Rucete ✏ AP Environmental Science In a Nutshell
6. Energy Resources and Consumption
This unit covers types of energy (renewable and nonrenewable), global consumption trends, fossil fuels, nuclear power, alternative energy sources like wind and solar, and methods of energy conservation. It explores the environmental and economic impacts of different energy choices.
6.1 Renewable and Nonrenewable Resources
Renewable Resources
• Replenished on a human timescale (e.g., sunlight, wind, rain, tides, waves, geothermal).
• Provide ~12% of U.S. energy (2021); key to climate change mitigation.
Nonrenewable Resources
• Fossil fuels (coal, oil, natural gas) and uranium form over millions of years and are finite.
• Benefits: high energy yield, existing infrastructure.
• Concerns: pollution, greenhouse gases, finite supply.
6.2 Global Energy Consumption
Trends
• Energy demand projected to increase ~50% by 2050, mostly in developing countries.
• Industrial sectors use the most energy globally.
• Electricity demand expected to grow ~70% by 2040.
Current Energy Mix
• Majority from coal, oil, natural gas; renewables growing fast.
• Coal still dominant in electricity generation (~40% in 2018).
6.3 Fuel Types and Uses
Wood
• Renewable but causes deforestation, erosion, air pollution.
Peat
• Semi-renewable organic material; forms in bogs; high carbon sink but slow growth rate.
Coal
• Types: lignite (lowest quality), bituminous, anthracite (highest quality).
• Pros: abundant, high net energy, low cost.
• Cons: air pollution, acid rain, mining damage, health risks.
Natural Gas (CH₄)
• Cleaner than coal and oil; used for heating, electricity, and transportation.
• Fracking releases methane and contaminants.
Oil
• Used mainly in transportation; declining reserves and geopolitical concerns.
• Causes pollution, oil spills, and contributes to climate change.
6.4 Distribution of Natural Energy Resources
Global Variability
• Energy resource availability depends on geology, climate, and political factors.
• Oil: concentrated in the Middle East, Venezuela, and Russia.
• Natural gas: found in Russia, U.S., Iran, and Qatar.
• Coal: widely distributed (U.S., China, India, Russia).
• Uranium: Australia, Kazakhstan, Canada have major reserves.
Geopolitical Implications
• Countries with energy resources gain economic and strategic influence.
• Energy trade creates international dependencies and conflict potential.
6.5 Fossil Fuels
Extraction Methods
• Coal: surface mining (strip, mountaintop removal) and subsurface mining.
• Oil: drilling, offshore platforms, and oil sands.
• Natural Gas: extracted via fracking (hydraulic fracturing).
Environmental Concerns
• Habitat destruction, water use, methane leaks, oil spills.
• Air pollution: CO₂, SO₂, NOₓ, and particulates.
• Climate change driven by CO₂ and CH₄ emissions.
6.6 Nuclear Power
How It Works
• Uranium-235 undergoes fission → releases heat → boils water → steam spins turbine → generates electricity.
• Controlled reaction with fuel rods, moderators, and control rods.
Advantages
• No air pollutants or greenhouse gases during operation.
• High energy density; small fuel quantity yields large output.
Disadvantages
• Radioactive waste requires long-term storage (10,000+ years).
• Risk of accidents (e.g., Chernobyl, Fukushima).
• High cost and long construction time.
6.7 Energy from Biomass
Biomass Sources
• Organic material from plants, animals, and waste (e.g., wood, crop residue, manure).
• Used for heating, cooking, and electricity production.
Biofuels
• Ethanol: produced from corn or sugarcane; added to gasoline to reduce emissions.
• Biodiesel: made from vegetable oils or animal fats; cleaner than petroleum diesel.
Pros
• Renewable and carbon-neutral (in theory).
• Can use waste products.
Cons
• Deforestation and land use change for biofuel crops.
• May compete with food production.
• Emissions from combustion and transportation.
6.8 Solar Energy
Passive Solar
• Uses building design to capture sunlight for heat (e.g., south-facing windows).
Active Solar
• Uses mechanical systems to collect, store, and convert sunlight to electricity or heat.
• Includes solar thermal collectors and photovoltaic (PV) cells.
Photovoltaic Cells
• Convert sunlight directly into electricity using semiconductors (e.g., silicon).
• Efficiency depends on sunlight, panel quality, and installation angle.
Pros
• No fuel cost or emissions during operation.
• Renewable and scalable.
Cons
• Intermittent (only works during daylight).
• Requires large land area and rare materials.
• High upfront cost (but decreasing over time).
6.9 Hydroelectric Power
How It Works
• Water stored in reservoirs behind dams is released through turbines to generate electricity.
• Kinetic energy of moving water is converted into mechanical energy, then into electricity.
Types
• Impoundment: uses a dam to control water flow (e.g., Hoover Dam).
• Run-of-the-river: channels a portion of river flow without a large dam.
• Pumped storage: water is pumped uphill when energy demand is low and released when demand is high.
Pros
• No air pollution or greenhouse gas emissions during operation.
• Reliable, renewable, and efficient.
• Can provide flood control, irrigation, and recreation.
Cons
• Disrupts aquatic ecosystems and fish migration.
• Reservoirs flood habitats and displace communities.
• Sediment buildup reduces storage capacity over time.
6.10 Geothermal Energy
How It Works
• Heat from Earth’s interior is used to generate steam, which spins turbines to produce electricity.
• Can also be used directly for heating buildings and greenhouses.
Pros
• Reliable, renewable, and low emissions.
• Small land footprint compared to solar and wind.
Cons
• Limited to geologically active areas (e.g., Iceland, western U.S.).
• Drilling and construction are expensive.
• May release trace gases (e.g., hydrogen sulfide) and cause minor earthquakes.
6.11 Hydrogen Fuel Cells
How They Work
• Hydrogen gas (H₂) reacts with oxygen (O₂) in a fuel cell → produces electricity, heat, and water vapor.
• Unlike batteries, fuel cells generate electricity continuously if fuel is supplied.
Pros
• Clean—only water is emitted.
• Efficient and quiet operation.
• Can power vehicles, buildings, or backup generators.
Cons
• Hydrogen is not freely available—must be extracted (usually from natural gas or water via electrolysis).
• Energy-intensive and expensive production.
• Storage and transportation are difficult due to hydrogen’s low density and flammability.
6.12 Conservation and Efficiency
Energy Efficiency
• Using technology that delivers the same service with less energy (e.g., LED lights, efficient appliances, hybrid cars).
• Reduces demand and saves money and resources.
Energy Conservation
• Changing behaviors to use less energy (e.g., turning off lights, using public transport, adjusting thermostat).
• Often low-cost or no-cost with immediate environmental benefits.
Building Design
• Insulation, passive solar heating, high-efficiency HVAC systems, smart thermostats.
• LEED certification and green buildings promote sustainability.
Transportation Efficiency
• Mass transit, electric and hybrid vehicles, biking, and walking reduce fossil fuel use.
• Policies like fuel economy standards (e.g., CAFE standards in the U.S.) encourage innovation.
In a Nutshell
Energy use is central to modern society, but different sources carry different environmental and economic costs. Fossil fuels dominate but contribute heavily to pollution and climate change, while renewables offer cleaner alternatives with growing potential. Efficient technologies, conservation practices, and sustainable planning can reduce our reliance on nonrenewable resources and support a cleaner energy future.