Cars and Trucks: Emissions Calculations

In the case of the Light-Duty Gasoline Trucks, the quality-of-fit of this data to the National Inventory Report target is nearly perfect for some years (e.g. 2011-2014), low for some years (e.g. 2006-2010) and high for other years (2016-2023). The estimator should be at least slightly wrong because it isn't supposed to include the small number of diesel-powered light truck vehicles, but it currently does. However, if we imagine removing the emissions contributions from diesel vehicles from the PlanZero estimator, then the estimator would be lower, and therefore more-wrong for years 2006 to 2010. Another possible source of the discrepancy is accounting around ethanol: it represents 5-10% of fuel, and produces ${\mathrm{C}\mathrm{O}}_2$, but it is not a fossil fuel. A third possibility is the reclassification of vehicles within either the NIR, or the NEUD, or both, because car makers have blurred the line between cars, crossover vehicles, and SUVs. Still, the estimator is relatively accurate, at least by the standards of this PlanZero first pass.

Critical Success Factors

The arithmetic of emissions in this sector is such that some combination of the following is required:

1. Reduce number of gasoline vehicles of this class
2. Reduce distance travelled by this class of vehicle under gasoline power
3. Improve gasoline engine efficiency

Barriers

Before we get into barriers, it must be stated that the obvious and preeminent strategy for emissions reduction in this sector is a transition to EVs.

• Comfort: People like to drive, and they like to drive at high speeds, in relative privacy inside large, spacious personal vehicles. This requires additional energy.
• Identity: Brand marketing plays a strong role in car puchasing decisions. Vehicle choices have become an integral part of many people's professional and personal image.
• Longevity: Annual vehicles sales are only about 10% of the number of vehicle registrations. It could take decades to change the technology mix within this sector.
• EV Range: Battery power density is such that EVs cannot yet match the range that's possible using a large gasoline tank. Charging a battery isn't as convenient as refilling a tank.
• EV Sticker Price: Conventional internal combustion vehicles are cheaper than similar hybrid and EV variants.
• EV Cost Complexity: The total cost of ownership for EVs is less than conventional vehicles in many use cases, but not all, and the calculation depends on several factors, not all of which are top-of-mind or even well-known to buyers.
• EV Pace of Deprecation: The relatively rapidly evolving technology in EVs may discourage some buyers (holding out for e.g. better range at lower cost next year), and some sellers (who wish their mid-life EVs commanded higher resale prices).
• EV Range Anxiety: Managing a battery charge level is different from keeping a gasoline tank full. In some cases it's easier, but in some cases it's more difficult. EV charging infrastructure lags gasoline refuelling infrastructure by most of a century; charging an EV on the road can be an inconvenience, or a real challenge.
• Lithium batteries degrade in cold temperatures: Cold temperatures degrade lithium-ion battery performance more than gasoline engine performance. Sodium ion batteries are more robust to cold, may help in future designs.
• Lithium Battery Fire Concerns: EV batteries (especially lithium-ion batteries) can cause fires, especially in the event of a vehicle crash. These fires are considered less likely than gasoline fires in crash scenarios, but the fires introduce new fire-fighting challenges when they occur.
• Gasoline engine efficiency is hard to improve: Gasoline engines have already been refined over almost a century of intense engineering. Higher fuel efficiency is possible, but such engines are expensive relative to their fuel savings.

Strategies

The overarching strategy for emissions reduction in this sector is a transition to EVs. EV makers provide drop-in replacement vehicles for many roles currently carried out by gasoline vehicles. Many operational light-duty trucks could be replaced with EVs of today's price and capability when they're due for replacement, in such a way that the replacements would provide equivalent or better functionality at a lower total cost of ownership. The strategies required to eliminate direct emissions from light-duty trucks are incentives that encourage individuals and fleet managers to buy the EVs already for sale.

