, Germany), which has EVA software, version 8.7, which allows us to identify the different crystal compounds present in the biochar samples. Finally, the chemical surface characterization of the samples was performed using ATR-FTIR 4700 Fourier Transform Infrared Spectrophotometry (FTIR) equipment manufactured by JASCO (Tokyo, Japan). The absorbance spectra were measured covering a spectral range between 400 cm−1 to 4000 cm−1 with a resolution of cm−1. Sixteen scans were recorded per sample with an acquisition time of 13 s per spectrum.

3. Results and Discussion

This section has been divided by subheadings to provide a precise description of the experimental results and their interpretation.

3.1. Degradation Process of Biomass

A thermogravimetry analysis (TGA) of plantain rachis (PR) and cassava peel (CP) biomasses was carried out to inquire about the degradation process of samples during pyrolysis. Both biomasses have exhibited a significant mass loss due to the decomposition of the organic polymers present in plants (cellulose, hemicellulose, and lignin), as shown in Figure 1a,b. According to literature, the degradation process of hemicellulose usually takes place in the temperature range from 200 °C to 315 °C; cellulose between 300 °C and 400 °C; and lignin between 160 °C and 900 °C, with a more complex mechanism of degradation [30]. From derived curves (DTGA), three principal degradation stages are distinguished in our samples, Figure 1a,b. The temperature ranges of these stages have been identified for each biomass: 20–170 °C, 170–350 °C, and 350–600 °C for PR biomass and 20–210 °C, 210–365 °C, and 365–600 °C for CP biomass. The first stage (<200 °C) is commonly associated with evaporation of the retained moisture in biomass, in our samples with a mass loss smaller than 7% specifically, PR-3.16% and CP-6.02%. The second degradation stage corresponds to a combined thermal decomposition of the total hemicellulose and a partial amount of cellulose and lignin for both biomasses, while the decomposition of the remaining proportion of cellulose and lignin has undergone in the third stage. These results are well correlated with the findings of some reported studies [31].
Regarding the mass loss, at the second stage it was 59.12% for PR biomass and 72.93% for CP biomass, while at the third stage it was 19.90% (PR biomass) and 16.11% (CP biomass), obtaining a solid residue percentage of 17.82% and 4.94% for PR and CP biomass samples, respectively. These results show that the CP biomass sample had a higher total mass loss compared to PR biomass. It is commonly accepted that a higher mass fraction of lignin in biomass implies less volatilization, while a higher proportion of hemicellulose and cellulose results in more volatilization and therefore a higher mass loss [32,33]. Accordingly, these results allow us to categorize the PR sample as a lignin-rich biomass and the CP sample as a cellulose-rich biomass. Because the role of lignin is to provide structural rigidity and tensile strength to plants, allowing them to grow vertically [34], it is reasonable to observe that the branches and stems of plants include a higher mass fraction of lignin, as we have seen in the case. The above results are summarized in Table 2.
Some authors have reported the content of hemicellulose, cellulose, and lignin of plantain rachis and cassava peel, which are summarized in Table 3 and Table 4, respectively. These tables demonstrated that there is variation in the reported values of these polymer content measurements for each type of biomass. This variation can be attributed to several factors, including the variety of agricultural products, the nutrient content of the growing soil, and the method used to calculate these percentages. However, a comparison of the reported data reveals that plantain rachis typically exhibits higher lignin richness than cassava peel, which is well correlated with our TGA results.

3.2. Biochar Production

As previously mentioned, the biochar samples were obtained from PR and CP biomass by slow pyrolysis. In this method, the thermochemical conversion of biomass is typically performed at relatively low temperatures, with low heating rates and long residence times to favor the production of biochar. In our case, the biomass samples were pyrolyzed at different temperatures, such as 300 °C, 400 °C, and 500 °C, for 30 min under an inert atmosphere.
For the biochar samples, physical parameters such as yield and moisture were obtained in accordance with the processes described in Section 2.4 using Equation (1) and Equation (2), respectively. These are displayed in Table 5.
The yield results indicate that an increase in pyrolysis temperature is correlated with a decrease in yield for both types of biochar, PR biochar and CP biochar. This is due to the increase in polymer decomposition, as observed in the TGA results (Figure 1). However, it is noteworthy that the yield is lower for CP biochar samples compared to PR biochar samples, likely because of their high cellulose-richness, which increases the volatilization of biomass [32,33].

