Valorization of Agave durangensis bagasse for cardboard-type paper production circular economy approach

2.1 Sampling and pretreatment

The A. durangensis residues (agave bagasse) were donated by La Planta Tradiciones Mezcaleras S.P.R de R. L″ located in the municipality of Nombre de Dios, Durango (Coordinates: 23°51′N 104°15′W). The A. durangensis species is found in this municipality with an area of 15 ha. The area has a slope of 5 %, the climate of the area is semi-arid (BS) with rainfall in summer. The average rainfall is 520 mm, and the average annual temperature is 29 °C. The predominant soil type is Regosol. The agave bagasse for this research was separated into solid and liquid because it was received in the wet phase, after which it was cleaned to remove impurities from the solid phase, leaving only agave fibers (raw material or precursor). The raw material was dried using two drying techniques: Oven and Solar (H-T). The solar method consisted of placing the sample to dry for a week until reaching a constant weight; it should be noted that the drying time may vary residues were subjected for 8 h in the RIOSSA Laboratory Drying Oven MOD. H-62D. The dry residues were processed in an industrial mill to reduce the size of elongated and intertwined particles. These “fibers” are organic in nature. The ground material was sieved using sieves No. 20, 40, 60 and 80. The dry raw material was fractionated to facilitate sieving; No. 40 and 60 sieves were used to ensure optimal fiber size for the pulping process and physicochemical characterization [17], 34].

Nevertheless, there are modern technologies that improve the drying process of various types of agro-industrial waste. These technologies include solar drying, radiation drying, freeze drying, microwave drying, radiofrequency drying, osmotic drying, dielectric drying, spray drying, microencapsulation, and nanotechnology [35], 36]. However, since drying is an energy-intensive process, advanced drying technologies face significant criticism from a sustainability perspective. Studies indicate that approximately 40 % of the world’s energy is used to dry food and agricultural products, which contributes to 40 % of global greenhouse gas emissions [37], 38]. In this context, solar and oven drying technologies that use renewable energy sources are emerging as crucial solutions [39], 40]. These technologies have several advantages. They can be manufactured with locally available materials and primarily optimize solar radiation, which is free and environmentally friendly. These advantages position solar dryers as valuable tools for achieving multiple Sustainable Development Goals (SDGs), particularly those focused on poverty reduction, food security, sustainable agriculture, and environmental conservation. Specifically, the selection of solar and kiln drying systems to treat A. durangensis waste incorporates low-cost, affordable processes and lower environmental impact – essential elements for developing sustainable, economically viable technologies for the agroindustrial sector [41], 42].

These factors respond to a traditional approach aimed at minimizing energy costs effectively. This approach contrasts with more advanced drying methods, such as microwaves or ultrasound, which require specialized, expensive equipment. Kiln drying is more efficient in terms of temperature control, allowing for rapid and uniform evaporation of moisture. This improves liquor penetration in the modified Kraft process. This method can be adequately controlled to prevent thermal damage to the fibers [43].

On the other hand, solar drying is classified as a gentler method, which maintains the integrity of the lignocellulosic fibers and, therefore, improves pulp quality and chemical utilization by achieving a more open and porous fibrous and lignocellulosic structure. These two operating directions provide a compromise between efficient process operation and pulp quality considerations and can result in more efficient and environmentally sustainable pulp. Kiln drying provides constant thermal control that facilitates rapid and uniform moisture reduction, improving liquor penetration in the modified Kraft process, although it must be carefully managed to avoid thermal degradation of the fibers. Meanwhile, solar-shaded drying is a less aggressive method that preserves the structural integrity of the lignocellulosic fibers, promoting higher pulp quality and chemical efficiency due to a more open and receptive fiber structure [44].

