Improper waste disposal is one of the leading causes of environmental pollution, impacting soil, water, and air quality. In coffee plantations, each kilogram of beans produced generates an equal amount of husk, emphasizing the urgent need for sustainable practices to process this residual biomass into valued products. This study aimed to evaluate the potential of coffee husks for pellet production. Three coffee husk types were selected with distinct chemical compositions and granulometries: I (>5.3 mm), II (>2.6 mm and <5.3 mm), and III (<1.77 mm). The biomass was characterized for elemental, structural, and proximate composition. Pellets were produced with two knife heights (15 and 20 mm) and assessed for moisture content, density, length, and mechanical resistance, which were compared with the EN 14691-6 standard (DIN, 2012). Pelletizer productivity was also evaluated. Pellets from biomass III had an ash content of 12.09%, exceeding the <10% requirement. Other treatments met the ash content standard, category B. Pellets from biomass I (17.55%) and II (18.1%) at 15 mm length did not meet the <15% moisture content standard. The remaining pellets met category B standards. Only pellets from origin III (1.62%) met the nitrogen content requirement for international trade (<2%). Pelletizer productivity was higher with smaller granulometry biomass. Coffee husk has demonstrated its potential for pellet production, highlighting the valorization and use of this waste for clean energy generation, contributing to greenhouse gas emissions mitigation, and strengthening circular economy.

This study explores a circular economy approach in charcoal production, utilizing combustion gases from the process itself to optimize efficiency and quality, minimizing waste and reducing emissions. The research investigates the pre-drying of Eucalyptus sp. wood with these gases before carbonization, through an innovative system that directs gases from the carbonizing furnace to a separate drying furnace. Wood samples were dried at 120 °C and 150 °C for 15, 22.5, and 30 h before carbonization. The analysis included the gravimetric yield of charcoal, semi-carbonized wood, and fines, in addition to evaluating key charcoal properties. Results demonstrated that drying with combustion gases at 150 °C increased the charcoal yield by 7%, regardless of drying time. Furthermore, this pre-drying improved charcoal quality, raising fixed carbon content from 74.68% to over 81% and reducing volatile matter from 24.40% to below 18%. These findings highlight that the utilization of combustion gases for wood drying not only significantly enhances the efficiency and quality of charcoal production but also contributes to the reduction in greenhouse gas emissions, promoting a more sustainable and environmentally friendly alternative compared to conventional methods.

Brazil is the world’s largest coffee producer, resulting in the production of 1 kg of husk and 0.5 kg of parchment for every 1 kg of coffee beans. Given the large amount of biomass and the constant need for energy production, this study raises the possibility of using waste for pellet production. Samples of coffee husks and parchment were characterized by moisture content (dry basis), proximate analysis (volatile matter, ash and fixed carbon), calorific value, elemental analysis, and thermogravimetry, and the pellets were characterized by moisture content (dry basis), bulk density, energy density, mechanical durability, percentage of fines, and hardness. The results were compared with the ISO 17225-6. The parchment had a higher carbon, 49.5%, C/N 45.1%, and lignin 26.2% and lower ashes 2.8% and extractives 14.2%, resulting in higher calorific value, while coffee husks obtained 46.5%, 26.3%, 24.6%, 5.5%, and 34.3%, respectively. Pellets produced with parchment had a higher density 622 kg/m³ and lower moisture content 10.5%, resulting in higher energy density. The parchment pellets met all the parameters of the ISO 17225-6, while the coffee husk pellets did not meet the parameters for moisture, which is less than 15%, and bulk density, greather than 600 kg/m³. Both types of biomass showed potential for pellet production, with further studies needed on coffee husks.

Bioenergy production from agro-industrial waste has the potential to contribute to climate change mitigation. In Brazil, the pequi (Caryocar brasiliense Camb.) production chain makes an economic, environmental, and social contribution. However, the collection and processing of the fruit produce large amounts of waste, such as the peel, whose improper disposal leads to significant environmental impacts. This study evaluated how moisture and carbonization temperature influence the energy properties of charcoal briquettes made from pequi peel waste. Carbonization was performed at two final temperatures (360 °C/480 °C) with a heating rate of 1.5 °C min⁻¹ and residence times of 4 h and 5 h 20 min, respectively. Carbonization yields were calculated based on dry mass. Briquettes were produced from pequi peel at moisture contents of 5%, 7.5%, and 10% (wet basis). After carbonization, the charcoal briquette samples were characterized by proximate analysis, higher heating value (HHV), bulk density, energy density, and mechanical durability. Carbonization temperature exerted a more pronounced effect on the properties of the carbonized briquettes than the initial moisture content. Carbonization at 480 °C increased the fixed carbon content (76.38%, 74.25%, and 75.10% for treatments 1, 2, and 3) and the HHV (25.10–25.31 MJ kg⁻¹), while reducing the gravimetric yield (32.84–33.25%). The influence of moisture content was more evident in carbonizations carried out at 360 °C, indicating a temperature-dependent interaction. The use of pequi peel for solid biofuel production promotes the valorization of agro-industrial residues and supports strategies aimed at the circular bioeconomy and the decarbonization of the energy matrix.

The world’s energy matrix faces challenges in replacing fossil fuels and reducing greenhouse gas emissions. Pellet production is effective for the correct disposal of agricultural waste through the production of biofuels. The objective of this work was to produce and characterize pellets from blends of pine and coffee straw residues, in addition to their compliance with ISO 17225-6/2021. The biomasses were subjected to analysis of dry and wet base moisture, bulk density, upper and lower calorific value (HCV and LCV dry), immediate, structural and elemental chemistry, chloride content, and thermogravimetric behavior. The pellets were produced in nine blends with the Amandus Kahl pellet mill, model 14-175, being submitted to analysis of productivity, moisture in dry and wet base, HCV and LCV dry, chloride, immediate chemistry, hardness, diameter and length, durability and percentage of fines, the analyses were compared by the Scott-knott test at the level of 95% probability. The blends that presented the best overall performance were 100% pine and a mixture of 87.5% pine and 12.5% coffee straws, especially for the higher calorific value (20.65 and 20.65 MJ/kg), moisture (8.98 and 9.17%), and ash (0.22 and 1%), but had limitations regarding mechanical durability (96.74 and 97.12%). The use of blends in pellet production is promising to promote the sustainable use of agricultural waste and the generation of clean energy.

Forest operations consume a large amount of fossil fuels. Storing wood in the field reduces the weight of the wood, optimizing transportation and reducing fuel consumption. However, there are few studies linking these variables. The objective was to evaluate the drying of logs with different diameters and assess the fossil fuel consumption considering the mass of dry wood transported. Eucalyptus logs were divided into two diameter classes: 6 ≤ D1 ≤ 11 cm and 11.1 ≤ D2 ≤ 14 cm. These logs were arranged in a stack, divided into base, intermediate, and top positions, and subjected to drying. The wood moisture values were correlated with the amount of transported dry wood, fuel consumption, and costs. These calculations were based on a vehicle with a load capacity of 41.6 Mg, a fuel consumption rate of 1.82 L/km, and a road cost of 0.51 R$·Mg⁻¹·km⁻¹. The moisture content was lower in smaller-diameter logs located at the top of the storage stack and higher in larger-diameter logs in the intermediate position and in both diameter classes at the bottom position after 365 days of drying. Storage for 365 days, on average, increased the dry wood transport capacity by 90%, resulting in similar gains in fuel economy and the final cost of transportation. Storing wood outdoors has proven effective in reducing its moisture content, resulting in lower fossil fuel consumption during forestry operations, reducing environmental impact, and generating economic gains.