3.3. Characterization of Biochar

3.3.1. Scanning Electron Microscopy Analysis

The morphological characteristics of the biochar samples derived from PR and CP biomasses pyrolyzed at 300 °C, 400 °C, and 500 °C can be observed on the SEM images from Figure 2. The PR biochar samples have evidenced a smooth surface with an almost imperceptible porosity for samples pyrolyzed at 300 °C and 400 °C (Figure 2b,c) and the presence of holes with large diameters (>20 μm) for the sample pyrolyzed at 500 °C (Figure 2c). The formation of these holes is probably a result of the lignin degradation process that the RP biomass undergoes in the third stage of decomposition. In contrast, the Images of CP biochar samples clearly reveal a porous surface with a pore diameter ranging from 2.0 to 6.7 μm for CP-300 biochar; 1.3 to 5.7 μm for the CP-400 sample; and 1.2 to 3.0 μm for CP-500 biochar (Figure 3b–d). However, adsorption measurements are necessary for the estimation of an accurate average pore diameter in biochar samples.
The porous morphology of CP biochar has also been reported by other authors [28,29]. S.O. Odeyemi et al. reported the presence of pores on the CP biochar’s surface obtained by the carbonization process under a peak reactor temperature of 338 °C for 160 min [28]. The BET surface area and BJH pore diameter of the biochar were obtained to be 319.784 m2/g and 2.447 nm, respectively. In a related study, I. Maman Hamissou et al. investigated the synthesis of biochar from CP pyrolyzed at 400 °C. Their analysis revealed an average pore diameter of 1.44 nm, with a total pore volume of 0.8 cm3/g as determined by the BJH method [29]. Furthermore, the nitrogen adsorption/desorption analysis conducted by these authors demonstrated the simultaneous presence of micropores and mesopores in their samples. On the other hand, N. Abdullah et al. have reported the synthesis of biochar from stem plantain obtained from the slow pyrolysis experiment at 500 °C [27]. With regard to the morphology of their samples, some pores were evident from FESEM images. Additionally, the results of BET analysis showed a surface area of 1.078 m2/g and a total pore volume of 0.005 cm3/g. As in our case, a comparison of the results reported by other authors regarding biochar obtained from PR and CP clearly indicates that, although the PR biochar does contain pores, its porosity tends to be much lower than the CP biochar.
The morphology differences between P and CP biochar samples appear to have an answer in the correlation between our SEM and TGA results. This indicates that lignin-rich biomass favors the synthesis of smooth biochar with high specific surface area, while cellulose-rich biomass leads to the synthesis of porous biochar, which is in agreement with what has been mentioned by some authors [35,36]. Regarding the porous surface of the CP biochar samples, the SEM images show the average pore size tends to decrease with increasing pyrolysis temperature (Figure 3b,d). It is worth noting that in the literature there is no consensus on the effect of pyrolysis temperature on the biochar pore size; while some authors have reported the pore size of biochar increases with increasing pyrolysis temperature [37], other authors have reported the opposite [38]. This is due to biomass feedstock strongly influencing the resultant biochar physical properties [39,40].

3.3.2. Energy Dispersive X-Ray (EDX) and X-Ray Diffraction Analysis

The energy dispersive X-ray (EDX) analysis of biochar samples has shown carbon (C), oxygen (O), and potassium (K) as the elements with the highest concentration in the samples, as illustrated in Figure 4 and Figure 5. The EDX spectra also detect elements such as calcium (Ca), silicon (Si), phosphorus (P), and magnesium (Mg). In the case of CP biochar samples, the measurements reveal the carbon and potassium proportions tend to increase with increasing pyrolysis temperature (Figure 5). In accordance with some reported studies, the pyrolysis temperature affects the carbon concentration in biochar because of its lignin decomposition, and the higher temperature increases the content of decomposed lignin [40]. Regarding PR biochar samples, the potassium proportion also tends to increase with increasing temperature (Figure 4).
Moreover, the XRD patterns of PR and CP biochar samples evidenced the formation of different crystalline compounds regarding the pyrolysis temperature, which is related to the complex degradation processes of some minerals present in the biomass and its typical organic polymers [41]. The XRD pattern of CP-300 biochar exhibits a wide band (range of 20 to 30°) centered around 2θ = 26.0°, evidencing an amorphous structure (Figure 6b). The diffractogram of the CP-400 biochar sample has revealed several fine peaks ascribed to magnesium silicate (MgO3Si), calcite (CaO3), kalicinite (CKO3), and phosphonate phosphate;silicon (O7P2Si) (Figure 6b). These last three compounds have also been evidenced in the XRD pattern of the CP-500 sample, but it reveals other peaks related to arcanite (K2O4S) and carbonyl dichloride (CCl2O) compounds (Figure 6b). Otherwise, the XRD diffractogram of PR-300 biochar shows the presence of magnesium silicate, potassium oxalate (C2K2O4) and sylvite (ClK) (Figure 6a). The kalicinite, arcanite, sylvite, wollastonite (CaO3Si), have been detected in the PR-400 sample, while the XRD peaks in PR-500 biochar were ascribed only to calcite, kalicinite, and wollastonite (Figure 6a). A detailed comparison of XRD peaks in PR and CP biochar samples is shown in Table 6.

3.3.3. Fourier Transform Infrared Spectroscopy Analysis

An FTIR analysis of PR and CP biochar samples was carried out to delve into the effect of pyrolysis temperature on the surface functional groups. The spectra of both PR and CP biochar samples synthesized at 300 °C exhibit a broad band between 3200 cm−1 and 3400 cm−1, which usually refers to the O–H stretching vibrations of hydrogen-bonded hydroxyl groups (Figure 7a,b). However, it is worth pointing out that this band is significantly reduced with increasing pyrolysis temperature because of the gradual breakage of the OH group and the separation of bound water at higher temperatures [42].
The spectra of CP biochar samples reveal other peaks between 3000 cm−1 and 3200 cm−1, but these are almost undetectable in the spectra of PR biochar samples. These peaks are related to the stretching vibrations of the C−H bond of aliphatic functional groups with asymmetrical and symmetrical stretching at 2935 cm−1 and 2885 cm−1, respectively [42,43]. A peak around 1700 cm−1 is associated with the C=C and C=O stretching vibrations of carbonyl and carboxyl groups. It is evident in CP biochar samples that the intensity of those peaks tends to decrease with increasing pyrolysis temperature due to the thermal degradation leading to a substantial loss of oxygen atoms [42,44,45]. In the case of the PR biochar samples, a shoulder peak is slightly detected for the sample pyrolyzed at 300 °C, and it is practically not evident at higher temperatures (Figure 7a). Another peak between 1550 cm−1 and 1650 cm−1 is observed in all samples, which is usually ascribed to C=C stretching of aromatic components and C=O stretching of conjugated ketones and quinones. This peak is slightly distinguished in the spectra of CP biochar samples, in contrast with PR biochar samples, when the peak is highly detected and undergoes a shift towards higher wavenumbers (~1600 cm−1) when pyrolysis temperature reaches 500 °C. However, the shift is still located in the established range [42,46].
In the range of 1000 cm−1 to 1500 cm−1, the FTIR spectra have exhibited several peaks. For all samples, a shoulder peak is slightly detected between 1470 cm−1 and 1490 cm−1, which is related to the C=C asymmetric stretching vibrations of lignin and C−H2 stretching of lignin carbohydrates [42,46]. In both PR and CP biochar samples, the peak around 1380 cm−1 is observed, and according to the literature, it corresponds to the characteristic stretching vibrations in the benzene rings zone, which tends to increase the intensity with increasing the pyrolysis temperature [42,46]. Between 1050 cm−1 and 1250 cm−1 the peaks are associated with the C–O–C stretching vibrations of cellulose and hemicellulose [42,46] while the peaks in the range from 600 cm−1 to 832 cm−1 represent the C–H stretching of aromatic and heteroatomic compounds [42,46]. The background signal in some of our spectra was detected around 2300 cm−1. The variability in functional groups on the PR biochar and CP biochar surfaces regarding the pyrolysis temperature is summarized in Table 7.

