Biofuels have grabbed the attention of engine researchers ever since the oil-crisis and escalating costs of petro-chemicals cropped up in the ׳70s. Ethanol and methanol were the most widely researched alcohols in IC engines. However, the last decade has witnessed significant amount of research in higher alcohols due to the development of modern fermentation processes using engineered micro-organisms that improved yield. Higher alcohols are attractive second/third generation biofuels that can be produced from sugary, starchy and ligno-cellulosic biomass feedstocks using sustainable pathways. The present work reviews the current literature concerning the effects of using higher alcohols ranging from 3-carbon propanol to 20-carbon phytol on combustion, performance and emission characteristics of a wide range of diesel engines under various test conditions. The literature is abound with evidence that higher alcohols reduce carcinogenic particulate emissions that are prevalent in diesel engines. NOx emissions either increased or decreased based on the domination of either cetane number or heat of evaporation. Brake specific fuel consumption (BSFC) of the engine usually suffered due to low energy content of alcohols. A notable feature is that the combination of higher alcohols (like butanol or pentanol), high exhaust gas recirculation (EGR) rates and late injection timing enabled low temperature combustion (LTC) in diesel engines that can simultaneously reduce smoke and NOx emissions with improved engine efficiency. It can be concluded that higher alcohols reduce smoke emissions with their fuel-borne oxygen; enhance air/fuel mixing by offering long ignition delay and eventually replace fossil diesel (partially or wholly) to enable a clean and efficient combustion in compression-ignition engines. The chief thrust areas include developing mutant strains with higher yield, higher tolerance to toxic inhibition and low-cost substrates for fermentation. Further work is required in stipulating optimum blend-fuel characteristics and ensuring the long-term durability of the engines using these fuels.

Use of higher alcohol biofuels in diesel engines: A review

Effect of biodiesel–butanol fuel blends on emissions and performance characteristics of a diesel engine

Effect of exhaust gas recirculation (EGR) on performance and emissions of a constant speed DI diesel engine fueled with pentanol/diesel blends

Combustion and emissions characteristics of high n-butanol/diesel ratio blend in a heavy-duty diesel engine and EGR impact

This article brings a comprehensive literature review with the objective of presenting butanol, its characteristics and properties. The focus of this work is to gain a better understanding of this alcohol and evaluate its potential use as biofuel, mainly for the automotive industry. An overview on the butanol production is shown, with emphasis on processes and raw materials for the production of biobutanol. The new and growing studies to improve the acetone-butanol-ethanol (ABE) process are also reviewed showing new developments focused in new strains and usage of different feedstock for fermentation, in search of better process yield. On the application of butanol as fuel, some highlights on other author's studies focused in the chemical kinetics of butanol are introduced and are useful to start a debate about the potential of this alcohol – or its blend with gasoline or diesel – as a new and environmentally interesting biofuel.

Zheng Chen

Papers

Combustion and emissions characteristics of high n-butanol/diesel ratio blend in a heavy-duty diesel engine and EGR impact

Study on performance and emissions of a passenger-car diesel engine fueled with butanol–diesel blends

Effects of port fuel injection (PFI) of n-butanol and EGR on combustion and emissions of a direct injection diesel engine

The influence of alcohol additives and EGR on the combustion and emission characteristics of diesel engine under high-load condition

Impact of higher n-butanol addition on combustion and performance of GDI engine in stoichiometric combustion