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Climate risk assessment is critical for organisations, especially in sectors such as the processed food sector in Colombia. This study addresses the identification and assessment of the main climate transition risks using an approach that combines fuzzy logic with several multi-criteria decision-making methods. This approach makes it possible to handle the inherent imprecision of these risks and to use linguistic expressions to better describe them. The results indicate that the most critical risks are price volatility and availability of raw materials, the shift towards less carbon-intensive production models, increased carbon taxes, technological advances, and associated development or implementation costs. These risks are the most significant for the organisation studied and underline the need for investments to meet regulatory requirements, which are the main financial drivers for organisations. This analysis highlights the importance of a robust framework to anticipate and mitigate the impacts of the climate transition. [ABSTRACT FROM AUTHOR]

Thermodynamic criteria as a feedstock selection tool for decentralised downdraft gasifiers coupled to spark-ignition engines are presented in this work. The methodology consists of an energy and exergy analysis of gasification process. The analysis is carried out by computational modelling of the gasification process as a function of biomass type (ultimate analysis, moisture content and heating value) and fuel/air ratio. Considering a system operating with different wood species, analysed parameters are gas heating value, energy and exergy efficiencies and engine fuel quality (EFQ). With a fixed fuel/air ratio (2.6) and moisture content (20%wt), it is highlighted that as the carbon-oxygen molar ratio of wood decreases from 2.0 to 1.78 as model input, reaction temperature increases by 9%, energy and exergy efficiencies diminish by 1.8% and 4.2%, respectively, while EFQ increases by 3.2%. Therefore, for decentralised power plants, biomass should be selected to produce higher EFQ. [ABSTRACT FROM AUTHOR]

The effect of composition and heating value of torrefied biomass under an oxidizing atmosphere at different conditions (180, 210, and 240 °C during 30, 75, and 120 minutes) was studied relative to downdraft gasification performance. An extended model for gasification in thermochemical equilibrium was used to evaluate the effect of pretreated biomasses, fuel to- air equivalence ratio, and char byproduct production on the producer gas composition, reaction temperature, cold gas efficiency (CGE), and the engine fuel quality (EFQ). The model was validated with experimental data, reaching a global relative error of 8.5%. For raw or torrefied biomasses, with regard to char production, the CGE decreases if char increases; this is due to the fact that the process tends to combustion regimes when a lower amount of carbon is involved in the gasification reaction. Otherwise, the CGE and EFQ increase (up to 80% and 2.5 MJ/kg, respectively) if fuel-to-air ratio increases. With regard to the torrefied biomass, it is highlighted that CGE and EFQ increase from 77% to 82% and from 2.2 MJ/kg to 2.5 MJ/kg, respectively, when the torrefaction conditions (temperature and/or time) increase. This behavior is related to the increase of the autothermal zones in the gasification process and due to the higher heating value of torrefied biomass. [ABSTRACT FROM AUTHOR]

Socioeconomic conditions and the main firewood species used for cooking in three Colombian regions are studied in this work. The species collected were Cordia alliodora, Guazuma ulmifolia, Eucalyptus grandis, and Pinus patula. The used patterns of biomass and socioeconomic conditions of the selected regions were defined by means of secondary information. Firewood was physicochemically characterized and the species are compared with fossil fuels with regard to emissions of CO2, energy density, and costs. The studied regions require solutions to use firewood in eco-efficient systems, since in these rural regions people use biomass as an energy source. Studied firewood species are suitable to be gasified in fixed bed reactors due to their high volatile matter content (>80%) and low ash content (<1.8%). Pinus patula is the one with the highest fuel value index, mainly due to its low ash content (0.4%). The firewood consumption in advanced stoves has environmental advantages resulting from its low CO2 emissions: a cubic meter of Eucalyptus could replace 113 liters of kerosene or 120 m3 of natural gas for cooking applications. [ABSTRACT FROM AUTHOR]

The objective of this work was to study the effect of torrefaction temperature on properties of patula pine (Pinus patula) wood that could be of interest for further thermochemical processing. Torrefaction temperature was varied from 200 to 300 °C for 30 minutes using a batch spoon type reactor. Raw and torrefied materials were characterized for proximate and ultimate analyses, thermogravimetry, and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). Results showed that torrefied pine has greater higher heating value and chemical exergy due to the reduction of O/C and H/C ratios. Compared with raw biomass, the material torrefied at 200 and 250 °C did not present significant changes in chemical composition and thermal behavior. Conversely, material torrefied at 300 °C did show important changes in both chemical composition and thermal behavior. Py-GC/MS results suggested that the main constituents of biomass, i.e., hemicellulose, cellulose and lignin, suffer a progressive thermal degradation with increase in torrefaction temperature. [ABSTRACT FROM AUTHOR]

