Air pollution from power generation

At 7 pm on Tuesday, April 24 2018, at the point of generation, Ontario power plants collectively emitted 258 metric tons of carbon dioxide (CO₂), which is the main human-made greenhouse gas. In addition to those 258 tons of CO₂, the following amounts of other types of air pollution were also produced:

83 kilograms of particulate matter (PM).
133 kg of oxides of nitrogen (NOx).
5 kilograms of oxides of sulfur (SOx).

All of this air pollution originated in power plants that burn combustible fuel—see combined cycle gas, simple cycle gas, steam cycle gas, and biofuel/other (and before May 2014, coal) in the table above.

The combustible-fired plants contributed 4% of Ontario’s in-province generated electricity in the selected hour.

The non-emitting plants—mainly nuclear (62%) and hydro (28%), with some contribution from wind (7%)—made 96% of Ontario’s electricity and contributed nothing to this point-of-generation air pollution.

At the point of generation, each kilowatt-hour of Ontario grid electricity came with roughly 17 grams of CO₂.

If we want to lower the CO₂ content of grid electricity, we must use less combustible fuel. That means adding more zero-emitting generation capacity.

Electricity and energy

Not counting the food we eat, Ontarians use over 500 billion kilowatt-hours of bulk, engineered energy every year. We use three major types of bulk energy. These are:

Transportation energy. This is the energy that moves cars, trucks, airplanes, and trains, and other motorized vehicles. Ontarians use more than 200 billion kWh of transportation energy every year. Most transportation energy comes from gasoline, some from diesel. Transportation energy produced roughly 45 million tons of carbon pollution in 2014.
Heat energy. This is what keeps our homes, schools, hospitals, and other buildings warm in the winter and prevents our water and sewage pipes from freezing. It cooks our food all through the year, and keeps us supplied with hot water. We use around 152 billion kWh of heat every year, most of it in the months following September and before May. Most of our heat comes from burning fossil fuels. Fossil-fired heat in Ontario produced close to 30 million tons of carbon pollution.
Electricity. Electricity is a super-category of energy. It can do the same thing as the fossil fuels that provide transportation and heat energy, but it also powers our homes and cities, radio, TV, and the internet, and most vital infrastructure, including moving water and sewage. Ontarians use roughly 150 billion kWh of electricity per year. In 2014, all Ontario electricity generators produced less than 7 million tons of carbon pollution—one-sixth the pollution from transportation, and one-quarter the pollution from heat.

Each kilowatt-hour of gasoline energy comes with roughly 253 grams of CO₂; a kWh from diesel comes with 275 grams. In the selected hour—7 pm on Tuesday, April 24 2018—each kilowatt-hour of Ontario electrical energy came with 17 grams of CO₂.

Most heat energy comes by burning natural gas. At its most efficient, natural gas-fired heat energy comes with roughly 188 grams of CO₂ per kWh. Again, compare that with the 17 grams of CO₂ that came with each kWh of Ontario electricity generated at at 7 pm on Tuesday, April 24 2018.

It is obvious that Ontario electricity is, almost always, much cleaner than the energy we use for transportation and heating. To understand why this is, browse different dates and hours in the table above. As you do, note the amounts of energy that each type of generator produced at that date or time, and the amount of air pollution that came with that energy.

Wind+Gas and pollution

The combination of wind and gas generators made 1,533 megawatt-hours (10%) of Ontario’s elecricity at 7 pm on Tuesday, April 24 2018. At the point of generation, how much air pollution came with the 1,533 MWh generated in that time period?

224 metric tons of CO₂.
9 kilograms of PM.
73 kg of NOx.
1 kilograms of SOx.

What if wind+gas replaced nuclear?

What if wind and gas replaced nuclear in the selected hour?

If a combination of wind and gas had replaced the 62%—9,455 megawatt-hours—that the nuclear fleet produced, then at the point of generation wind+gas in that hour would have emitted 3,170 tons of CO₂—11.78 times as much as all generators collectively emitted.

And what about the other air pollutants? How much of them would wind+gas have emitted at 7 pm on Tuesday, April 24 2018, if wind+gas had replaced nuclear? Here’s how much:

198 extra kg of PM, on top of the 83 kg already emitted.
1,035 additional kg of NOx, on top of the 133 kg already emitted.
20 kg of SOx, in addition to the 5 kg that were actually emitted.

FUEL	MWh
Nuclear
Combined cycle gas
Simple cycle gas
Steam cycle gas
Biofuel
Solar
Wind
Hydro
TOTAL
Wind+Gas