That said, there are operational roles that EVs still struggle with: for vehicles that aren't driven enough, an EV won't save enough on fuel to achieve a lower cost of ownership; for vehicles that are driven too much, an EV risks inconveniencing its driver by needing to be charged (slowly) while en-route rather than while parked overnight. Research in better batteries may address these challenges, although more radical ideas have been proposed, such as providing inductive charging capabilities underneath roadways, or charging lines that hang down from overhead. Such radical proposals would probably never be justified for only light-duty passenger vehicles, but radical solutions might be required to eliminate emissions from heavy-duty trucks (heavy-duty EV trucks today are not as close to performance parity with diesel ones, compared to what we see in light-duty cars and trucks). If such systems are developed for heavy-duty trucks, they may be useful to light-duty vehicles as well.

Conclusion

Canadians live far apart, drive a lot, and increasingly, they like to drive SUVs and pickup trucks. Combined, emissions in these sectors are on the rise and account for about 11% of Canada's net emissions. Historically, vehicles in these classes have been universally powered by fossil fuels. More recently, plug-in hybrids and purely battery-electric vehicles have been brought to market, and accounted for about 16% of new vehicle sales in 2024. I think it's likely that these EVs can and will replace the gasoline models over time, although I expect consumers will continue to push for better power-to-weight batteries than the ones in today's new vehicles. Cars are getting so reliable that some of the 1.5 million gasoline-powered vehicles sold in 2024 could still be on the road in 2050. That said, most cars are used for only 10-15 years. It remains to be seen how quickly EVs improve, and how much government intervention would be required to substantially eliminate emissions from this sector by 2050.

This post has introduced a relatively accurate estimator of emissions based on data from Natural Resources Canada's National Energy Use Database. The Transport / Road Transport / Light-Duty Gasoline Vehicles and Transport / Road Transport / Light-Duty Gasoline Trucks pages have been refreshed to feature this estimator, as well as updated critical success factors, barriers to those success factors, and strategies to address those factors and barriers. The next post in this series will look at enteric fermentation, the methane released during digestion by all livestock, but especially ruminants, and especially cattle.

Until then,

- James Bergstra

P.S. A note on why a little gasoline produces so much ${\mathrm{C}\mathrm{O}}_2\mathrm{e}$

I did not implement the PlanZero estimator by multiplying a quantity of fuel by an emission factor, because the NEUD had done that already. If I had done that, I would have had a natural reason to mention that the emission factor for gasoline is 2.307 kg ${\mathrm{C}\mathrm{O}}_2\mathrm{e}$ per litre of gasoline, and point out (because I don't think it's common knowledge but it should be), that the emissions from burning gasoline are more than the mass of the gasoline. Here, as a concluding remark on this post, I'm going to write about this anyway.

The reason combustion produces more mass in ${\mathrm{C}\mathrm{O}}_2$ from the tailpipe than is put into the fuel tank as gasoline, is that gasoline contains only hydrogen and carbon atoms. It is a mixture of many hydrocarbon molecules of various configurations, such as octane (8 carbon atoms and 18 hydrogen atoms), heptane (7 and 16), and benzene (6 and 6), but there's very little of anything else. Gasoline combustion requires oxygen, and when it combusts it produces carbon dioxide (${\mathrm{C}\mathrm{O}}_2$) and water vapour in a reaction like the following, for octane as an example:

$$2{\mathrm{C}}_8{\mathrm{H}}_{18}+25{\mathrm{O}}_2\to 16\mathrm{C}{\mathrm{O}}_2+18{\mathrm{H}}_2\mathrm{O}$$

In other words, 25 oxygen molecules are required to combust 2 octane molecules. Although gasoline is a somewhat variable mixture of octane and other molecules, typically about 2.3 to 2.65 kg of pure oxygen is required to combust a litre of gasoline. This is equivalent to roughly 9,000 liters of air at standard temperature and pressure. The reason the emissions weigh more than the fuel is that most of the mass of the ${\mathrm{C}\mathrm{O}}_2$ emissions are from the oxygen, not the gasoline. The emission factor for gasoline used in the NIR is 2.307 kg ${\mathrm{C}\mathrm{O}}_2$ / litre (NIR Annex 6: Emission Factors). Burning a standard tank of gas, say 65 litres, burns about 50kg of gasoline, and produces about 150 kg of ${\mathrm{C}\mathrm{O}}_2$ emissions.