Investigation of Pyrolysis/Gasification Process Conditions and Syngas Production with Metal Catalysts Using Waste Bamboo Biomass: Effects and Insights

Abstract

The primary objective of this study was to examine the catalytic behaviors exhibited by diverse metal catalysts such as CaO, NiO, and K₂CO₃ for pyrolysis and gasification application with waste biomass. The investigation involved fine tuning the conditions of pyrolysis/gasification by optimizing the pyrolysis atmosphere, catalyst addition methods, and catalyst quantities. The behaviors were investigated using thermal analysis (TG-DTA), and the production gaseous contents were analyzed via GC-FID. The results showed that Ar gas proved to be well suited for the pyrolysis reaction. The incorporation of catalysts through mixing and impregnation techniques ensured the homogeneous dispersion of catalyst particles within the sample, offering a clear advantage over the two-stage approach. Among the various catalysts explored, K₂CO₃ demonstrated the most favorable catalytic impact, resulting in an enhancement of char yield from 20.2 to 26.8%, while the tar yield was reduced from 44.3 to 38.6%. Furthermore, the presence of K during gasification reactions was found to foster accelerated reaction rates and an increase in syngas production yield.

1. Introduction

Given the limitations posed by storage and environmental concerns, the global scarcity of fossil fuels presents a formidable challenge. One of the noteworthy considerations pertains to the finite nature of fossil resources, signifying that their available reserves are dwindling, with estimations suggesting imminent exhaustion. As a result, these reserves are poised to be depleted in the foreseeable future. Furthermore, the extraction and utilization of fossil fuels have emerged as pressing environmental issues, owing to their role in exacerbating global warming, altering climate patterns, and inflicting irreparable harm upon natural ecosystems [1,2]. In light of this urgent situation, there has been a heightened focus on clean and sustainable energy sources, encompassing biomass energy, wind energy, solar energy, and hydrogen-based energy solutions. Consequently, within this amount of energy resources, biomass residue, categorized as a sustainable form of energy, exhibits rich diversity, owing to disparities in vegetation types and land utilization practices. This resource is exceptionally plentiful, boasting the potential for an annual worldwide production of 140 billion metric tons sourced primarily from agricultural activities [3]. Biomass resources are anticipated to emerge as a viable and sustainable alternative to address this issue in the future due to their abundant availability and easy storage and transportation [4,5]. Yusuf et al. characterized Matooke peel as a potential fuel, and found that it has higher volatile matter content which leads to a higher HHV and less heat required for the thermochemical reactions [6]. Dhanuskar et al. produced high-yield pyrolytic oil via the thermal cracking of RAME under optimized conditions in a micro fixed-bed reactor using castor oil [7,8,9,10,11,12]. Additionally, Wongsiriamnuay et al. found that steam enhances the quality of fuel gas, showing higher contents of H₂, CO, and LHV [13].

Thermochemical biomass convention technologies include combustion, pyrolysis, and gasification. These technologies not only provide renewable fuels but also generate various productions, including bio-oil and syngas. Pyrolysis constitutes an endothermic decomposition process conducted within an oxygen-deficient and high-temperature environment, resulting in the production of bio-oil, syngas, and biochar [14,15]. Gasification is carried out at elevated temperatures in the presence of a gasifying agent, transforming biomass into valuable and clean syngas [16]. Pyrolysis constitutes a crucial preliminary stage for both combustion and gasification processes. The generation of syngas is regarded as one of the most promising and dependable methods for converting biomass. This versatile resource finds applications across diverse sectors, including chemical synthesis, power generation, and heating supply, as well as hydrogen and biofuel production [17]. However, tar is an inevitable byproduct of the pyrolysis/gasification of biomass, and its generation poses one of the most formidable challenges in the realm of biomass gasification applications. This is owing to its capacity to deactivate catalysts during the refinement process and diminish the yield of syngas. Furthermore, tar has the propensity to condense within equipment pipelines and filters, giving rise to intricate structures that hold the potential to induce mechanical failures across the entire system. Additionally, it is worth noting that tar contains aromatic compounds, including hazardous substances like toxic benzene and polycyclic aromatic hydrocarbons (PAHs), which have adverse environmental implications. Consequently, the imperative for the commercialization of this technology is to tackle tar removal and its transformation into syngas [17,18,19].

