This integrative critical review examines how biomass and bioenergy can contribute to energy diversification while accounting for constraints related to climate mitigation, energy security, resource availability, and technology readiness. The review combines a targeted literature synthesis with expert-informed insights from the international seminar Energy Transition and Biofuels held at the Federal University of Itajubá in October 2025. The seminar and COP30-related discussions were used as contextual and conceptual inputs, while peer-reviewed literature, policy documents, and technical reports provided the evidentiary basis for the analysis. The manuscript evaluates biomass and biofuels utilization, refinery integration, sustainable aviation fuels, biochar, BECCS, hydrogen synergies, life-cycle assessment, artificial intelligence, and logistics. The synthesis indicates that biomass is not a universal substitute for fossil fuels. Still, it has distinctive value in applications requiring renewable carbon, dispatchable energy, process heat, liquid fuels, carbon removal, and compatibility with existing infrastructure. The analysis also shows that these contributions are contingent on feedstock governance, land and water safeguards, logistics, fertilizer inputs, technology maturity, and verified life-cycle performance. The food–fuel discussion is therefore reframed as a context-specific problem of land-use, access, productivity, and governance rather than a simple competition between energy and food production. The study concludes that bioenergy can most credibly support the energy transition when deployed through differentiated pathways tailored to regional resources, sustainability constraints, and sector-specific decarbonization requirements.

Earth-air heat exchangers (EAHE) provide a promising low-grade heating and cooling solution for buildings in temperate climates, with extensive experimental and numerical studies. However, rational design procedures for building-EAHE systems capable of fully offsetting thermal loads, serving as the sole active conditioning system, remain underdeveloped. This paper establishes practical limits and a rational sizing procedure from this overlooked perspective. The strategy starts by identifying extreme weather conditions (heating or cooling) to set two goals: the required temperature difference along the EAHE, defining heat exchanger effectiveness, and the total airflow rate to compensate building load. To ensure feasible total airflow and prevent infinite flow, supply air temperature must exceed minimum comfort temperature in heating (or fall below maximum comfort temperature in cooling) by a margin called hysteresis. Applying steady-state heat transfer and fluid flow equations yields three key variables: branch pipe length, diameter, and velocity, determining branch airflow. Total airflow is met using parallel branches fitted to available land. With two degrees of freedom, an optimization via minimum entropy generation (EGM) identifies a theoretical optimum and practical design range, minimizing fan energy. This physically grounded method avoids complex CFD or computational optimization, enhancing accessibility for architects and HVAC practitioners. A worked example demonstrates the approach.

Energy recovery from by-products of wastewater treatment plants (WWTPs) can increase operational efficiency and reduce environmental impacts. This full-scale study evaluated the integrated use of biogas from upflow anaerobic sludge blanket (UASB) reactors and the dried sludge produced in a thermal dryer as fuels for the sludge drying process itself. Monitoring covered biogas production and composition, physicochemical and microbiological characterization of the dried sludge, dryer performance, and stack emissions. Biogas production yielded 5.9 & times; 104 MJ d- 1, whereas dried sludge, produced at 1.1 t h- 1 with a total solids content of 88.8% (wet basis) and a dry-basis lower heating value (LHV) of 11.2 MJ kg- 1, supplied 2.96 & times; 105 MJ d- 1. Together, these fuels provided 3.55 & times; 105 MJ d- 1 against a thermal demand of 3.64 & times; 105 MJ d- 1, meeting approximately 97% of the process requirement. The specific consumption of 3.89 MJ kg- 1 of water removed was consistent with values reported for sludge dryers. The dried sludge met the criteria for Class A biosolids under Brazilian regulations, showed relevant macronutrient contents, and, within the measured parameter set, its agricultural use was conditioned on controlling zinc levels. Emissions remained compliant with legal limits, and sludge cocombustion was associated with lower CO and vanadium emission rates and higher particulate matter and NO2 emission rates than the wood-chip-only test, without loss of regulatory compliance. The results indicate that integrating internal energy streams in WWTPs with UASB reactors is an effective strategy for waste valorization and promotion of the circular economy.

