Renewable resources can be naturally replenished at or near the rate we use them; nonrenewable resources exist in a fixed amount and can’t be easily replaced by natural processes. In AP terms: renewables (solar PV/thermal, wind turbines, hydroelectric dams, geothermal, biomass/biofuels, tidal/wave) are reusable or continuously supplied by Earth systems. Nonrenewables (coal, petroleum, natural gas, uranium for nuclear fission) require transforming stored geologic energy and are depleted as they’re extracted. Key differences for the exam: replenishment rate (renewable = rapid/continuous; nonrenewable = geologic timescale), and environmental trade-offs (e.g., renewables lower greenhouse-gas emissions but need storage/land; nonrenewables release CO2 and have extraction impacts). Review EK ENG-3.A.1 and EK ENG-3.A.2 in the CED, and brush up with the Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE)—and practice questions are at (https://library.fiveable.me/practice/ap-environmental-science).

They’re nonrenewable because—even though fossil fuels come from natural sources—they form far too slowly to be replaced at the rate we use them. EK ENG-3.A.1 in the CED says nonrenewables exist in a fixed amount and can’t be easily replaced. Coal, petroleum, and natural gas form from buried organic matter under heat and pressure over millions of years, so burning them depletes a finite stock. By contrast, renewables are replenished at or near the rate we use them (EK ENG-3.A.2), like solar or wind. For the AP exam, you should be able to identify examples (coal, petroleum, natural gas, uranium/nuclear) and explain the time-scale reason for nonrenewability (Unit 6, Topic 6.1; learning objective ENG-3.A). For a quick review, see the Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE) and try practice questions (https://library.fiveable.me/practice/ap-environmental-science).

A renewable resource is one that can be naturally replenished at or near the rate you use it, so it won’t run out on human timescales. In AP terms (ENG-3.A), renewables are replenished naturally (solar, wind, hydro, geothermal, biomass/tidal/wave) while nonrenewables exist in a fixed amount (coal, petroleum, natural gas, uranium). Key idea: rate matters—sunlight and wind are effectively unlimited for us, but a forest is only renewable if you harvest slower than it regrows. Also consider reuse and energy transformation: renewables often require storage or conversion (solar PV, wind turbines, hydroelectric dams, biofuels). This distinction is tested on the exam under Topic 6.1 (identify differences between renewable and nonrenewable sources). For a quick review, see the Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE) and practice problems (https://library.fiveable.me/practice/ap-environmental-science).

Fossil fuels (coal, petroleum, natural gas) form from buried organic matter that’s been subjected to heat and pressure over geologic time—typically millions to hundreds of millions of years. For example, much coal formed in Carboniferous swamps ~300 million years ago; oil and gas often form over tens to hundreds of millions of years. That timescale matters because it makes these fuels nonrenewable: the Earth’s stock is essentially fixed on human timescales, so once we burn them we can’t replenish them at the rate we consume them (EK ENG-3.A.1). Practically, this drives resource depletion, price/energy-security issues, and strong incentives to switch to renewables (EK ENG-3.A.2)—a core idea in Unit 6 (10–15% of the AP exam). For a quick review, see the Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE) and more practice questions at (https://library.fiveable.me/practice/ap-environmental-science).

Nonrenewable. Nuclear power (fission) uses uranium, which exists in a fixed, mined supply and isn’t replenished at the rate we use it—so it fits EK ENG-3.A. Fission releases heat to make steam and turn turbines (not by burning fuel), and while nuclear plants emit very little CO2, they depend on limited uranium resources and produce long-lived radioactive waste and meltdown risks (see Chernobyl examples in the CED multiple-choice items). For AP you should link this to ENG-3.A.1 (fixed amount) vs. ENG-3.A.2 (replenishable sources like solar or wind). For a quick refresher, check the Topic 6.1 study guide on Fiveable (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE) and practice nuclear questions in Unit 6 (https://library.fiveable.me/ap-environmental-science/unit-6).

