Canada’s Air Pollutant Emissions Inventory Report 2025: chapter 2.3

2.3 Nitrogen Oxides

Approximately 1.2 Mt of nitrogen oxides (NOx) were released in Canada in 2023 (Table 2–5). Transportation and Mobile Equipment was the largest contributor, accounting for 38% (467 kt) of total NOx emissions. Within this source category, Off-Road Diesel Vehicles and Equipment, Heavy-Duty Diesel Vehicles, Domestic Marine Navigation, Fishing and Military and Rail Transportation sectors were the largest emitters, collectively contributing 32% (388 kt) of total NOx emissions. The Oil and Gas Industry accounted for 37% (452 kt) of total NOx emissions in 2023, with the Upstream Oil and Gas Industry sector accounting for nearly all of the Oil and Gas Industry total (96% or 432 kt). Electric Power Generation (Utilities) contributed 7.3% (90 kt) of total NOx emissions, with coal-fired generation contributing 3.8% (46 kt) of the national total. The remaining 18% of NOx emissions were distributed across multiple sources.

In 2023, national NOx emissions were 45% (1.0 Mt) below 1990 levels and 46% (1.0 Mt) below 2005 levels (Figure 2–3). Significant drivers of this trend were the decrease in emissions from Heavy-Duty Diesel Vehicles as well as Light-Duty Gasoline Trucks and Vehicles. Despite a 168% increase in total VKT from Heavy-Duty Diesel Vehicles and a 28% increase in the total fuel consumption of Light-Duty Gasoline Trucks and Vehicles, improved fuel economy and implemented regulations have effectively lowered NOx and hydrocarbon emissions from engines.Footnote 6 

Within Electric Power Generation (Utilities), coal-electric power generation contributed to the downward trend across the time series, with a gradual decrease in emissions from 1998 to 2023. This decrease can be attributed to coal-fired power plants that have closed down and been replaced by lower-emission sources such as natural gas power plants.

The Oil and Gas Industry experienced an increase of 31% (108 kt) in emissions since 1990. This increase is attributed to expansion and growth in the industry. Between 2019 and 2021, most major contributors to NOx emissions experienced decreases. Notably, the Upstream Oil and Gas Industry saw a significant decrease between 2019 and 2020, a slight decrease between 2020 and 2021 and a minor increase between 2021 and 2023, resulting in an overall decrease of 17 kt (3.6%) over this five-year period. This can be attributed primarily to a 5.1% reduction in reported fuel gas consumption from 2019 to 2023.

The most significant changes in NOx emissions from 1990 to 2023 include:

The most significant changes in NOx emissions from 2005 to 2023 include:

Figure 2–3: Trends in Canadian NOx Emissions (1990 to 2023)

Figure 2–3: Trends in Canadian NOx Emissions (1990 to 2023)
Long description for Figure 2-3

Figure 2–3: Trends in Canadian Nitrogen Oxides Emissions for 1990 to 2023.

Figure 2–3 is a stacked area graph displaying the seven major contributors to national nitrogen oxides trends. They are the following: Domestic Marine Navigation, Fishing and Military, Rail Transportation, Light-Duty Gasoline Trucks and Vehicles, Coal (Electric Power Generation), Heavy-Duty Diesel Vehicles, Off-Road Diesel Vehicles and Equipment, Other, and Upstream Oil and Gas Industry. The figure shows that Other and Upstream Oil and Gas Industry have the biggest shares in the total national nitrogen oxides emissions in 2023. The following table displays the contributions (kt) for the years 1990 to 2023.

Trends in Canadian Nitrogen Oxides Emissions for 1990 to 2023 (kt)
Sector 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023
Upstream Oil and Gas Industry 308 303 322 346 377 396 409 453 468 484 427 419 419 461 392 397 401 424 435 431 425 439 431 436 446 447 439 447 453 452 427 422 427 432
Other 724 703 703 700 714 714 718 727 715 720 740 711 738 700 679 636 558 548 512 474 500 488 454 441 435 422 408 417 416 412 382 386 390 397
Off-Road Diesel Vehicles and Equipment 305 276 265 279 294 298 306 322 312 316 333 311 293 296 291 288 266 246 233 200 221 226 211 206 191 201 188 202 197 185 156 151 142 132
Heavy-Duty Diesel Vehicles 336 312 315 330 365 396 407 430 426 431 414 379 375 397 395 399 382 387 382 367 359 320 287 271 253 213 177 165 160 145 124 127 123 119
Coal (Electric Power Generation) 206 205 211 192 188 198 208 222 235 227 225 220 215 209 194 186 173 181 169 151 153 132 126 124 129 115 117 110 92 88 66 62 52 46
Light-Duty Gasoline Trucks and Vehicles 296 316 356 409 467 477 502 508 517 497 484 456 423 365 326 275 244 226 197 175 155 110 97 88 77 69 62 53 49 44 33 32 31 32
Rail Transportation 147 149 145 144 153 149 146 148 143 139 140 139 137 123 122 126 125 120 114 96 102 101 100 95 94 87 79 79 79 79 71 67 66 68
Domestic Marine Navigation, Fishing and Military 60 61 62 63 63 64 66 67 68 69 70 72 73 75 76 78 77 76 75 74 72 71 69 68 67 65 65 68 71 71 62 62 67 70