Over recent decades, human activities have essentially depended on fossil fuels. The last Intergovernmental Panel on Climate Change reports recommend a shift to renewables and a more energy-efficient economy. To fulfill the potential of bioenergy, tools are required to overcome the complexities of the decision-making processes for viable projects. This work presents a decision-making tool to select the most feasible biomass residues and a case study of the state of Minas Gerais, in Brazil. Among the 13 evaluated criteria, eucalyptus residues demonstrated the highest potential for electricity production, followed by sugarcane bagasse and coffee husks. The choice of Minas Gerais as a case study is important due to its diverse agricultural landscape and the potential for biomass residue generation. The presented methodology uses the Analytical Hierarchy Process (AHP), a multi-criteria decision-making method (MCDM). Thirteen criteria were required to enable the best choice of biomass residue alternatives for electricity generation, which experts in the bioenergy field evaluated. The technical criterion was shown to be the one with the highest degree of importance. The results of the study identified that CO2eq emissions (11.46%) and electricity demand (ED) were the most relevant sub-criteria for prioritizing the viability of agricultural waste. Eucalyptus was ranked as the most promising biomass, followed by sugarcane bagasse and coffee husks. In addition, the use of GIS tools made it possible to map the regions with the greatest potential in Minas Gerais, providing a robust approach to identifying strategic sites for bioenergy.

This study presents a methodology for assessing the technical and economic potential of electricity generation from biomass residues, using thermochemical conversion technologies. Applied in the state of Minas Gerais, Brazil, the analysis focuses on residues from corn, soybean, coffee, eucalyptus, and sugarcane. A multi-criteria decision-making (MCDM) approach, integrated with GIS, was used to identify the most viable biomass sources and most suitable conversion technologies, namely the Rankine cycle, organic Rankine cycle, and gasification with internal combustion engines, based on Technological Readiness Levels (TRLs). Eucalyptus emerged as the most suitable residue due to its high energy density, while sugarcane residues were the most abundant. The economic feasibility analysis indicates levelized costs ranging from USD 0.10 to USD 0.24 per kWh, with the conventional Rankine cycle emerging as the most cost-effective option for plants with a capacity exceeding 5 MWe. The proposed methodology supports strategic bioenergy planning by integrating geospatial, technological, and economic factors.

Harnessing soil low-depth thermal energy to support mechanical systems for buildings’ thermal comfort has been considered one pathway for reducing the buildings’ energy demand (avoid) and adding renewable energy to buildings. The literature addressed those issues in many ways. However, this work introduces two key novelties: (1) the optimization of the duct’s configuration and (2) a strategy for the optimal use of the duct assembly to attend to the time-variable energy demand throughout the year. Both are based on the minimization of entropy generation. The irreversibility mechanisms relate to heat transfer and fluid flow in the EAHE and the coupled building-environment-soil-EAHE thermodynamic system. This approach was carried out by numerically solving the mathematical model (3-D, transient, heat-conduction finite volume with an upwind scheme and heat convection inside the ducts by known convective correlations) developed considering a solid parallelepiped domain on the ground (WLH), crossed parallel to its central horizontal axis by several channels of rectangular section (wLh), positioned in arrangements of variable geometry. The design degrees of freedom are the number of ducts, their dimensions, and the spacing among them while meeting prescribed thermal comfort temperatures for each season. Results show that if the energy access of the EAHE is enhanced or optimized for a date in the year, it may not be helpful in other seasons, thus showing that the greater access of the ground thermal energy throughout the year requires a compromise in the EAHE design.