Renewable energy sources we actually use today include: solar (photovoltaic panels and solar thermal systems), wind turbines, hydroelectric dams, geothermal power, biomass and biofuels, and emerging tidal/wave energy—plus energy storage systems (batteries, pumped hydro) that help integrate these variable sources. These fit the CED definition of renewables: they’re naturally replenished at or near the rate we use them (EK ENG-3.A.2). On the APES exam you’ll see these terms (solar photovoltaic, solar thermal, wind turbines, hydroelectric dams, geothermal, biomass/biofuels, tidal energy, wave energy, energy storage) in Unit 6 questions (Unit 6 = 10–15% of the exam). For more detail and quick examples tied to the CED, check the Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE). Want practice Qs on how these compare to nonrenewables on exams? Try the practice problem bank (https://library.fiveable.me/practice/ap-environmental-science).

Short answer: you can't just make more oil and coal because they’re nonrenewable—they formed from buried ancient biomass over millions of years under heat and pressure, so they exist in a fixed amount and can’t be replaced at the rate we use them (CED EK ENG-3.A.1). Making “new” fossil fuels would either take geologic timescales or require huge energy inputs (e.g., synthesizing fuels from CO2 and hydrogen), which is costly and usually produces more emissions than it saves. That’s why we treat coal, petroleum, and natural gas as finite resources and focus on conserving them and switching to renewables (solar, wind, hydro, geothermal) covered in Topic 6.1–6.5. For quick review of these CED concepts, check the Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE), the Unit 6 overview (https://library.fiveable.me/ap-environmental-science/unit-6), and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Short answer: yes—hydroelectric power is classified as a renewable energy source under the CED (it’s replenished by the water cycle), but dams can create serious environmental trade-offs. Why it’s “renewable” (CED language): EK ENG-3.A.2 says renewables are replenished naturally at or near the rate of use. Flowing water is continuously recycled by precipitation and evaporation, so hydropower fits that definition. However, the CED also lists “hydroelectric dams” as a keyword because of their ecological impacts—they alter river flow, fragment habitat (blocking fish migration), trap sediment, change water temperature and quality, and can inundate land. Large reservoirs can also produce greenhouse gases (methane) from decomposing organic matter. For AP exam purposes (Unit 6), you should be able to: identify hydro as a renewable resource, explain how dams affect ecosystems (impacts on fisheries, sediment transport, and water quality), and propose trade-off solutions (fish ladders, dam removal, pumped-storage alternatives). Review Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE) and more unit review (https://library.fiveable.me/ap-environmental-science/unit-6). For practice, try the APES problem sets (https://library.fiveable.me/practice/ap-environmental-science).

“Replenished naturally” means the resource is renewed by natural processes fast enough to replace what you use. Per the CED (EK ENG-3.A.2), a renewable energy source can be replenished naturally at or near the rate of consumption. For example, sunlight and wind are effectively unlimited on human timescales, and forests or biomass can regrow if harvest rates don’t exceed regrowth (the sustainable yield). The key idea for the AP exam: pay attention to rate—a resource is only renewable if natural replenishment keeps up with use. If you overuse (cut forests faster than they regrow, overfish, or deplete groundwater faster than recharge), a “renewable” resource can become depleted in practice. For more AP-aligned review and examples, see the Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Solar panels (photovoltaic, PV) convert sunlight directly into electricity. In a PV cell, photons hit a semiconducting material (usually silicon), knocking loose electrons and creating an electric current; cells are wired into panels and an inverter changes that direct current (DC) into alternating current (AC) for homes. There’s also solar thermal: mirrors concentrate sunlight to heat a fluid and produce steam to drive turbines. Both transform solar radiation into usable energy without burning fuels. Solar is considered renewable because sunlight is naturally replenished at or near the rate we use it (EK ENG-3.A.2). It doesn’t rely on a fixed stock like coal or oil (EK ENG-3.A.1) and produces little direct greenhouse-gas pollution; storage (batteries) or grids are used to handle intermittency. For AP review, this maps to Topic 6.1 (solar photovoltaic/solar thermal)—see the Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE) and practice problems (https://library.fiveable.me/practice/ap-environmental-science).