2.2 Physicochemical characterization of bagasse

2.3 Pulping process

2.3.1 Kraft pulping method for delignification

Classical delignification methods use reagents such as sodium hydroxide, chlorite, and sodium hypochlorite to remove as much lignin as possible, leaving cellulose and hemicellulose behind. One traditional lignin removal process is the alkaline Kraft method, which gets its name from the use of an alkali and sodium sulfide (Na₂S) to increase the delignification rate [20]. The heterogeneous delignification process causes the lignin in the lignocellulosic solid matter to react with the liquid alkali and break down, incorporating it into the liquid phase. This results in the isolation of cellulose in the solid phase. For this study, the modified Kraft method was implemented (Figure 1). In the traditional Kraft process, wood is cooked (digested) using sodium hydroxide (NaOH) and sodium sulfide (Na₂S) in an extremely alkaline, highly reducing environment to dissolve lignin. However, our modified Kraft method uses different and lower effective alkali concentrations and includes Na₂CO₃ and Na₂SO₄. These modifications help better control the pH and selectivity of lignin delignification. Consequently, polysaccharide retention improves, and cellulose degradation and chemical consumption during cooking decrease [46]. The conventional Kraft process is typically carried out at elevated temperatures (between 150 and 180 °C) under pressure to accelerate chemical reactions and complete cooking in 1–2 h. In contrast, our modified Kraft method operates at a lower temperature of 343 K (70 °C) without pressure and with an extended cooking time of 24 h. This gentle, extended cooking helps preserve the integrity of the cellulose fibers better [47]. The aqueous extracts were determined using Soxhlet extraction with water and ethanol for 24 h, in triplicate. Lignin determination was adapted from Han and Rowell [48]. The lignin content was determined by delignification with 72 % sulfuric acid (H₂SO₄) for 1 h. The sample was treated in an autoclave and filtered in triplicate.

Figure 1:

Modified Kraft method.

2.4 Paperboard Thickness

Agave bagasse can be processed into cardboard-type paper. Its thickness typically ranges from 0.0137795 to 0.0277559 inches, depending on the industrial process. Corrugated cardboard can potentially reach 5 mm (0.1968504 inches). This material, derived from the fibrous residue of agave plants after sugar extraction, offers a sustainable alternative to wood-based paper products [49]. Paper thickness is measured using a micrometer as the perpendicular distance between two parallel, flat, circular surfaces. Sheets of ecological paper were manufactured using each drying technique in triplicate with the cellulose pulp obtained, and thickness was determined. Thickness is a crucial parameter in the paper industry because it affects the material’s physical, optical, and electrical properties. Uniform paper thickness positively impacts paper used for printing applications. Thickness is an essential characteristic that affects the performance of specialty papers, such as those used for capacitors, blotting, and wrapping. Precise control of paper caliper is vital to ensuring the paper’s suitability for its intended purpose. Variations in thickness can significantly impact the paper’s performance, making caliper measurement a critical quality control metric in the manufacturing process. Maintaining consistent, appropriate paper thickness is fundamental to optimizing the performance and end-use characteristics of the final product, whether for printing, packaging, or specialized applications requiring specific thickness parameters [50].

2.5 Statistical analysis

The collected data were analysed for statistical significance using R version 4.2.2 software. All experiments were repeated at least three times, and the average ± standard deviation represents the statistical significance of each dataset. The experimental data were treated with one-way analysis of variance (ANOVA) at 95 % confidence level and with the differences at p < 0.05 considered statistically significant [51].

3.1 Physicochemical properties of bagasse

The chemical composition of bagasse was 44 % cellulose, 20 % hemicellulose, 25 % lignin, and 11 % ash. In general, this composition corresponds well with reported values for cellulose content (44.5 %). Using the same bagasse, other authors have reported cellulose values between 40 and 65 % [52], 53].