It is well known that the widespread utilization of fossil fuels contributes to climate change, so exploring new sustainable energy sources is more important than ever for energy transition pathways. The variability and intermittency of solar and wind sources are of concern. Hydrogen (H2) utilization as an energy carrier can address this issue. The technology for producing hydrogen from biomass gasification has not yet reached a high level of technological maturity. The main novelty of this work is to evaluate the state of the art of the technologies for producing H2 from solid biomass, taking into account technological, economic, and environmental indicators and the results of a bibliometric study, and also the calculation of the technical potential for hydrogen production through biomass gasification on a worldwide and Brazilian scale. The most frequently mentioned technology to boost H2 production efficiency is the addition of catalysts to the gasifier. Primary catalyst utilized in biomass gasification for hydrogen enhancing enhancement, such as olivine, CaO, and CeO2-Ni-CaO are reviewed in the article. As a result, the syngas had an H2 content rise of 511%, 659.6%, and 853.4%, respectively. According to the reviewed literature, the levelized cost of hydrogen production can reach an average value of USD3.15/kg of H2, and the average yield is 0.1 kg-H2/kg-biomass. The worldwide potential for hydrogen production from solid biomass in an optimal trends scenario for 2050 is estimated to be 45.03 EJ, and Brazil’s potential is 6.5 EJ.

Carbon capture, utilization, and storage (CCUS) has been recognized as a crucial path to mitigating the effects of greenhouse gas emissions on climate change. Mineral Carbonation (MC) processes are among the safest and most promising alternatives for CCUS due to on-site product stability. However, technical challenges need to be overcome to scale up the technology, such as energy penalties and sufficiently fast kinetics. The constructal design method provides a path to achieve those goals altogether. This paper first addresses the constructal design of a mineral carbonation porous bed reactor for post-combustion carbon capture. Analytical models allowed to obtain optimized parameters for the aspect ratio of the elemental volume, which is then packed in hierarchical flow structures to minimize pressure losses (energy penalties). Numerical full-scale models show the validity of the proposed relations. The trade-off between pressure losses and rate of reaction is then explored by the ratio with which the first construct is filled with reacting material. Results for the multi-scale design show that it is possible to associate geometric configurations with pressure drops for the carbon capture devices and to seek configurations that lead to lower energy expenditure. The findings can be applied for other types of fixed bed reactors.

Sludge is the solid byproduct resulting from sewage treatment, excluding screened materials and sand. Effective management of sludge is crucial to ensure the anticipated environmental and sanitary benefits of sewage systems. The formation and chemical composition of sludge are significantly influenced by the wastewater treatment technology applied during the liquid phase. For instance, in traditional aerobic treatment methods like activated sludge, the average per capita sludge production reaches 70 gSST/day. In this context, we capitalized on thermal drying, utilizing methane as an energy source produced in sewage treatment. Following the drying process, the sludge retained 84

The Constructal Law has recently passed its 25th anniversary. At the 2023 Constructal Law Conference in Turin, we have looked back, presenting insights on how knowledge of the Constructal Law has spread globally. Here, we expand on our earlier article. Since our initial study, we have seen a daily average of three new publications that mention the term “constructal” in the Scopus database. In parallel, the number of laboratories affiliated with this research has grown from 10,956 to 12,787. Overall, we see a stable annual growth rate exceeding 25 % in our corpus, as well as a global coverage denser than ever. Studying old and new data, we expand on our earlier article not only with new statistics but also with a new insight: the dissemination paths of constructal thinking were initially tree-shaped, but they have presently become a network of overlapping trees. This insight seamlessly aligns with the predictions of the Constructal Law. According to the Constructal Law, trees grow and spread to become forests of trees, which eventually look like networks. This Constructal Law prediction is evidently confirmed in our corpus.

