Feasibility of Charcoal Briquette Production from Organic Solid Waste Streams Generated in the University of Maiduguri, Nigeria

265 Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 265-274 p ISSN: 2635-3342; e ISSN: 2635-3350 Original Research Article Feasibility of Charcoal Briquette Production from Organic Solid Waste Streams Generated in the University of Maiduguri, Nigeria *1Kolo, Z.K., 2Jones, A.N. and 2Musa, M.A. 1Department of Civil Engineering Technology, Ramat Polytechnic, P.M.B Maiduguri 1070, Borno State, Nigeria. 2Department of Civil and Water Resources Engineering, University of Maiduguri P.M.B.1060, Maiduguri, Borno State, Nigeria. *zkyariko[email protected]m http://doi.org/10.5281/zenodo.18060804 ARTICLE INFORMATION ABSTRACT Article history: Received 25 Jun. 2025 Revised 21 Sep. 2025 Accepted 02 Oct. 2025 Available online 30 Dec. 2025 This paper assessed the potential of charcoal briquette production from sawdust and fallen leaves generated within the University of Maiduguri campus. The composition of the materials used for briquette production were 100% sawdust, 100% leaves, and a combination of 50% sawdust and 50% leaves with particle sizes of 1.18 mm and 0.3 mm. Cassava starch and Gum Arabic pastes were used as binding materials. Physical and combustion properties of the produced briquettes were determined to identify the briquettes with the greatest physical integrity. Results revealed that briquettes produced from leaves with gum Arabic binder had the highest density of 1.889 g/cm3, compressive strength of 5.98 bars, and moisture content of 7.83 % with a calorific value of 23.657 MJ/kg from a particle size of 0.3 mm. Similarly, briquettes produced from sawdust and cassava starch binder had the highest volatile matter of 27.10 % with 0.3 mm particle size. However, a briquette of leaves + cassava starch had the highest ash content of 15.56 % with 0.3 mm particle size. Therefore, briquette sample produced from 100 % fallen leaves with gum Arabic as binder had the highest combustion properties and could be scaled up for domestic and small-scale industrial application. © 2025 RJEES. All rights reserved. Keywords: Briquettes Gum Arabic Leaves Sawdust Particle size 1. INTRODUCTION The demand for energy from renewable raw materials is receiving more attention at local, national and global scale than ever before. These could be attributed to the high rise in the price of conventional fuels, and environmental pollution leading to climate change. Renewable energy from biomass materials including municipal wastes, agricultural food and feed crops, energy crops and trees, 266 Z.K. Kolo et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 265-274 agricultural crop wastes, wood wastes and other waste materials are considered as one of the major potential sources for energy production (EPA, 2009; Sivakumar and Mohan 2010). Studies have shown that renewable energy which is considered as energy source in many developed and developing countries could significantly improve the quality of air, water, land, economy and energy security at large (Balat, 2009; Uzun and Kanmaz, 2013). Research demonstrates that the conversion of renewable raw materials to energy could significantly reduce fossil fuel consumption and the emission of greenhouse gases (Laryea-Goldsmith et al., 2011). Large quantity of solid and liquid organic waste materials is generated in the University of Maiduguri. The solid waste consists of fallen leaves, sticks, plastics, yards, bottles and cans which is collected, dumped around gate III of the University campus. Due to climate factors like high temperature and humidity along with high organic matter content, the waste decomposes rapidly resulting in the release of methane gas (CH4) which is more harmful to the environment than CO2 (Naushin et al., 2022). Moreover, it was observed that the huge quantity of the waste is burnt freely in to the atmosphere contributing to greenhouse gases (GHG) emission. However, several studies have revealed that, dumping without treatment and burning are unhealthy to human health and the environment (Binxian et al., 2015; Hussein et al., 2018). Therefore, fallen leaves and sticks were separated from the waste streams and used for the production of charcoal briquettes. Furthermore, the product would serve as alternative energy with the capacity to replace conventional wood charcoal in terms of cost effectiveness, environmentally friendliness, and sustainability for the university community and beyond. Akpenpuun et al. (2022) studied the combined biomass of groundnut shell, rice husks and sawdust with different mix ratios carried out with same pressing pressure where increase in binder starch proportion improves durability. Ajith et al. (2022) Study explore the characteristics of briquettes produced from different proportion of dry leaves, sawdust and rice husk with a starch binder compressed at a pressure of 150mpa, where briquettes from100% leaves showed highest heating value, water resistance and