3.1.2 Analysis TGA

Figure 2 shows the thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses, which reveal the mass loss and heat flow of the sample with a heating ramp of 10 °C/min. The thermogravimetric analysis shows three notable mass losses. The first loss is minimal and due to the loss of volatile components of the sample at 60 °C. The second loss is pronounced in the temperature range of approximately 220 °C–360 °C and is attributed to the degradation of the hemicellulose and cellulose contained within the sample. Finally, the degradation of lignin occurs in the range of 360 °C–700 °C until total mass loss was obtained. In fact, the presence of different alcohols impregnated in the bagasse increases the heat of combustion. These preliminary results show that the byproducts generated by alcoholic beverage production can be used as an alternative fuel source. Consequently, the desorption process depends on the strength of the interaction between water molecules and the materials’ hydroxyl groups through hydrogen bonds [56].

Figure 2:

Thermogravimetric analysis (TG)‐differential scanning calorimetry (DSC) analysis curve of bagasse.

3.2 Characterization of bagasse exposed to different drying treatments

3.3 Proposed Kraft pulping method for delignification

The chemical composition of the isolated cardboard-type paper (cellulose) was determined according to Vieira et al. [57], compared to bagasse. Figure 5 shows the results of Kraft pulping in comparison to other raw materials. A closed, controlled pulping system at 70 °C was used for 24 h (triplicate experiments) for each type of drying (H-T). Cellulose yields ranging from 48 % to 54 % were obtained (see Table 5).

Figure 3:

Cellulose pulp. a) Solar drying, b) oven drying.

Figure 4:

Cellulose pulp by the Kraft method. a) Solar drying, b) oven drying.

Additionally, our improved Kraft method includes pretreatment, which involves drying the raw material. This can be done by kiln drying or sun-drying in the shade. Pre-drying reduces the moisture level of the A. durangensis residue, which significantly improves the penetration and action of chemical reagents during cooking. Kiln drying provides stable thermal control, which helps decrease the moisture content quickly and uniformly. Conversely, solar shade drying is a gentle process that preserves the fiber structure, resulting in high-quality fibers and optimal chemical usage. Additionally, our method may include adding chemicals or pretreatments to improve pulp yield. For example, we can add chemicals that reduce pulping time and increase delignification, pulp yield, and quality. Pretreatments with green or black liquor can enhance chemical penetration and improve process efficiency [58]. The modifications implemented in our modified Kraft process are motivated by several objectives: increased pulp yield and polysaccharide retention; lower chemical and energy consumption; reduced cellulose losses; and improved mechanical properties of the final product. These modifications also help minimize environmental impact and reduce toxic effluents, including chlorinated compounds [59]. The need for such modifications arises from the desire to produce pulp more efficiently and with higher quality standards, allowing for better control of delignification and less damage to the cellulose (see, Figures 3 and 4).

The values in Table 5 reflect the direct measurement of the volume of black liquor obtained in each experimental replicate. This approach enabled consistent quantification of the lignocellulosic byproduct generated under different drying conditions (solar and oven), showing that drying method influences black liquor volume. At this stage, however, volumetric measurement of black liquor provides relevant information on three factors: (1) the efficiency of the Kraft process, (2) reproducibility between replicates, and (3) variations associated with drying treatments.