This paper makes projections of the theoretical and technical potentials of bioenergy supply for 2050. The projections consider changes in available land for bioenergy and food for the global demand and advancements in yield, productivity, expansion of bio-waste recovery, and energy conversion. We present a literature review on projections. We introduced a novel logical and transparent forecasting model. Three future scenarios were established: business as usual (BUS), optimistic trends (OPT), and full adaptation response (FAR). The projection is carried out based on four adjusting factors. An uncertainty analysis was carry-out based on a Monte-Carlo method. Projections of bioenergy production in 2050 were compared with other projections in the literature. The FAR scenario showed that it would be possible to produce twenty-one times the current primary bioenergy supply and to even supply all global primary energy demand in 2050, mostly by energy crops. The assumptions adopted for the BUS and OPT scenarios make their projections more likely. Therefore, the contribution of bio-energy in the global energy matrix is expected to be between 64 and 313 EJ (7.5%-37%) in 2050. There would be a significant change in the composition of the bioenergy supply from today's mostly firewood to energy crops and biowastes. The technical potential for fuel and electric power mostly follow the supply trends for primary bioenergy (theoretical). The potential avoided greenhouse emissions are estimated. The heuristics and the level of transparency of the novel model will allow adjustments and exploration of other scenarios as time passes.

This work shows an analysis of the construction of the geometric arrangement of blocks mounted on the surfaces of a channel subject to a laminar, incompressible flow, with forced convection in a two-dimensional domain. The construction is carried out through a construction function based on the system performance indicator, i.e., the heat transfer rate from the arrangement to the fluid flow. For the assembly of the arrangement, a methodology based on the principles of the Constructal Theory is used. To solve the convection problem, the mass, momentum and energy conservation equations are solved with the Finite Volume Method, more precisely using the FLUENT software. The objective of this work is to understand how the construction of the initial blocks of the array (N = 3 blocks) occurs in an area occupied by the channel in flows with forced convection and Reynolds and Prandtl numbers of ReH = 100 and Pr = 0.71. The best and worst cases for N = 2 led to an increase of 93.21% and 28.59%, respectively, compared to the N = 1 case. Results demonstrated that the construction that led to the best thermal performance was the configuration where there is the highest momentum between blocks (intensifying the convective heat transfer coefficient) and with the lowest interaction between the thermal boundary layers, which is in agreement with the principle of optimal distribution of imperfections.

Water resources are increasingly scarcer and more expensive to collect, treat and distribute. Advanced industrial wastewater treatment methods, such as electrocoagulation (EC), have become more via-ble. However, the design of EC reactors is very complex and costly since it varies significantly with wastewater composition. In order to ease the efforts in design, this paper proposes a novel proce-dure for the simulation of EC systems, which couples computational fluid dynamics (CFD) with a kinetic model for pollutant removal. A CFD model was calibrated with an experimentally fitted kinetic model for Reactive Blue dye 5G removal from synthetic solution to predict the residual concentration profile in a lab-scale continuous flow reactor. Simulations were carried out with a current density of 8.65 mA center dot cm-2, initial dye concentrations of 25 and 40 mg center dot L-1, and flow rates of 0.5-2 L center dot min-1. Results were compared to experimental data from a 23-point sampling mesh of the reactor. The model suc-cessfully predicted the reactor concentration profile for a range of low flow velocities (from 0.5 to 1 L center dot min-1), presenting a relative error of less than 2% for a dye removal of 87%-98% at the reactor exit. This paper shows that coupling a kinetic model for pollutant removal based on experimental obser-vation with CFD offers reliable information for EC reactor design with a good compromise between time and resources. The use of computational tools with the proposed methodology can aid in designing EC reactors, thus helping to solve a major obstacle to expanding this promising technology.

A qualidade do ar nos grandes centros é um tema de preocupação constante. Além dos poluentes primários emitidos pelas fontes fixas e/ou móveis, também são formados os poluentes secundários, por reações químicas entre os poluentes primários e a luz solar.

Com o crescimento da frota de motociclos e devido à relevância de suas emissões de gases poluentes, foi implantado o PROMOT em 2002. O programa estipulou um cronograma para redução gradual das emissões, sendo necessária a adoção de novas tecnologias e sis