The cooling stage is the main bottleneck in charcoal production using masonry kilns, as it can account for several days of downtime before kiln unloading and directly limits process productivity. The objective of this study is to develop and validate a Computational Fluid Dynamics (CFD) model capable of predicting the natural cooling stage of masonry charcoal kilns. The proposed model accounts for coupled heat transfer by conduction, natural convection, and radiation. The charcoal bed is modeled as a packed bed permeated by pyrolysis gases. Heat transfer between the charcoal particles and the gases in the bed is accounted for by adding a source term to the energy equation. The kiln exchanges heat with the environment by natural convection and radiation. To avoid explicitly simulating the carbonization stage, an initial temperature field is reconstructed from experimental measurements at the onset of cooling. Model predictions for a two dimensional geometry are validated against full-scale experimental data obtained from a rectangular masonry kiln, with a total of ten temperature measurements distributed in the charcoal bed, gas region, and kiln walls. All temperatures predicted by the model have a mean absolute percentage error below 6.1%. The best performance is achieved for wall temperatures, with mean absolute percentage errors below 3% and an R2 of 0.98. A sensitivity analysis indicates that kiln cooling is primarily governed by the thermal capacity of the walls and external heat transfer resistances, whereas gas-bed heat transfer parameters have a secondary influence. The proposed CFD framework provides an important tool for analyzing the natural cooling of masonry kilns and offers a basis for the design and optimization of technologies aimed at reducing cooling time and increasing charcoal production productivity.
Aggregate hierarchy, the organization by which microaggregates form progressively larger, structurally distinct macroaggregates, is central to soil stability, governing resistance to erosion and response to disturbance. However, the mechanisms and extent of hierarchical breakdown remain poorly quantified across different soil types and land management. In this study, we addressed this gap by evaluating the stepwise breakdown of soil structure into aggregates, driven by incremental sonication energy, across a range of soils differing in mineral composition and management practices. By applying a quantitative modelling framework, we derived three key parameters: the disruption constant (k₁), reflecting the rate of aggregate breakdown; the dispersion constant (k₂), which describes particle release; and the critical energy threshold (Ecrit), which denotes the transition point between aggregate disruption and full particle dispersion. These parameters were used to evaluate the degree of hierarchy in aggregate breakdown, whereby higher k₁/k₂ ratios signal a pronounced stepwise (hierarchical) disintegration, and ratios near unity indicate direct dispersion into clay-sized particles. Our results indicated that soils enriched in 2:1 phyllosilicate clay minerals, such as Luvisols, exhibited markedly higher k₁/k₂ ratios in larger aggregates, demonstrating a structured, multi-step breakdown process. In contrast, oxide-rich soils like Ferralsols and Andosols typically lacked such hierarchy, dispersing rapidly into smaller fractions, which is consistent with a stronger role of mineral-mineral binding relative to organic-mediated aggregation. In the studied Luvisols, direct seeding was associated with higher stability (higher Ecrit) and a greater degree of hierarchy than conventional tillage, emphasizing the synergistic effects of organic matter input and reduced disturbance on soil structural integrity. These findings highlight the mechanistic roles of distinct pedogenic groups and management practices in controlling aggregate hierarchy and stability. Our study shows that sonication-derived indicators can differentiate not only distinct pedogenic groups but also soil management. These indices can be further developed to provide a quantitative insight into the structural organization that underpins water retention, erosion resistance, and other soil functions critical for conservation.
This study examines renewable energy consumption, renewable energy technology trade, and agricultural productivity relationships across 53 African countries (1995–2023) using cross-sectional augmented distributed lag (CS-DL) estimation with 4 productivity measures: Solow residuals, agricultural output per capita, output per worker, and stochastic frontier efficiency. Results reveal that renewable energy consumption generates mixed long-run effects on productivity (coefficients: − 0.95, + 1.60, − 0.99, and − 0.16 across the four productivity measures, respectively), while renewable energy technology trade exhibits consistently negative effects (− 0.37, − 1.83, − 0.36, and − 0.13). However, their interaction produces uniformly positive effects (0.10, 0.36, 0.10, and 0.03), confirming essential complementarity between domestic adoption and international technology transfer. Robustness analyses reveal substantial heterogeneity; low productivity countries demonstrate interaction coefficients of 0.00007–0.0002 compared to high productivity countries’ 0.00000014–0.0002. Renewable energy adoption follows discrete patterns with 87.3
In post-mining landscapes of Amazonia, evaluating faunal responses during early successional stages is essential for understanding habitat restoration trajectories and for identifying sensitive bioindicators capable of tracking ecosystem recovery. Herbivorous beetles constitute a highly host-dependent group whose diversity, specialization, and spatial turnover can reveal how resource heterogeneity and vegetation structure shape community reassembly in regenerating ecosystems. The objective of this study was to assess whether a five-year period of natural regeneration provides sufficient structural and resource heterogeneity to support a weevil community (Coleoptera: Curculionidae) converging toward that of adjacent forest remnants. We sampled leaf-dwelling Curculionidae across seven natural regeneration sites and seven altered primary forest remnants using standardized arboreal arthropod beating methods. We recorded 482 individuals across 114 morphotypes, with forest remnants harboring greater richness, higher effective diversity, and distinct dominance–evenness patterns compared to natural regeneration sites. Tree richness was the main predictor of weevil abundance, species richness, and diversity of common taxa. Both habitats exhibited high species turnover among sampling units, yet multivariate analyses revealed clear compositional differences between forest and regenerating areas. Our findings indicate that five years of natural regeneration is insufficient for re-establishing a Curculionidae community structurally or compositionally comparable to forest remnants. These results demonstrate that the recovery of weevil assemblages remains strongly limited by reduced host-plant heterogeneity and suggest that enrichment planting of key tree species may accelerate restoration trajectories.
Valorizing macrophyte biomass as animal feed represents a promising circular economy strategy, yet its safety remains uncertain. To address this, the present study explicitly evaluates the human health risks associated with consuming Nile Tilapia (Oreochromis niloticus) fed with Azolla spp. biomass cultivated during a 10-day phytoremediation period in swine wastewater rich in copper (Cu) and zinc (Zn). This study addresses this issue through a Quantitative Chemical Risk Assessment (QCRA) supported by Monte Carlo Simulation. Results indicate that Zn poses no significant risk to adults or children, whereas Cu presents a considerable concern, particularly for children and under 16 h light conditions. Sensitivity analysis identifies plant metal concentration and fish developmental weight as the main risk drivers. The model demonstrates that the risk is manageable rather than prohibitive: a controlled 15-day supplementation period effectively reduces Cu hazards up to sixfold in adults and 12-fold in children. Safety is therefore dependent on biomass supplementation duration, offering a practical route to safely incorporate phytoremediation biomass into aquaculture. This study establishes the first quantitative framework for assessing and managing metal transfer risks, transforming a theoretical circular economy concept into a viable and evidence-based practice for sustainable aquaculture systems.
