Biodiesel exhaust: the need for health effects research.

摘要: The use of plant oils as fuels in the compression ignition engine is old itself (Knothe 2001). Although vegetable oil alone proved too viscous for continuous diesel engine, oil–based were developed during early part 20th century 2005). Biodiesel today describes an alkyl ester that can be used unmodified engine. Feedstocks production biodiesel are renewable sources biologic origin. animal to produce biodiesel, more abundant and represent most feedstock on a commercial scale United States. Currently, primary feedstocks States Europe soybean rapeseed oil, respectively. fatty acids triacylglycerols contain unsaturated carbon bonds thus tend remain liquid form at low temperatures. These currently require modified limiting their usefulness alternative fuel source this time. Chemical modification required Base-catalyzed transesterification current industrial reaction method (Figure 1). This process reacts with alcohol (i.e., methanol) presence catalyst [e.g., potassium hydroxide (KOH)] methyl ester) glycerol (Schuchardt et al. 1998). Alkylated less dense than therefore separate basis density. by-product removed from bottom vessel. further refined pharmaceutical cosmetic industries. type performed batch which scaled up depending capacity design reactor. Figure 1 Transesterification producing triglycerides where R1, R2, R3 long chains saturated/unsaturated hydrocarbons fatty-acid chains). Typically (KOH) catalyst. Biodiesel began 1970s. Cooperatives small producers have provided limited supply number cars farm equipment. Production now increasing. 2004 was approximately 25 million gallons 2). enactment American Jobs Creation Act marked important turning point future At heart bill provision allows distributors blends (mixed petroleum diesel) receive federal excise tax credit. There greater economic incentive increasing By end 2005, industry 75 gallons, 300% increase 1 year. Current capacity, however, stands just over 300 gallons/year; expansion new construction could double industry’s within few years. Figure 2 Estimated U.S. per Data National Board (2005). The transportation sector first adopt competing alternative. Growing numbers municipal fleets across country turned preferred fuel, demonstrating commitment public officials environmental stewardship. Other sectors technically capable using include marine transportation, residential heating, mining. However, operating peak production, it estimated will meet < 1.0% demand (Swanson 2006). Clearly, not replacing terms usage foreseeable future.