Mani Natarajan

Biodistillate Transportation Fuels 2. - Emissions Impacts

Diesel vehicles are significant sources of NOx and PM emissions, and to a lesser extent, emissions of CO, HC, and toxic species. For many years, biodiesel fuel (and blends of biodiesel) has been promoted as a “clean fuel” alternative to conventional diesel. Based upon previous reviews by EPA, a common understanding has arisen that biodiesel usage reduces CO, HC, and PM emissions significantly, but increases NOx emissions slightly. This paper discusses a recent review of 94 published reports, from the period of 2000-2008. Assessments were made of the emissions impacts of biodistillate fuels from various engine types, operating conditions, control technologies, and fuel type. In each situation, emissions from the biodistillate case were compared with emissions from a reference diesel fuel case. Graphical displays were developed to show the effects of biodistillate blend level upon 4 emissions species (NOx, CO, HC, PM) from 3 engine types [heavy-duty (HD), light-duty (LD), and single cylinder test engine (TE)]. Results showed that use of biodistillates, even at a 20% blend level, substantially decreased emissions of CO, HC, and PM – generally by 10-20%. Although results varied considerably from one study to the next, similar benefits were seen in both LD and HD engines, regardless of engine technology or test condition. While data were much more limited for renewable diesel cases, these hydroprocessed fuels appeared to provide similar emissions reduction benefits for CO, HC, and PM. NOx emissions impacts were much smaller, and more difficult to discern. Though highly variable, most studies indicated a slight NOx increase when using B100 fuel. For HD engines, the authors’ best estimates are that NOx emissions increase 2-3% with B100, but are unchanged from conventional diesel fuel for B20 blends. Thus, this review indicates smaller NOx effects of biodistillates in HD engines than defined by EPA several years ago. In LD engines, NOx effects appear to be somewhat larger, with increases of 10-15% observed when using B20 and B100, respectively. More sophisticated statistical analyses are required to assess the significance of these small effects. INTRODUCTION AND BACKGROUND This effort is part of a larger study sponsored by the Coordinating Research Council (CRC), with the overall objective of assessing the state of knowledge regarding biofuels as blending materials for ultra-low sulfur diesel (ULSD) fuel in transportation applications. Besides emissions impacts, the entire study dealt with policy drivers, feedstocks, fuel production technologies, fuel properties and specifications, in-use handling and performance, and life-cycle impacts. Companion papers address these non-emissions topics. In this paper, the comprehensive term, biodistillate, is used to include all plantand animal-derived middle distillate fuels intended for use in diesel engines, regardless of the production technology used to manufacture the fuels. The two major biodistillate categories are:

Real-World Vehicle Emissions: A Summary of the Sixteenth Coordinating Research Council On-Road Vehicle Emissions Workshop

Abstract The Coordinating Research Council held its 16th workshop in March 2006, with 83 presentations describing the most recent mobile source-related emissions research. In this paper, we summarize the presentations from researchers who are engaged in improving our understanding of the contribution of mobile sources to air quality. Participants in the workshop discussed evaluation of inuse emissions control programs, effects of fuels on emissions, emission models and emission inventories, results from gas- and particle-phase emissions studies from spark-ignition and diesel-powered vehicles, and efforts to improve our capabilities in performing on-board emissions measurements, as well as topics for future research.

Biodistillate Transportation Fuels 1. Production and Properties

Biodistillate transportation fuels include biodiesel (produced via transesterification of animal fats and vegetable oils) and renewable diesel (produced via catalytic hydroprocessing of the same feedstocks). Production and use of biodistillates are increasing dramatically, both in the U.S. and globally. This paper describes the policy drivers prompting growth of biodistillate fuels in the U.S., Europe, and selected other countries. Trends in fuel production volumes and feedstocks supplies are presented for these fuels. Current feedstocks are dominated by soybean oil in the U.S. and rapeseed oil in Europe. However, there is much interest in developing alternative, non-edible feedstocks such as jatropha and microalgae. Currently, biodiesel is the dominant biodistillate in use, though interest in renewable diesel is increasing. This paper describes different conversion processes used to manufacture these fuels, and discusses the pros and cons of each. Chemical and physical properties of biodistillates are presented, along with a discussion of the relevant fuel specifications established by ASTM and other organizations. Measures to assure satisfactory fuel quality are explained. Finally, in-use handling and performance of biodistillates are discussed, focusing on issues such as fuel stability and low-temperature operability where special precautions may be necessary to ensure satisfactory quality.

Biodistillate Transportation Fuels 3 - Life Cycle Impacts

Life-cycle assessments (LCA) of biodistillate fuels are becoming increasingly important for policy decisions regarding alternative fuels. However, due to the dataintensive and assumptive nature of LCAs, rarely do two different studies produce comparable results. To add to the complexity, effects of indirect land use changes are now being incorporated into LCA models. This development is influencing policy decisions and generating much controversy. A literature survey of 55 different LCA studies of biodistillate fuels was conducted. The comparison of energy requirements and global warming potential (GWP) impacts of these studies help to illustrate which data inputs and assumptions most strongly affect the results, and wherein the major discrepancies lie. Life-cycle energy results are typically reported as energy return (ER), meaning the heating value of the biofuel divided by the total fossil energy inputs to produce the fuels. Most studies report significantly higher ER values for biodistillates (both biodiesel and renewable diesel) compared to conventional diesel fuel. Similarly, most LCA studies show significant GWP reductions for biodistillates compared to conventional diesel. However, due to lack of consistency in LCA approaches and assumptions, considerable uncertainty still exists regarding the accuracy of most LCA results.

