Addressing Fuel Quality and Vehicle Operability Concerns Arising from the Use of Alternative Fuels

摘要

The need to reduce the adverse affects of vehicle emissions on air quality, particularly in urban areas has been the prime focus of European transport policies in the latter stages of the 20th century. The resulting 'Euro' emission standards and suitably modified 'EN' fuel standards have together resulted in a significant reduction in the contribution of road transport to air pollution despite the continued growth in the transport sector. As a result with the exception of particulates and low level ozone formation the major air quality issues have now been largely addressed. The focus has therefore shifted towards climate change and limiting greenhouse gas (GHG) emissions. Contrary to the so called regulated emissions, CO{sub}2 emissions have continued to increase as a result of both the increased transport volume and the additional energy required to produce fuels to tighter specifications. In addition, efforts by car manufacturers to improve fuel efficiency have been constrained by the need to meet the legislated emissions standards. Industry bodies are therefore lobbying EU legislators to limit any further reductions in regulated emissions to levels for which there is a proven requirement rather than continuing the established trend. Energy security is an issue which has also received greater attention in recent years with transport being perceived as being particularly vulnerable given its almost total reliance on fossil fuel reserves. Alternative fuels are therefore supported by the European Commission as a means of both substituting oil (with a target of 20% by 2020 having been set) and reducing GHG emissions. Such initiatives are by no means limited to Europe. Indeed in many areas, alternative fuel activities are more advanced than within the EU. For instance, Brazil has led the World in the use of ethanol both as a dedicated fuel and as a blending component. Similarly, in recent years ethanol has been increasingly used in the US to substitute methyl tertiary butyl ether. In addition, whilst many of the countries within Asia Pacific are affected by the same environmental, strategic and economic drivers these are often further compounded by the growth forecasts for the region. As a result countries such as Australia, China, the Philippines, India and Thailand have responded with programmes designed to optimise alternative fuel strategies to their individual requirements. Fuel quality, handling and vehicle operability requirements need to be addressed where fatty acid methyl ester, biomass to liquid, ethanol and ethyl tertiary butyl ether are used in the diesel and gasoline pools. The main technical issues are reviewed in the body of this paper. In addition, the potential for such fuels to contribute to improvements in urban air quality are discussed.