The catalyst is recognized as a pivotal determinant in biomass gasification, capable of mitigating thermal and mass transfer hindrances while concurrently reducing the activation energy of the reactions and increasing syngas production. French et al. employed a bifunctional Pt/TiO₂ catalyst within a fixed-bed reactor, employing co-fed H₂ to enhance product yield and minimize coke formation [20]. Li et al. employed waste aluminum dross (Al₂O₃), which exhibited an enhanced capability to enhance the reforming and cracking processes, leading to the fragmentation of comparatively heavy volatile chains into lighter molecules and gases. As a result, they achieved substantial gas production along with a reduced rate of char deposition, accompanied by a significant elevation in H₂ yield [21]. Across the temperature span of 500 to 900 °C, the inclusion of KCl led to an augmentation in gas output and a decline in tar formation. Furthermore, it impeded the generation of levoglucosan while fostering the production of H₂ [22].

Metal catalysts are frequently regarded as pivotal elements for addressing the aforementioned challenges. Firstly, these catalysts must demonstrate a high level of effectiveness in efficiently removing tars, a critical requirement for ensuring the purity of the end product. Additionally, if the desired output is syngas, these catalysts must possess the capability to reform methane into this valuable intermediate. Furthermore, the catalysts must yield a syngas ratio appropriate for the intended process, ensuring compatibility with production goals. To prolong their operational lifespan, these catalysts should exhibit resistance to deactivation resulting from carbon fouling and sintering, enhancing their durability. Simultaneously, ease of regeneration is essential for maintaining consistent catalytic activity. In pursuit of sustainability and cost-efficiency, the catalysts should also be economically accessible while maintaining their structural integrity and strength. These collective attributes will underpin the successful implementation of catalysts in our process, enabling us to achieve our research objectives effectively [23]. Nonetheless, the catalytic efficacy may be subject to influence by a range of variables, including heating temperature, gasification atmosphere, and other pertinent factors.

Consequently, it becomes imperative to elucidate and comprehensively characterize the catalytic behaviors exhibited across diverse pyrolysis and gasification conditions. Such an investigation is essential for a thorough understanding of the catalyst’s performance and its potential applications in varied operational environments, thereby contributing to an advancement in our scientific knowledge in this field. This study delved into the thermal decomposition and CO₂ gasification characteristics of waste bamboo biomass. Pyrolysis atmospheres using Ar and CO₂ gases were employed to assess their impact on thermal decomposition behaviors. Notable alkali, alkali earth, and transition metals, K₂CO₃, CaO, and NiO, were introduced to investigate their roles in thermal decomposition and CO₂ gasification. The optimal conditions for pyrolysis/gasification reactions were utilized for the analysis of syngas production.

2. Materials and Methods

2.1. Materials and Chemicals

Two species of waste bamboo biomasses, madake (Phyllostachys bambusoides) and moso bamboo (Phyllostachys edulis), were sampled from Anhui Province, China. The samples were ground below 250 μm. CaO, NiO, and K₂CO₃, purchased from Wako Pure Chemical Industries, Co., Ltd., Oosaka, Japan, were used as reducing metal catalysts. Ar and CO₂ gas for the pyrolysis and gasification processes were obtained from Suzuki Shokan Co., Ltd., Tokyo, Japan.

The proximate and ultimate analysis results are presented in

Table 1. The proximate and ultimate analysis of waste bamboo samples (wt.%).

Samples	Proximate Analysis				Ultimate Analysis
	M	VM	A	FC	C	H	N	O+S
Madake	4.59	80.2	0.648	14.5	44.8	5.82	0.260	48.5
Moso bamboo	4.85	80.6	0.229	14.3	45.4	6.00	0.270	48.1
K-loaded moso	4.85	71.6	3.11	20.5	35.9	5.58	0.440	54.9

. Moisture content was determined by weighing the initial and post-oven drying masses at 105 °C for 1 h. Ash content was quantified by comparing the samples pre- and post-heating using a muffle furnace at 815 °C following the JIS M8812 standard [24]. Volatile matter was assessed by weighing the sample before and after subjecting it to muffle furnace heating at 900 °C, contained in a crucible. The fixed carbon content was computed by subtracting the combined values of moisture content, ash content, and volatile matter content from 100%. The ultimate analysis was conducted using CHN-CORDER (Model MT-5 Yanaco, Co., Ltd., Yanaco, Japan) for comprehensive assessment.

