In 1970, the U.S. passed the Clean Air Act, putting limits on the emissions produced by motor vehicles. Since then, emissions regulations have become even more stringent, with modifications made in 1977 and again in 1990. Nearly every country in the world has implemented similar increasingly stringent emissions standards. In response, automotive manufacturers have developed innovative new technologies (such as improved engine performance and exhaust aftertreatment) and systems (including on-board vapor recovery and on-board diagnostics) to meet the latest regulations. The result: a nearly 99% reduction in criteria pollutants—which include carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2) and particulate matter (PM).
While a 99% reduction is an impressive accomplishment, the regulations and associated technical improvements that have been implemented don’t address carbon dioxide (CO2) emissions in any meaningful way. CO2 is the main by-product of combustion and it is now considered to be a primary contributor to global warming.

U.S. transportation accounts for 31% of CO2 emissions, with 61% of that being attributed to passenger vehicles and 23% being attributed to heavy-duty vehicles. Source: EPA.
Currently, transportation sources account for 31% of total U.S. CO2 emissions, with passenger vehicles and heavy-duty vehicles contributing 61% and 23%, respectively. As population growth drives greater energy usage, CO2 emissions will surely increase unless we make some significant changes. With more vehicles on the road, and more miles driven, the U.S. has already witnessed a 12% jump in transportation CO2 emissions between 1990 and 2010 (this includes on-highway vehicles as well as air, marine and rail transportation). And, the U.S. Environmental Protection Agency forecasts further increases of 1.5% a year through 2020. At the same time, U.S. vehicle fuel economy has remained largely unchanged over the last few decades and, in some cases, is worse due to the popularity of larger, heavier vehicles like SUVs and light-duty trucks.
Transportation CO2 emissions have increased 12% between 1990 and 2010 and are expected to grow by 1.5% a year through 2020. Source: EPA.
Going forward, we must focus our efforts on reducing fuel consumption and, in turn, CO2 emissions. Doing so will have a positive economic effect, especially since the price for a gallon of regular fuel is topping $3.35 nationwide and $3.62 in California, where I live. Better yet, by addressing all sources of CO2—including commercial vehicles for which regulations were first introduced last year— and focusing all of our attention on improving efficiency while maintaining our current levels of criteria pollutants, we will have the most positive environmental effect possible.
At Achates Power, we’ve transformed a 100-plus-year-old diesel engine architecture that, in its day, set combined records for power density and fuel efficiency. Taking advantage of modern tools and technologies, we’ve made this opposed-piston, two-stroke engine clean, more fuel efficient and lower cost. Twenty-one percent more fuel efficient than the best diesel engine, and roughly 55% more fuel efficient than gasoline engines, the Achates Power engine architecture is sure to help automotive manufacturers address CO2 concerns and government fuel-efficiency regulations, both now and in the future.

Clean Diesel Engine Emissions Engine Design