TransForum Vol. 3, No. 1

ETHANOL FUEL ADDITIVE MAY HELP SOLVE THE DIESEL EMISSIONS PUZZLE

The quest to reduce atmospheric emissions associated with diesel-fueled vehicles has faced a longstanding "Catch-22"conundrum: lower particulate matter (PM) emissions, and the emissions of nitrogen oxides (NOx) increase; push down the NOx levels, and PM emissions rise. Both PM and NOx are major contributing factors to smog (ozone) and other air pollution problems. Not long ago (see TransForum, Volume 1, Number 4), researchers at Argonne found a high-tech way to resolve this paradox their solution involved a revolutionary new membrane technology and closely controlled operating conditions. The discovery, hailed by former U.S. Department of Energy (DOE) Secretary Bill Richardson as a major step in addressing air pollution associated with diesel engines, was originally tested on a locomotive engine. The ongoing diesel engine research program at Argonne has uncovered another promising approach to solving the diesel conundrum.

Testing of a 1.9-L Volkswagen diesel engine by Argonne researchers revealed that particulate and NOx emissions can be significantly reduced by using a diesel-ethanol blend.

Within certain operating ranges, it turns out, using an ethanol fuel additive reduces both PM and NOx emissions. "We expected to see a decrease in particulate matter," says Roger L. Cole, a researcher at Argonne's Center for Transportation Research. "What was unexpected was the large decrease in NOx."

According to Cole, "Our tests of this fuel-additive alternative covered almost all of the U.S. Environmental Protection Agency's (EPA's) two test cycles: the FTP (city and suburban) and the US 06 (faster accelerations, higher speeds). The range in which both PM and NOx were reduced represents a fraction of our test area; we are confident that, with more research, we can achieve a broader range."

Using special facilities at AutoResearch Laboratories (Chicago, Illinois), Cole and his colleagues tested the enhanced fuel, E-Diesel a proprietary formulation of diesel, ethanol, and a solubilizing agent (called Puranol) developed by Pure Energy Corporation of New York on a 1.9-L Volkswagen diesel engine. With the addition of 15% ethanol, PM emissions were reduced by up to 75% and NOx emissions by up to 84%. These very striking results were obtained in an operating region corresponding to loads greater than 105 ·m (50% load) and engine speeds less than 1,700 rpm. This region (high loads at low speeds) is of greatest interest for heavy-duty engines, but the research can also be applied to automobile diesel engines.

The engine used in the Argonne testing was equipped for exhaust-gas recirculation (EGR), which can affect emissions levels; similar tests with modified EGR rates, modified fuel injection timing, and modified turbocharger boost are needed to broaden the range of these results. Heavy-duty trucks and buses today account for about one-third of NOx emissions and one-quarter of PM emissions from mobile sources. In some urban areas, the contribution is even greater. With more stringent heavy-duty diesel engine standards set to take effect in 2002, and extremely low emissions levels targeted for 2007, Argonne's findings about the effects of the ethanol additive on diesel fuel emissions point the way for industry to meet the upcoming EPA emission standards, which allow for use of alternative fuels. "Eliminating the visible smoke and the harmful emissions associated with diesel engines," Cole suggests, "will go a long way toward making diesel trucks, and perhaps even diesel cars, more acceptable."

The use of ethanol-enhanced diesel fuel in vehicles, trucks, buses, trains, shipping, power generation, and other major petroleum markets could also lead to significant energy savings. In addition, the successful blending of ethanol and diesel fuel could stimulate both the ethanol industry in Illinois (with an annual production of more than 600 million gallons, the leading producer of ethanol in the United States) and the agricultural economy across the nation. Says Cole, "This research will provide another approach to breaking the barrier of NOx and particulate trade-offs."

The work was sponsored by the Illinois Department of Commerce and Consumer Affairs and the U.S. Department of Energy.