What does energy do to the air, the climate and people’s lives?

Burn a tonne of coal, gas or oil: count its CO₂, leaked methane and air pollutants, follow the smoke downwind, then weigh Prairie City’s energy bills against income

F11 of Energy Systems, Step by Step: burn one tonne of coal, natural gas or oil and count its CO₂, the methane leaked before gas is burned and its air pollutants before and after controls; see how the harm spreads with distance and what EPA estimates it costs; then read energy burden by household income in Prairie City.
  • Foundations · L1
  • 20 min guided · about 10 min practice
  • After F4

The idea in two tables: one tonne burned, and who carries the bills

One tonne burned in a large boiler, before → after the controls AP-42 describes (illustrative coal and oil; EPA factors).
Fuel CO₂ CO₂ per MWh of heat SO₂ NOx Fine particles Health harm (EPA estimate)
Coal 2.44 t 341 kg 38.0 → 3.8 kg 11.0 → 5.5 kg 5.21 → 0.38 kg $3,130 → $330
Natural gas 2.69 t 202 kg 0.01 → 0.01 kg 4.5 → 3.3 kg 0.18 → 0.18 kg $60 → $50
Oil 3.19 t 267 kg 4.0 → 4.0 kg 3.4 → 1.4 kg 0.22 → 0.22 kg $310 → $290
  • Methane. If 2.3% of the gas leaks before it is burned, a tonne of gas adds 23.5 kg of methane, about 0.70 t of CO₂e over 100 years (GWP 29.8).
  • Where it goes. In the lesson's spreading toy (illustrative), each person 300 km away breathes 1.3% of the dose at 10 km, yet 74% of the toy's exposure beyond 10 km happens more than 100 km away.
  • Health. Dollar values are EPA's 2025 benefit-per-ton estimates for power plants (2019 dollars): $57,000 per short ton of SO₂, $7,710 of NOx, $113,000 of fine particles.
Prairie City is fictional; its numbers are illustrative. Burden = home energy spending ÷ income for each group's representative household (its average spending ÷ its average income).
Group Average income Home energy a year Burden (representative household)
0-30% of area median income $13,000 $1,940 14.9%
30-50% of area median income $33,000 $2,131 6.5%
50-80% of area median income $53,000 $2,252 4.2%
80-100% of area median income $74,000 $2,417 3.3%
100% of area median income or more $145,000 $2,702 1.9%

The 6% and 10% lines are conventions (ACEEE; DOE's LEAD tool calls 6% or more high), not physical limits. With JavaScript on, you run each step yourself.

  • Real values. Heat and CO₂ are the 2006 IPCC Guidelines' defaults; pollutants are EPA's AP-42 factors for large boilers; dollar values are EPA's 2025 benefit-per-ton estimates (2019 dollars).
  • Illustrative. The coal's 2% sulfur and 10% ash, the oil's 0.2% sulfur, the controls chosen and the spreading toy are set for teaching.
  • Prairie City is fictional; its numbers are illustrative. Its household groups come from the course's shared city data, anchored to Wichita's incomes and Kansas's 2025 prices.

Need a refresher? F4 follows a fuel's heat through a power plant to the wire.