The drying method applied to bagasse significantly influences the cellulose yield and the amount of lignin byproduct generated due to the structural and chemical changes that the biomass undergoes during the process. Drying affects the distribution and accessibility of lignin and hemicellulose. This, in turn, modulates the efficiency of the delignification process and the purity of the obtained cellulose. During drying, especially at high temperatures, such as in a kiln, the lignocellulosic matrix can become more compact and reorganized, which hinders the penetration of chemical reagents during pulping and affects lignin solubilization. Conversely, solar drying generally occurs at lower temperatures and with greater exposure to air. This favors a more porous and less compact structure, which facilitates lignin extraction and improves cellulose yield. These effects are reflected in quantifiable differences in the amount of lignin recovered and the percentage of cellulose isolated. For example, the work of Cardona-López et al. [60] reported that treatments that promote cellulose exposure and lignin solubilization increase cellulose yield in sugarcane bagasse. Likewise, Mascaña-LPI et al. [61] found that the drying method and conditions influence the crystallinity and purity of the obtained cellulose, which directly affects its yield. Specifically, solar drying achieved a cellulose percentage of 48.5 %, while oven drying (using a RIOSSA Laboratory Drying Oven MOD. H-62D at 105 °C) achieved a higher value of 54.3 %. The greater efficiency of oven drying in removing residual moisture and limiting enzymatic or microbial degradation of the fiber explains this difference. This process favors the preservation and concentration of the cellulose fraction. The higher variability observed in oven drying (±10.5 %) compared to solar drying (±15.9 %) suggests that thermal gradients and potential molecular rearrangement effects during thermal drying generate heterogeneities in the lignocellulosic matrix. These heterogeneities affect the uniformity of the final product. This finding is consistent with other studies indicating that fiber structure and accessibility are key determinants of pulping efficiency and pulp quality [62]. This difference can be attributed to three factors: (1) the optimization of time and temperature parameters during Kraft pulping in our study; (2) the specific characteristics of the A. durangensis species; and (3) the enhancing effect of thermal pretreatments, such as drying, which modify the lignocellulosic structure and facilitate the penetration of chemical reagents. It is important to note that the cellulose content of agave bagasse depends on the drying method used, as well as on other factors such as species, stage of maturity of the plant, chemical digestion method, and operating conditions [63]. For example, previous studies have reported cellulose values of 43.0 % in Agave tequilana Weber and 47.3 % in Agave salmiana [64], as well as 48.04 % in Agave angustifolia [65]. These differences reflect genetic variability among species, as well as differences in cellulose extraction and purification procedures. From an industrial perspective, these findings have practical implications. Solar drying might be preferable when consistency and reproducibility between batches are prioritized, whereas oven drying is suitable for maximizing average yield provided the variability is managed. The choice of drying method should also be evaluated based on energy costs, environmental impact, and process scalability [66]. Figure 5 shows a comparison of the chemical compositions of the cellulose pulps obtained by the Kraft method. As illustrated, the cellulose content of the bagasse pulp increased from 48 % to 54 % when transitioning from oven drying to solar drying. Meanwhile, the lignin content increased from 5.2 % to approximately 1.2 %, while the hemicellulose content remained constant, though there was a significant change in extractive content.

Figure 5:

The chemical composition of the pulps from the cellulosic treatment and the literature on pine wood [67].

3.4 Wise bleaching method

The average pulp bleaching yield was obtained using the two drying techniques. Values ranged from 46 % to 51 % when using the Wise bleaching method (Table 6), which required 0.3 g of sodium chlorite and 0.2 ml of acetic acid for each gram of cellulose obtained from Kraft pulp. This process was repeated for four rounds. After washing with distilled water and acetone, the pulps were dried at 70 °C until they reached a constant weight. This yielded a lower value than that recorded during the Kraft pulping process due to the elimination of residual lignin, which is characteristic of the process.

The variability in pulp bleaching yields (46–51 %; see Table 6) when using the Wise method with solar versus oven drying can be attributed to differences in residual lignin content and fiber accessibility resulting from the drying treatments applied. The Wise method uses sodium chlorite and acetic acid to remove residual lignin from Kraft pulp. This explains why the yields are lower than those of the initial pulping process, since lignin is removed during bleaching. Drying methods influence the physical and chemical structure of bagasse fibers. Oven drying involves higher temperatures, which can result in fiber compaction and reduced porosity. This limits the penetration of bleaching agents and results in variable efficiency in lignin removal. In contrast, solar drying generally preserves a more porous structure, which improves chemical accessibility and potentially increases bleaching yield. Sun et al. [68] demonstrated that, in biomass pretreatment, lignin structure and fiber accessibility are critical factors affecting bleaching efficiency. Similarly, Li et al. [69] found that the presence of residual lignin and the morphology of the fibers after thermal treatment affect the effectiveness of the bleaching process.