Raw material sample (2 g) and K₂CO₃ (0.1:1 and 0.05:1 wt.%) were mixed with distilled water, stirred at room temperature for 1 h, and dried overnight at 105 °C to remove moisture completely to make a K-loaded moso bamboo sample.

2.2. Reaction Behaviors with Different Metal Catalysts

The pyrolysis and gasification behaviors of waste bamboo samples were analyzed using thermogravimetry differential thermal analysis (TG-DTA, DTG-60, Shimazu Co., Ltd., Kyoto, Japan). The pyrolysis reaction was carried out within an Ar atmosphere, utilizing a gas flow rate of 100 mL/min, while maintaining a constant heating rate of 10 °C/min. The temperature was gradually raised from room temperature to reach a final temperature of 1000 °C. The gasification reaction was conducted using Ar gas, with increasing temperature from room temperature to 600 °C, and was then further switched to a CO₂ atmosphere until the temperature reached 1000 °C. Finally, exclusive exposure to a CO₂ atmosphere was employed, with the temperature steadily increasing from room temperature to 1000 °C. In order to comprehensively explore the impacts of various catalysts and their respective reaction conditions, the experimental setup involved the sequential introduction of CaO, NiO, and K₂CO₃. These catalysts were introduced through a two-stage process and using mixing techniques, as illustrated in Figure 1. The mass ratio of catalyst/raw material (wt.%) was kept at 0.1:1 and 0.05:1, respectively.

2.3. Analysis of Gas Components

The gas components of pyrolysis and gasification reactions were conducted using a fixed-bed pyrolysis/gasification reactor (Figure 2) and analyzed using GC-2014 (Shimazu, Co., Ltd., Kyoto, Japan). The pyrolysis reaction was executed within an Ar atmosphere, involving a temperature escalation from room temperature to 900 °C. Subsequently, the gasification process was initiated using Ar gas, gradually raising the temperature from room temperature to 900 °C, followed by a transition to a CO₂ atmosphere. The catalyst employed in this study was K₂CO₃, incorporated at a mass ratio of 0.05:1. The catalyst was uniformly introduced through an impregnation method, ensuring even distribution within the sample.

3. Results and Discussions

3.1. Reaction Behaviors

3.1.1. Pyrolysis and Gasification Behaviors of Bamboo Samples

The outcomes of the investigation into the thermal decomposition behavior of two distinct bamboo materials using TG-DTA are presented in Figure 3a. Analyzing the weight change curves, it becomes evident that a reduction in mass due to dehydration reactions occurs within the temperature range of 20 to 200 °C. Concurrently, thermal decomposition reactions manifest between 200 and 600 °C. The volatile matter content was fully decomposed and released to the outer surface of the carbon matrix. Notably, no further weight alterations were observed beyond 600 °C, indicating near-completion of the thermal decomposition reactions [20]. At this point, the weight loss of madake and moso bamboo was 78% and 80%, respectively. This indicates a higher VM content for moso bamboo, which has been characterized in Table 1 accordingly. After 600 °C, the carbonization stage occurred to produce char content [25].

Moreover, both madake and moso bamboo showcase pronounced weight loss between 200 and 400 °C, attributable to the decomposition of cellulose molecules. However, the onset temperatures for these reactions differ, standing at 220 °C for the former and 250 °C for the latter. This distinction implies a higher thermal decomposition temperature for the moso bamboo. A comparison of residual weights post-reaction underscores that moso bamboo retains a lower residual weight. This observation aligns with industrial analysis findings, pointing toward higher volatile content and suggesting lower ash content. According to Table 1, both madake and moso bamboo contained higher volatile matter content compared with other biomass wastes in the literature reported for soybean oil cake ~69.81%, cherry tree ~71%, and oak acorn ~75.1%, etc. [26,27]. In instances where the VM content constitutes a significant proportion of the biomass’s weight, the biomass fuel tends to undergo vaporization before the actual combustion process, whereas biomass containing a lower VM fraction is more inclined to combust, leading to the formation of char residues [3]. Consequently, both of the species of bamboo materials are more favorable for gasification applications.