Real-World Vehicle Emissions: A Summary of the Seventeenth Coordinating Research Council On Road Vehicle Emissions Workshop

Abstract The Coordinating Research Council, Inc. (CRC) held its 17th On-Road Vehicle Emissions Workshop in March 2007, where results of the most recent on-road vehicle emissions research were presented. We summarize ongoing work from researchers who are engaged in improving our understanding of the role and contribution of mobile sources to ambient air quality and emission inventories. Participants in the Workshop discussed efforts to improve mobile source emission models, light- and heavy-duty vehicle emissions measurements, on- and off-road emissions measurements, effects of fuels and lubricating oils on emissions, as well as emerging issues and topics for future research.

Real-World Vehicle Emissions: A Summary of the Thirteenth Coordinating Research Council On-Road Vehicle Emissions Workshop

Abstract The Coordinating Research Council held its thirteenth Vehicle Emissions Workshop in April 2003, when results of the most recent on-road vehicle emissions research were presented. Ongoing work from researchers who are engaged in improving understanding of the contribution of mobile sources to ambient air quality and emission inventories is summarized here. Participants in the workshop discussed efforts to improve mobile source emission models, the role of on-board diagnostic systems in inspection and maintenance programs, light- and heavy-duty vehicle emissions measurements, on- and off-road emissions measurements, effects of fuels and lubricating oils on emissions, as well as topics for future research.

Real-world vehicle emissions: A summary of the 15th coordinating research council on-road vehicle emissions workshop.

Abstract The Coordinating Research Council held its 15th workshop in April 2005, with nearly 90 presentations describing the most recent mobile source-related emissions research. In this paper, the authors summarize the presentations from researchers who are engaged in improving our understanding of the contribution of mobile sources to air quality. Participants in the workshop discussed emission models and emission inventories, results from gas- and particle-phase emissions studies from spark-ignition and diesel-powered vehicles (with an emphasis in this workshop on particle emissions), effects of fuels on emissions, evaluation of in-use emissions control programs, and efforts to improve our capabilities in performing on-board emissions measurements, as well as topics for future research.

Emissions of Toxicologically Relevant Compounds Using Dibutyl Maleate and Tripropylene Glycol Monomethyl Ether Diesel Fuel Additives to Lower NOx Emissions

A previous paper reported (SAE Paper 2002-01-2884) that it was possible to decrease mode-weighted NOx emissions compared to the OEM calibration with corresponding increases in particulate matter (PM) emissions. These PM emission increases were partially overcome with the use of oxygenated diesel fuel additives. We wanted to know if compounds of toxicological concern were emitted more or less using oxygenated diesel fuel additives that were used in conjunction with a modified engine operating strategy to lower engine-out NOx emissions. Emissions of toxicologically relevant compounds from fuels containing triproplyene glycol monomethyl ether and dibutyl maleate were the same or lower compared to a low sulfur fuel (15 ppm sulfur) even under engine operating conditions designed to lower engine-out NOx emissions. The emissions of toxicologically relevant compounds using a 100% Fisher Tropsch fuel, a recognized clean fuel, were equivalent to or less than emissions from the two oxygenated diesel fuels. These results suggest that these oxygenated diesel fuel additives can be used to lower engine-out NOx emissions without risking any increase in tailpipe emissions of compounds of toxicological concern.

Emissions of toxicologically relevant compounds using fischer-tropsch diesel fuel and aftertreatment at a low NOx, low power engine condition

Previously we reported (SAE Paper 2005-01-0475) that emissions of toxicologically relevant compounds from an engine operating at low NOx conditions using Fischer-Tropsch fuel (FT100) were lower than those emissions from the engine using an ultra-low sulfur (15 PPM sulfur) diesel fuel (BP15). Those tests were performed at two operating modes: Mode 6 (4.2 bar BMEP, 2300 RPM) and Mode 11 (2.62 bar BMEP, 1500 RPM). We wanted to evaluate the effect on emissions of operating the engine at low power (near idle) in conjunction with the low NOx strategy. Specifically, we report on emissions of total hydrocarbon (HC), carbon monoxide (CO), NOx, particulates (PM), formaldehyde, acetaldehyde, benzene, 1,3-butadiene, gas phase polyaromatic hydrocarbons (PAHs) and particle phase PAHs from a DaimlerChrysler OM611 CIDI engine using a low NOx engine operating strategy at Mode 22 (1.0 bar BMEP and 1500 RPM). Mode 22 did produce some differences in emissions levels and aftertreatment performance for toxicologically relevant species compared to Modes 6 and 11. Further, uncontrolled step changes in these emissions were observed to occur at the low exhaust temperature of Mode 22. Nevertheless the emissions for Mode 22 with Fischer-Tropsch diesel fuel were generally consistent with Modes 6 and 11.