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In this study, we investigate the dual-fuel operation of compression ignition engines using biodiesel at varying concentrations in combination with biogas, with and without hydrogen enrichment. A response surface methodology, based on a central composite experimental design was employed to optimize energy efficiency and minimize pollutant emissions. The partial substitution of diesel with gaseous fuel substantially reduces the specific fuel consumption, achieving a maximum decrease of 21% compared with conventional diesel operation. Enriching biogas with hydrogen, accounting for 13.3% of the total flow rate, increases the thermal efficiency by 0.8%, compensating for the low calorific value and reduced volumetric efficiency of biogas. Variations in biodiesel concentration exhibits a nonlinear effect, yielding an additional average efficiency gain of 0.4%. Regarding emissions, the addition of hydrogen to biogas contributes to an average reduction of 5% in carbon monoxide emissions compared to the standard dual-fuel operation. However, dual-fuel operation leads to higher unburned hydrocarbon emissions relative to neat diesel; hydrogen enrichment mitigates this drawback by reducing hydrocarbon emissions by 4.1%. Although NOx emissions increase by an average of 26.6% with hydrogen addition, dual-fuel strategies achieve NOx reductions of 11.5% (hydrogen-enriched mode) and 33.3% (pure biogas mode) relative to diesel-only operation. Furthermore, the application of response surface methodology is robust and reliable, with experimental validation showing errors of 0.55–8.66% and an overall uncertainty of 4.84%.

The generation of electric energy using alternative energy sources has been constantly studied by researchers owing to concerns regarding energy supply alternatives and the desire to reduce environmental impacts in its generation. This study evaluated the performance of an electricity generator operating in dual mode using biogas and biodiesel blends, which were obtained from a swine-waste biodigester and residual frying oil, respectively. The experiment was performed using blends B8, B20, B50, B80, and B100. The electrical power generated was higher in the dual mode corresponding to a load of 5.0 kW, showing differences of 18.7% for B8 and 21.7% for B100. In normal and dual modes, the B8 blend exhibited the lowest specific consumption of liquid fuel with values of 389.2 and 270.2 g kWh-1, respectively. The efficiency was higher in the normal mode, showing results of 22.0 and 24,7% using B8 and B100, respectively, compared to 17 and 20% in the dual mode corresponding to a load of 5.0 kW. These results indicate that biodiesel from residual frying oil can be used in normal mode and in combination with biogas in dual mode.

The safflower (Carthamus tinctoriusL.) has an uneven flowering and fruiting, which can cause problems in seed production and harvesting in regions with hot and humid climates. However, little is known about the optimal safflower harvest time. Therefore, this study evaluated the optimumtiming for seed harvest of three safflower genotypes (2106, S-325, and 7329).The experiment was a randomized complete block design with six replications. The harvest started 16 days after flowering (DAF) and ended at 52 DAF. Ten harvests were made in total. Seed water content, seeds fresh and dry matter, seed germination, and first germination counts were evaluated.Genotypes 2106 and 7329 had germination rates of 79% and 91%, respectively, at 34 and 38 DAF, while genotype S-325 had 90% germination at 37 DAF. Harvesting at 52 DAF combined with a rainy season impaired the germination of safflower seeds. The harvest time most suitable for safflower occurred between 34 and 42DAF, when the seeds have the seed water content between 26% and 33%. RESUMO: O cártamo (Carthamus tinctoriusL.) apresenta flores e frutos irregulares, o que pode causar problemas na produção e colheita de sementes em regiões com clima quente e úmido. No entanto, pouco se sabe sobre o tempo ideal de colheita de cártamo. Portanto, o objetivo desteestudo foi avaliar o momento ideal para a colheita de sementes de três genótipos de cártamo(2106, S-325 e 7329). O experimento foi delineado em blocos casualizados, com seis repetições. A colheita começou 16 dias após o florescimento (DAF) e terminou aos 52 DAF. Dez colheitas foram feitas no total. Foram avaliados o teor de água das sementes, matéria fresca e seca das sementes, germinação das sementes e primeira contagem de germinação. Os genótipos 2106 e 7329 tiveram taxas de germinação de 79% e 91%, respectivamente, aos 34 e 38 dias após a floração (DAF), enquanto o genótipo S-325 teve 90% de germinação aos 37 DAF. A colheita aos 52 DAF combinada com uma estação chuvosa prejudicou a germinação das sementes de cártamo. A época de colheita mais adequada para o cártamo ocorreu entre 34 e 42 DAF, quando as sementes apresentam teor de água entre 26% e 33%.