Considering the eventual amalgamation of the generated char from thermal decomposition with gasifying agents such as CO₂ to synthesize fuel gases, the pursuit of materials yielding elevated char quantities becomes pivotal.

3.1.2. Effects of Pyrolysis Atmosphere and Catalyst Addition Method

With moso bamboo boasting notably high volatile content, there arose an expectation of substantial tar generation during the thermal decomposition reactions [21]. As a result, recognizing its aptness for probing approaches that amplify gasification rates and concurrently curtail tar formation, moso bamboo was selected as the focal material for dissecting the impacts of catalyst varieties, modes of catalyst introduction, and thermal decomposition atmospheres on the intricate processes of biomass thermal decomposition and gasification.

Analyzing the outcomes depicted in Figure 4, it becomes evident that distinct thermal decomposition atmospheres exert minimal influence on the thermal decomposition tendencies of the waste bamboo samples. The marginal divergences in residual weight were likely attributed to errors introduced during the transitions between atmospheres. However, upon contrasting the gasification reactivity of chars generated during thermal decomposition, those synthesized under a CO₂ atmosphere displayed subtly superior attributes. These included heightened reaction rates and lower onset temperatures for all parameters. The diminished gasification reactivity observed in chars under an Ar atmosphere cannot only be ascribed to the previously mentioned atmosphere switch error, but also to the intrinsic potential of a CO₂ atmosphere to amplify the gasification reactivity of the sample.

Furthermore, observations from Figure 4b suggested that the post-atmosphere-switch mass increase beyond 600 °C could stem from the partial reaction of certain Ca catalyst components with CO₂, leading to the formation of CaCO₃. This reaction likely impeded the progression of gasification reactions until attaining the CaCO₃ decomposition temperature at 900 °C. Subsequently, the reaction rate was enhanced by the addition of Ca. Firstly, it adsorbed carbon dioxide from the generated syngas, promoting the water–gas shift reaction. Secondly, CaO potentially acted as a catalyst to facilitate the steam reforming of hydrocarbons [22]. This observation is in agreement with the study of Mitsuoka et al. [28], who found that the Ca-based catalyst accelerated the gasification rate of char produced from Japanese cypress via catalytic action.

In contrast, for samples incorporating the K catalyst, the thermal decomposition reaction under an Ar atmosphere proceeded with enhanced celerity, yielding an improved decomposition rate, as illustrated in Figure 4c. Moreover, despite the reduced weight loss under CO₂ compared to Ar, the similar residual weight implied the commensurate presence of participating char in actual gasification reactions. However, the weight divergence at 600 °C signaled that the char under CO₂ still retained a relatively higher volatile content, casting uncertainty on the accuracy of a high char yield from CO₂ and suggesting that a stable Ar atmosphere might offer analogous effects by enhancing stability.

According to Figure 5, it becomes evident that the distinct catalyst Ni did not exhibit the capacity to lower the temperatures for reaction onset or the peaks of maximum reaction rates by altering the addition methods. Nevertheless, for the Ca catalyst, the mixed addition method yielded a slight yet discernible improvement in gasification reaction rates and a concurrent reduction in residual weight. This outcome suggests a trend toward more progressive reactions. In the context of the K catalyst, regardless of the thermal decomposition atmosphere, the temperatures required to achieve maximum reaction rates were approximately 880 °C and 780 °C for the two-stage addition and mixed addition methods, respectively. Significantly, the mixed addition method yielded a notable temperature reduction of about 100 °C compared to the two-stage addition approach. This differential implies that the mixed addition technique holds promise in further amplifying gasification reactions. This distinction can be attributed to the enhanced surface coverage and uniform interaction of catalyst particles with the sample achieved through the mixed addition method in contrast to the two-stage approach. Consequently, the introduction of a catalyst onto the sample using the mixed addition method is believed to promote a more homogeneous dispersion of catalyst particles, potentially leading to the emergence of additional catalytic effects.