density. There is incomplete or limited data and utilization of organic solid waste generated in the University of Maiduguri. Therefore, this study will provide information on the energy potentials, and suitable treatment for reducing the high concentration of pollutants which could help the concerned authorities to relate between what is discharged to the environment and its potential transformation to useful byproduct. Additionally, this research might help in the decision-making processes of developing commercial-scale treatment method of organic solid waste. This work investigates the use of organic solid waste (fallen leaves and sticks) generated within the University of Maiduguri and sawdust from Baga road timber shade, with cassava flour and gum Arabic as binding materials. Particle size and calorific value of the briquettes were evaluated. 2. MATERIALS AND METHODS 2.1. Material Collection and Preparation of Samples In this study, some of the materials and equipment used include: sawdust, leaves (Azadirachta indica, Black plum and Red river gum), gum Arabic, cassava flour, forced air drying oven (VNB300, Memmert Germany), drying cabinet (FSM 140, Ohaus core USA), Digital Analytical balance (PA214), Pioneer Ohaus USA), Porclain crucibles, and muffle furnace (P-Select 2000368, select HORN Ohaus USA). The sawdust sample used for this study was collected from a timber shade along Baga Road, Maiduguri while the leaves sample was collected from a dump site within the University of Maiduguri Campus. Subsequently, both the gum arabic and cassava samples were purchased from a local market (KasuwanGamboru) in Maiduguri. 267 Z.K. Kolo et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 265-274 2.2. Methods 2.2.1. Sample preparation The sawdust and the leaves were screened from impurities like sand, metallic objects, grits and chips of wood. The sawdust was sun-dried to reduce moisture content. Sawdust and leaves were artificially carbonized in an enclosed drum at a temperature of 400 °C for 4 hours (Nattaporn et al 2013). Cooled carbonized biomass, gum arabic, and cassava were ground into pulverized form and settled using 1.18 mm and 0.3 mm sieve sizes (Taiwo 2012) to ensure steady grain size and ease of compression. The biomass material and the corresponding binders were mixed in a ratio of 1:1 where 25 g of each sample was adopted for all materials using a digital weighing scale. 2.2.2. Production of briquettes The mixture of materials used for the production of the briquettes are presented in Table 1. The binders were made into non-thick gel using the moisture content of each binder introduced to briquettes. The biomass and the binders were mixed as presented in Table 1. Each mixture was filled into a cylindrical mold and placed on a pressing hydraulic jack machine and compacted at a pressure of 29.94 MPa, as read from the pressure gauge inserted at the pressing point of the machine, which has helped in regulating the constant compaction pressure and preventing oozing out of the binder. A total of twelve (12) (6 from each of the above biomass to binder combination for the 2 sieve sizes) cylindrical briquettes with a mean diameter of 2.54cm and height of 5 cm were produced. The produced briquettes were sundried for 8 days. (to ensure thorough dryness of briquettes sample). Table 1: A combination of biomass and binder for briquettes production Biomass Binder Sawdust Cassava Leaves Cassava Sawdust + Leaves Cassava Sawdust Sawdust Leaves Gum Arabic Sawdust + Leaves Gum Arabic 2.2.3. Determination of physical and combustion properties of the produced briquettes Some of the physical and combustion properties of the produced briquettes determined include: the density, compressive strength, moisture content (MC), ash content (AC), volatile matter (VM), and calorific value (CV). 2.2.4. Determination of the density of the produced briquette The equivalent mass (m) of each of the briquettes in grams (g) was divided by its subsequent volume (v) in cm. d = 𝑀 𝑉 (1) 2.2.5. Determination of moisture content of the produced briquettes A two-gram portion of the grated sample of the briquettes produced was evenly spread on a clean, dried, and pre-weighed container, which was promptly placed in an oven (UNB 300) preheated to 103 °C without a lid. Thereafter, the briquettes sample was left to dry for 3 hrs before the lid was replaced on the container and removed from the oven (to prevent any form of moisture that might arise from the lid cap). Thus, the briquettes sample was left to cool in a drying cabinet (FSM 140) at less than 20 % humidity and then reweighed again to determine the moisture content (MC). 268 Z.K. Kolo et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 265-274 MC (%) = (𝑚3−𝑚1) (𝑚2−𝑚1) × 100 (2) where:m1 = weight of glass container (g), m2 = weight sample and glass container before drying (g), and m3 = weight of sample glass container after drying (g) 2.2.6. Compressive strength of the produced briquettes A briquette sample was inserted between two plates on a compressing machine and subjected to compression. The ratio between the maximum breaking force recorded by the pressure gauge in bar and the cross-sectional area of the sample indicates the resistance to breaking by compression. 