Agroforestry systems integrating tree and forage growth are important for maintaining soil health but may change the soil’s physical-hydric properties. Our goal was to investigate the impact of introducing Eucalyptus trees into a pasture on the soil water content throughout the soil profile. The study was conducted in a 6-year-old agroforestry system where two species of Eucalyptus were introduced into a palisade grass pasture. Soil moisture was sampled at 0.0 (planting row), 2.0, 4.0, and 6.0 m (midpoint between tree rows) from the Eucalyptus tree rows. A monoculture palisade grass pasture was used as a control. The soil water content down to a depth of 50 cm was lowest in the tree row and increased with distance from the trees. In the Eucalyptus row, the soil water content in the 0–50 cm layer was lower than in the monoculture pasture. Agroforestry systems decreased the water content in the superficial layers of the soil in the rainy months; in the dry season, the soil water contents in all layers were similar between the Eucalyptus inter-rows. In most seasons, the agroforest systems reduced the forage production close to the Eucalyptus tree rows, up to 2 m from the trees, likely due to the soil water content decrease. Overall, this study showed that in tropical regions with sandy soils, the grass and trees’ competition must be considered when establishing integrated agroforestry systems in order to maximize the advantages and benefits of the diversified agroecosystem.

The screening of cover crops is essential for improving the physical-hydric properties of compacted soils. This study aimed to evaluate the effects of mixed or single cover crops on improving the physical-hydric properties of compacted Oxisol. Species with tap-rooted and fibrous-rooted rooting patterns were evaluated. The species included pearl millet (Pennisetum americanum), pigeon pea (Cajanus cajan), sunn hemp (Crotalaria spectabilis), velvet bean (Mucuna pruriens), white oat (Avena sativa), black oat (Avena strigosa), rye (Secale cereale), black oat + forage turnip (Raphanus sativus), black oat + white lupin (Lupinus albus L.), and black oat + group pea (Pisum arvense L.). Mixing cover crops did not improve the physical properties of the soil. The tap-rooted pigeon pea effectively reduces bulk density and increases porosity and saturated hydraulic conductivity (Ksat) in compact soils. The selection of cover crops with characteristics that improve soil physical-hydric properties is crucial for compacted areas.

Biodiesel properties have a significant impact on engine performance. The disadvantages of biodiesel include poor atomization. To overcome this problem, engine parameters such as the injection angle can be changed. The objective of this study was to evaluate the effect of changes in the injection angle of an injector pump on the performance of a diesel engine fueled with various biodiesel blends. The experimental design involved testing three injection angles: 26°, 28°, and 30°; and four biodiesel blends: B0, B8, B15, and B20. The effects of variations in these factors were evaluated in terms of the maximum power, rotation at maximum power, torque at maximum power, maximum torque, rotation at maximum torque, specific fuel consumption, engine elasticity index, torque reserve, and rotation reserve. The engine fueled with the biodiesel blends showed a lower specific consumption without losing power or torque, when the crank angle of the injector pump was changed from its original configuration of 26° to 28°.

Due to its origin and hardiness, safflower is usually cultivated in low-fertility soils with few inputs and no irrigation. In Brazil, little is known about its response to nitrogen (N) and irrigation. This study was carried out near the city of Engenheiro Coelho, SP, Brazil, in 2014, in order to determine the effect of increasing nitrogen application rates (0, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550 and 600 kg ha-1) on safflower cultivation under irrigation and rainfed conditions. The use of irrigation during drought periods allowed stress reduction and significantly increased yield components and grain yield. Safflower yield was influenced by the interaction between water regimes and nitrogen rates. Grain yield may vary depending on several factors, however, maximum yield was achieved with rates of 208 and 214 kg N ha-1 under irrigation and rainfed conditions, respectively. For oil yield, 200 kg N ha-1 were sufficient, regardless of the water regime.

