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.

High and variable moisture in wood logs limits their use in continuous carbonization reactors. Artificial drying emerges as a solution to homogenize the moisture of the raw material, optimizing the process, increasing yield, and improving the quality of charcoal. This study aimed to develop an experimental fixed-bed drying system for logs, evaluating the effects of cutting layout (40 cm, 20 cm, and split), diameter class (>12 cm, 12.1–14 cm, 14.1–16 cm, and 16.1–18 cm), and residence time (30, 60, and 90 min) at 300 °C. Split logs showed higher heating and drying rates, positively impacting efficiency. However, split and 20 cm logs subjected to 90 min of drying underwent combustion, indicating operational limits for these layouts under the tested conditions. The heartwood and sapwood regions of split logs heated more rapidly, resulting in higher drying rates and moisture loss, directly affecting drying efficiency. Split logs dried for 60 min showed the best drying efficiency and greatest moisture reduction, making this the most recommended treatment. This study not only demonstrates the technical feasibility of artificial drying of logs for continuous carbonization but also establishes fundamental guidelines for the development of more efficient, safe and sustainable industrial technologies in the charcoal production sector.

A utilização da biomassa lignocelulósica proveniente de resíduos domésticos tem se tornado uma escolha favorável na produção de bioenergia. No estado de Minas Gerais, a cadeia produtiva do pequi (Caryocar brasiliense Camb.) desempenha importante papel econômico e social. No entanto, a comercialização em grande escala desse produto pode gerar resíduos que, se não forem adequadamente gerenciados, representam um desafio ambiental significativo. Neste trabalho, foi avaliado o potencial energético da biomassa da casca de pequi para confecção de briquetes em diferentes proporções de umidade. Foram avaliadas propriedades físicas, mecânicas e térmicas da biomassa in natura em estudo. A caracterização imediata da biomassa revelou um alto teor de material volátil (74,41%), de carbono fixo (22,69%) e cinzas (2,90%), além de um poder calorífico de 14,23 MJ kg-1, mostrando a eficácia do material para produção de energia. A análise química evidenciou 69,38% de extrativos, 10,27% de lignina e 20,35 % de holocelulose. A análise termogravimétrica da casca se mostrou similar com a termo decomposição de biomassas lignocelulósicas. A confecção dos briquetes foi realizada em uma prensa hidráulica em diferentes proporções de umidade (5%, 7,5% e 10%). Os testes de resistência à compressão mostraram que briquetes com menor umidade possuem maior resistência. Os resultados deste estudo sugerem que a densificação da casca de pequi não apenas reduz significativamente o volume dos resíduos, como também resulta em uma diminuição de aproximadamente 90,42% do peso total, facilitando seu manejo e armazenamento, mas também oferece uma solução sustentável para a produção de bioenergia.

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.

The scarcity of information on the combined influence of harvest age and genetic material on the wood quality of Eucalyptus and Corymbia still limits the optimization of charcoal production for the Brazilian steel industry. This study aimed to evaluate the effect of harvest age on the quality of wood and charcoal produced from five genotypes, four Eucalyptus clones and one Corymbia citriodora × C. torelliana hybrid, at five, six, and seven years of age. Physical, anatomical, chemical and energy-related properties of the wood were characterized, in addition to muffle furnace carbonization tests. Increasing harvest age promoted higher basic density (from approximately 440 to 625 kg m ^-3 ), a relative reduction in sapwood proportion, and lower ash content in both wood (~ 0.2–0.6%) and charcoal (~ 0.7–1.7%), enhancing energy performance and suitability for steelmaking applications. The Corymbia citriodora × C. torelliana hybrid stood out at earlier harvest ages due to its high wood density (> 580 kg m ^-3 at 5 years, reaching ~ 625 kg m ^-3 at 7 years) and good charcoal quality, whereas tri-cross Eucalyptus clones met or exceeded the recommended industrial threshold (> 500 kg m ^-3 ) from six years onward. Wood higher heating value remained stable (19.0–20.0 MJ kg ^-1 ), while energy density increased from approximately 8,400 to over 12,400 MJ m ^-3 with age. Charcoal gravimetric yield remained stable (33–35%), and higher heating value ranged from 6360 to 7690 kcal kg⁻¹, with most values above the 7000 kcal kg ^-1 threshold required for steelmaking. The combination of higher lignin content (25–32%), cellulose crystallinity (up to 79%), and basic density resulted in charcoals with high yield and heating value, while low nitrogen (0.04–0.09%) and absence of sulfur indicated a lower potential for atmospheric pollutant emissions. In terms of productivity, the Corymbia hybrid increased charcoal production from 5.5 to 10.7 t ha ^-1 year ^-1 between 5 and 7 years, outperforming Eucalyptus clones by up to 25%. These results demonstrate that the integrated selection of clone and harvest age is decisive for maximizing charcoal yield and quality, contributing to more efficient, competitive, and environmentally sustainable bioenergy production systems in the context of the national steel industry.

Caryocar brasiliense Camb., popularly known as pequi, is a tree species native to Brazil with significant cultural, social, and environmental value, especially in the northern region of the state of Minas Gerais. However, during its commercialization process, a significant challenge is the proper utilization of the waste generated from its shell. This study aims to characterize the biomass and charcoal obtained from pequi bark, evaluating different carbonization temperatures (350, 400, and 450°C). The lignocellulosic characterization indicated a high content of extractives (56.82%) and holocellulose and lignin contents of 29.43% and 13.74%, respectively. The proximate analysis showed 71.36% volatile material, 20.63% fixed carbon, and 8.01% ash, while the calorific value found for the biomass was 18.99 MJ kg-1. In the charcoal, increasing the final carbonization temperature was directly proportional, resulting in higher percentages of ash, fixed carbon, pH, electrical conductivity, and calorific value, with the exception of volatile material and charcoal gravimetric yield, which decreased. The results demonstrated the technical feasibility of converting pequi bark into charcoal, with potential applications in the energy sector, effluent treatment, and as a soil conditioner. It also contributes to regional sustainable development and the mitigation of greenhouse gas emissions.