Will New EPA Rules Kill the Internal Combustion Engine?

Proposed regulations are sweeping and cut allowable emission levels deeply.

The Environmental Protection Agency has been setting U.S. motor vehicle emissions standards for over half a century, and in the process has reduced the output of unburned hydrocarbons, particulate matter, oxides of nitrogen and carbon monoxide by several orders of magnitude since the unregulated engines of the 1950s. Today, however, the Biden Administration is proposing a set of rules that include strict CO2 emissions limits. With no technical way to remediate CO2 emissions from internal combustion engines, the rules may set the stage for the eventual elimination of gasoline and diesel-powered cars and light trucks. 

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Episode Transcript:

For over half a century, tailpipe emissions from American cars and trucks have been regulated by the Environmental Protection Agency. EPA regulations have been highly influential in other Western nations, as well, and with the importance of the U.S. market to automakers, any change in rules has profound impacts in how vehicles are engineered worldwide.

The EPA has authority under the U.S. Clean Air Act to set these regulations through a standard post and review process, and the latest generation of these rules for vehicle model years 2027 through 2032 are the most stringent yet.

So stringent, in fact, that some in the industry believe that they may trigger the end of combustion engine development among major automakers.

Notably, the regulations affect light-duty vehicles, cars and light trucks, as well as Class III medium-duty commercial vehicles. For electric vehicles, the new rules will mandate battery durability and warranty requirements for light-duty applications. The draft proposal for the amendments is 758 pages long, and casts a net that covers motor vehicle manufacturers, commercial importers of vehicles and vehicle parts, companies that convert vehicles to run on alternative fuels as well as commercial truck replacement engine makers.

The EPA notes that to date, increasingly stringent limits on CO, NOx, unburned hydrocarbons and particulate matter have been addressed by exhaust after-treatment and tighter control of the combustion process through computer-controlled direct injection advanced ignition and valve timing control, as well as tighter manufacturing tolerances on escape pathways such as piston ring blow-by. The proposed rules will require the use of alternate fuels or battery-electric hybrid drive lines to achieve the standards which now include a strict CO2 component.  

In 2022, pure electric vehicles accounted for just under 6 percent of the new light-duty fleet. Plug-in hybrids will likely be the main driver in reduced exhaust emissions, with S&P Global predicting that by 2030, pure electric and combustion or hybrid electric-combustion vehicles will form over two-thirds of the vehicle fleet, with about 10 percent powered by hydrogen.

While pollutants such as hydrocarbons, particulate matter, oxides of nitrogen and carbon monoxide can be addressed with exhaust after-treatment technology and combustion control, tight CO2 limits are impossible to address with engine technology. CO2 is a natural by-product of clean combustion, and the chemistry dictates that it can’t be scrubbed after the combustion chamber.

For the light-duty fleet, the proposed rules require an industrywide target of 82 g per mile of CO2 by model year 2032, an over 50 percent reduction from the existing already difficult 2026 standards. Medium duty trucks will be required to hit 275 g per mile by 2032, a 44 percent reduction in 2026 standards.

In the past, automakers used less stringent truck rules to reclassify SUVs and light trucks used primarily for personal use under the more relaxed category, allowing larger, more powerful engines. The new EPA rules will greatly reduce the difference between cars and light trucks in emissions, while medium-duty vehicles will have levels set on a work factor metric which uses inputs of payload, towing capacity and four-wheel-drive equipment.

And perhaps most significantly in the near term, the traditional ability of automakers to average, trade and bank CO2 output will be eliminated. In the past, automakers building large relatively fuel-inefficient vehicles could buy credits from EV makers or more fuel-efficient vehicle producers.

There are many other changes affecting both internal combustion engines and electric vehicle production, but the rule changes represent a watershed: the tipping point where no amount of improved emission control technology will allow a purely internal combustion engine vehicle fleet to stay in compliance. In less than a decade, almost every light-duty vehicle will have a battery and electric motor, either as the primary drive system or supported by a smaller, more fuel-efficient internal combustion engine.

Written by

James Anderton

Jim Anderton is the Director of Content for ENGINEERING.com. Mr. Anderton was formerly editor of Canadian Metalworking Magazine and has contributed to a wide range of print and on-line publications, including Design Engineering, Canadian Plastics, Service Station and Garage Management, Autovision, and the National Post. He also brings prior industry experience in quality and part design for a Tier One automotive supplier.