Amber Broch

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:

Laboratory pelletization of hydrochar from woody biomass

Pelletization is an important method for increasing the mass and energy density of raw woody biomass materials and improving their handling and transport. Further increases in mass and energy density are possible by thermal pretreatment of raw biomass prior to pelletization, via torrefaction or hydrothermal carbonization (HTC). In this work, standardized laboratory test methods were developed, validated, and utilized to provide reliable assessments of pellet properties – both before and after immersion in water, as water immersion is a severe test of pellet durability. Pellets of raw or torrefied woody biomass cannot survive a standard tumbler durability test after water immersion, while pellets of hydrochar (produced by HTC processing) demonstrate excellent durability under these conditions. In part, the excellent pellet binding behavior of hydrochar is due to resins produced in the HTC process. Hydrochar can also be used as a binder to substantially improve the pelletization of raw wood and torrefied wood.

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.

Development of the Renewable Energy Deployment and Display (REDD) Facility at the Desert Research Institute

The Desert Research Institute (DRI) has developed a Renewable Energy Deployment and Display (REDD) Facility as an off-grid capable facility for exploration of integration, control, and optimization of distributed energy resources (DER) with an emphasis on solar and wind energy. The primary goal of the facility is to help grow DRI’s capabilities and expertise in areas of renewable energy research, development, demonstration, and deployment. The facility is powered by four solar PV arrays (6 kW total) and two wind turbines (3 kW total) during off-grid operation. Energy storage is achieved via two 2.5 m3 hydrogen storage tanks and a 9 kWh battery bank. The hydrogen is produced via a 5 kW electrolyzer and is used to fuel an internal combustion engine (ICE) with an alternator when needed.The REDD Facility consists of a 111.5 m2 residence and a 56 m2 workshop. The REDD House features over 37 m2 of solar thermal collectors used to provide hot water to either a 15.9 kW heat exchanger or a 17.6 kW absorption chiller. The REDD Workshop features a 54 m2 solar collector air heater and thermal storage via water and air in the floor. Also housed in the REDD Workshop is a modified 3-cylinder 950cc naturally aspirated renewable gas engine connected to a 5 kW generator to be used for future biomass-related research.Future research at the REDD Facility will include continued investigation into the use and regulation of site-built solar air collectors, solar cooling technologies, and the advancement of hydrogen as energy storage for residential applications. The facility is also continually used for education and outreach purposes. Lastly, DRI encourages the use of the REDD Facility as a test bench for new technologies; whether for proof of concept or demonstration.© 2014 ASME