3.4. Applications of Biochar

Biochar has demonstrated that it possesses valuable properties that are applicable to numerous environmental proposals [47,48,49]. This included water remediation, soil amendment, air purification, and use as construction materials.
The physical and chemical properties of biochar (high surface area, porosity, surface functional groups, and chemical composition) allow for the removal of various types of contaminants, including organic (dyes, phenols, polycyclic aromatic hydrocarbons (PAH), pesticides, and antibiotics) and inorganic (heavy metals, nitrate, phosphate, and fluoride) compounds [47,48,49]. However, the elimination efficiency of a given type of pollutant depends on the unique characteristics of the biochar, which are determined by the biomass and the synthesis parameters used.
According to Section 3.3.2, the XRD measurements demonstrate the existence of different inorganic compounds in our biochar samples derived from plantain rachis and cassava peel. One of the important compounds present in biochar lies in their application in soil amendment, because they can be released in soil to minimize nutrient deficiencies (N, P, K, Ca, Mg, and Si). The previously mentioned points have been documented in a variety of studies. For instance, in a study by A. Freitas et al., noteworthy outcomes were obtained through the evaluation of various types of biochar derived from wood chips (maple and pine) and poultry litter (consisting of chicken manure, sawdust, and straw) when utilized as a substitute for commercial inorganic phosphorus fertilizer [45]. Other authors have shown a 40% release of P after five days [50] and a 70% release of N over 12 days in water and 25 days in soil [51] from corn stover biochar; cumulative release of N, P, and K reached about 45% after 7 days from wheat straw biochar pyrolyzed at 400 °C [52]. In our case, the biochar samples have a significant K-richness. The PR biochar and CP biochar pyrolyzed at 400 °C and 500 °C have exhibited compounds with the potential to release potassium, such as CKO3 and C2K2O4; for example, PR biochar pyrolyzed at 300 °C (Table 6). Additionally, CP biochar samples pyrolyzed at 400 °C and 500 °C have also been shown to contain O7P2Si, a compound subject to releasing phosphorus.
The use of biochar has also demonstrated a significant influence on soil pH, which is a relevant aspect because soil acidity is one of the most significant factors limiting plant growth and yield. Several studies have shown some compounds of biochar can stabilize organic matter in soils by means of carbonates and silicates of calcium and magnesium because they tend to raise the pH, neutralizing the acidity in water-wet soils, a fundamental aspect to achieving an efficient absorption of minerals [44,45,53]. Our biochar samples have revealed the presence of both carbonates and silicates of calcium and magnesium. Specifically, PR-300 and CP-400 biochar samples have exhibited the MgO3Si compound, while CaO3Si was detected in the PR-400 and PR- and CP-500 biochar samples.
On the other hand, the functional groups on the biochar surface also have a fundamental role for applications in soil and water remediation because they can interact with many chemical elements and compounds. In the case of water, these groups act as binding sites for suspended particles, organic matter, and other materials present, removing impurities and improving the water quality. Specifically, the organic functional groups on the biochar surface tend to facilitate chemisorption through H-bonding with the hydroxyl groups. This process occurs because OH groups act as H-donors [54]. Therefore, the presence of H-donors, such as -NH and -OH, or H-acceptors, including benzene rings, on the biochar surface or the organic pollutant, facilitates the H-bonding [55]. For soils, the functional groups can absorb nutrients in the form of cations and anions and then release them gradually as needed by plants. This helps to reduce the leaching of nutrients, improving soil fertility.
As shown in FTIR characterization, our samples have exhibited interesting functional groups on their surfaces, such as hydroxyl and carboxyl groups. These specific groups have been shown to interact with water molecules through hydrogen bonds, enhancing the ability of soil to retain water [35]. Furthermore, these groups have demonstrated the capacity to entrap a wide range of heavy metals, including aluminum (Al), arsenic (As), cadmium (Cd), chrome (Cr), copper (Cu), and lead (Pb), as documented by several papers [56,57,58].
In our case, although both types of biochar have evidenced significant properties (e.g., high potassium content; the presence of inorganic compounds such as carbonate of calcium and calcium and magnesium silicates, as well as hydroxyl and carboxyl functional groups), the CP biochar offers more advantages than RP biochar for applications such as soil amendment and water remediation due to its morphology with pores. It is well known that the presence of pores in biochar facilitates the release of nutrients, improves moisture retention in soil, and enhances the trapping of contaminants in water. Furthermore, our results showed that increasing the pyrolysis temperature reduces the pore size of CP biochar and enhances the presence of mineral inorganic compounds, which play a crucial role in supplying nutrients in soils. For instance, the CP biochar pyrolyzed at 500 °C exhibited the smallest range of pore size and the highest number of inorganic compounds present. In this regard, this type of biochar derived from Caribbean agricultural waste can facilitate the restoration of soils and natural water bodies in the Caribbean geographic region, which in several areas have been seriously degraded due to extreme climatic conditions and poor environmental practices.