Short answer: it’s about replenishment rate and timescale. The CED defines renewables as resources that can be replenished naturally at or near the rate we use them (EK ENG-3.A.2) and nonrenewables as fixed amounts that can’t be replaced on human timescales (EK ENG-3.A.1). Wood comes from living trees that regrow in decades to a few centuries if managed sustainably, so you can harvest and replenish forests on a timescale people can control. Coal formed from plant material buried and compressed over millions of years under heat and pressure—that process takes far longer than humans can wait, so coal is a fixed stock (a fossil fuel) and is nonrenewable. For AP practice, this distinction ties directly to ENG-3.A (identify differences between renewable and nonrenewable sources). For a quick review, see the Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE) and try related practice problems (https://library.fiveable.me/practice/ap-environmental-science).

If we completely ran out of nonrenewable oil, the effects would be economic, technological, and environmental—not an instant “shutdown,” but a big, painful transition. Oil is a fixed, nonrenewable resource (CED EK ENG-3.A.1), so scarcity would drive prices up, disrupt transportation, agriculture (fertilizers, diesel), and petrochemical products (plastics, solvents). You’d see rapid shifts to alternatives: natural gas, biofuels, electricity from renewables, and increased recycling and material substitution. On the APES exam, connect this to energy transformation, resource limits, and solutions (Unit 6: Energy Resources and Consumption). Policies and tech (efficiency, electrification, renewable deployment, and conservation) would be needed to reduce demand and replace services oil provided. For review, check the Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE), the Unit 6 overview (https://library.fiveable.me/ap-environmental-science/unit-6), and practice questions (https://library.fiveable.me/practice/ap-environmental-science) to prep for related free-response and multiple-choice concepts.

Renewable energy sources are better for the environment because they’re replenished naturally (solar, wind, hydro, geothermal, biomass) and generally produce far fewer greenhouse gases and pollutants than nonrenewables (coal, petroleum, natural gas, uranium for fission). Burning fossil fuels releases CO2 and other pollutants that drive climate change, lower air quality, and cause acid deposition; mining and drilling also damage habitats and cause spills. Renewables usually have lower lifecycle emissions and reduce dependence on finite resources (CED EK ENG-3.A, ENG-3.A.2). They also help meet AP exam themes: energy transfer, sustainability, and solutions (Unit 6 is 10–15% of the exam). Trade-offs exist (e.g., hydro dams affect rivers, biomass can emit CO2 if mismanaged), so you should know pros/cons for FRQs. For a focused review, see the Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE) and practice problems (https://library.fiveable.me/practice/ap-environmental-science).

Short answer: geothermal can be used in most places for heating/cooling, but for large-scale electricity generation it’s limited to certain geologic settings. Why: geothermal is a renewable energy source (replenished by Earth’s internal heat per EK ENG-3.A/3.A.2), but high-temperature resources ideal for power plants occur where Earth’s heat is close to the surface—e.g., volcanic zones, tectonic plate boundaries, hot spots, or areas with hydrothermal reservoirs (lots of active volcanoes/earthquakes). Everywhere else you can still use ground-source (geothermal) heat pumps for efficient heating and cooling because shallow ground temps are fairly uniform. So: electricity production = site-specific; heating/cooling = broadly available. For AP prep, know this distinction (Topic 6.1 keywords: geothermal energy)—it’s the kind of concept that shows up on multiple-choice or free-response (Unit 6) (study guide: https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE; unit overview: https://library.fiveable.me/ap-environmental-science/unit-6). Practice questions: https://library.fiveable.me/practice/ap-environmental-science.

Scientists determine a renewable resource’s replenishment rate by measuring how fast the system naturally produces or restores usable material and comparing that to how fast people use it. For biological resources (forests, fisheries, biomass) they measure primary productivity, population growth rates, recruitment, age structure, and recruitment variability from field surveys, samples, and long-term monitoring. For physical resources (groundwater, soil, wind, solar) they measure inputs like recharge rates, sediment deposition, wind speed distributions, or solar irradiance and model seasonal/annual averages. Scientists combine empirical data with population or hydrologic models to estimate a sustainable yield—the maximum harvest rate that won’t deplete the resource (harvest ≤ replenishment). These estimates feed exam-style analysis and quantitative problems (practice in AP tasks 5 & 6). For review, see the Topic 6.1 study guide (https://library.fiveable.me/ap-environmental-science/unit-6/renewable-nonrenewable-resources/study-guide/WLwymwWnydiu1fqTWjNE) and try related practice problems (https://library.fiveable.me/practice/ap-environmental-science).