3.1.3. Effect of Metal Catalysts

By configuring the thermal decomposition atmosphere as Ar and adopting the mixed addition approach for catalyst integration, a comparative analysis of the diverse catalyst effects was conducted, with the results being showcased in Figure 6.

Drawing insights from Figure 6a, it is clear that the introduction of catalysts had minimal impact on both the temperature and rate of the thermal decomposition reactions. Expanding upon these findings, the repercussions on gasification reactions, as depicted in Figure 6b, revealed a distinctive pattern governed by gasification initiation temperatures: Ca (800 °C) = no catalyst (800 °C) > Ni (780 °C) > K (650 °C). Correspondingly, the hierarchy temperatures at the maximum reaction rate were as follows: no catalyst > Ni > Ca > K. This sequence closely mirrors the conclusions reached by Huang et al. [29].

The possibility that Ca struggled to function as a catalyst due to its innate inclination to engage with CO₂ is strong, giving rise to the formation of CaCO₃. This circumstance inherently limited its catalytic influence. The mass loss beyond 900 °C was attributed to the decomposition of CaCO₃ [30]. There were no typical observations that showed any difference in gasification initiation temperature using the Ni catalyst. However, a noticeable surge in reaction rate post-addition hinted that the Ni catalyst might interact with the tar present in the gaseous or liquid phase, instead of directly impacting the char surface at the particle level [31].

In the case of K, the gasification initiation temperature underwent a significant reduction, plummeting from 800 °C to 650 °C, culminating in reaction completion by 900 °C, a testament to its potent catalytic effect. However, for curves exceeding 800 °C, the weight reduction was shaped not only by char gasification but also by the decomposition of K₂CO₃. This phenomenon remained consistent across other catalysts as well. As a result, the variance in thermal properties and reactivity among the catalysts emerged as a pivotal determinant profoundly shaping the outcomes of the thermal decomposition and gasification investigations.

3.1.4. Effect of Catalyst Dose

During reactions, catalysts can go through the formation of highly refined particles or bulk structures, influenced by factors such as temperature, atmosphere, or intermediate species, which consequently impact their reactivity [23]. Stated differently, the quantity of catalyst added can exert an influence on both thermal decomposition and gasification reactions. With this consideration, experiments were undertaken by comparing catalyst addition ratios of 10% and 5% loading, respectively, and the results are presented in Figure 7.

Through the formulation of a K catalyst with a 5% addition ratio, the thermal decomposition initiation temperature experienced a reduction from 200 °C to 150 °C. Although a slight decline in reaction rate was observed, an overall lowering of reaction temperature was achieved. It is worth noting that notable distinctions in the influence on gasification reaction temperatures did not manifest. Nevertheless, a faster maximum reaction rate at the same temperature was evident with the 5% catalyst loading. Since this study did not encompass measurements spanning varying catalyst addition ratios through multiple stages, a definitive conclusion on 5% catalyst loading as the optimal ratio for the reaction cannot be drawn.

However, considering the augmented reaction achieved, the catalyst loading for ensuing experiments measuring product outcomes was adjusted to 5%. This decision found its basis in the insight that as the quantity of alkali metal additives increases, the likelihood of forming bulk structures, which enhance catalytic reducibility rather than fine particle configurations, becomes more prominent. Consequently, this alteration influences the resultant carbon’s morphology and fosters the development of fibrous carbon susceptible to coke deposition, as outlined in the work by Jin et al. [22].

3.2. Pyrolysis/Gasification Gas Production Components

3.2.1. Pyrolysis Gas Production

The thermal decomposition gas yield and its comparative results are presented in Figure 8. Additionally, the char yield and tar yield resulting from thermal decomposition were calculated for both the moso bamboo samples without a catalyst and the K-loaded samples.