In this work is studied the effect of biomass packing factor (PF) and oxygen enriched air as gasifying agent (GA) on fixed bed biomass gasification. Oxygen concentrations in GA are 21, 24 and 29% vol. The biomass used as fuel is Jacaranda Copaia wood with three defined particle forms: square prism, cylindrical and chips. Flame front velocity and biomass consumption rate increase with oxygen concentration in the GA. These results are due to smaller amount of nitrogen involved in the process, which leads to decrease thermal energy losses by nitrogen heating. Moreover, lower convective cooling effect of gas over solid phase and lower radiation attenuation in the solid are reached with less nitrogen concentration in GA. The efficiency slightly increases when PF increases, this is due to less radiation penetration from the oxidation zone to drying and pyrolysis stages, thereby biomass consumption rate decreases. [ABSTRACT FROM AUTHOR]

SUMMARY This study aimed at presenting a model to simulate downdraft biomass gasification under steady-state or unsteady-state conditions. The model takes into account several processes that are relevant to the transformation of solid biomass into fuel gas, such as drying; devolatilization; oxidation; CO2, H2O, and H2 reduction with char, pressure losses, solid and gas temperature, particle diameter, and bed void fraction evolution; and heat transfer by several mechanisms such as solid-gas convection, bed-wall convection, and radiation in the solid phase. Model validation is carried out by performing experiments in two lab-scale downdraft fixed bed reactors (unsteady-state conditions) and in a novel industrial pilot plant of 400 kWth-100 kWe (steady-state conditions). The capability of the model to predict the effect of several factors (reactor diameter, air superficial velocity, and particle size and biomass moisture) on key response variables (temperature field, maximum temperature inside the bed, flame front velocity, biomass consumption rate, and composition and calorific value of the producer gas) is evaluated. For most response variables, a good agreement between experimental and estimated values is attained, and the model is able to reproduce the trend of variation of the experimental results. In general terms, the process performance improves with higher reactor diameter and lesser air superficial velocity, particle size, and moisture content of biomass. The steady-state simulation appears to be a versatile tool for simulating different reactor configurations (preheating systems, variable geometry, and different materials). Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We consider M/G/1-type Markov chains where a transition that decreases the value of the level triggers the phase to a small subset of the phase space. We show how this structure—referred to as restricted downward transitions—can be exploited to speed up the computation of the stationary probability vector of the chain. To this end we define a new M/G/1-type Markov chain with a smaller block size, the G matrix of which is used to find the original chain's G matrix. This approach is then used to analyze the BMAP/PH/1 queue and the BMAP[2]/PH[2]/1 preemptive priority queue, yielding significant reductions in computation time. [ABSTRACT FROM AUTHOR]

Visual analytics (VA) is a paradigm for insight generation by using visual analysis techniques and automated reasoning by transforming data into hypotheses and visualization to extract new insights. The insights are fed back into the data to enhance it until the desired insight is found. Many applications use this principle to provide meaningful mechanisms to assist decision-makers in achieving their goals. This process can be affected by various uncertainties that can interfere with the user decision-making process. Currently, there are no methodical description and handling tool to include uncertainty in VA systematically. We provide a unified workflow to transform the classic VA cycle into an uncertainty-aware visual analytics (UAVA) cycle consisting of five steps. To prove its usability, three real-world applications represent examples of the UAVA cycle implementation and the described workflow. [ABSTRACT FROM AUTHOR]