4. Conclusions

The synthesis of biochar samples from the typical agricultural waste of the Caribbean region, such as plantain rachis and cassava peel, has been carried out by the slow pyrolysis method. The cellulose richness in the cassava peel is enabled to produce biochar samples with a porous surface, in contrast to the biochar derived from the plantain rachis, which tends to generate biochar samples with a smooth surface and fewer pores but a higher yield because of its lignin richness. Evidence has demonstrated that both types of biochar have evidenced relevant characteristics for soil amendment applications. However, the cassava peel biochar offers more advantages due to its porous surface, which facilitates the release of nutrients, improves moisture retention, and enhances the trapping of contaminants. Specifically, the cassava peel biochar pyrolyzed at 500 °C exhibited the best properties. Finally, the results of our research have demonstrated the feasibility of producing biochar from the local agricultural waste in the Caribbean for scalable industrialization using sustainable processes, e.g., cheap and removable raw materials and low-cost synthesis methods, which operate generating a minimal environmental impact.

Author Contributions

Conceptualization, A.P.H. and D.N.M.; methodology, A.P.H., A.Z., L.M., J.M. and D.N.M.; formal analysis, A.P.H. and D.N.M.; investigation, A.P.H. and D.N.M.; writing—original draft preparation, A.P.H. and D.N.M.; writing—review and editing, A.P.H., A.Z., J.M. and D.N.M.; supervision, D.N.M.; project administration, D.N.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Data that support the findings of this study are available from the corresponding author upon reasonable request.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Cervigón, F. Variability and sustainability of the Southern Subarea of the Caribbean Sea large marine ecosystem. Environ. Dev. 2017, 22, 30–41. [Google Scholar] [CrossRef]
  2. Schuhmann, P.W.; Mahon, R. The valuation of marine ecosystem goods and services in the Caribbean: A literature review and framework for future valuation efforts. Ecosyst. Serv. 2015, 11, 56–66. [Google Scholar] [CrossRef]
  3. Ecological Threat Report 2024: Analysing Ecological Threats, Resilience & Peace, Sydney, October 2024. Institute for Economics & Peace. Available online: http://visionofhumanity.org/resources (accessed on 14 October 2024).
  4. Wuddivira, M.N.; De Gannes, V.; Meerdink, G.; Dalrymple, N.; Henry, S. Challenges and Opportunities for Food and Nutrition Security in the Americas: The View of the Academies of Sciences, 2017, The Inter-American Network of Academies of Sciences (IANAS-IAP). Available online: https://ianas.org/wp-content/uploads/2020/07/fnb02c-1.pdf (accessed on 14 July 2018).
  5. FAO. Latin America and the Caribbean Regional Synthesis for the State of the World’s Biodiversity for Food and Agriculture; FAO: Rome, Italy, 2019. [Google Scholar] [CrossRef]
  6. UN Environment. Waste Management Outlook for Latin America and the Caribbean. United Nations Environment Programme, Latin America and the Caribbean Office. Panama City, Panama. 2018. Available online: https://www.unep.org/ietc/resources/publication/waste-management-outlook-latin-america-and-caribbean (accessed on 1 October 2018).
  7. UN Environment. Global Waste Management Outlook. United Nations Environment Programme. 2015. Available online: https://www.unep.org/ietc/resources/publication/global-waste-management-outlook-2015 (accessed on 6 March 2015).
  8. Manyuchi, M.M.; Mbohwa, C.; Muzenda, E. Potential to Use Municipal Waste Biochar in Wastewater Treatment for Nutrients Recovery. Phys. Chem. Earth Parts A/B/C 2018, 107, 92–95. [Google Scholar] [CrossRef]
  9. Kamali, M.; Appels, L.; Kwon, E.E.; Aminabhavi, T.M.; Dewil, R. Biochar in Water and Wastewater Treatment—A Sustainability Assessment. Chem. Eng. J. 2021, 420 Pt 1, 129946. [Google Scholar] [CrossRef]
  10. Amoah-Antwi, C.; Kwiatkowska-Malina, J.; Thornton, S.F.; Fenton, O.; Malina, G.; Szara, E. Restoration of Soil Quality Using Biochar and Brown Coal Waste: A Review. Sci. Total Environ. 2020, 722, 137852. [Google Scholar] [CrossRef] [PubMed]
  11. Guo, M.; Song, W.; Tian, J. Biochar-Facilitated Soil Remediation: Mechanisms and Efficacy Variations. Front. Environ. Sci. 2020, 8, 521512. [Google Scholar] [CrossRef]