2.2.7. Determination of ash content of the produced briquettes Approximately 5 g of a grated briquette sample was evenly spread on a weighed container (crucible) and placed into a muffle furnace (P-select 200 368, select HORN) set at 570 °C. The sample was kept at the above temperature until it appeared light grey; hence, the crucible was removed and placed in a drying cabinet (FSM 140), which was left to cool and reweighed immediately. The ash content (AC) was then calculated using Equation 3. AC = (𝑚𝑐−𝑚𝑎) (𝑚𝑏−𝑚𝑎) × 100 (3) Where ma = weight of porcelain crucible (g), mb = weight of porcelain crucible and sample (g), mc = weight of porcelain crucible and ash (g) 2.2.8 Determination of volatile matter of the briquettes produced Grated briquette sample (5g) was evenly spread on a weighed crucible and placed in a muffle furnace (Pselect 2000368, select HORN) set at 750 oC and left for 7 min. (Lina et al 2015) Thereafter, the crucible was removed and placed in a drying cabinet (FSM 140), which was left to cool and weighed immediately. Equation 4 was then used to calculate the volatile matter (VM). VM (%) = 𝑤1 − 𝑤2 ÷ 𝑤1 𝑥 100 (4) Where: w1 = weight of initial sample (g); w2 = weight of sample after heating (g) 2.2.9. Determination of calorific value of briquettes The calorimeter used for the determination of calorific values was calibrated by combusting 1 g of benzoic acid, which has a known CV. About 1 g of a briquette sample was placed in a metal sample cup which was placed into a holding slot between two electrodes extending from the lid of a stainless-steel container. Thereafter, a thin metal wire fuse was attached to the electrodes, which forms a loop into the coal sample and then placed into a “bomb container”. Thus, the bomb containing the briquette sample was transferred to a water bath where an electrical current was used to spark the sample which ignites the bomb. The sample in turn heated the water bath; hence, the change in water – bath temperature was used to determine the calorific value of the sample. 3. RESULTS AND DISCUSSION The results of the physical and combustion analysis of leaves, sawdust and mixture of leaves and sawdust with cassava starch and gum Arabic pastes as binders are presented in this section. The properties of the briquettes produced were limited to the determination of percentage moisture content, density, compressive strength, percentage ash content, percentage volatile matter and calorific value. Table 2 presents the density of the briquettes produced. 269 Z.K. Kolo et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 265-274 Table 2: Density of produced briquettes S/N Biomass + binder combination Particle size 1.18 mm 0.3 mm 1. Sawdust + Cassava 0.89 0.93 2. Sawdust + Gum 0.74 0.95 3. Leaves + Cassava 0.78 0.99 4. Leaves + Gum 0.90 1.08 5. Sawdust + Leaves + Cassava 0.66 0.89 6. Sawdust + Leaves + Gum 0.78 0.99 The density of all briquette samples increased as the particle size decreased. This is attributed to the compression of finer particles, which reduces void spaces and enhances compaction. The highest density (1.08 g/cm²) was recorded in the LG sample at 0.3 mm, indicating that leaf-based briquettes with finer particles and the GA additive support better densification. In contrast, the SLC sample had the lowest densities, likely due to poor bonding or less cohesive material structure. This trend aligns with previous studies, such as Oladeji (2012) and Onuegbu et al. (2012), which reported that smaller particle sizes lead to higher briquette densities, improved mechanical strength, and more efficient combustion. These findings confirm that particle size plays a critical role in optimizing the physical and energy properties of biomass briquettes. It is therefore evident that the briquetting process has been able to obtain increased density, which is a valuable factor in briquetting. The compressive strength results reveal that both binder type and particle size significantly affect the mechanical integrity of the briquettes (Table 3). Across most samples, briquettes produced from the coarser 1.18mm particles exhibited higher compressive strength compared to those from 0.3 mm particles. This aligns with findings by Oladeji (2010), who reported that coarse particles improve internal bonding and allow better compaction in biomass briquettes. In terms of binder performance, gum arabic-based briquettes (e.g., LG, SLG) consistently showed higher compressive strength than their cassava starch-based counterparts (e.g., LC, SLC). LG (Leaves + Gum Arabic) recorded the highest strength values across both sieve sizes, indicating that gum arabic provides stronger bonding and better structural stability, particularly with fibrous materials like leaves. This supports the findings of Sotannde et