Tema X CS

In base to the model of production of bioethanol from fruit waste, which of the next answers better justify the reason why this waste from the economical and technical approach should be included in the feedstock regardless of its low yield in ethanol?. Rotten fruit has lower collection costs due to its greater availability in urban waste systems, which directly compensates for its lower conversion efficiency. Rotten fruit has a higher free glucose content due to previous enzymatic degradation processes, allowing the maximum theoretical yield of 0.511 g EtOH/g glucose to be achieved without the need for pretreatment. Although rotten fruit has a final ethanol yield between 15–25% lower, its enzymatic pre-hydrolysis reduces the energy requirements of pretreatment and can shorten the lag phase of fermentation, improving the efficiency of the overall process. The exclusive use of rotten fruit allows the distillation stage to be completely avoided, since the fermentation reaches concentrations higher than the inhibition limit of ethanol (14% v/v).

Biofuels are often described as “carbon neutral”. Which of the following statements best explains this concept?. Biofuels do not emit CO₂ during combustion. Biofuels emit CO₂, but it is balanced by recent CO₂ absorption during biomass growth. Biofuels have higher energy density than fossil fuels. Biofuels do not require combustion to release energy.

Por que razão as regiões em desenvolvimento apresentam tipicamente uma maior quota de biomassa tradicional na sua mistura energética, comparativamente às regiões industrializadas?. A biomassa tradicional tem maior densidade energética do que os combustíveis fósseis. O acesso limitado a serviços energéticos modernos leva as populações a recorrer a recursos locais como lenha e carvão vegetal.

During combustion, different fuels release different amounts of energy depending on their chemical composition. Considering hydrocarbons with similar molecular sizes, which type of hydrocarbon generally has the highest heating value per unit mass?. Alkanes. Aromatic hydrocarbons. Alcohols. Carboxylic acids.

During catagenesis, the transformation of kerogen into hydrocarbons occurs without external addition of hydrogen. What is the dominant mechanism and its most relevant consequence?. Ionic mechanisms dominate the reaction, leading to preferential production of aromatic compounds. Radical mechanisms dominate and variations in H/C rations occur through internal hydrogen transfer, simultaneously producing hydrogen-rich compounds (such as oil) and hydrogen-poor compounds (such as graphite or methane). The reaction proceeds through radical mechanisms, but there is no variation in the H/C ratio of kerogen throughout the process. Radical mechanisms dominate and hydrogen is exclusively consumed in methane formation, with no production of liquid hydrocarbons.