  12. De la Rosa, J.M.; Santa-Olalla, A.; Campos, P.; López-Núñez, R.; González-Pérez, J.A.; Almendros, G.; Knicker, H.E.; Sánchez-Martín, A.; Fernández-Boy, E. Impact of Biochar Amendment on Soil Properties and Organic Matter Composition in Trace Element-Contaminated Soil. Int. J. Environ. Res. Public Health 2022, 19, 2140. [Google Scholar] [CrossRef]
  13. Chen, W.-H.; Hoang, A.T.; Nižetić, S.; Pandey, A.; Cheng, C.K.; Luque, R.; Ong, H.C.; Thomas, S.; Nguyen, X.P. Biomass-derived Biochar: From Production to Application in Removing Heavy Metal-Contaminated Water. Process Saf. Environ. Prot. 2022, 160, 704–733. [Google Scholar] [CrossRef]
  14. Sri Shalini, S.; Palanivelu, K.; Ramachandran, A.; Vijaya, R. Biochar from biomass waste as a renewable carbon material for climate change mitigation in reducing greenhouse gas emissions—A review. Biomass Conv. Bioref. 2021, 11, 2247–2267. [Google Scholar] [CrossRef]
  15. Rex, P.; Mohammed Ismail, K.R.; Meenakshisundaram, N.; Barmavatu, P.; Bharadwaj, A.V.S.L.S. Agricultural Biomass Waste to Biochar: A Review on Biochar Applications Using Machine Learning Approach and Circular Economy. ChemEngineering 2023, 7, 50. [Google Scholar] [CrossRef]
  16. Seow, Y.X.; Tan, Y.H.; Mubarak, N.M.; Kansedo, J.; Khalid, M.; Ibrahim, M.L.; Ghasemi, M. A Review on Biochar Production from Different Biomass Wastes by Recent Carbonization Technologies and its Sustainable Applications. J. Environ. Chem. Eng. 2022, 10, 107017. [Google Scholar] [CrossRef]
  17. Mishra, R.K.; Mohanty, K. A review of the next-generation biochar production from waste biomass for material applications. Sci. Total Environ. 2023, 904, 167171. [Google Scholar] [CrossRef]
  18. Uddin, M.N.; Techato, K.; Taweekun, J.; Rahman, M.M.; Rasul, M.G.; Mahlia, T.M.I.; Ashrafur, S.M. An Overview of Recent Developments in Biomass Pyrolysis Technologies. Energies 2018, 11, 3115. [Google Scholar] [CrossRef]
  19. Ogunsuyi, H.; Olawale, C. Evaluation of Plantain Biomass (Musa paradisiaca L.), as Feedstock for Bio-Ethanol Production. Green Sustain. Chem. 2021, 11, 59–71. [Google Scholar] [CrossRef]
  20. Mustofa, A. Bioethanol Production From Banana Stem By Using Simultaneous Saccharification and Fermentation (SSF). IOP Conf. Ser. Mater. Sci. Eng. 2018, 358, 012004. [Google Scholar] [CrossRef]
  21. Castañeda-Niño, J.P.; Mina Hernandez, J.H.; Solanilla Duque, J.F. Potential of Plantain Pseudostems (Musa AAB Simmonds) for Developing Biobased Composite Materials. Polymers 2024, 16, 1357. [Google Scholar] [CrossRef]
  22. Evelyn, E.; Okewale, A.O.; Owabor, C.N. Optimization, Kinetics and thermodynamic modeling of pulp production from plantain stem using the kraft process. Clean. Chem. Eng. 2025, 11, 100129. [Google Scholar] [CrossRef]
  23. Kouteu Nanssou, P.A.; Jiokap Nono, Y.; Kapseu, C. Pretreatment of cassava stems and peelings by thermohydrolysis to enhance hydrolysis yield of cellulose in bioethanol production process. Renew. Energy 2016, 97, 252–265. [Google Scholar] [CrossRef]
  24. Hartulistiyoso, E.; Farobie, O.; Zaky, M. Delignification of Cassava Peel as Bioethanol Raw Material using Combined Alkali and Microwave Heating Methods. IOP Conf. Ser. Earth Environ. Sci. 2022, 1038, 012021. [Google Scholar] [CrossRef]
  25. Abdullah; Azzahra Eka, N. Kinetics Study of Bioethanol Production from Cassava Peels Waste using Saccharomyces diastaticus. Int. J. Chem. Biochem. Sci. (IJCBS) 2024, 25, 884–892. [Google Scholar] [CrossRef]
  26. Marvie, I.; Sitanggang, A.B.; Budijanto, S. Characterization of Insoluble Fiber in Cassava Peel and Its Hydrolyzate Potential as a Prebiotic for Lactobacillus Plantarum. In Proceedings of the 6th Food Ingredient Asia Conference—6th FiAC, Bogor, Indonesia, 14–16 October 2020; pp. 31–37. [Google Scholar] [CrossRef]
  27. Abdullah, N.; Taib, R.M.; Mohamad Aziz, N.S.; Omar, M.R.; Disa, N. Banana pseudo-stem biochar derived from slow and fast pyrolysis process. Heliyon 2023, 9, e12940. [Google Scholar] [CrossRef]
  28. Odeyemi, S.O.; Iwuozor, K.O.; Emenike, E.C.; Odeyemi, O.T.; Adeniyi, A.G. Valorization of waste cassava peel into biochar: An alternative to electrically-powered process. Total Environ. Res. Themes 2023, 6, 100029. [Google Scholar] [CrossRef]
  29. Hamissou, I.G.M.; Appiaha, K.E.K.; Sylviec, K.A.T.; Ousmaila, S.M.; Casimir, B.Y.; Benjamina, Y.k. Valorization of cassava peelings into biochar: Physical and chemical characterizations of biochar prepared for agricultural purposes. Sci. Afr. 2023, 20, e01737. [Google Scholar] [CrossRef]