Microalgal biomass has been widely investigated as a source of renewable energy, but currently, some alternatives are not economically competitive. Thermochemical conversion of biomass is an alternative way to transform their organic compounds into liquid and gaseous fuels. The aim of this work is twofold; first, the pyrolytic process of the microalga Botryococcus braunii (BB) by thermogravimetric analysis, as well as the relevant reaction kinetic constants and related activation energies, is assessed. Secondly, a sensitivity analysis of the biomass gasification process with air using a thermochemical model was conducted to predict the composition of a syngas as a function of the biomass moisture content and the biomass/air ratio. The results showed that BB biomass is composed mainly of carbon (62.4 wt.%) with volatile solids of 84 wt.%, while the fixed carbon represents around 7 wt.%. Additionally, observed values for heating (27.86 MJ kg−1) and activation energy (~ 110 kJ mol−1) were different from other algal feedstocks due to the capacity of accumulation of liquid hydrocarbons of this. On the other side, the gasification process showed it was found that the moisture content in the biomass and biomass/air ratio variables are key parameters for reaction temperature and producer gas composition. Accordingly, with a suitable combination of these variables, it is possible to obtain a syngas composed of gaseous species with high energy content (CO, 18 vol.%; H2, 17 vol.%; and CH4, 2 vol.%.), which can be transformed through processes such as Fisher-Tropsch process into liquid biofuels such as kerosene or gasoline. [ABSTRACT FROM AUTHOR]

In this work, chemical properties and structure of patula pine wood chips torrefied under air atmosphere are studied. Oxidative conditions instead of inert environment are an interesting way to reduce torrefaction operating costs. In this way, the torrefaction process was carried out in a batch rotary kiln by varying temperature (180, 210, and 240 °C) and residence time (30, 75 and 120 min). Sample amount (∼50 g), heating rate (10 °C/min), airflow (1 slpm), and particle size (between 10 and 20 mm) were fixed. Proximate, ultimate, and heating value analyses, as well as the contents of hemicellulose, cellulose and lignin of raw and torrefied biomasses were determined. Similarly, changes in thermal behavior by DTG, chemical structure by FTIR, surface area by BET, and cell-wall structure by SEM were analyzed. A severe degradation of both hemicellulose and cellulose was found at 240 °C, and a char-like material rich in lignin with high LHV is obtained. At this temperature, oxidation reactions are favored leading to highest specific surface area (174.95 m 2 /g) at 75 min. In addition, the reactivity of torrefied biomasses were higher than the raw material; particularly, those produced at 180 and 210 °C. Likewise, their structure exhibited a higher aromaticity with torrefaction severity. Therefore, torrefaction under air conditions upgrades the quality of patula pine wood as a solid biofuel for further thermochemical processing such as combustion or gasification. [ABSTRACT FROM AUTHOR]

The effects of torrefaction under an oxidizing atmosphere on the physicochemical properties of patula pine wood chips were studied. Raw and torrefied pine were characterized to evaluate the effect of temperature and residence time on biofuel properties, such as bulk density, equivalent Hardgrove grindability index (HGIeq), ultimate and proximate analyses, heating value, and fuel value index (FVI). In contrast, the torrefaction process was characterized by mass and energy yields, and by the energymass co-benefit index (EMCI). Torrefaction was performed in a rotary kiln at temperatures between 180 °C and 240 °C during residence times between 30 min and 120 min. The torrefaction process under an oxidizing atmosphere tended to increase the fixed carbon/volatile matter ratio (from 0.19 to 2.5), while the H/C and O/C atomic ratios decreased 73% and 55%, respectively. The best properties of wood reached in the experimental plan were obtained at 210 °C during 75 min. For this torrefaction condition, energy yield, FVI, and EMCI were 85.91%, 1.91 MJ/cm3, and 4.41%, respectively. Additionally, the lower heating value for torrefied pine (18.65 MJ/kg) was higher than for the raw material (17.76 MJ/kg), and the HGIeq was 17% greater, which resulted in a better grindability behavior. [ABSTRACT FROM AUTHOR]

The production of synthetic or substitute natural gas (SNG) from coal is a process of interest in Colombia where the reserves-toproduction ratio (R/P) for natural gas is expected to be between 7 and 10 years, while the R/P for coal is forecasted to be around 90 years. In this work, the process to produce SNG by means of coal-entrained flow gasifiers is modeled under thermochemical equilibriumwith the Gibbs free energy approach. The model was developed using a complete and comprehensive Aspen Plusmodel. Two typical technologies used in entrained flow gasifiers such as coal dry and coal slurry are modeled and simulated. Emphasis is put on interactions between the fuel feeding technology and selected energy output parameters of coal-SNG process, that is, energy efficiencies, power, and SNG quality. It was found that coal rank does not significantly affect energy indicators such as cold gas, process, and global efficiencies. However, feeding technology clearly has an effect on the process due to the gasifying agent. Simulations results are compared against available technical data with good accuracy. Thus, the proposed model is considered as a versatile and useful computational tool to study and optimize the coal to SNG process. [ABSTRACT FROM AUTHOR]

