Review: utilization of rapeseed oil, rapeseed oil methyl ester of diesel fuel: exhaust gas emissions and estimation of environmental effects

摘要

The use of rapeseed oil fuels in diesel engines has been intensively investigated since the beginning of the on-going energy crisis. In the beginning, the emphasis was placed on the technical possibilities associated with the use of rapeseed oil as a fuel. However, research has shown that pure rapeseed oil can only be used in specially designed engines. Research that followed indicated that rapeseed oil methyl ester (RME) was a suitable replacement for petroleum diesel fuel (DF). After this discovery, research has focused on the engine exhaust emissions that result when fueling with both unmodified rapeseed oil and RME. Initially, research concentrated on the federally regulated hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NO{sub}x) exhaust gas emissions. These components, and occasionally particulate matter (PM), have been investigated in a large number of studies and reports involving engine exhaust emissions testing. In addition, a series of current publications compare the environmentally important but non-regulated polycyclic aromatic hydrocarbons (PAH), aldehydes, ketones and in some cases, the aromatic compounds. According to the United States Clean Air Act, butadiene, benzene, formaldehyde, acetaldehyde and polycyclic organic material are the principal toxic airborne exhaust gas components found in engine exhaust gas emissions. Butadiene, however, has not been reported when examining the exhaust gases of engines fueled with rapeseed oil and RME. Likewise, the influence of rapeseed oil fuels on the formation of photochemical smog, whose main component is ozone, is unknown. The undisputed advantages of rapeseed oil fuels, however, lie in their sulfur-free emissions and the reduced atmospheric CO{sub}2 emissions. An estimation of the environmental effects caused by emissions from engines fueled with rapeseed oil and rapeseed oil methyl ester fuels can be made by a relative comparisons with DF. An evaluation of the potential health effects, as presented recently for gasoline and diesel-powered engines in an environmental assessment of the "Sachverstandigenrates fur Umweltfragen" must be replicated for RME and rapeseed oil fuels. The goal of this review is to summarize the published emissions measurements from different authors, to compare these results and, where possible, identify trends that may exist. In order to classify and evaluate the conclusions, it is necessary to begin with a description of the experimental conditions applied, or in other words, the engine testing procedures. The current state of knowledge concerning the environmental effects of the components of exhaust gas are discussed, in order to assess the environmental relevance of the test results. Section 4 contains a summary of the measured values, that are discussed under conclusions in section 5 regarding their environmental importance, whereby also some standing problems, whose research needs exist, are examined.