Introducing the K catalyst to the samples for the thermal decomposition reaction resulted in a substantial increase in char yield, rising from 20.2% (no catalyst) to 26.8%. Conversely, the production of tar significantly decreased from 44.3% to 38.6%. Consequently, it can be inferred that K not only enhanced the gasification rate of the samples but also had a pronounced effect on diminishing tar formation. Considering the approximately 6% change in yield for both char and tar, the augmented char yield was mainly attributed to the reduction in other components, particularly tar constituents. Hence, the addition of the catalyst contributes to an enhancement in gas yield from the thermal decomposition process.

The production of CO and CO₂ was predominantly observed in the temperature range of 200 to 600 °C, as depicted in Figure 8a. In contrast, CH₄ was primarily emitted between approximately 400 and 700 °C. These three gas species ceased emission around 700 °C, indicating the nearing completion of the sample’s thermal decomposition. Beyond this temperature, only H₂ was gradually liberated in the high-temperature regime. The decomposition of hemicellulose and cellulose mainly contributed to the formation of CO and CO₂. Conversely, the thermal breakdown of lignin primarily yielded H₂ and CH₄, wherein the dominant source of gradually evolving H₂ in the elevated temperature range was attributed to lignin. This observation concurred with the findings of Yang et al. [28]. The reaction mechanisms underlying thermal decomposition can be formulated using the following Equations (1)–(4) [32,33].

(C₆H₁₂O₅)n → 6nC + 5nH₂O

(1)

C + H₂O → CO + H₂

(2)

C + 2H₂O → CO₂ + 2H₂

(3)

2CO + 2H₂ → CH₄ + CO₂

(4)

According to Figure 8b,c, the incorporation of the K catalyst led to a notable increase in the yield of thermal decomposition gases, particularly syngas and CO₂. Additionally, the onset temperature for their formation was reduced by approximately 50 to 100 °C compared to the reaction without a catalyst, underscoring the catalytic enhancement provided by K. The findings further suggest that K facilitates the dehydration and cracking of tar that persists in the vapor phase during thermal decomposition. This process triggers the breakdown of certain aromatic compounds, yielding gaseous products, while the residual aromatic clusters recombine to form char. The catalytic reactions at play can be expressed through the following Equations (5)–(7) [34]. At elevated temperatures, carbon atoms within the biomass engage in reactions with K₂CO₃, resulting in the production of carbon monoxide and K. Concurrently, K interacts with the CO₂ gas generated by the thermal decomposition reaction, leading to the formation of K₂O. Similarly to K₂CO₃, K₂O also engages with carbon atoms within the biomass, contributing to the generation of gaseous components. These reactions serve to enhance the syngas production process. Notably, by-products such as tar primarily comprise carbon-based compounds. K, potassium oxides, and carbonates can similarly react with these by-products, facilitating their decomposition and consequently yielding additional syngas.

2C + K₂CO₃ → 2K + 3CO

(5)

2K + CO₂ → K₂O + CO

(6)

K₂O + C → 2K + CO

(7)

The emergence of CO₂ generation around 700 °C is thought to be a result of the reaction between the syngas produced from H₂ generation, as indicated by Equations (2) and (3). Consequently, the noticeable rise in gas yield observed in this study is hypothesized to stem from K-induced enhancement of thermal decomposition and carbonization in the sample, which promotes gas formation. Additionally, the release of gas can be attributed to tar cracking and the liberation of dense condensates [35].

3.2.2. Gasification Gas Production

The gas yield results for CO₂ gasification are presented in Figure 9. Furthermore, the ash and tar yields for the thermal decomposition of the moso bamboo sample without a catalyst and with a K-loaded catalyst decreased from 8.99% to 3.95% and 56.3% to 46.3%, respectively.

