Briquetted biomass, like sugarcane bagasse, a by-product of sugar mills, is a renewable energy source. This study aimed at the production and characterization of bagasse briquettes. The production of briquettes was carried out with different blending ratios (5, 10, and 15%) and average particle sizes (0.75, 2.775, and 4.8 mm) with various binders of cow dung, waste paper, and admixture (molasses and wastepaper). The bagasse underwent drying, size reduction, sieving, binder addition, and densification using a manual press during the briquetting process. Characterization of the physical and combustion parameters of briquettes, such as density, shatter resistance, proximate, and calorific value, followed the American Society for Testing and Materials procedures. The result shows that the maximum density of briquettes was 0.804 g/cm³, while shatter resistance varied from 83.051 to 94.975% (4.8mm, 5% cow dung and 0.75mm, 5% admixture binders respectively). ANOVA analysis showed that the factors and their interactions had a significant influence (p value < 0.05) on the physical properties. The optimum parameters of briquettes achieved were 14.953% admixture binder, 0.776 mm particle size, 0.805 g/cm³ density, and 95.811% shatter resistance. Bagasse briquettes with a 5% cow dung binder achieved a high calorific value of 39927.05 kcal/kg. The ultimate analysis revealed a composition of 47.49% carbon (C), 5.133% hydrogen (H), 1.557% nitrogen (N), 0.374% sulfur (S), and 45.446% oxygen (O). Therefore, bagasse has a high calorific value and can be used for briquetting to replace fossil fuel and firewood in different applications. In addition, due to its availability, utilizing as fuel source has economic advantage. Graphical abstract

Fossil fuels dominate the world's energy consumption, including transportation, chemicals, and materials generation. Conversely, using conventional energies has resulted in massive environmental damage and climate change. This study looks into developing briquettes from sorghum stalks and groundnut husks utilizing cow dung as a binder for fuel production using the low-pressure compaction method, an important renewable energy source. The briquettes were labeled with cow dung binder compositions (5–25%), ratios (75–95%), and particle sizes ranging from 1 to 3 mm. The raw materials were collected and cleaned, then sun-dried, followed by carbonized and ground using a mortar grinder. Design of Expert (DOE) software, Excel, and analysis of variance (ANOVA) were used to perform numerical and graphical data analyses. After briquetting, the proximate properties of the moisture content were 3.16%, fixed carbon 13.04%, volatile matter 80.20%, and ash 3.6%. The briquette had 51.56% carbon, 6.302% hydrogen, 0.0042% nitrogen, 42.134% oxygen, and 0.00093% sulfur. The calorific value of mixed briquettes varies from 20.08 to 24.36 MJ/kg. The maximum calorific value was achieved with a particle size of 1 mm and a 25% cow dung binder content, as a minimal particle size was preferred. According to the analysis, the created briquettes were smokeless, low in Ash content, and had a high Calorific value for burning above 17 MJ/kg for industrial driving and above 13 MJ/kg for household usage. The result of standardization on the diet of cow dung revealed that grain-fed dung offered a higher calorific value of 20 MJ/kg, while a higher shatter resistance of 90% was recorded using grass straw fed, which outlines the importance of diet on the efficiency of the binder. Developing briquettes from these biomasses can increase job prospects, decrease greenhouse gas emissions, and improve waste management. Graphical Abstract

Rapid industrialization unleashes toxic hexavalent chromium (Cr(VI)) from textile effluents into waterways, threatening ecosystems and human health in water-stressed regions like Ethiopia. This study harnesses abundant corncob waste to fabricate chemically activated carbon (CCAC) via KOH impregnation and pyrolysis, optimizing Cr(VI) removal from real post-biological wastewater of MAA Garment Factory, Mekelle (initial 1.35 mg/L Cr(VI)). Batch experiments using response surface methodology (central composite design, 29 runs) identified optimal conditions: 0.175 g/L dosage, pH 6.5, 75 min contact time, 200 rpm achieving 99.45% removal (residual < 0.007 mg/L, below WHO/EPA limits) and Langmuir qₘ of 515.5 mg/g (R²=0.999). Pseudo-second-order kinetics and FTIR/SEM confirmed chemisorption via –OH/C = O groups on porous surfaces, outperforming many biomass adsorbents. This low-cost, regenerable solution advances circular economy principles, directly supporting SDGs 6 (clean water), 9 (innovation), and 12 (waste valorization). Pilot scaling and multi-metal tests promise industrial viability for sustainable wastewater polishing.

The world's energy is dominated by technology that uses fossil fuels to generate electricity, chemicals, and materials. On the other side, the usage of conventional energies has resulted in massive environmental damage and climate change. This study looks into the development of briquettes from sorghum stalks and groundnut husks utilizing cow dung as a binder for fuel production using the low-pressure compaction method, which is an important source of renewable energy. The briquettes were labeled with cow dung binder compositions (5% to 25%), ratios (75% to 95%), and particle sizes ranging from 1 to 3 mm. The raw material was collected, cleaned, sun-dried, carbonized, and processed using a mortar grinder. DOE software, excel, and ANOVA were used to do numerical and graphical analyses of the data. After briquetting, the moisture content was 3.16%, fixed carbon 13.04%, volatile matter 80.20%, and ash 3.6%. The briquette had 51.56% carbon, 6.302% hydrogen, 0.0042% nitrogen, 42.134% oxygen, and 0.00093% sulfur. The calorific value of mixed briquettes varies from 20.08 to 24.36 MJ/kg. The maximum calorific value was achieved with a particle size of 1 mm and a 25% cow dung binder content, as a minimal particle size was preferred. According to the analysis, the created briquettes were smokeless, low in Ash content, and had a high Calorific value for burning above 17 MJ/kg for industrial driving and above 13 MJ/kg for residential usage. The development of briquetting technology leads to increased job prospects, decreased greenhouse gas emissions, and the establishment of entrepreneurs.

The increasing industrial use of chromium, particularly in the textile sector, presents significant environmental challenges due to the improper disposal of chromium-laden wastewater. This study explores the potential of corncob-derived activated carbon as an effective adsorbent for removing hexavalent chromium (Cr (VI)) from wastewater generated by the MAA Garment Textile Factory in Mekelle, Ethiopia. Corncobs were collected from nearby agricultural fields in Quiha, Mekelle. They were then crushed using an electric grinder to a particle size of less than 100 mesh, followed by carbonization in a furnace at a temperature of 500 ℃. A comprehensive analysis of corncob revealed a moisture content of 7.95%, volatile matter at 75.24%, and an elemental composition of 51.21% carbon, 5.49% hydrogen, 0.3% nitrogen, and 43% oxygen. The functional groups of the activated carbon, chemically activated with potassium hydroxide, were analyzed using FTIR spectroscopy. Experimental results demonstrated a remarkable chromium removal efficiency of 99.45% within 75 minutes at a pH of 6.5 and a dosage of 0.175 grams, with an equilibrium adsorption capacity of 7.67 mg/g. The adsorption characteristics were effectively modeled using the Langmuir isotherm, indicating a maximum adsorption capacity of 515.5 mg/g under optimal conditions, with both pseudo-second-order kinetics and Langmuir model (R² = 0.999) accurately describing the process. This research underscores the feasibility of utilizing agricultural waste for chromium recovery, contributing to environmental management and resource conservation while promoting sustainable industrial practices in Ethiopia and beyond. Future studies should focus on scaling these methods for broader application across various industries to enhance environmental sustainability.