Combustibles Sostenibles

Why is biomass often considered a carbon-neutral fuel in comparison with fossil fuels?. Because biomass does not release carbon dioxide when burned. Because the carbon released during biomass combustion was only recently absorbed from the atmosphere during biomass growth. Because biomass contains no carbon in its chemical composition. Because biomass is always produced without any energy input.

Sentence I: Natural gas is a fossil fuel composed almost entirely of ethane and propane. Sentence II: Natural gas is a primary energy source used both to produce fuels and to generate electricity. Sentence I is True; Sentence II is False. Sentence I is False; Sentence II is True. Both sentences are True. Both sentences are False.

Nowadays, nuclear power is a significant component of the global energy mix, providing a significant level electricity generation. According to the concepts discussed regarding current energy sources and their importance, which of the following best describes the classification and environmental impact of nuclear fission energy?. It is considered a renewable source since uranium occurs naturally, but the complex fission process results in a high carbon footprint. It is a non-hydrocarbon source, yet the continuous fission of uranium and plutonium still releases significant greenhouse gases. It is a non-renewable source limited by finite reserves, but it has a zero carbon footprint because generating this energy does not rely on combustion. It is currently classified as a fully sustainable and renewable resource since modern power plants run exclusively on nuclear fusion rather than fission.

As shown in the figure below, which illustrates the evolution of renewable power capacity by technology between 2019 and 2024, along with a target for 2030, the capacities of Solar PV, Wind Power, and Biopower/Geothermal/Ocean/CSP all increase significantly. In contrast, hydropower capacity remains almost constant, even in the 2030 projection. Which of the following reasons explains why global hydropower capacity remains nearly unchanged in the target 2030, despite the strong growth of other renewable energy sources?. Most of the economically viable global hydropower potential has already been exploited. Hydropower technology is still insufficiently developed to support large scale expansion. Demand for hydropower electricity has been declining, reducing incentives for new projects. The stagnation is mainly due to countries prioritizing pumped hydro storage instead of building new hydropower plants.

Which of the following organizations is mentioned as a source of data for statistics and information on energy?. World Bank Energy Council. International Energy Agency (IEA). Global Fuel Association. United Climate Laboratory.

In the context of the energy transition, many countries have strongly invested in increasing electricity generation from renewable sources. However, this strategy alone does not ensure a rapid decarbonisation of global final energy consumption. Which of the following statements best explains this limitation?. Electricity is a primary energy source; therefore, increasing its supply automatically replaces fossil fuels in all final uses. Renewable electricity is essential, but final energy consumption still remains largely dependent on fossil fuels; moreover, electricity is an energy carrier rather than a primary energy source, and the integration of renewables differs greatly across sectors, especially in transport. The main problem of the current energy system is primarily the geological scarcity of oil, while natural gas and coal have already lost their structural relevance in global energy supply. Decarbonisation depends exclusively on changes on the supply side, whereas actions aimed at improving energy efficiency in final consumption sectors are of little relevance.

According to the International Energy Agency (IEA), which of the following trends is expected to remain largely unchanged across different future energy scenarios?. Fossil fuels will disappear from the global energy mix before 2050 due to rapid electrification and renewable expansion. The world’s energy needs are expected to increase, and fossil fuels will still supply a large share of global energy demand. Global energy demand will stabilize due to declining population growth and decreasing living standards. Universal access to modern energy will be achieved globally by 2030 regardless of policy actions.

The slides discuss future energy scenarios developed by the International Energy Agency (IEA) and how different policy choices influence global energy demand, emissions, and sustainability outcomes. These scenarios are used to evaluate possible pathways for the global energy system and help policymakers understand how different levels of climate ambition affect future energy consumption and emissions. Which of the following best describes the objective of the Sustainable Development Scenario (SDS) presented by the International Energy Agency (IEA)?. It assumes no significant policy changes and projects energy demand growth based purely on market forces and current trends. It aims to meet the United Nations Sustainable Development Goals by ensuring universal access to energy, reducing air pollution, and limiting global temperature rise to well below 2 °C. It prioritizes economic growth by increasing fossil fuel production while maintaining current emission levels through technological efficiency improvements. It focuses mainly on increasing renewable energy production while ignoring other sustainability goals such as energy access and air pollution reduction.

In the context of global energy systems, which of the following statements best explains why biomass is often considered a “carbon-neutral” energy source compared to fossil fuels?. Biomass does not release CO₂ when burned. Biomass absorbs CO₂ during its growth, balancing emissions released during combustion. Biomass contains no carbon compounds. Biomass produces less energy than fossil fuels and therefore emits less CO₂.

Which statement correctly explains why biomass is often considered a carbon-neutral energy source?. Because biomass combustion does not produce carbon dioxide. Because biomass is composed mainly of hydrocarbons formed millions of years ago. Because the carbon dioxide released during biomass combustion was recently absorbed from the atmosphere during plant growth. Because biomass is not derived from organic material.