  30. Mukherjee, A.; Patra, B.R.; Podder, J.; Dalai, A.K. Synthesis of Biochar from Lignocellulosic Biomass for Diverse Industrial Applications and Energy Harvesting: Effects of Pyrolysis Conditions on the Physicochemical Properties of Biochar. Front. Mater. 2022, 9, 870184. [Google Scholar] [CrossRef]
  31. Collard, F.X.; Blin, J.A. Review on pyrolysis of biomass constituents: Mechanism and composition of the products obtained from the conversion of cellulose, hemicellulose and lignin. Renew. Sustain. Energy Rev. 2014, 38, 594–608. [Google Scholar] [CrossRef]
  32. Yang, H.; Yan, R.; Chen, H.; Lee, D.H.; Zheng, C. Characteristics of hemicellulose, cellulose and lignin pyrolysis. Fuel 2007, 86, 1781–1788. [Google Scholar] [CrossRef]
  33. Lv, D.; Xu, M.; Liu, X.; Zhan, Z.; Li, Z.; Yao, H. Effect of cellulose, lignin, alkali and alkaline earth metallic species on biomass pyrolysis and gasification. Fuel Process. Technol. 2010, 91, 903–909. [Google Scholar] [CrossRef]
  34. Zhang, C.-B.; Chen, L.-H.; Jiang, J. Why fine tree roots are stronger than thicker roots: The role of cellulose and lignin in relation to slope stability. Geomorphology 2014, 206, 196–202. [Google Scholar] [CrossRef]
  35. Li, Y.; Xing, B.; Ding, Y.; Han, X.; Wang, S. A critical review of the production and advanced utilization of biochar via selective pyrolysis of lignocellulosic biomass. Bioresour. Technol. 2020, 1312, 123614. [Google Scholar] [CrossRef]
  36. Li, W.; Wang, D.; Zhu, Y.; Chen, J.; Lu, Y.; Li, S.; Zheng, Y.; Zheng, Z. Efficient ex-situ catalytic upgrading of biomass pyrolysis vapors to produce methylfurans and phenol over bio-based activated carbon. Biomass Bioenergy 2020, 142, 105794. [Google Scholar] [CrossRef]
  37. Setyawan, H.Y.; Safira, L.; Mulyarto, A.R.; Wijana, S.; Pranowo, D. The effect of pyrolysis temperature and ball-milling duration on characteristics of micro bio-char derived from oil palm empty fruit bunches. Sustain. Environ. 2023, 9, 2173041. [Google Scholar] [CrossRef]
  38. Yang, C.; Liu, J.; Lu, S. Pyrolysis temperature affects pore characteristics of rice straw and canola stalk biochars and biochar-amended soils. Geoderma 2021, 397, 115097. [Google Scholar] [CrossRef]
  39. Figueiredo, C.; Lopes, H.; Coser, T.; Vale, A.; Busato, J.; Aguiar, N.; Novotny, E.; Canellas, L. Influence of pyrolysis temperature on chemical and physical properties of biochar from sewage sludge. Arch. Agron. Soil Sci. 2018, 64, 881–889. [Google Scholar] [CrossRef]
  40. Weber, K.; Quicker, P. Properties of Biochar. Fuel 2018, 217, 240–261. [Google Scholar] [CrossRef]
  41. Samer, M. Pyrolysis; InTech: Vienna, Austria, 2017. [Google Scholar] [CrossRef]
  42. Xue, Y.; Wang, C.; Hu, Z.; Zhou, Y.; Xiao, Y.; Wang, T. Pyrolysis of sewage sludge by electromagnetic induction: Biochar properties and application in adsorption removal of Pb(II), Cd(II) from aqueous solution. Waste Manag. 2019, 89, 48–56. [Google Scholar] [CrossRef]
  43. Sahoo, S.S.; Vijay, V.K.; Chandra, R.; Kumar, H. Production and characterization of biochar produced from slow pyrolysis of pigeon pea stalk and bamboo. Clean. Eng. Technol. 2021, 3, 100101. [Google Scholar] [CrossRef]
  44. Behazin, E.; Ogunsona, E.; Rodriguez-Uribe, A.; Mohanty, A.K.; Misra, M.; Anyia, A.O. Mechanical, Chemical, and Physical Properties of Wood and Perennial Grass Biochars for Possible Composite Application. BioRes 2015, 11, 1334–1348. [Google Scholar] [CrossRef]
  45. Freitas, A.M.; Nair, V.D.; Harris, W.G. Biochar as Influenced by Feedstock Variability: Implications and Opportunities for Phosphorus Management. Front. Sustain. Food Syst. 2020, 4, 510982. [Google Scholar] [CrossRef]
  46. Qin, L.; Wu, Y.; Hou, Z.; Jiang, E. Influence of biomass components, temperature and pressure on the pyrolysis behavior and biochar properties of pine nut shells. Bioresour. Technol. 2020, 313, 123682. [Google Scholar] [CrossRef]
  47. Haghighi Mood, S.; Pelaez-Samaniego, M.R.; Garcia-Perez, M. Perspectives of Engineered Biochar for Environmental Applications: A Review. Energy Fuels 2022, 36, 7940–7986. [Google Scholar] [CrossRef]
  48. Rizwan, M.; Murtaza, G.; Zulfiqar, F.; Moosa, A.; Iqbal, R.; Ahmed, Z.; Irshad, S.; Khan, I.; Li, T.; Chen, J.; et al. Sustainable manufacture and application of biochar to improve soil properties and remediate soil contaminated with organic impurities: A systematic review. Front. Environ. Sci. 2023, 11, 1277240. [Google Scholar] [CrossRef]