• Biochars (BCs) from main biomass commodities traded worldwide are characterized. • Gasification temperature of wood pellets (WP) is higher than that of chips (WCH). • High density and temperature lead to increase the gasification efficiency by ∼41 %. • As BC from WP has 367.33 m2/g and 29.25 MJ/kg, it is a suitable solid biofuel. • WP as compared to WCH is a better feedstock to co-produce producer gas and BC. Wood pellets (WP) and chips (WCH) are the most frequently sold products worldwide to produce bioenergy under thermochemical processes. The effects of the bulk density of patula pine (Pinus patula) WP (555.97 kg/m3) and WCH (151.29 kg/m3), and their gasification conditions were studied on the properties of the produced biochars (BCs). The aim of this study was to generate a good-quality gas fuel (producer gas), as well as a BC with properties that would enable it to be used as a solid biofuel instead of being considered as a byproduct or waste. An atmospheric reverse-downdraft gasifier was used, setting the air flow at 0.12 kg/m2/s for the samples of biomasses studied. With regard to the gasification performance, the temperature inside the reactor was found to increase by 70 % for WP, obtaining a higher cold gas efficiency (51.6 %) in comparison with the efficiency achieved for WCH (36.7 %). Concerning the properties of the BCs, the highest gasification temperature allowed to reach a pellet-derived biochar (WP-BC) with a surface area (BET) larger than that one obtained for the chip-derived biochar (WCH-BC), with 367.33 m2/g and 233.56 m2/g, respectively. Furthermore, the WP-BC heating value was found to be 29.25 MJ/kg, while this parameter for the WCH-BC was 28.36 MJ/kg. It is highlighted the low probability of corrosion and ash fusion occurrence within the reactor when using these biofuels (raw and BCs). Additionally, regarding the pyrolysis kinetics of the raw biomasses, WCH showed a higher reactivity with an activation energy (E α) of 80.84 kJ/mol in comparison with the E α value obtained for WP (124.38 kJ/mol). [ABSTRACT FROM AUTHOR]

In Latin America, one of the key tasks of Community and Liberation Psychology has been to recover the memories of marginalized and excluded communities that have experienced multiple pasts marked by political violence. In Chile, researchers have focused on poor urban neighborhoods, where the question of how memories are transmitted in areas where conflicts and violence are still present has been overlooked. In this context, the following article aims to analyze the ways in which memories are transmitted in a neighborhood that has a long organizational history in the struggle against social inequalities; while at the same time being classified as a critical area by the state due to its current levels of violence and social conflict. The researchers led a 3‐year case study from an ethnographic perspective, and applied a collaborative methodology that brought together the research team and the members of a territorial organization. The analysis is based on 72 interviews, 5 conversation groups and ethnographic observation. The data was analyzed using discourse analysis. The results revealed that the main form of memory transmission is not based on intergenerational narratives of the past, but rather on joint action; namely, dialogical practices among neighborhood residents that generate an ethos; a common way of life. [ABSTRACT FROM AUTHOR]

The aim of this research was to evaluate four different cacao ( Theobroma cacao L.) fermentation conditions and their effect on fermented bean quality, in order to be able to recommend the most suitable condition to producers in the municipality of Huimanguillo, Tabasco, Mexico. Fermentations were carried out in square wooden boxes with capacity for 1000, 300, and 100 kg of fresh beans, as well as a rotary drum with capacity for 500 kg thereof. The fermentation process was carried out for 7 days, and the response variables measured were mass temperature, total soluble solids ( TSS), pH, and acidity. The TSS were totally depleted after 2 days, during which time the yeasts transformed them into ethanol at temperatures of 25-35°C. The most notable temperature increase in the four treatments was 49°C on the third day, corresponding to a decrease in pH from 6.31 ± 0.40 to 4.76 ± 0.03 and an increase in acidity from 0.38 ± 0.04 to 1.17 ± 0.25 g kg−1, due to the formation of organic acids. There were no significant differences among the four treatments (Tukey α = 0.05). The cut test showed that fermentation in 300- and 100-kg boxes and in the 500-kg rotary drum produced the same effect on fermentation quality, but the 1000-kg boxes exhibited lower quality (Tukey α = 0.05). [ABSTRACT FROM AUTHOR]