3.5 Sheet forming

Four duplicate prototypes of four sheets of cardboard-type paper were made. The circular sheets are about 1.0 mm thick and light brown/yellow in color. Two sheets were made for each drying technique (Figure 6). Due to its fibrous structure and small imperfections caused by the manufacturing process, the thickness of the paper is usually inconsistent. The sheets are circular and approximately 1.0 mm thick. Two sheets of cardboard-like paper were produced for each drying technique, as shown in Figure 6. Paper thickness is usually inconsistent due to its fibrous structure and small imperfections inherent in the manufacturing process. The grammage, caliper, and bulk density for the oven treatment were quantified as 160.9 g/m², 0.87 mm, and 0.40 g/cm³, respectively. The grammage, caliper, and bulk density for the solar treatment (temperature of 23 °C and relative humidity of 30 % for 5 h) were quantified as 122.6 g/m², 0.70 mm, and 0.31 g/cm³, respectively.

Figure 6:

Experiments 1 and 2 of prototype cardboard-type paper sheets.

In the industry, commercial cardboard typically weighs between 120 and 400 g per square meter and varies in thickness depending on the type of board. For instance, paperboard is around 0.3 mm thick, whereas corrugated board exceeds 2.0 mm. Therefore, the paperboard in this study is similar in weight to the lightest paperboard, yet considerably thinner than the heaviest. For comparison, consider commercial paperboard weighing 144.73 g/m² and with a thickness of 0.2 mm. The significant difference in density suggests that eco-friendly paper is less compact and more porous than commercial paperboard, which directly influences its mechanical properties and load-bearing capacity [70]. However, weight, gauge, and density are solid indicators of a paper’s mechanical strength. These physical properties are closely related to the structure and density of the material, both of which directly influence its behavior under tension. Lalpuria et al. [71] developed paperboard made from an interwoven network of cellulose fibers with a grammage greater than 250 g/m². This packaging material is widely used and manufactured from renewable sources. The boards are 0.2–1.0 mm thick, and the weight of the raw paper per surface area varies from 120 to 700 g/m². The paper industry uses two parameters to characterize paper and board: caliper (thickness) and density (weight per unit area) [72].

3.5.1 Scanning electron microscopy analysis (SEM)

Scanning electron microscopy (SEM) analysis provides a detailed view of the morphological structure of A. durangensis bagasse prior to delignification. Microphotographs were obtained at magnifications ranging from 1000 to 2500 using a JEOL IT-300 scanning electron microscope.

Microscope analysis revealed that both drying techniques resulted in compact bagasse fiber conformations. More specifically, microphotographs (Figure 7) show that fibers dried in an oven have an oval base, while fibers dried using the solar technique have a cylindrical shape. Despite the difference in fiber shape, there was no noticeable effect on fiber stiffness under either drying condition. This detailed analysis of A. durangensis bagasse fiber morphology is crucial for understanding its structure and potential applications in subsequent delignification and valorization processes.

Figure 7:

Microphotographs of bagasse of A. durangensis ground, sieved and dried with the techniques (oven (a), solar (b)) before the delignification process.

Figure 8 shows micrographs of bagasse that has undergone the Kraft process. These images reveal tubular fibers with visible delignification. Additionally, the morphology of the tubular cellulose fibers and their typical skeleton are more clearly visible, as is the separation of cellulose and lignin. Figure 8(a) and (b) also indicate that microfibril arrays twist after treatment. After the lignocellulosic matrix decomposes, cellulose microfibrils become more accessible for obtaining nanofibrils due to the removal of non-cellulosic components. This same observation was recently reported in research [53]. Specifically, the observed structure and chemical properties of cellulose are used to determine stiffness. Surface chains have fewer internal hydrogen bonds, which makes them more reactive and capable of binding more water through hydrogen bonds. Humidity modifies the structure and physical properties of the fibers. Drying controls this interaction in order to preserve the fibers’ chemical and mechanical integrity. Natural fibers are hygroscopic, meaning they absorb and release water. This causes swelling and shrinkage, affecting their physical and mechanical properties. Proper drying is essential to avoid structural damage, improve strength, and optimize the quality of the final product. Stiffness is inferred using models based on morphology observed by scanning electron microscopy (SEM). Tensile strength is measured directly because it is a more accessible and reproducible parameter [73].