Table 2–5: National Summary of Annual NOx Emissions (tonnes)

Source 1990 2000 2005 2018 2019 2020 2021 2022 2023
Ore And Mineral Industries 100,000 99,000 110,000 82,000 80,000 77,000 82,000 79,000 85,000
Oil And Gas Industry 340,000 460,000 430,000 470,000 470,000 440,000 440,000 440,000 450,000
Downstream Oil and Gas Industry (Oil And Gas Industry) 35,000 30,000 31,000 17,000 16,000 17,000 17,000 17,000 20,000
Upstream Oil and Gas Industry (Oil And Gas Industry) 310,000 430,000 400,000 450,000 450,000 430,000 420,000 430,000 430,000
Electric Power Generation (Utilities) 260,000 330,000 250,000 130,000 120,000 100,000 100,000 94,000 90,000
Coal (Electric Power Generation (Utilities)) 210,000 230,000 190,000 92,000 88,000 66,000 62,000 52,000 46,000
Diesel (Electric Power Generation (Utilities)) 3,200 8,500 8,500 9,800 9,900 9,800 8,400 9,800 11,000
Landfill Gas (Electric Power Generation (Utilities)) 45 400 300 150 140 130 100 100 130
Natural Gas (Electric Power Generation (Utilities)) 20,000 65,000 38,000 18,000 18,000 18,000 23,000 25,000 25,000
Other (Electric Power Generation) (Electric Power Generation (Utilities)) 27,000 27,000 21,000 8,900 8,800 8,100 7,000 7,300 7,200
Manufacturing 190,000 180,000 140,000 72,000 70,000 66,000 70,000 70,000 70,000
Transportation and Mobile Equipment 1,300,000 1,600,000 1,300,000 610,000 580,000 490,000 480,000 480,000 470,000
Air Transportation (LTO) (Transportation and Mobile Equipment) 5,100 5,900 5,900 7,500 7,500 3,800 4,100 6,400 7,100
Domestic Marine Navigation, Fishing and Military (Transportation and Mobile Equipment) 60,000 70,000 78,000 71,000 71,000 62,000 62,000 67,000 70,000
Heavy-Duty Diesel Vehicles (Transportation and Mobile Equipment) 340,000 410,000 400,000 160,000 150,000 120,000 130,000 120,000 120,000
Heavy-Duty Gasoline Vehicles (Transportation and Mobile Equipment) 37,000 35,000 25,000 9,200 7,700 5,700 5,200 4,600 4,800
Heavy-Duty LPG/NG Vehicles (Transportation and Mobile Equipment) 6,700 340 140 86 97 87 90 100 95
Light-Duty Diesel Trucks (Transportation and Mobile Equipment) 4,000 7,900 5,800 720 670 590 660 680 650
Light-Duty Diesel Vehicles (Transportation and Mobile Equipment) 1,900 2,300 1,700 230 220 180 190 200 180
Light-Duty Gasoline Trucks (Transportation and Mobile Equipment) 110,000 230,000 150,000 31,000 29,000 22,000 21,000 21,000 22,000
Light-Duty Gasoline Vehicles (Transportation and Mobile Equipment) 190,000 250,000 120,000 17,000 16,000 11,000 11,000 11,000 10,000
Light-Duty LPG/NG Trucks (Transportation and Mobile Equipment) 290 50 25 6.3 5.3 3.1 3.7 3.5 3.7
Light-Duty LPG/NG Vehicles (Transportation and Mobile Equipment) 0.95 0.69 0.20 0.073 0.072 0.12 0.23 0.20 0.23
Motorcycles (Transportation and Mobile Equipment) 660 970 980 1,700 1,700 1,400 1,500 1,400 1,500
Off-Road Diesel Vehicles and Equipment (Transportation and Mobile Equipment) 310,000 330,000 290,000 200,000 190,000 160,000 150,000 140,000 130,000
Off-Road Gasoline/LPG/NG Vehicles and Equipment (Transportation and Mobile Equipment) 62,000 62,000 46,000 36,000 36,000 33,000 33,000 32,000 33,000
Rail Transportation (Transportation and Mobile Equipment) 150,000 140,000 130,000 79,000 79,000 71,000 67,000 66,000 68,000
Tire Wear and Brake Lining (Transportation and Mobile Equipment) NA NA NA NA NA NA NA NA NA
Agriculture 2,100 2,200 2,100 2,800 2,900 2,600 2,700 2,900 2,800
Commercial/Residential/Institutional 63,000 70,000 68,000 67,000 68,000 62,000 59,000 62,000 58,000
Incineration And Waste 6,700 6,700 7,900 4,300 4,400 5,200 4,600 4,600 3,700
Paints and Solvents NA NA 35 15 51 40 35 140 140
Dust NA NA NA NA NA NA NA NA NA
Fires 7,500 1,400 890 600 670 530 520 1,200 230
Grand Total 2,200,000 2,700,000 2,300,000 1,400,000 1,400,000 1,300,000 1,200,000 1,200,000 1,200,000

Notes:
Totals may not add up due to rounding.
0.00 Indicates emissions were truncated due to rounding.
NA Indicates no emissions.

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2025-03-14