What you just did, as diagrams

Carbon in, CO₂ out
Every tonne of carbon burned makes 3.67 t of CO₂: a tonne of oil makes 3.19 t, gas 2.69 t and coal 2.44 t.
Compare by heat
Per MWh of fuel heat coal sends 341 kg of CO₂ and gas 202 kg; per MWh of useful heat or electricity, the equipment's efficiency comes in too.
Leaks count too
A 2.3% leak adds about 0.70 t of CO₂e to a tonne of gas over 100 years.
Pollutants can be caught
Controls cut coal's SO₂ from 38 to 3.8 kg a tonne; no control on this page touches its CO₂.
Burden, not bill
Energy burden is home energy spending divided by income: Prairie City's lowest-income group spends less than the highest, yet its representative household carries 14.9% against 1.9%.
Go deeper · AnalystGross and net heat, and why coal varies per tonne
  • Net heat. The IPCC counts the net calorific value: the heat a fuel gives, leaving out the heat in the water vapour it forms.
  • Gross heat is about 5% higher than net for coal and oil, and about 10% higher for most natural gas.
  • Gross-heat sources. EPA’s AP-42 and EIA count gross heat, so their CO₂ per unit of heat is a little lower than the IPCC’s for the same fuel.
  • Coal types vary much more per tonne than per unit of heat. Sub-bituminous coal holds 18.9 GJ a tonne: 1.82 t of CO₂ a tonne, yet 346 kg per MWh of heat, close to bituminous coal’s 341.
Go deeper · AnalystMethane over 100 years or 20
  • A global warming potential (GWP) compares the warming from a tonne of a gas with a tonne of CO₂ over a chosen horizon.
  • Fossil methane’s 29.8 over 100 years includes the CO₂ it finally turns into; the GHG Protocol uses it for leaks from oil and gas systems.
  • The horizon is a value choice. Methane breaks down within decades while CO₂ stays far longer, so a 20-year horizon counts methane much more: say which you use.
Go deeper · AnalystThe spreading toy, as a formula

Winds from every direction carry the particles out through ever wider rings while rain and the ground remove them. From \(r_0\) = 10 km out, each person at distance \(r\) (km) breathes, relative to the dose at \(r_0\),

\[c(r) = \frac{r_0}{r}\, e^{-(r - r_0)/L}, \qquad \text{share within } R = 1 - e^{-(R - r_0)/L}\]

  • \(L\) = 300 km is the toy’s illustrative reach; people live evenly around the plant, so the people in a ring grow with \(r\) while each one’s dose falls.
  • At 100 km: \(c\) = 7.4% of the dose at 10 km, and 74% of the toy’s exposure beyond 10 km happens farther out.
  • Inside 10 km the toy says nothing: there a tall stack’s plume may not yet have reached the ground.
  • Real estimates use air-quality models with real winds, chemistry and where people live: EPA’s benefit-per-ton values come from such models across the continental United States.
Go deeper · AnalystWork the numbers yourself
  • Carbon to CO₂. Burning 2 t of carbon makes 2 × 44 ÷ 12 = 7.33 t of CO₂: each carbon atom (12 g/mol) joins two oxygen atoms, and CO₂ weighs 44 g/mol.
  • A 2% leak. The leak is a share of all the gas produced, so 0.02 ÷ 0.98 = 0.0204 t of methane escapes per tonne burned, × 29.8 = 0.608 t of CO₂e.
  • Short tons. EPA's $57,000 is per short ton of SO₂ (907.18 kg), so 38 kg is 38 ÷ 907.18 × 57,000 = $2,388, in 2019 dollars.
  • Next. Which CO₂ number answers which question, with emission factors: A10.
Go deeperWhat this lesson leaves out
  • Life-cycle emissions from mining, drilling, shipping and building plants, beyond the gas leaks counted here.
  • Methane from coal mines and oil wells, ozone, mercury, water and land.
  • How much electricity a tonne makes in a power plant: F4.
  • Which CO₂ number answers which question: A10.
  • Who pays for a city's plan, and how burden changes with it: Analyst lesson A13.

Check yourself

Practice, about 10 minutes: four myths, then four questions.

Myth or fact? “Per tonne, coal sends more CO₂ into the air than any other fuel.”

  • Myth
  • Fact
Answer

Myth. A tonne of oil makes 3.19 t and gas 2.69 t against coal's 2.44 t; per MWh of heat, coal's 341 kg is the most.

Myth or fact? “A scrubber and a particle filter also cut a coal plant's CO₂.”

  • Myth
  • Fact
Answer

Myth. They cut SO₂ from 38 to 3.8 kg and fine particles from 5.2 to 0.4 kg a tonne, but the 2.44 t of CO₂ is unchanged.