al. (2010), who observed that binder type plays a crucial role in determining briquette strength and durability. On the other hand, cassavastarch-bound briquettes, especially LC (Leaves + Cassava), showed the lowest compressive strength, possibly due to weaker binding interactions with the leaf fibers. Mixed-material briquettes such as SLG and SLC showed intermediate strength values, with gum arabic again outperforming cassava starch. Table 3: Compressive strength of produced briquettes S/N Biomass + Binder combination Particle size 1.18 mm 0.3 mm 1. Sawdust + Cassava 0.568 0.278 2. Sawdust + Gum 0.378 0.314 3. Leaves + Cassava 0.240 0.240 4. Leaves + Gum 0.587 0.598 5. Sawdust + Leaves + Cassava 0.521 0.210 6. Sawdust + Leaves + Gum 0.573 0.578 The moisture content results from this study reveal a subtle interaction between particle size and moisture retention in biomass materials (Table 4). While most samples (e.g., SC, SG, SLC) display a decrease in moisture with reduced particle size, some samples such as LG and SLG exhibit a slight increase. This trend aligns with recent findings of Varela et al. (2023) in lignocellulosic biomass studies which demonstrated that moisture strongly affects how biomass fractions pass through fine sieves, particularly with wetter materials leading to increased retention in fines. Similarly, Waheed et al. (2023) showed that higher moisture content severely impacts flow behavior, especially for milled samples. 270 Z.K. Kolo et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 265-274 Table 4: Percentage moisture content of produced briquettes. S/N Biomass + Binder combination Particle size 1.18 mm 0.3 mm 1. Sawdust + Cassava 6.52 5.61 2. Sawdust + Gum 6.96 5.75 3. Leaves + Cassava 5.95 5.91 4. Leaves + Gum 7.83 7.32 5. Sawdust + Leaves + Cassava 5.96 5.84 6. Sawdust + Leaves + Gum 7.29 7.20 The result is also in agreement with the MC of between 5% and 10% for quality briquettes, as obtained by Pallari et al. (2013). Additionally, the work on pellet forming by Liu et al (2018) indicates that the combination of small particle size (0.2-1.4 mm) and moderate moisture (16%) leads to optimal physical properties, supporting the observation in this study that finer fractions sometimes retain more moisture. However, trends observed are consistent with the current understanding that moisture behavior in biomass is complex, affected by particle size, moisture level, and material structure. With low MC, briquettes will easily ignite and higher calorific values from the briquettes are expected (Akowuah et al., 2012). In this study, volatile matter (VM) for briquettes made from sawdust and leaves with cassava flour and gum arabic binders ranged approximately 20.6%-27.1%, depending on particle size (1.18 mm and 0.30mm), binder, and biomass types (Figure 1). This align with the findings of Sabo et al (2022) who studied coconut shell (CS) and corncobs using starch and gum arabic binders, and reported VM values ranging from (16.4919.30%) for starch and (7.74-13.33%) for gum arabic, much lower than the values obtained from this study, this could possibly be due to differences in biomass type, particle size or binder proportion. However, the consistent trend of starch-based binders producing higher VM supports the influence of binder type on the thermal behavior of biomass briquettes. This moderate VM is notably lower than values reported for highly volatile biomass mixtures of rice straw and banana peel with cassava binder (39-44%) (John and Alice, 2024). This is much higher, possibly because materials were less carbonized, and more volatile organics were present. Though values higher than values obtained for woody biomass briquettes, where gum arabic was used in lower proportion (Anguruwa et al., 2024). Figure 1: Percentage volatile matter in the briquettes produced The trend observed is that finer particle size tends to increase VM, as cassava binder tends to give slightly higher VM than gum arabic in several cases. The implication is that one might use coarser particle sizes with a lower binder proportion. However, high volatile matter of briquette indicates ease of ignition, rapid burning, and proportionate increase in flame length but low heating values. The produced briquettes have a 0 5 10 15 20 25 30 S+C S+G L+C L+G S+L+C S+L+G Volatile matter (%) Biomass + binder combination 1.18mm 0.3mm 271 Z.K. Kolo et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 265-274 percentage volatile matter that falls within the range of 10 – 25% for good quality briquettes as reported by Akintaro et al. (2017). Two particle sizes were considered (1.18 mm and 0.30mm) to assess their influence on ash content (Figure 2). The results indicated that briquettes made solely from sawdust exhibited lower ash content compared to those made from leaf biomass or their mixtures. Specifically, sawdust with cassava flour (SC) had ash contents of 7.319% at 1.18 mm and 5.57% at 0.30 mm, while sawdust with gum arabic (SG) recorded 6.09% and 5.44%, respectively. In