Figure 8:

Microphotographs of prototype cardboard-type paper sheets using a processed Kraft method, oven (a), and solar (b).

3.5.2 Infrared spectroscopy analysis (FTIR)

The efficiency of the cardboard-type paper (cellulose) is expressed through the FT-IR spectra of the raw bagasse and the produced cardboard-type paper. Figures 9 and 10 show the FT-IR spectra of initial bagasse (10a) from the cellulose extraction processes using a kiln (HP) and solar (SP) drying, respectively. Figure 10(b) and 10(c) show the differences in drying pretreatments using the same cellulose (cardboard) extraction method. Overall, significant solubilization of lignin was observed by the absence of the peak at 1,512 cm⁻¹, associated with C–C stretching of aromatic molecular vibration in lignin [74], 75]. Additionally, the decrease in peak intensity at 1,246 cm⁻¹ is attributed to the C–O stretching characteristic of the p-hydroxyphenyl, guaiacyl, and syringyl rings in lignin [76].

Figure 9:

Infrared spectroscopy (IR) of bagasse sample of A. durangensis with oven-drying technique. Black line bagasse with pretreatment (drying) and blue line after treatment (cardboard paper).

Figure 10:

Infrared spectroscopy (IR) of bagasse sample of A. durangensis with solar-drying technique. Black line bagasse with pretreatment (drying) and blue line after treatment (cardboard paper).

The disappearance of the peak at 1,743 cm⁻¹ is attributed to acetyl and uronic ester groups in hemicellulose or ester bonds in carboxyl groups. The increase in the bands at 3,412 and 2,902 cm⁻¹, respectively, is due to the stretching of the O–H and C–H bonds, which are characteristic of cellulose and hemicellulose molecules in cardboard-type paper [74]. It is worth mentioning that the intensity of these peaks increases with the purity of the cellulose in the obtained materials, which is why there is a significant difference between the two proposed drying processes.

On the other hand, the graph shows the points where different biopolymers, such as cellulose, hemicellulose, and lignin, were present. Figures 10 and 11 show representative signals of the O–H bonds characteristic of hemicellulose and humidity at a frequency of 3,500–3,400 cm⁻¹. Between 1,730 and 1,739 cm⁻¹, there are C=O bonds indicative of carboxylic groups, which confirm the presence of hemicellulose and lignin. The methoxide groups, found between 1,515 and 1,604 cm⁻¹, are characteristic of the C=C and C=O bonds of aromatic lignin compounds. Finally, the peaks found between 1,000 and 1,400 cm⁻¹ are characteristic signals of cellulose, as reported by Raspolli [74]. The FTIR spectra of bagasse revealed the presence of numerous functional groups in its structure, primarily long-chain polymers such as cellulose, hemicellulose, and lignin. Biologically derived materials with high contents of protein, starch, or high-molecular-weight polymers, such as bagasse, generally have strongly bound water due to the numerous polar sites on their surfaces, as verified by the FTIR spectra of our samples.

Figure 11:

Peak area for infrared spectroscopy (IR).

Finally, we analyzed the FTIR area to determine quantification using equations (4) and (5), as shown in Figure 11. It is important to note that the intensity of the considered bands increases proportionally with the increase in area, depending on the pretreatments.