  49. Zhu, H.; An, Q.; Mohd Nasir, A.S.; Babin, A.; Saucedo, S.L.; Vallenas, A.; Li, L.; Baldwin, S.A.; Lau, A.; Bi, X. Emerging applications of biochar: A review on techno-environmental-economic aspects. Bioresour. Technol. 2023, 388, 129745. [Google Scholar] [CrossRef]
  50. Sepúlveda-Cadavid, C.; Romero, J.H.; Torres, M.; Becerra-Agudelo, E.; López, J.E. Evaluation of a Biochar-Based Slow-Release P Fertilizer to Improve Spinacia oleracea P Use, Yield, and Nutritional Quality. J. Soil. Sci. Plant Nutr. 2021, 21, 2980–2992. [Google Scholar] [CrossRef]
  51. Cen, Z.; Wei, L.; Muthukumarappan, K.; Sobhan, A.; McDaniel, R. Assessment of a Biochar-Based Controlled Release Nitrogen Fertilizer Coated with Polylactic Acid. J. Soil. Sci. Plant Nutr. 2021, 21, 2007–2019. [Google Scholar] [CrossRef]
  52. Ye, Z.; Zhang, L.; Huang, Q.; Tan, Z. Development of a carbon-based slow release fertilizer treated by biooil coating and study on its feedback effect on farmland application. J. Clean. Prod. 2019, 239, 118085. [Google Scholar] [CrossRef]
  53. Amoakwah, E.; Shim, J.; Kim, S.; Lee, Y.; Kwon, S.; Sangho, J.; Park, S. Impact of silicate and lime application on soil fertility and temporal changes in soil properties and carbon stocks in a temperate ecosystem. Geoderma 2023, 433, 116431. [Google Scholar] [CrossRef]
  54. Wang, X.; Liu, Y.; Zhu, L.; Li, Y.; Wang, K.; Qiu, K.; Tippayawong, N.; Aggarangsi, P.; Reubroycharoen, P.; Wang, S. Biomass derived N-doped biochar as efficient catalyst supports for CO2 methanation. J. CO2 Util. 2019, 34, 733–741. [Google Scholar] [CrossRef]
  55. Gasim, M.F.; Choong, Z.-Y.; Koo, P.-L.; Low, S.-C.; Abdurahman, M.-H.; Ho, Y.-C.; Mohamad, M.; Suryawan, I.W.K.; Lim, J.-W.; Oh, W.-D. Application of Biochar as Functional Material for Remediation of Organic Pollutants in Water: An Overview. Catalysts 2022, 12, 210. [Google Scholar] [CrossRef]
  56. Uchimiya, M.; Chang, S.; Klasson, K.T. Screening biochars for heavy metal retention in soil: Role of oxygen functional groups. J. Hazard Mater. 2011, 190, 432–441. [Google Scholar] [CrossRef] [PubMed]
  57. Ahmad, M.; Rajapaksha, A.U.; Lim, J.E.; Zhang, M.; Bolan, N.; Mohan, D.; Ok, Y.S. Biochar as absorbent for contaminant management in soil and water: A review. Chemosphere 2014, 99, 19–33. [Google Scholar] [CrossRef] [PubMed]
  58. Tan, Z.; Wang, Y.; Zhang, L.; Huang, Q. Study of the mechanism of remediation of Cd-contaminated soil by novel biochars. Environ. Sci. Pollut. Res. 2017, 24, 24844–24855. [Google Scholar] [CrossRef] [PubMed]
Processes 13 02059 g001
Figure 1. TGA and derived TGA curves of (a) PR and (b) CP biomasses.
Figure 1. TGA and derived TGA curves of (a) PR and (b) CP biomasses.
Processes 13 02059 g001
Processes 13 02059 g002
Figure 2. Top-view SEM images of (a) PR biomass; (b) PR biochar pyrolyzed at 300 °C; (c) PR biochar pyrolyzed at 400 °C; (d) PR biochar pyrolyzed at 500 °C.
Figure 2. Top-view SEM images of (a) PR biomass; (b) PR biochar pyrolyzed at 300 °C; (c) PR biochar pyrolyzed at 400 °C; (d) PR biochar pyrolyzed at 500 °C.
Processes 13 02059 g002
Processes 13 02059 g003
Figure 3. Top-view SEM images of (a) CP biomass; (b) CP biochar pyrolyzed at 300 °C; (c) CP biochar pyrolyzed at 400 °C; (d) CP biochar pyrolyzed at 500 °C.
Figure 3. Top-view SEM images of (a) CP biomass; (b) CP biochar pyrolyzed at 300 °C; (c) CP biochar pyrolyzed at 400 °C; (d) CP biochar pyrolyzed at 500 °C.
Processes 13 02059 g003
Processes 13 02059 g004
Figure 4. EDX spectra of PR biochar samples pyrolyzed at (a) 300 °C, (b) 400 °C, and (c) 500 °C.
Figure 4. EDX spectra of PR biochar samples pyrolyzed at (a) 300 °C, (b) 400 °C, and (c) 500 °C.
Processes 13 02059 g004
Processes 13 02059 g005
Figure 5. EDX spectra of CP biochar samples pyrolyzed at (a) 300 °C, (b) 400 °C, and (c) 500 °C.
Figure 5. EDX spectra of CP biochar samples pyrolyzed at (a) 300 °C, (b) 400 °C, and (c) 500 °C.
Processes 13 02059 g005
Processes 13 02059 g006
Figure 6. DRX patterns of (a) PR biochar samples and (b) CP biochar samples pyrolyzed at 300 °C, 400 °C, and 500 °C.
Figure 6. DRX patterns of (a) PR biochar samples and (b) CP biochar samples pyrolyzed at 300 °C, 400 °C, and 500 °C.
Processes 13 02059 g006
Processes 13 02059 g007
Figure 7. FTIR spectra of (a) RP biochar samples and (b) CP biochar samples pyrolyzed at 300 °C, 400 °C, and 500 °C.
