Feasibility of bioethanol and biobutanol as transportation fuel in spark-ignition engine: a review

Fossil fuels depletion is a globally main issue because it is the primary transportation fuel. Furthermore, environmental issues including global warming and climate changes are problems that need to be dealt with immediately. Therefore, biofuels (bio-based fuels), i.e. bio-alcohols (bioethanol and biobutanol) which are produced from natural materials have emerged as promising transportation fuels because of their sustainability and environmental benefits which can reduce the dependency on crude oil reserves. Today, bioethanol is widely used as an option for transportation fuel or additives to gasoline in spark ignition (SI) engine due to its attractive properties of high octane number and reduced exhaust emissions. The next promising and competitive biofuel is biobutanol which has superior properties to be used in SI engine without engine modification. The aim of the present review is to highlight on the feasibility of the bioethanol and biobutanol as alternative transportation fuels in SI engine. The first section of this paper is an overview on bioethanol and biobutanol as gasoline alternatives. In the next section, comparative physicochemical properties of gasoline, bioethanol and biobutanol and their potential sources of production are presented. The effect of bioethanol and biobutanol with gasoline blends on engine performances, combustion analysis, exhaust emissions, engine durability and their effect on lubricating oil are discussed in the next section. The review study acknowledges that the bioethanol and biobutanol are capable of improving engine performances, combustion and also reducing exhaust emissions. However, the addition of alcohols in fuel blends leads to negative impacts on the engine durability and lubricating oil properties. Bio-alcohols (bioethanol and biobutanol) which are produced from natural materials have emerged as promising transportation fuels because of their sustainability and environmental benefits which can reduce the dependency on crude oil reserves.