Myth or fact? “A tall stack's pollution harms only the people who live next to it.”

  • Myth
  • Fact
Answer

Myth. Nearby downwind communities can be heavily exposed, but in the spreading toy 74% of the exposure beyond 10 km happens more than 100 km away; EPA's estimates count harm across the continental United States.

Myth or fact? “A high energy burden means a high energy bill.”

  • Myth
  • Fact
Answer

Myth. Prairie City's lowest-income group spends $1,940 a year, less than the highest group's $2,702, yet its burden is 14.9% against 1.9%.

A household earns $30,000 a year and spends $2,100 on home energy. What is its energy burden?

  • 0.7%
  • 7.0%
  • 14%
Answer

7.0%: 2,100 ÷ 30,000 = 0.070, above the 6% line ACEEE calls high.

Per tonne, oil sends the most CO₂; per MWh of fuel heat, coal does. Why can both be true?

  • A tonne of coal gives much less heat
  • Coal's controls add CO₂
  • Oil's CO₂ is counted over 100 years
Answer

A tonne of coal gives 7.2 MWh of heat against oil's 11.9 MWh, so each MWh of coal's heat carries more CO₂: 341 kg against 267.

A 2.3% leak adds about 0.70 t of CO₂e to a tonne of gas. About how much would a leak half as large add?

  • About 0.35 t
  • About 0.70 t
  • About 1.4 t
Answer

About 0.35 t: half the leak is about half the methane, so about half the CO₂e. The slider shows 0.33 t at 1.1% and 0.36 t at 1.2%.

With controls, EPA's estimate for a tonne of coal falls from about $3,130 to about $330. What do these dollars stand for?

  • The price of the coal
  • Health harm, mostly early deaths
  • What the controls cost
Answer

Health harm: EPA's estimate, in 2019 dollars, of the early deaths and illness from the fine particles the tonne's pollution makes; an estimate, not a price.

Numbers, sources and what’s next

Numbers to remember

Number What it means Source
2.44 · 2.69 · 3.19 t CO₂ from burning one tonne of bituminous coal, natural gas and diesel or heating oil (IPCC default values). IPCC, 2006 Guidelines, Vol. 2, Ch. 1, Tables 1.2 and 1.4 · 2006
29.8 Tonnes of CO₂ that warm the climate as much over 100 years as one tonne of fossil methane (IPCC AR6, as compiled by the GHG Protocol). GHG Protocol, IPCC Global Warming Potential Values, p. 2 · 7 Aug 2024
2.3% Methane from the U.S. oil and gas supply chain in 2015, as a share of gross gas production: about 60% above the EPA inventory's estimate (study abstract). Alvarez et al., Science 361, 186 · 2018
$57,000 EPA's 2025 estimate of the health harm avoided per short ton of SO₂ not emitted by U.S. power plants (2019 dollars): an estimate, not a price. EPA, benefit-per-ton technical support document, Table 8, p. 22 · June 2024
4.2 million Premature deaths worldwide in 2019 from outdoor air pollution, 89% of them in low- and middle-income countries. World Health Organization, fact sheet “Ambient (outdoor) air pollution” · 24 Oct 2024
6% · 10% Energy burdens that ACEEE calls high and severe; DOE's LEAD tool calls 6% or more high. Conventions, not physical limits. ACEEE, How High Are Household Energy Burdens? · Sep 2020

Keep going

Back to the course map

In the real world

WHO counts 4.2 million premature deaths worldwide in 2019 from outdoor air pollution, and 99% of the world's people lived where its air quality guideline levels were not met.

ACEEE found 25% of U.S. households with a high energy burden and 13% with a severe one, using 2017 survey data.

Both are estimates with their own methods and dates; read the sources below before quoting them.

Sources and further reading

Spotted an error, or stuck? Write to hlli@ksu.edu. Corrections are made in place and dated here.

Text licensed CC BY 4.0, code MIT: teachers and students may reuse and adapt it, with credit to Honglin Li.