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Preliminary Test Report Shows No Significant Change in Vehicle Emissions from Intermediate Ethanol Blends
7 October 2008
|Average percentage change in criteria emissions and fuel economy for all vehicles compared to E0 fuel on the LA92 cycle. Bars show average for all vehicles, while discrete data points show the change for each vehicle tested. Click to enlarge.|
A preliminary report released by the US Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) and Oak Ridge National Laboratory (ORNL) on the use of intermediate E15 and E20 ethanol blends (15% and 20% ethanol respectively) in 13 vehicles and 28 small non-road engines found that most of the regulated vehicle emissions from E15 and E20 use were within the normal test variation. No statistically significant change was detected.
The E10 (10% ethanol) blend market in the US will likely be saturated (at less than 15 billion gallons per year) in the next few years, possibly as soon as 2010. At the same time, the Renewable Fuel Standard (RFS) calls for 36 billion gallons of renewable fuel by 2022. The DOE says that while it remains committed to expanding the E85 infrastructure, that market represented less than 1% of the ethanol consumed in 2007 and will not be able to absorb projected volumes of ethanol in the near-term. Given this reality, DOE and others have begun assessing the viability of using intermediate ethanol blends as a way to accommodate growing volumes of ethanol. (Earlier post.)
In August 2007, the US Department of Energy (DOE) initiated a test program to assess the potential impacts of higher intermediate ethanol blends on conventional vehicles and other engines that rely on gasoline. The test program focuses specifically on the effects of intermediate blends of E15 and E20 on emissions, catalyst and engine durability, drivability or operability, and materials associated with these vehicles and engines.
In the study described in the report, an initial group of 11 vehicles was selected primarily to span evolution in emission control system technology and focused on two model years, 2003 and 2007. Five additional popular model vehicles were selected from a set of vehicles identified as particularly likely to be sensitive to increased ethanol content in gasoline. These five vehicles included three 1999 models, one 2001 model, and one 2004 model. The initial report describes results from 13 of the 16 vehicles.
All of the vehicles were tested on federal certification gasoline (E0), E10, E15, and E20. Due to time constraints in obtaining match-blended fuels, splash blends were used in this study&madsh;i.e., the E0 certification fuel was diluted with appropriate amounts of fuel grade ethanol. Match-blended and splash-blended fuels have different hydrocarbon and volatility characteristics. The report notes that while the different fuel characteristics were not expected to have significant impact on the temperature measurements, the emissions results may have been influenced slightly due to unintended changes in the vehicle cold start and warm up.
Vehicle results include the following when E15 and E20 were compared with traditional gasoline:
All 13 vehicles exhibited a loss in fuel economy commensurate with the energy density of the fuel. (Ethanol has about 67% of the energy density of gasoline on a volumetric basis.) With E20, the average reduction in fuel economy (i.e., the reduction in miles per gallon) was 7.7% compared to E0. Limited evaluations of fuel with as much as 30% ethanol were conducted, and the reduction in miles per gallon continued as a linear trend with increasing ethanol content.
Tailpipe emissions were similar. As ethanol content increased, NOx and NMOG showed no significant change; NMHC and CO emissions dropped slightly on average, although CO did not change appreciably from E10 to E20; ethanol emissions increased; acetaldehyde emissions increased; formaldehyde emissions increased slightly; and benzene and 1,3-butadiene were expected to decrease due to dilution, but measurements were only conducted on a subset of the vehicles and have not been thoroughly analyzed to date.
At closed-loop operating conditions, catalyst temperatures were cooler or unchanged with higher levels of ethanol. Seven of the 13 tested vehicles adjusted fueling with increased ethanol content to maintain a consistent fuel:air equivalence ratio† at wide-open throttle (WOT). In these cases, the catalyst temperatures at equivalent operating conditions were lower or unchanged with ethanol.
Six of the 13 tested vehicles ran leaner (albeit still rich) with E20 fuel than with E0 fuel at WOT. For these vehicles catalyst temperatures were between 29ºC and 35ºC higher at E20 relative to E0.