ABSTRACT Guar (Cyamopsis tetragonoloba L.) is commonly grown in arid lands, because of its high drought-tolerance. However, soil compaction may be a limiting factor to its growth. This study aimed to evaluate the guar growth, according to the soil penetration resistance (0.20 MPa, 0.33 MPa, 0.50 MPa, 0.93 MPa and 1.77 MPa, in a layer with depth between 0.15 m and 0.20 m), in a Rhodic Acrudox soil. The shoot and root dry mass, root length by the Q1/2 index (mechanical soil penetration resistance in which the root growth is reduced by 50 %) and root diameter were evaluated. The impairment of the guar shoot growth begins when the penetration resistance is greater than around 1 MPa. The soil compaction alters the distribution of guar roots in the soil profile, concentrating them in the 0.15 m layer, but it does not prevent roots from penetrating this layer and developing in depth. The root diameter increases in the compacted layer. A soil penetration resistance of up to 1.77 MPa does not influence the root length density below the compacted layer, as well as the total root length density of guar. Although the guar Q1/2 index is greater than 1.58, the shoot and root dry mass are impaired. RESUMO O guar (Cyamopsis tetragonoloba L.) é comumente cultivado em terras áridas, por ser altamente tolerante à seca. No entanto, a compactação do solo pode ser um fator limitante ao seu cultivo. Objetivou-se avaliar o crescimento de guar, em função da resistência do solo à penetração (0,20 Mpa; 0,33 Mpa; 0,50 Mpa; 0,93 Mpa; e 1,77 Mpa, em camada com profundidade entre 0,15 m e 0,20 m), em Latossolo Vermelho Distroférrico. Avaliaram-se a massa seca da parte aérea e raiz, o comprimento radicular a partir do índice Q1/2 (resistência mecânica do solo à penetração na qual o crescimento radicular é reduzido à metade) e o diâmetro radicular. O crescimento da parte aérea de guar começa a ser prejudicado por resistência superior a cerca de 1 MPa. A compactação do solo altera a distribuição das raízes de guar no perfil do solo, concentrando-as na camada de 0,15 m, mas não impede que as raízes penetrem nessa camada e se desenvolvam em profundidade. O diâmetro de raiz aumenta na camada compactada. A resistência à penetração no solo de até 1,77 MPa não influencia na densidade de comprimento radicular abaixo da camada compactada, bem como na densidade de comprimento radicular total de guar. Embora o índice Q1/2 de guar seja superior a 1,58, a massa seca da parte aérea e da raiz são prejudicadas.

The generation of electric energy using alternative energy sources has been constantly studied by researchers owing to concerns regarding energy supply alternatives and the desire to reduce environmental impacts in its generation. This study evaluated the performance of an electricity generator operating in dual mode using biogas and biodiesel blends, which were obtained from a swine-waste biodigester and residual frying oil, respectively. The experiment was performed using blends B8, B20, B50, B80, and B100. The electrical power generated was higher in the dual mode corresponding to a load of 5.0 kW, showing differences of 18.7% for B8 and 21.7% for B100. In normal and dual modes, the B8 blend exhibited the lowest specific consumption of liquid fuel with values of 389.2 and 270.2 g [kWh.sup.-1], respectively. The efficiency was higher in the normal mode, showing results of 22.0 and 24,7% using B8 and B100, respectively, compared to 17 and 20% in the dual mode corresponding to a load of 5.0 kW. These results indicate that biodiesel from residual frying oil can be used in normal mode and in combination with biogas in dual mode.

Rapid urbanization has exacerbated climatic imbalances, including the urban heat island effect, and rising regional temperatures. Green roofs, which combine multiple layers of vegetative cover over a structural base, offer an ecological solution. This study investigates the potential of incorporating recycled construction and demolition waste (CDW) into green roofs to improve thermal efficiency; CDW, more specifically the byproduct of its recycling process, commonly referred to as ‘recycled sand’, contains a mixture of concrete and ceramic fragments. The study was conducted in Cascavel, S Brazil. The research compared green roofs made from recycled materials like concrete and ceramic fragments with traditional roofing. Various proportions of recycled sand and clay soil were tested in the substrates. Temperature analysis was carried out under both natural and humid conditions to evaluate thermal performance. The substrates containing recycled sand enhanced thermal efficiency, thus reducing internal temperatures by up to 3.4 °C on hot days. Additionally, sandy substrates retained heat better in colder periods but performed less efficiently when saturated. This study demonstrates the viability of using CDW to improve the thermal and energy performance of green roofs, particularly in hot climates.