What is the main reason that fossil fuels contribute to a net increase in atmospheric CO2, while biomass is often considered carbon-neutral?. Fossil fuels release long-stored carbon. Biomass does not release any carbon during combustion. Biomass does not undergo combustion. Biomass absorbs more CO2 during combustion than fossil fuels.

Crude oil is described as a complex mixture of hydrocarbons. Why is refining necessary before its use?. Crude oil contains no usable energy. It cannot be transported in its natural form. It must be separated into fractions with properties suitable for specific applications. None of the options.

Which statement best explains why electricity is considered a secondary energy source rather than a primary one?. Because all primary energy is fossil-based, whereas electricity is not. Because electricity must generally be produced by transforming primary energy sources. Because electricity has higher energy quality than primary energy sources such as fossil fuels. Because electricity cannot be stored in large enough quantities to be considered a primary source.

Why does fossil fuels (oil, natural gas & coal) remain an important energy source globally in forecasts despite its environmental impact?. Because the share of fossil fuels in the total energy consumption is projected to keep increasing. Because they are the most efficient fuel type. Because fossil fuels are deeply imbedded in infrastructure and supply chains, making them difficult to phase out. Because there are virtually unlimited reserves available for extraction.

“Why are fossil fuels expected to remain an important part of the global energy system in many future energy scenarios?”. Renewable energy technologies alone cannot generate enough electricity to meet the increasing demand. Existing energy infrastructure and long investment lifetimes make rapid transitions to alternative energy systems challenging. Fossil fuel resources are expected to remain abundant and economically competitive in many regions. Global energy demand is expected to continue increasing, meaning that new energy sources often supplement rather than immediately replace fossil fuels.

Why is global energy production higher than final energy consumption?. Because energy is lost during transformation and distribution processes. Because countries overproduce energy to compete economically. Because energy consumption is difficult to track and thus usually underreported. Because machines create extra energy during use, increasing total supply.

Which of the following best explains why global oil production may decline even if significant oil resources remain underground?. Oil becomes chemically unstable over time. Energy return on investment will decrease. Oil demand eventually drops to zero. Oil prices will drop, making production economically unfeasible.

Internal combustion engines can be classified according to how combustion occurs. What is the main difference between external combustion engines and internal combustion engines?. External combustion engines use liquid fuels while internal combustion engines use gaseous fuels. In external combustion engines the fuel burns outside the engine cylinder, while in internal combustion engines combustion occurs inside the cylinder. External combustion engines only use renewable fuels. Internal combustion engines do not produce heat during operation.

What can be inferred from the relationship between solar energy’s installed capacity and the electricity it actually produces?. Solar energy production is proportional to its installed capacity. Solar energy is underutilized compared to its installed capacity. Solar energy is the world’s main source of electricity. Solar energy produces more electricity than fossil fuels.

Why is biomass, compared to fossil fuels, considered a carbon-neutral energy source?. Because biomass does not contain carbon atoms in its chemical structure. Because when biomass is burned, it does not release carbon dioxide. Because when biomass is burned, it releases carbon that plants have recently absorbed from the atmosphere. Because biomass has a higher energy density than fossil fuels.

When considering Sustainable Fuels, which of the following is classified as an alternative source of renewable hydrocarbons?. Shale Glass. Nuclear fussion. Biomass. Oil Sands.

Why is nuclear energy considered a non-renewable energy source, even though it produces very low direct CO₂ emissions during electricity generation?. Because nuclear fuel (e.g. uranium) is a finite resource that cannot be replenished on a human time scale. Because nuclear reactions produce significant amounts of CO₂ during electricity generation. Because nuclear reactions are very dangerous and can cause severe environmental damage. Because nuclear reactions rely on combustion processes similar to fossil fuels.

“What is NOT a primary energy source?”. Coal. Electricity. Solar Energy. Nuclear Energy.

Which of the following best describes a secondary energy source (energy vector)?. Energy that is directly extracted from natural resources without transformation. Energy that results from the transformation of primary energy sources. Energy that exists naturally in the form of fossil fuels in the Earth’s crust. Energy that can only be produced from renewable resources.

Are all renewable fuels automatically environmentally friendly?. No, renewable fuels are not always environmentally friendly, because their overall impact depends on factors like land use, resource consumption, and production methods. Renewable fuels have zero environmental impact because they come from natural sources. Renewable fuels are always more harmful to the environment than fossil fuels. Yes, all renewable fuels are completely environmentally friendly regardless of how they are produced.

Which of these is NOT listed as one of the main energy sources?. Oil. NG. Geothermal. Hydroelectric powers.

Can sustainable fuels realistically replace fossil fuels entirely, or only partially?. Sustainable fuels are likely to replace fossil fuels only partially. Sustainable fuels can completely replace fossil fuels in all sectors with no major technological challenges. Sustainable fuels cannot replace fossil fuels at all and will remain insignificant. Sustainable fuels will replace fossil fuels instantly once production increases slightly.