No operability or driveability issues were identified using any of the ethanol blends during the limited time of the project. Each vehicle accumulated at least 100 miles on each ethanol blend, and at least 200 miles on gasoline (E0 fuel). Mileage accumulations for the vehicles ranged from 500–1,200 due to additional tests on some of the vehicles.
None of the vehicles displayed a malfunction indicator light (MIL) as a result of the ethanol content of the fuel. No fuel filter plugging symptoms were observed. No cold start problems were observed in 75°F and 50°F laboratory conditions. No fuel leaks or conspicuous degradation of the fuel systems were observed.
Small non-road engine results include the following when E15 and E20 were compared with traditional gasoline:
Regulated emissions remained largely unchanged;
Engine and exhaust temperatures increased;
Engine performance was inconsistent, even with traditional gasoline;
Commercial engines, as well as more sophisticated residential engines, exhibited no particular sensitivity to ethanol from a durability perspective; and,
The effect of E15 and E20 on the durability of smaller, less expensive residential engines (e.g., line trimmers) was not clear given that a number of these engines failed regardless of fuel type.
Other studies currently underway on the use of intermediate ethanol blends in addition to the work reported on in this study include:
Emissions of various gasoline and ethanol blends. Performed in collaboration with EPA and CRC (Coordinating Research Council), this study will assess the impacts of varying Reid vapor pressure (RVP), T50, T90, and aromatic content of gasoline and different ethanol/gasoline fuel blends on tailpipe emissions and performance of 19 new and 3 in-use vehicles. About 30 different match-blended fuels will be used to collect emissions data on criteria pollutants [HC, CO, NOx, and particulate matter], ethanol, and carbonyl compounds. Co-funding from CRC will support blending and testing of two of the fuels. Detailed HC speciation data will be collected for all vehicles tested in this task. Detailed PM and semivolatile organic compound data will be collected for a subset of the fuels.
Evaporative emissions. This study, being conducted in collaboration with CRC will measure evaporative emissions associated with testing gasoline fuels of varying RVP (volatility) and ethanol blends on eight vehicles. Five fuels with defined vapor pressures and ethanol content ranging from 0 to 20% will be tested on four Tier-2 near-zero low-emission vehicles and four “enhanced” 1996–2001 model year vehicles. Static permeation, running loss, hot soak, and diurnal emissions will be measured.
Catalyst durability. This task will assess the impact of intermediate ethanol blends on the full useful life of the catalyst system. In Phase I, the study will initially screen 25 vehicles for catalyst performance and key temperatures during open-loop (WOT) operation. Full-life (120,000 miles) studies on about 10 engine families will follow in Phase II. For each engine family, eight vehicles will be tested—with a pair dedicated to one of four fuels ranging from E0 to E20. A total of 80 vehicles will be tested (10 models × 4 fuel types × 2 vehicles per pair). Engines will have compression and leakdown checks performed at each emissions testing interval. Any operational issues observed will also be reported.
Driveability. This study evaluates impacts of intermediate blends on the driveability of six late-model non-FFVs and of various E85 fuels in 20 FFVs. The standard driveability test, developed by CRC, was used. Fuels tested in the study include E0, E15, and E20 with prescribed vapor pressures.
Materials compatibility. This will evaluate the durability of wetted components of fuel systems in non-FFVs when exposed to E10 and E20. This study will measure effects on all materials found in the fuel system, including plastics, elastomers, O-rings, and hose materials.
Specialty engines. This task will consider the effects of intermediate ethanol blends on various other non-automotive engine types (e.g., marine, motorcycles, snowmobiles). Preliminary planning meetings have been held with industry representatives to guide the development of test plans for these engines.
Brian West, Keith Knoll, Wendy Clark, Ronald Graves, John Orban, Steve Przesmitzki, Timothy Theiss (2008) Effects of Intermediate Ethanol Blends on Legacy Vehicles and Small Non-Road Engines, Report 1 (NREL/TP-540-43543, ORNL/TM-2008/117)
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