contrast, leaf-based briquettes with cassava flour (LC) exhibited significantly higher ash content, increasing from 14.51% at 1.18 mm to 15.56% at 0.30 mm, while the leaf-gum arabic variant (LG) ranged from 13.65% to 15.04%. Mixed biomass briquettes (sawdust + leaves) showed intermediate values, with SLC ranging from 9.43% to 11.18% and SLG from 10.15% to 11.42%, depending on particle size. However, this result is slightly higher than values reported in findings of Sotannde et al. (2010), who found ash contents of approximately 3.35% for cassava-bonded and 4.45% for gum arabicbonded sawdust briquettes. The higher values in this study may be attributed to differences in material quality, presence of contaminants, or binder-to-biomass ratios. Figure 2: Percentage ash content (%) of produced briquettes These findings reveal several trends: biomass type was the most influential factor, with leaf biomass producing notably higher ash content due to its higher inherent mineral content compared to sawdust, gum arabic generally produced slightly lower ash values than cassava flour, particularly in sawdust-based briquettes, likely due to its cleaner composition and lower non-combustible residue, sawdust with decreased particle size and reduced ash content suggests better removal of impurities and tighter packing of fine particles. However, this study confirms that biomass type, particle size and binder play significant roles in determining the ash content of briquettes. Hence, low ash content offers higher heating value with less dust emission that leads to air pollution, whereas high ash content results in lower calorific value as it influences burning rate due to minimization in heat transfer (Obi et al., 2013). The calorific value of briquettes produced from sawdust and leaves using cassava flour and gum arabic as binders at particle sizes of 1.18 mm and 0.3 mm is presented in Figure 3. The results showed that while sawdust based briquettes generally recorded higher energy content at larger particle size (e.g., SC: 23.09 MJ/kg at 1.18 mm and 21.09 MJ/kg at 0.3 mm), leaf-based briquettes particularly those bound with gum arabic demonstrated opposite trend, with finer particles yielding higher calorific values (e.g., LG: 22.92 MJ/kg at 1.18 mm and 23.66 MJ/kg at 0.3 mm), suggesting that particle size and binder type interact differently depending on biomass type. The findings align with values obtained by Ugwu et. al (2011) with reported calorific value of 23.600mj/kg and slightly below that obtained by Gilbert et al (2021) with 24.60mj/kg. Similarly, values trend with studies of Anguruwa et al. (2024), Sotannde et al. (2010), and findings from Handra et al. (2018), where calorific values of between 30-37 MJ/kg were reported for briquettes from woody or clean agricultural residues with optimized particle size, binder ratio, and 0 4 8 12 16 S+C S+G L+C L+G S+L+C S+L+G Ash content(%) Biomass + Binder combination 1.18mm 0.3mm 272 Z.K. Kolo et al. / Nigerian Research Journal of Engineering and Environmental Sciences 10(2) 2025 pp. 265-274 compaction pressure, indicating that the maximum value of (23.66 MJ/kg) from this study fall within an acceptable range for mixed biomass. Hence, further optimization particularly in ash content reduction and moisture control could significantly enhance energy output to match or exceed levels reported in above literature. Thus, minimum value obtained from this study is higher than the minimum value set by the wood pellet association of Canada (calorific value ≥ 16000mj/kg). Therefore, it will be agreed that produced briquettes have good combustion properties that would be acceptable for domestic use and small – scale industrial purposes. Figure 3: Calorific value of the produced briquettes 4. CONCLUSION Fossil fuels and wood are the major source for energy in Nigeria today. The excessive use of these fuels contributes to climate change, causing more harm to the environment, which could lead to air pollution and desertification. In this study, it was observed that the combination of leaves and sawdust using natural binders in briquettes production as an alternative source of energy has great potential to low income communities. It was clear that gum Arabic is considered a better binder than cassava starch in the production of briquettes. Moreover, a decrease in particle size and moisture content has shown a significant impact on the density of the briquette. Additionally, the calorific value of the briquette obtained from leaves and gum arabic is higher than that of the dry wood, which is within the stipulated standard (C.F. Niels en A/S, a member of RUF briquetting systems). Furthermore, this work demonstrated that the utilization of organic solid waste through carbonization can improve access to energy. Therefore, more and different waste and binder combinations should be investigated for energy production, and the calorific values compared with those of some locally used charcoals 5. 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