(4) A = lim n → ∞ ∑ k = 1 n I 1638 Δ W + I 1317 Δ W + I 1024 Δ W   ∀   n = 3

(5) A = lim n → ∞ ∑ k = 1 n I 1418 Δ W + I 1020 Δ W   ∀   n = 2

3.6 Agroindustrial waste and circular economy

According to the United Nations’ Sustainable Development Goals (SDGs), the demand for resources is expected to increase significantly in the coming decades. Addressing these challenges requires developing sustainable global strategies, which hinges on understanding the relationship between the SDGs and the circular economy. This study examined the connection between the SDGs and the circular economy by using mezcal industry residues to produce cellulose pulp and ecological paper. This practice exemplifies a principle of the circular economy: the revaluation of waste. In addition to environmental benefits, such as reduced pollution and waste accumulation, this practice creates economic opportunities by transforming waste into valuable resources for new applications, including scientific research. Implementing a circular economic model can contribute to sustainable and inclusive global economic growth. Mezcal production generates substantial waste that can cause environmental and health problems. However, a circular economy approach can repurpose these byproducts as raw materials in the paper manufacturing process. This research case study focuses on the innovative use of these waste materials (Figure 12). The current circular economy utilizes waste management and multiple material resources to take a holistic approach to technological innovations and production processes. Preliminary research on A. durangensis bagasse shows that this approach significantly reduces virgin raw material consumption, increases renewable resource use, decreases landfill space needs, and improves environmental quality, as reported in recent studies [77]. Plastinina et al. [77] used a life-cycle assessment (LCA) approach to evaluate the economic efficiency of production and activities related to paper production waste recycling at various stages. Despite the considerable economic potential of reusing secondary resources, such as waste paper, the research showed that the circular economy index indicated a medium level of development, leaving room for improvement. Calculations showed that using secondary raw materials, such as agroindustrial waste, in a paper mill reduces direct material costs by about 65 %. This reduction is due to the lower price of used paper compared to virgin raw materials (about 4.5 times lower), as well as a significant decrease in water and energy consumption (40 % and 55 %, respectively). With an average industry profitability of 30–45 %, the profitability of such production increases significantly. Specifically, these data demonstrate the feasibility of scaling up and integrating paperboard into production lines for the mezcal industry [78], 79].

Figure 12:

Circular economy model in the production of the mezcal process.

Thus, the proof of concept must be accounted for. This will allow the benefits of the proposal to be summarized. The text that follows will explain the benefits in more detail.

1. The proof of the experiment shows that the production of paper from bagasse can be more sustainable than traditional paper manufacturing under the proposed methodology.

2. A remarkable fact is that bagasse, derived from the short-cycle, renewable process of mezcal production, offers an easily accessible, eco-friendly alternative. Additionally, its lower lignin content reduces the need for extensive staining, minimizing chemical use and environmental impact.

3. In terms of practical implementation, papermakers can help mitigate habitat loss and preserve biodiversity by reducing pressure on forest ecosystems and conserving water when using bagasse. Bagasse-based paper production reduces solid waste generation and offers high reuse potential, meeting circular economy standards and reducing demand for virgin pulp. The industrial-scale application is inexpensive and feasible.

4. In the context of a circular economy, our research emphasizes the full utilization of bagasse, a lignocellulosic byproduct generated in large quantities by mezcal production. According to the attached manuscript, 15 kg of bagasse are produced for every liter of mezcal. Instead of disposing of this byproduct or using it for low-value applications, the developed process transforms the bagasse into cellulosic pulp and then into environmentally friendly cardboard. This paradigm shift significantly reduces the demand for virgin fibers and contributes to the conservation of forest resources. Our work aligns with literature that highlights the potential of agroindustrial waste to replace traditional raw materials in the paper industry. Furthermore, the proposed system follows the closed-loop principle of the circular economy. Bagasse, traditionally considered an environmental liability, is reincorporated into the production chain as a secondary raw material. This approach aligns with international models that promote material recirculation and waste reduction in agroindustry [80]. Integrating bagasse into the mezcal industry’s waste management system is also a key aspect. Using this waste for papermaking mitigates local environmental issues, such as soil and water pollution, while adding economic value to the regional production chain. Studies have shown that incorporating agroindustrial waste into circular economy systems improves the competitiveness and sustainability of traditional sectors [81].