Figure 7. FTIR spectra of (a) RP biochar samples and (b) CP biochar samples pyrolyzed at 300 °C, 400 °C, and 500 °C.
Processes 13 02059 g007
Table 1. Income level of countries and territories in the Caribbean.
Table 1. Income level of countries and territories in the Caribbean.
Income LevelCountry or Territory
LowHaiti
Lower–middleEl Salvador, Guatemala, Guyana, Honduras, Nicaragua
Upper–middleBelize, Colombia, Costa Rica, Cuba, Dominica, Dominican Republic, Ecuador, Grenada, Jamaica, Mexico, Panama, Peru, Saint Lucia, Saint Vincent and the Grenadines, Suriname, Venezuela.
HighAntigua and Barbuda, Bahamas, Barbados, Saint Kitts and Nevis, Trinidad and Tobago
Table 2. Mass loss values of PR and CP biomasses for each degradation stage.
Table 2. Mass loss values of PR and CP biomasses for each degradation stage.
Biomass Mass Loss Solid Product
First StageSecond StageThird Stage
Plantain rachis3.16 (%)59.12 (%)19.90 (%)17.82 (%)
Cassava peel6.02 (%)72.93 (%)16.11 (%)4.94 (%)
Table 3. Content of hemicellulose, cellulose, and lignin of plantain rachis.
Table 3. Content of hemicellulose, cellulose, and lignin of plantain rachis.
ApplicationHemicellulose (%)Cellulose (%)Lignin (%)Reference
Bioethanol28.029.041.3[17]
Bioethanol19.444.636.0[18]
Paper pulp3.4658.0338.51[20]
Table 4. Content of hemicellulose, cellulose, and lignin of cassava peel.
Table 4. Content of hemicellulose, cellulose, and lignin of cassava peel.
ApplicationHemicellulose (%)Cellulose (%)Lignin (%)Reference
Bioethanol30.557.71.3[21]
Bioethanol15.6659.0112.79[22]
Bioethanol15.644.036[23]
Prebiotic4.4955.797.32[24]
Table 5. The yield data for the PR and CP biochar samples.
Table 5. The yield data for the PR and CP biochar samples.
ParametersPR-300 PR-400PR-500CP-300CP-400CP-500
Yield (%)65.745.633.762.037.525.4
MC (%)8.97.15.110.310.39.2
Table 6. Crystalline compounds present in PR and CP biochar samples pyrolyzed at 300 °C, 400 °C, and 500 °C.
Table 6. Crystalline compounds present in PR and CP biochar samples pyrolyzed at 300 °C, 400 °C, and 500 °C.
Compound PR BiocharCP Biochar
300 °C400 °C500 °C300 °C400 °C500 °C
MgO3Si✓ ✓
CCaO3 ✓ ✓✓
CKO3 ✓✓ ✓✓
O7P2Si ✓✓
CCl2O ✓
K2O4S ✓
C2K2O4✓
ClK✓✓
CaO3Si ✓✓ ✓
Table 7. Variability in functional groups on the PR biochar and CP biochar surfaces regarding the pyrolysis temperature.
Table 7. Variability in functional groups on the PR biochar and CP biochar surfaces regarding the pyrolysis temperature.
Compound PR BiocharCP Biochar
300 °C400 °C500 °C300 °C400 °C500 °C
3200–3400 O–H stretching of H-bonded hydroxyl groups✓✓ ↓–✓✓↓–
3000–3200 C-H bond of aliphatic functional groups–––✓✓ ↑✓↑
1700–1740 C=C and C=O stretching of carbonyl
and carboxyl groups		✓––✓✓↓–
1550–1650 C=C stretching of aromatic components, C=O stretching of conjugated ketones and quinones✓✓ ✓✓✓ ↓✓↓
1470–1490 C=C asymmetric stretching of lignin and C-H2 stretching of lignin carbohydrate–✓ ↓✓↓✓✓ ↓✓↓
1380 stretching in the benzene rings zone✓✓ ↑✓↑–✓ ✓
1050–1250 C–O–C stretching of cellulose
and hemicellulose		–✓ ↑✓↑–✓ ✓
600–832 C–H stretching of aromatic and heteroatomic compounds–✓ ↑✓↑––✓↑
The up arrow (↑) indicates that the intensity of the FTIR peak tends to be enhanced with increasing pyrolysis temperature, while the down arrow (↓) means the opposite.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Herazo, A.P.; Zambrano, A.; Marín, L.; Mass, J.; Montenegro, D.N. Production of Biochar from Plantain Rachis and Cassava Peel Towards Sustainable Management of Caribbean Agricultural Waste. Processes 2025, 13, 2059. https://doi.org/10.3390/pr13072059

AMA Style

Herazo AP, Zambrano A, Marín L, Mass J, Montenegro DN. Production of Biochar from Plantain Rachis and Cassava Peel Towards Sustainable Management of Caribbean Agricultural Waste. Processes. 2025; 13(7):2059. https://doi.org/10.3390/pr13072059

Chicago/Turabian Style

Herazo, Adriana Patricia, Alejandra Zambrano, Lorena Marín, Julio Mass, and Diana Nathalie Montenegro. 2025. "Production of Biochar from Plantain Rachis and Cassava Peel Towards Sustainable Management of Caribbean Agricultural Waste" Processes 13, no. 7: 2059. https://doi.org/10.3390/pr13072059

APA Style

Herazo, A. P., Zambrano, A., Marín, L., Mass, J., & Montenegro, D. N. (2025). Production of Biochar from Plantain Rachis and Cassava Peel Towards Sustainable Management of Caribbean Agricultural Waste. Processes, 13(7), 2059. https://doi.org/10.3390/pr13072059

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop