Organic Matter in Cometary Environments

Comets contain primitive material leftover from the formation of the Solar System, making studies of their composition important for understanding the formation of volatile material in the early Solar System. This includes organic molecules, which, for the purpose of this review, we define as compounds with C–H and/or C–C bonds. In this review, we discuss the history and recent breakthroughs of the study of organic matter in comets, from simple organic molecules and photodissociation fragments to large macromolecular structures. We summarize results both from Earth-based studies as well as spacecraft missions to comets, highlighted by the Rosetta mission, which orbited comet 67P/Churyumov–Gerasimenko for two years, providing unprecedented insights into the nature of comets. We conclude with future prospects for the study of organic matter in comets.

Potential of Briquette Produced with Torrefied Agroforestry Biomass to Generate Energy

Agroforestry industries, such as sugar-alcohol, food, and logging, produce large quantities of waste, used to generate energy from direct burning. The application of other processes, such as torrefaction and briquetting, can increase the profits from the use of agro-industrial waste for energy generation. Briquetting is an alternative for using these wastes, allowing the compaction of the biomass, generating a biofuel with high energy density, and which is more homogeneous and easier to store and transport. The objective of this study was to evaluate the physical and chemical properties of four biomass types (wastes from sawed eucalypt and pine wood, coffee pruning wastes, and sugarcane bagasse) torrefied at 300 °C and compacted (briquetting) at pressures of 6.21, 8.27, and 10.34 MPa. The torrefaction increased the fixed carbon content, ash, and calorific value, and reduced the volatile material content and hygroscopic equilibrium moisture of the biomasses. The volatile material content was lower and the fixed carbon higher in the coffee pruning waste, the ash content higher in the sugarcane bagasse, and the calorific value higher in the pine and eucalypt wood. The briquetting and the torrefaction processes increased the biomass bulk density, and the useful calorific value, respectively, and consequently the energy density of the briquettes produced with torrefied raw material under high pressure. The mechanical properties of the briquettes produced with all materials increased with the compaction pressure. Torrefaction and briquetting increased the energy potential of the biomasses evaluated to produce energy from clean technology.

Briquettes Produced With a Mixture of Urban Pruning Waste, Glycerin and Cassava Processing Residue

The briquette is considered a solid biofuel, made from the compaction of lignocellulosic residues used for the generation of energy. This work aimed to study the production of briquettes from mixtures of Urban Pruning Waste (RPU) (pruning of leaves and thin branches of trees), glycerin and cassava bagasse (Manihot esculenta). Samples of RPU, cassava bagasse and glycerol were mixed to yield treatments T1 (100% RPU), T2 (92% RPU and 8% cassava bagasse), T3 (97% RPU and 3% glycerin), T4 (89% RPU, 8% cassava bagasse and 3% Glycerin), T5 (94.5% RPU, 4% cassava bagasse and 1.5% glycerin) and T6 (control). Following this step, physical, chemical and energetic analyses (moisture content, volatile material content, fixed carbon and ash content, superior, inferior and useful calorific value, mechanical resistance, apparent and energetic density) of the briquettes were carried out. Treatment T2 had a lower fixed carbon value and volatile content, as well as higher ash content and mechanical strength. The percentages of carbon, hydrogen and nitrogen did not differ statistically between the treatments. The higher, lower and useful heating values were higher in treatment T3. The results showed that treatments T1, T2 and T3 were more efficient, producing briquettes with properties that meet market specifications, besides presenting great energetic potential, being good substitutes for firewood.

Estimación de las propiedades físico-químicas de residuos agroindustriales para el aprovechamiento como biocombustible

In Ecuador maize (Zea mays L) it´s produced in the coastal, Andean and Amazon region, 45.521 hectares are harvested annually in Manabí. On the other hand, peanuts (Arachishypogaea) are another important crop in Manabí agriculture. Within the different agricultural or processing processes, heterogeneous waste, especially biomass, which represents an environmental problem due to the lack of techniques for its use, remaining in the field in the form of waste, which creates pollution problems. An assessment was made of the physicochemical properties that influence energy potential (humidity, ash, fixed carbon and volatile material) of these residues specifically of corn stalk (TM) and peanut shell (CM) for use in the development of a solid biofuel (péllet). CM's moisture content was 11.45% and TM 10.83%. The highest ash content in CM 18.93% and a lower content at TM=11.93%. The fixed carbon content in CM=15.78% and in TM=23.11%, similar values were obtained in the volatile material content between the two residues (CM=65.47% and TM=64.96%), these results indicate that the selected waste can be used for power generation as solid biofuels. In a pilot burner, pellets were burned for each selected agro-industrial waste reaching a maximum temperature of 751±39 °C for CM and 653±13 °C for TM in time of 9 and 4 minutes respectively. Index Terms— biomass, energy potential, solid biofuel.

Evaluation of Total Mercury in Sediments of the Descoberto River Environmental Protection Area—Brazil

To evaluate the total mercury accumulation (THg) in the Descoberto river basin environmental protection area (DREPA), nine sediment and water samples were collected from the Descoberto reservoir (lentic environment), and 23 in its tributaries (lotic environment), which are located in a densely urbanized area within the Descoberto river watershed, Brazil. The following physicochemical parameters of water were determined: dissolved oxygen (DO); hydrogen potential (pH); total dissolved solids (TDS); nitrate (NO3−); chloride (Cl−); temperature (T); sulfate (SO42−), and in sediment, the concentration of total mercury (THg) and volatile material (VM) was determined. THg concentrations in sediments showed a significant difference (p = 0.002) between tributaries (0.03 µg g−1 ± 0.02) and reservoir (0.08 µg g−1 ± 0.04), indicating accumulation in the lentic environment. Most of the results evaluated for ecotoxicological risks presented values below the concentration, at which adverse effects would rarely be observed, ERL (effects range low). However, in relation to the enrichment factor (EF), applied to identify the anthropogenic contribution, the results indicate that most of the samples are moderately polluted through atmospheric deposition due to vehicular traffic and agriculture. These results show that the likelihood of methylation in the lentic environment is higher than in the lotic environment.

Analysis of the Feasibility of Generating Solid Biofuel from Ulex Europaeus Plants

The Ulex europaeus (also known as Common Gorse) represents a threat to the native ecosystems of different Colombian regions. Recently, the Ministry of the Environment and Sustainable Development introduced protocols for its prevention and management. Even though the Ulex europaeus has a high calorific value, a wide-spread solution for its post-processing is not yet available in its affected areas. In Colombia, the most common method for the disposal of the harvested plant is incineration, given that this is the suggested method by Resolution 684 of 2018. Due to the importance of the problem, this investigation is focused on studying the viability of creating solid biofuel alternatives derived from the plant. Grinded material and briquettes were produced with different log/foliage ratios in order to investigate both the domestic and industrial applications of the plant; e.g. heating, cooking and cogeneration, respectively. A proximate and ultimate analysis was performed on the produced samples. The generated solid biofuel presents 75% of the carbon heat value, a high volatile material content (83.3%), and low ash and Sulphur residues (1.41% and 0.15% respectively). These results applied to both dry and humid samples, demonstrated that the produced solid biofuel is adequate for applications oriented towards heat generation. However, further analysis and process optimization is required in order to establish the generation of solid biofuel as an appropriate use of the Ulex europaeus remnants. By further analyzing the overall process; from plant removal, through residue disposal, and finally remnant conversion, the investigations value chain can be better established and possibly established for real world implementation.

THE EFFECT OF THE COMPOSITION OF MIXTURES OF CONDENSED FRACTIONS OF A VENEZUELAN RESIDUE ON THE QUALITY OF THE PRODUCTS OBTAINED FROM DELAYED COKING

The effect of the composition of resin and asphaltene on the quality of products obtained from delayed coking was evaluated. 10 mixtures with a controlled composition of S.A.R.A. (Saturates, Aromatic, Resin, Asphaltene) fractions with high percentage of resin and asphaltene, from a vacuum residue of Venezuelan crude commercially known as “Merey”, were processed in a delayed coking unit at laboratory scale. The physic-chemical characteristics of the mixtures and products (distilled and coke) were obtained. Results indicate that on increasing the resin and asphaltene content, there is a decrease in the content of volatile material and an increase in fixed carbon and ash. Metal and sulphur content were found in a lesser proportion in coke from the mixtures rich in resin while said content was higher for the mixtures rich in asphaltene. This showed the impact that the S.A.R.A composition of the feed has on the quality of the products obtained.

Cometary topography and phase darkening

Aims. Cometary surfaces can change significantly and rapidly as a result of the sublimation of their volatile material. Many authors have investigated this evolution; topographic data from all comets visited by spacecrafts have been used previously to derive a quantitative model that relates large-scale roughness (i.e. topography) with the evolution state of the nucleus for Jupiter-family comets (JFCs). Ground-based observers have published measurements of the phase functions of many JFCs and reported a trend in the phase darkening, with primitive objects showing a stronger darkening than evolved objects. Methods. We used a numerical implementation of this previous topographic description to build virtual comets and measure the phase darkening induced by the different levels of macro-roughness. We then compared our model with other published values. Results. We find that pure geometric effects such as self-shadowing can represent up to 22% of the darkening that is observed for more primitive objects, and 15% for evolved surfaces. This shows that although physical and chemical properties remain the main contributor to the phase darkening, the additional effect of the topography cannot be neglected.