The gasification reaction process follows the below Equations (8)–(10) [27]:

C + CO₂ → 2CO

(8)

C + H₂O → H₂ + CO

(9)

C + 1/2O₂ → CO

(10)

Under the same reaction time, gasification of the K-loaded sample progressed to completion, resulting in a residual quantity of 3.95%. This outcome closely corresponded with the proximate analysis result of 3.11% ash content, as presented in Table 1. However, it was evident that a significant portion of char in the residuals of the no catalyst samples remained unreacted. Notwithstanding this, the tar yield for the K-loaded sample was 10% lower than that of the no catalyst sample, suggesting that the K catalyst potentially played a role in facilitating the secondary decomposition of tar constituents. The tar yield exceeded the value derived solely from the thermal decomposition reaction, likely stemmed from the prolonged maintenance of elevated temperatures within the reaction stainless pipe. This extended duration might have impeded the rapid vaporization and liquefaction of tar in the gas phase, leading to a higher accumulation of tar being cooled and captured within the tar trap.

At 900 °C, the atmosphere was transitioned from Ar to CO₂ to induce gasification reactions. The resultant gas composition was primarily composed of CO, with a minor presence of H₂. As CO₂ served as the gasification agent, direct comparison was not feasible, and CH₄ was entirely undetected. Hence, the syngas yields are juxtaposed in Figure 9 for comparison.

The syngas yields during CO₂ gasification demonstrated varying quantities for individual components, while the trend of increased yields due to K catalyst addition remained consistent. In all instances, the introduction of the K catalyst notably expedited the rate of synthesis gas generation, effectively halving the reaction time. However, despite this acceleration, the analysis of curve areas revealed relatively marginal discrepancies, implying that the primary influence of K in gasification reactions lay in enhancing the reaction rate [33].

4. Conclusions

This study has investigated the reaction dynamics of thermal decomposition and gasification in two types of waste biomass, namely madake and moso bamboo, with a focus on their potential contributions to addressing the Sustainable Development Goals (SDGs). The research has explored the influence of CaO, NiO, and K₂CO₃ catalysts, as well as varying thermal decomposition conditions and gasification reactions under Ar/CO₂ atmospheres.

Moso bamboo, characterized by its low ash content and high volatile matter content, has proven to be well suited for gasification reactions. However, it was observed that exclusive CO₂ reactions, when combined with certain catalysts, could potentially interfere with its catalytic effects. On the other hand, thermal decomposition processes conducted under an Ar atmosphere demonstrated accelerated progression, indicating a promising avenue for efficient biomass utilization.

The effectiveness of the introduced metal catalysts followed the sequence K > Ni > Ca, leading to increased maximum reaction rates and lower starting reaction temperatures. K₂CO₃, in particular, emerged as a highly efficient catalyst. Notably, the presence of K in the pyrolysis process played a crucial role in consuming carbon-based volatile matter, resulting in an increased production of char and a simultaneous reduction in tar yield through cracking. Additionally, the inclusion of K during gasification reactions facilitated enhanced reaction rates.

In light of these findings, the application of K₂CO₃ as a cost-effective and efficient catalyst holds great promise for increasing syngas production and promoting the sustainable reuse of waste bamboo resources. By improving the efficiency of biomass conversion processes, this research aligns with SDGs related to sustainable resource management, clean energy production, and climate action. Ultimately, these outcomes contribute to the broader global effort to address critical sustainability challenges. This study also underscores the importance of responsible resource management by demonstrating how waste biomass, such as madake and moso bamboo, can be transformed into valuable syngas with reduced waste production. By maximizing resource utilization and minimizing waste, it aligns with SDG 12, which focuses on ensuring sustainable consumption and production patterns. This not only conserves precious natural resources but also reduces the environmental footprint associated with waste disposal. This research’s emphasis on efficient biomass conversion processes directly supports SDG 7, which aims to ensure access to affordable, reliable, sustainable, and modern energy for all. By generating syngas from bamboo waste, a renewable and carbon-neutral energy source, this study contributes to the transition toward cleaner and more sustainable energy solutions. This not only reduces greenhouse gas emissions but also provides an eco-friendly energy option for communities, especially in regions where bamboo is abundant. The findings of this research are particularly significant in the context of SDG 13, which seeks urgent action to combat climate change and its impacts. Through the efficient conversion of bamboo waste into syngas, the study mitigates carbon emissions that would have otherwise occurred during the decomposition or burning of waste. This aligns with global efforts to reduce carbon footprints, limit global warming, and transition to a low-carbon economy, whereby all of which are critical components of addressing climate change.