Coal combustion is the chemical reaction between coal and oxygen that releases energy, carbon dioxide, and water (EK ENG-3.E.1); in a power plant, that heat boils water into steam that spins a turbine to generate electricity, while also releasing SO2, NOx, particulate matter, and mercury.
Coal combustion is what happens when coal burns. Chemically, it's a reaction between the fuel and oxygen that yields carbon dioxide and water and releases energy (EK ENG-3.E.1). In a coal-fired power plant, that energy is used as heat to boil water into steam, the steam spins a turbine, and the turbine generates electricity (EK ENG-3.E.2). Notice the chain there. Coal doesn't make electricity directly; it just makes heat, and the steam-turbine system does the rest.
The catch is that coal isn't pure carbon. It's mostly carbon, but it also contains sulfur and other impurities. So burning it releases more than CO2 and water. You also get sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter (PM), and mercury. That pollutant list is what makes coal combustion the dirtiest of the fossil fuels, and it's why this one term ripples through Units 6, 7, and 9.
Coal combustion lives in Topic 6.5 (Fossil Fuels) in Unit 6: Energy Resources and Consumption. It directly supports two learning objectives. For 6.5.A you describe how fossil fuels generate power, which means knowing the combustion reaction and the steam-turbine sequence. For 6.5.B you describe the environmental effects, which means knowing the pollutant lineup. Coal also sets up the comparison game APES loves. Coal releases the most CO2 per unit of energy of the fossil fuels, so when a question asks why a city might switch from coal to natural gas, your answer comes straight from combustion chemistry.
Keep studying AP Environmental Science Unit 6
Fossil Fuels (Unit 6)
Coal combustion is one specific case of the general fossil fuel combustion reaction in EK ENG-3.E.1. All fossil fuels burn to release CO2, water, and energy, but coal carries the most impurities, so it produces the dirtiest exhaust per unit of energy.
Acid Rain (Unit 7)
The SO2 and NOx released by coal combustion react with water in the atmosphere to form sulfuric and nitric acid. When an FRQ asks where acid rain comes from, coal-fired power plants are the textbook source.
Greenhouse Gases (Unit 9)
The CO2 from coal combustion is the headline anthropogenic greenhouse gas. This is the bridge from Unit 6 (how we make energy) to Unit 9 (how that energy choice drives climate change).
Incomplete Combustion (Units 6-7)
Complete combustion gives you CO2 and water. When there isn't enough oxygen, incomplete combustion produces carbon monoxide instead, which is a major indoor air pollutant where coal or wood is burned for heating and cooking.
Coal combustion shows up most often in MCQs that test the chain of logic, not just the definition. Expect stems like a plant burning 500 tons of coal daily where you identify the primary energy-releasing reaction (carbon plus oxygen yielding CO2 and energy), or a city weighing a switch from coal to natural gas where you explain why natural gas emits less CO2 per unit of energy. Pollution-control technology comes up too. Fluidized bed combustion appears in questions asking what environmental benefit it offers over conventional pulverized coal burning (mainly reduced SO2 and NOx emissions). On FRQs, coal combustion is a go-to source when you're asked to identify the origin of SO2, particulate matter, mercury, or acid deposition. The skill being tested is tracing cause and effect from the smokestack to the environmental impact.
Both are fossil fuel combustion reactions that release CO2, water, and energy. The difference is the carbon-to-hydrogen ratio and the impurities. Coal is nearly all carbon with sulfur and mercury mixed in, so it produces the most CO2 per unit of energy plus SO2, particulates, and mercury. Natural gas (methane, CH4) gets a big chunk of its energy from hydrogen burning to water, so it emits roughly half the CO2 per unit of energy and almost none of coal's other pollutants. That's the chemistry behind every 'why switch from coal to natural gas' exam question.
Coal combustion is a chemical reaction between coal and oxygen that releases carbon dioxide, water, and energy (EK ENG-3.E.1).
Coal-fired plants make electricity indirectly. Burning coal produces heat, the heat turns water into steam, the steam spins a turbine, and the turbine generates electricity (EK ENG-3.E.2).
Because coal contains sulfur and other impurities, burning it also releases SO2, NOx, particulate matter, and mercury, making it the dirtiest fossil fuel.
Coal releases the most CO2 per unit of energy of the fossil fuels, which is why switching to natural gas reduces greenhouse gas emissions per unit of electricity.
The SO2 and NOx from coal combustion are the main precursors of acid rain (Unit 7), and the CO2 connects directly to climate change (Unit 9).
Fluidized bed combustion is a cleaner-burning technology that reduces SO2 and NOx emissions compared to conventional pulverized coal combustion.
It's the reaction between coal and oxygen that releases energy, CO2, and water. In a power plant, that heat boils water into steam that turns a turbine to generate electricity, while also releasing SO2, NOx, particulate matter, and mercury.
No. Complete combustion of pure carbon would give just CO2, but real coal contains sulfur and other impurities, so burning it also releases sulfur dioxide, nitrogen oxides, particulate matter, and mercury. That full pollutant list is exactly what the exam wants you to know.
Coal is nearly all carbon, so it emits the most CO2 per unit of energy plus SO2 and mercury from its impurities. Natural gas (methane) burns much of its hydrogen into water, so it releases roughly half the CO2 per unit of energy and far fewer other pollutants.
In four steps: combustion releases heat, the heat turns water into steam, the steam spins a turbine, and the turbine drives a generator that produces electricity. The exam loves asking you to put this sequence in order, and it's EK ENG-3.E.2 word for word.
Coal contains sulfur, so burning it releases SO2 along with NOx from high-temperature combustion. Those gases react with water vapor in the atmosphere to form sulfuric and nitric acids, which fall as acid rain (a Unit 7 topic that traces straight back to coal plants).