Environmental Science Energy Resources and Consumption 1 — Questions and Answers
Question 1: Which energy source accounts for the largest share of global primary energy consumption?
- Nuclear power
- Petroleum and other liquids (Correct answer)
- Renewable energy
- Natural gas
Correct answer: Petroleum and other liquids
Petroleum and other liquids remain the largest source of global primary energy, used heavily in transportation and industry.
Petroleum and other liquids consistently represent the largest share of global primary energy consumption, typically around 30-33%. Transportation is the dominant end-use sector for petroleum. While natural gas and coal are also major contributors, no single fossil fuel or renewable source currently surpasses petroleum on a global basis.
Question 2: The net energy yield of a fuel source is best described as:
- The total energy released during combustion
- The energy remaining after subtracting extraction and processing costs (Correct answer)
- The efficiency rating of the power plant burning the fuel
- The carbon dioxide emitted per unit of energy produced
Correct answer: The energy remaining after subtracting extraction and processing costs
Net energy yield = total energy output minus the energy required to find, extract, process, and deliver that fuel.
Net energy yield (expressed as Energy Return on Investment, EROI) compares the energy delivered to society to the energy required to obtain and process the fuel. A high EROI (conventional oil ~20:1) means much more energy is returned than invested. As a resource becomes harder to extract, its EROI falls, making it less economically and energetically attractive.
Question 3: Which of the following is a non-renewable energy source?
- Wind
- Biomass
- Natural gas (Correct answer)
- Hydropower
Correct answer: Natural gas
Natural gas is a fossil fuel formed over millions of years and cannot be replenished on a human timescale.
Non-renewable energy sources exist in finite quantities and cannot be replenished within a human lifetime. Natural gas, coal, and petroleum are fossil fuels derived from ancient organic matter. Biomass is renewable because new plant matter can be grown, wind is perpetually renewed by solar heating of the atmosphere, and hydropower relies on the water cycle.
Question 4: Cogeneration (combined heat and power) improves energy efficiency by:
- Using two types of fuel simultaneously
- Capturing waste heat from electricity generation for useful heating (Correct answer)
- Generating electricity from two separate turbines
- Mixing fossil fuels with biofuels
Correct answer: Capturing waste heat from electricity generation for useful heating
Cogeneration captures the heat that would otherwise be wasted in conventional power generation and uses it for space or process heating.
Conventional thermal power plants convert only about 30-40% of fuel energy into electricity; the rest exits as waste heat. Cogeneration (CHP) captures that heat for industrial processes, district heating, or hot water, raising overall efficiency to 70-90%. This significantly reduces fuel consumption and greenhouse gas emissions for the same useful energy output.
Question 5: The Hubbert Peak theory predicts that:
- Renewable energy will surpass fossil fuels by 2050
- Global oil production will eventually reach a maximum and then decline (Correct answer)
- Nuclear energy will plateau as uranium reserves are exhausted
- Coal consumption will peak due to environmental regulations
Correct answer: Global oil production will eventually reach a maximum and then decline
M. King Hubbert predicted in 1956 that oil production in any region follows a bell-shaped curve, rising to a peak then declining as reserves deplete.
Hubbert Peak theory (peak oil) models oil production over time as a roughly bell-shaped (logistic) curve. Production rises as new fields are discovered and developed, reaches a maximum when about half the recoverable resource has been extracted, then declines. Hubbert correctly predicted the 1970 peak in U.S. lower-48 oil production. The concept applies to any finite resource.
Question 6: Which sector consumes the most energy in the United States?
- Residential
- Commercial
- Transportation
- Industrial (Correct answer)
Correct answer: Industrial
The industrial sector - including manufacturing, mining, agriculture, and construction - is the largest end-use consumer of energy in the U.S.
In the United States the industrial sector (manufacturing, mining, agriculture, construction) typically accounts for about 35% of total end-use energy consumption, making it the largest sector. Transportation comes in as a close second (~28%), followed by residential and commercial sectors. Globally, industry is also the dominant energy consumer, driven by steel, cement, and chemical production.
Environmental Science Energy Resources and Consumption 1
Which energy source accounts for the largest share of global primary energy consumption?